Abstract: External Forcing of Land-Use Changes by Human Activities in Food Supply and Demand
Gilbert Ahamer,
Institute for Plant Ecology at the Justus-Liebig-University
Giessen / Germany; 1995
Abstract: In order to identify driving forces for the development of the current and future land use changes, in other words for agriculturally used area in the long term and on a global scale, an analysis of the driving forces in the system of global food demand and supply has been carried out. As a first step in direction to that target, a socio-economic database consisting of 880 variables as time series for 149 countries was designed on the basis of the FAO data and the World Bank data.
In a second step, data from different scientific areas are combined by its analytical tool that permits to derive secondary variables and to establish regressions on a per country scale between any such variables and finally to calculate trends and elasticities on a global, regional or per country level.The global system for food production is viewed from the demand side and is understood as a logical chain of subsystems being described by dimensionless intensity parameters. Results of trend analyses show the change in RAP and agricultural area to be mainly influenced from the demand side by food trade, distribution, quality and quantity of nutrition; from the supply side by the level of labour input, the degree of mechanization and fertilizer input in a given country. It is interesting to note, however, that in different regions of the earth different driving forces are predominant.
Be it mere population growth in Africa that drives the search for new agricultural land, the strong increaseof the population number is not the most pressing force: increase in food quantity, foodcomposition (the richer a nation is, the more meat is eaten) and changes in global patterns of foodtrade are dominating the search for new agricultural land in the more developed continents. For analysis of details, 19 scenarios for the area needed for future food production are proposed. Future research directions are identified: "Climate Impacts by Megatrends in Socio-economy",the vast area of energy consumption is being planned to be integrated in a future stage of the project.
SPECIES INFLUENCING ATMOSPHERIC CHEMISTRY
IN TROPICAL AFRICA
Ajit-L. N. Ajavon
Atmospheric Chemistry Laboratory, Facult des Sciences,
Universit du Bnin, B.P. 1515, Lom-TOGO
The tropospheric concentrations of most reactive chemical
species have been found to very in space and time all over
the tropical Africa. Two categories of chemical species play a
major role and are most involved in Africa tropospheric
chemistry: Aerosols and trace gases.
Aerosols originate from biomass burning, harmattan haze durst,
open-air house solid waste incineration and vehicular traffic
of unpaved as well as unswept paved roads and are composed of
TPM, POC, SOx, elemental carbon. Severe visibility reduction,
increased respiratory deceases and chest congestion complaints
are usually recorded during harmattan period.
Trace gases most of the time result from biomass burning,
engine exhausts, factory smokes. CO2, CH4, NOx, SOx, NMHC,
R(CH)x, 03 and aromatics are the major trace gases en-
countered.
These emissions to the atmosphere from both anthropogenic and
non-anthropogenic sources yield to increasing concentrations
of a number of trace gases, are responsible of Africa
temperatures increase through the greenhouse effect. The high
concentration and large scale increase of tropospheric ozone,
observed from data of field campaign experiments performed in
tropical Africa, indicate a fundamental change in the chemical
behaviour with perturbation of oxidant cycles in Africa
troposphere, leading to important photochemistry and climate
change.
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DETERIORATION OF LANDUSE DUE TO HUMAN ACTIVITIES
IN AMMAN AREA
H. Al-Kharabsheh
Royal Jordanian Geographic Centre
Amman - Jordan
To reach an understanding prognostic behaviour of global
change, we have to improve our current knowledge and pinpoint
critical gaps with components which aim to produce a simple
model of the globe.
Amman city development was taken as a case study, knowing that
Amman forms more than one-third of Jordan's population,
mediterranean climate, semi-arid area, it is located on an
important part of fertile land where it's considered as a crop
productive area. It played, until the seventies, an important
role in supplying Jordan with wheat.
Aerial photographs, maps and satellite images (Spot, Landsat)
corresponding to different dates are used in this study to
delineate the urban areas.
As a result of data analysis and image interpretation, we can
clearly see that the urbanization reduced and destroyed an
appreciable part of fertile land of Jordan. Results also show
the important impact of human activities on global change and
degradation of the earth, that allows us to survive. Also we
see the importance of resource planning and managing land
sustainably. These tools should be used by planners and
decision makers in order to protect the homosphere and
biosphere from dangerous changes.
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TOWARDS QUANTIFYING THE GLOBAL PATTERN
OF CARBON DIOXIDE FERTILIZATION EFFECT
G. A. Alexandrov1 and T. Oikawa2
1Institute of Atmospheric Physics, Russian Academy of Sciences
Pyzhevsky Per. 3,
Moscow, 109017, Russia
2Institute of Biological Sciences, Tsukuba University
Tsukuba, Ibaraki 305, Japan
It is conventional to assume that contemporary terrestrial
carbon budget includes a sink term resulted from CO2
fertilization effect. However, the empirical basis for
evaluating the magnitude of the sink is not sufficiently
strong: experimental studies show that plant response is
apparently species and site specific. In this paper we
quantify the role of biome-specific limitations such as
available solar radiation.We proceed from the model based on Monsi's principles (Oikawa,
1986), suppose that light-saturated photosynthetic rate is
proportional to atmospheric CO2 concentration (Ca), calculate
the buildup of net primary production (dNPP) per each ppmv of
Ca growth (dCa) and come to conclusion that fertilization
effect of CO2 (dNPP/dCa) is more pronounced with biomes
receiving more incident solar radiation. We estimate (Fig.)
the global dNPP/dCa at 1.5 Pg d.w./ppmv, tropical biomes
dNPP/dCa at 1 Pg d.w./ppmv and savannah dNPP/dCa at 0.5 Pg
d.w./ppmv.
[Place for Figure]
Fig. Proposed global pattern of carbon dioxide fertilization
effectThe inferred location of the sink (predominantly in the
tropical latitudes) is consistent with the indirect evidence
of the existence a tropical biotic sink that was obtained
(e.g., Enting & Mansbridge, 1991) from inverse calculatutions
using atmospheric transport models. This conclusion is also
supported by the data (Archer, 1989) on conversion of savannah
grasslands to savannah woodlands.
The obtained magnitude of CO2 fertilization effect is roughly
agreed with that was derived from 1981-1986 observations of
atmospheric carbon isotope ratio (Francey et al., 1995), but
significantly less than that was derived from 1989-1992 period
of the same observations. The causes of variations in the
magnitude of CO2 dependent terrestrial carbon sink are
discussed.References:
Archer, S (1989) Am.Nat., Vol. 134, pp. 545-561
Enting, I.G. and J.V. Mansbridge (1991) Tellus, Vol. 43,
pp.156-170 Francey, R.J. et al. (1995) Nature, Vol. 373, pp.
326-330
Oikawa, T. (1986) Bot. Mag. Tokyo, Vol. 99, pp. 419-430
>>>>>>>>>>>>>>>>>>>>
MODELLING OF MOISTURE RETENTION IN PEAT SOILS
J. Alm1, R. Weiss1, R. Laiho2 and J. Laine2
1Department of Biology, University of Joensuu
P.O. Box 111, FIN-80101 Joensuu, Finland
2Department of Forest Ecology
P.O. Box 24, FIN-00014, University of Helsinki, Finland
Water retention capacity of undisturbed surface peat samples,
collected from 38 undrained and drained pine mire sites and
four depths at each site, was measured gravimetrically for
matric potentials of pF 1.0, 1.5, 1.8, 2.0, 3.0 and 4.2. Peat
characteristics such as bulk density and botanical peat
components (remains of Sphagnum, Carex, Eriophorum and wood)
were also determined. We tested several common water retention
theories used for mineral soils, derived a semi-empirical
equivalent model for peat soil, and compared the predictions
of the most feasible models on our data. At saturation point
(pF 0), the models were defined to give the water content
calculated using the sample total porosity obtained from a
constant specific gravity value of 1.5 g cm-3 and the measured
sample bulk density.
To find the most feasible basic model types for peat soils, a
subset of 25 peat samples was used in a test run where each
model type was fitted using a non-linear regression algorithm
(sequential quadratic programming) and the prediction errors
were compared using F-statistics. Because of the few matric
potential values used, we had to reduce the number of
parameters used commonly in the models for mineral soils to
obtain higher degrees of freedom. Sensitivity analysis for the
remaining model types showed that the residual water content
of peat is only of minor importance for the matric suction
range of practical interest.
According to the F-test, the most suitable model type was the
Van Genuchten's model with the residual water content omitted:
3D s (1+(E0h)n)-1+1/n, where is volumetric peat water content
(cm3 cm-3), s is saturated soil water content, E0 and n are
shape parameters and h is matric suction value in H2Ocm (e.q.
10pF). To explain the variation in the shape parameters, we
used three different peat character sets in OLS-regression.
The first set consisted only of the polynomial terms of bulk
density; botanical peat components were added to the second
set, and an interaction term (Sphagnum-component with sampling
depth) was finally added to the third set. The variables in
the third set proved to be clearly the best predictors for E0
and n.
However, in the semi-empirical model 3D exp{ln( s) - [ln( s) -
ln( pF3D4.2)] (hpF /4.2)m} with shape parameter m, this single
shape parameter was clearly better explained by all of the
peat character sets than the two shape parameters of the Van
Genuchten model. When testing the final models by an overall
nonlinear regression, the semi-empirical model explained the
whole data set better (R23D0.93) than did the Van Genuchten
model (R23D0.90). We recommend that in pragmatic modelling
approaches the semi-empirical model should be used.
>>>>>>>>>>>>>>>>>>>>
A MECHANISTIC MODEL OF GLOBAL PHOTOSYNTHESIS
J.S. Amthor
Global Climate Research Division, Lawrence Livermore National
Laboratory
P.O. Box 808, L-256, Livermore, CA 94550, USA
The Lawrence Livermore National Laboratory, Global Climate
Research Division global terrestrial ecosystem carbon cycle
model is composed of three modules:
(1) plant photosynthesis;
(2) plant growth, respiration, and litter production; and
(3) litter and soil organic matter decomposition.
The global carbon cycle model is implemented at the spatial
scale of 1 latitude x 1 longitude. It has a nominal time step
of 1 hour. Actual vegetation cover and soil types are used.
The plant photosynthesis module, which will be described here,
is based on the biochemistry and physiology of C3 and C4
photosynthesis. The C4 photosynthesis submodel is used with
the C3 submodel for grasslands. The C3 submodel is used alone
for all other ecosystems. Effects of atmospheric [CO2] on
photosynthesis are explicitly accounted for by the module, due
to the biochemical equations used. Effects of solar radiation
(cloudiness), temperature, soil water content, and nitrogen on
CO2 assimilation are also included in the module. Canopy
conductance is calculated during the simulation of
photosynthesis, so the photosynthesis module is also used to
calculate transpiration.
Responses of global terrestrial photosynthesis to changes in
atmospheric [CO2] that have occurred during the past 200 years
will be presented. Then, photosynthetic response to a doubling
of present atmospheric [CO2] will be discussed.
The photosynthesis module is being tested at several sites
(the module is a "point" model that is applied globally as a
grid of points) with continuous measurements of whole-forest
CO2 exchange being made by the eddy correlation method. It is
also being tested with data from several field-scale
CO2-enrichment experiments.
This work was supported by Lawrence Livermore National
Laboratory's Laboratory Directed Research and Development
Program under the auspices of U.S. Department of Energy,
Environmental Sciences Division (contract No. W-7405-Eng-48).
>>>>>>>>>>>>>>>>>>>>
SPATIO-TEMPORAL LINKAGES BETWEEN NDVI AND EL NINO
OSCILLATION (ENSO) OVER AFRICA
Assaf Anyamba, J. Ronald Eastman
The Clark Labs for Cartographic Technology and Geographic
Analysis
Graduate School of Geography
950 Main St. Worcester, MA 01610, USA
During 1980s Africa has experienced prolonged periods of
drought often followed by wet phases. These variations have
been linked to low and high phases of the ENSO phenomenon. In
this study we use principal components transformation to
analyze the normalized difference vegetation index (NDVI) time
series data for Africa for the period 1986 - 1994 to
investigate spatio-temporal patterns of variation in the
vegetation index in relation climate variability. Results from
the analysis show that the NDVI data sets effectively
represents seasonal to interannual patterns of climate
variability. One spatial pattern that is centered on Botswana,
South Africa and Zimbabwe indicates strong temporal
correlations with other ENSO indicators including SOI, OLR and
SST anomalies. The patterns retrieved show areas affected by
both the 1986-1987 and 1992 droughts. These results first,
reaffirm the association between the ENSO phenomenon and
climate variability in the western dipole of the Southern
Oscillation. Second, the technique used illustrates a new
perspective for examining climate variability by extracting
separate and distinct spatial patterns from the NDVI time
series record. This offers new possibilities for a better
understanding of spatial manifestations of ENSO on the land
surface, monitoring vegetation conditions in data sparse
regions and in validating model forecasts of El Nino related
events at regional to continental scales.
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NON-STATIONARY NUMERICAL MODEL OF RADIATION
AND TEMPERATURE REGIME OF SOIL-VEGETATION-ATMOSPHERE
(SVA) SYSTEM
D.G. Atanassov
National Institute of Meteorology and Hydrology,
Blvd Tsarigradsko Chaussee 66, 1784 Sofia, Bulgaria
The main objectives of SVA modelling are the processes of
transport, photosynthesis and shortwave radiation; stationary
governing equations are usually used. To simulate the diurnal
meteorological variation of SVA system, infrared radiation and
non-stationary equation have to be included.
A one-dimensional model of horizontally homogeneous SVA system
is developed. A non-stationary equation for air temperature as
well as another one for plant temperature are used. The
source-sink terms of these equations refer to the contribution
of turbulent and radiation heat flux densities and to the
plant-air heat exchange. Goudriaan's scheme of shortwave
radiation transfer in plant canopies is applied. A new
infrared radiation scheme is developed. Linear absorption of
the irradiance on its way through the canopy is assumed,
instead of the common used exponential absorption assumption.
The soil surface temperature is calculated by the force-
restore method.
A sensitivity analysis to the canopy characteristics and to
the meteorological conditions is performed. To focus on the
radiation-heat interaction, the evaporation is not considered;
wind velocity profile and eddy exchange coefficient are
considered in a simple way. Numerical simulations show the
ability to model the complicated non-stationary and heat
transfer in SVA system.
>>>>>>>>>>>>>>>>>>>>
INTERANNUAL VARIATION OF CARBON EXCHANGE FLUXES IN TERRESTRIAL ECOSYSTEMS
F.-W. Badeck1, J. Kindermann2, G. H. Kohlmaier2
1Laboratoire d'Ecologie vgtale, Universit de Paris Sud XI,
B3t. 362, 91405 Orsay, France
2Institut f1r Physikalische und Theoretische Chemie, J. W.
Goethe Universit4t,
Marie-Curie-Str. 11, 60439 Frankfurt/M., FRG
Simulation results of the interannual variation in carbon
exchange fluxes between the atmosphere and the terrestrial
biosphere are presented. A prognostic physiologically based
model of the carbon budget in terrestrial ecosystems, the
Frankfurt Biosphere Model (FBM), is applied. Within the model
32 vegetation types are distinguished. The spatial resolution
is 0.50 x 0.50. The model simulates phenology based on a flux
balance approach and allometric relationships.
The data on climatic forcing are based on climate maps.
Interannual variation is introduced according to records of
temperature and precipitation anomalies. The model calculates
gross primary production, autotrophic respiration, net primary
production, heterotrophic respiration and the change in carbon
stocks for natural climax ecosystems.
Simulated interannual variation in the annual net exchange
flux between the atmosphere and the terrestrial biosphere is
compared to the biospheric signal deduced from 13C-measure-
ments. Biospheric activity can be identified as a major cause
of the variation in the increase of atmospheric carbon
dioxide.
The effects of the temperature response of gross primary
production and respiration as well as the response to soil
water availability are characterized. It can be shown that a
consistant correlation between mean annual temperature and net
carbon exchange can not be expected. Monthly temperature
anomalies and their effects on the duration of the vegetation
period as well as the relative changes in GPP and respiration
have to be taken into account. The same holds true for
precipitation and soil water content.
>>>>>>>>>>>>>>>>>>>>
PREDICTION OF BIOMASS AND TURNOVER TIME FOR USE IN
DIAGNOSTIC MODELS OF BIOSPHERIC CARBON EXCHANGE FLUXES
F.-W. Badeck, A. Ruimy, B. Saugier
Laboratoire d'Ecologie vgtale, Universit de Paris Sud XI,
B3t. 362, 91405 Orsay, France
With the current state of the art, many diagnostic models of
the carbon exchange fluxes of terrestrial ecosytems need
information on carbon density and turnover time in the living
biomass in order to calculate respiration, litter production
and C13 content. Yet, currently biomass can not be derived
from optical remote sensing due to saturating signals. The
technique for radar derived measurements is under development
and not yet applicable on the global scale.
We apply a prognostic global model of the terrestrial
biosphere in order to derive modules for the determination of
biomass as a function of the average gross primary production.
The Frankfurt Biosphere Model (FBM) is a global
process-oriented model of CO2 exchange between terrestrial
ecosystems and the atmosphere. The model is not confined to
the calculation of ecosystems in the climax steady state, but
can as well be used to simulate changes in carbon stocks with
growth stages. Based on this property the feasability of a
detection of non climax ecosystems will be explored.
Different methods to determine biomass for the grid elements
covered by the same vegetation type will be compared. The
sensitivity of a diagnostic model of the carbon exchange in
the terrestrial biosphere, TURC (Terrestrial Uptake and
Release of Carbon) to the resulting biomass maps will be
examined.
>>>>>>>>>>>>>>>>>>>>
ASSESSMENT OF SOIL CARBON IN CENTRAL U. S. AGROECOSYSTEMS
2T.O. Barnwell, Jr., A.S. 1Donigian, Jr., 2R.B. Jackson, IV,
1A.S. Patwardhan,
3K.B. Weinrich, 3A.L. Rowell, 1R.V. Chinnaswamy, 4C.V. Cole
1AQUA TERRA Consultants, Mountain View, CA 94043
2Environmental Research Laboratory, U.S. EPA, Athens, GA 30605
3Computer Sciences Corporation, Athens, GA 30605
4Natural Resources Ecology Laboratory, Fort Collins, CO 80523
We estimate the carbon sequestration potential for
agroecosystems of the central United States, assessing the
impact of current agricultural trends and conditions,
alternative tillage practices, cover crops, and Conservation
Reserve Program policy on soil carbon and providing evidence
of the value of agricultural residue management practices in
relation to CO2 emissions to the atmosphere. The Study Region
comprises 44% of the land area and 60%-70% of the agricultural
cropland of the conterminous United States.
The figure aggregates study results into a time-line of
agricultural soil carbon (SOC) for a 120-year period,
beginning with conversion of native vegetation to agriculture
in about 1907, through current conditions; three projections
through 2030 are included for different crop yield increases.
Total SOC values for 1990-2030 represent a continuation of
current cropping, rotation, and tillage practices, along with
the impacts of three alternative levels of annual increases in
crop yields--1.5%, 1.0%, 0.5%. These results were obtained by
summing the products of the unit area changes in SOC under
each crop/rotation/tillage combination and the area associated
with each combination within each CD, then summing the values
for all CDs in the Study Region, and dividing by the entire
Study Region area; thus the values are in units of grams C per
square meter (gC/m2) for a 20-cm soil layer.
The historical portion of the curve shows the well-documented
decrease in SOC following land conversion to agriculture in
about 1907, a continuing drop in SOC until 1950, a period of
stable and slightly increasing SOC through 1970, and
significant SOC increases through 2030. These results reflect
increasing crop yields during this period, modeling
assumptions that represent an associated increase in residues
remaining and returning to the soil, and a decrease in the
level and intensity of tillage beginning in 1972.
For the projection period, the increase in SOC is based on the
current mix of cropping and tillage practices, along with
assumed crop yield increases. The curves show steady, almost
linear increases in SOC from 1970-2030. If this general
pattern is accurate, agricultural SOC within the Study Region
made a comeback from a low of about 50% of original native
vegetation levels in 1950-70, to about 60% of these levels by
1990. Continuing the increase would lead to 2030 Total SOC
levels approaching 75% to 90% of the SOC prior to the onset of
agricultural production.
FIGURE 1.
The study concludes that reasonable extrapolation of current
agricultural practices and trends will lead to an increase
(sequestration) of about 1 to 2 Gt C within the Study Region
by the year 2030, or about 25 to 50 Mt C per year. This
represents about a 25% to 50% increase over current 1990
levels. Nationwide the increase could be 50% greater since our
Study Region includes only 60-70% of total U.S. cropland. The
key assumption underlying these predictions is the projection
of annual crop yield increase from 1990 to 2030; the lower
range reflects an increase of 0.5% per year, while the upper
limit of 50% increase reflects a 1.5% per year crop yield
increase. The validity of this assumption needs to be
re-assessed or confirmed, and if valid, policies and research
should be promoted to support the chances of agriculture
attaining these levels of yield increase.
Reference
Donigian, A S, T O Barnwell, Jr, R B Jackson, IV, A S
Patwardhan, K B Weinrich, A L Rowell, RV Chinnaswamy and C V
Cole, Assessment of Alternative Management Practices and
Policies Affecting Soil Carbon in Agroecosystems of the
Central United States, EPA/600/R-94/067, Environmental
Research Laboratory, Athens, GA, April 1994.
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APPLICATIONS OF PALEOCLIMATIC SIMULATIONS AND DATA SYNTHESES TO UNDERSTANDING THE CLIMATE SYSTEM
Patrick J. Bartlein
Department of Geography, University of Oregon
Eugene, OR 97403-1251, USA
The combined use of paleoclimatic simulations and data
syntheses can provide information on the mechanisms and
consequences of global climatic changes. Data syntheses, and
the individual paleoclimatic records they are composed of,
illustrate how climatically sensitive environmental systems,
such as vegetation or lake hydrology, have varied in response
to the large climatic variations of the past. Conceptual and
numerical climate models provide a means for examining the
physical processes that generate these variations. Together,
the simulations and syntheses can provide support for testing
hypotheses about the climate system and for developing a
framework for predicting its future.
The analysis of sequences of simulations and data syntheses
furnish a first-order validation of the general approach of
predicting variations of the climate system over time using
global-scale simulation models. The sequence of data syntheses
and general circulation model simulations assembled in the
COHMAP project, for example, demonstrate that when the
controls or boundary conditions of the climate system are
varied according to their known histories over the past 20,000
years, the observed global- and continental-scale features of
the climate system (as reconstructed from the
paleoenvironmental record) are simulated reasonably well.
Discrepancies between the observations and simulations point
to uncertainties in our understanding of what the past
climatic variations actually were, in the specification of the
boundary conditions, or to inadequacies of the models
themselves. The first source of uncertainty can be minimized
by focusing on robust climatic changes that are recorded by
multiple kinds of evidence, and the second by the retrieval of
the necessary time series of the controlling factors. When
these sources of uncertainty are minimized, mismatches between
simulations and observations point to model inadequacies as
the cause. Instead of being viewed as failures, these
mismatches should be seen as opportunities for further
refinement of the models.
There are several persistent discrepancies between
paleoclimatic simulations and observations that exist, and
jointly hint at the absence of feedback from changes in
vegetation and surface hydrology as the source. Some examples
include the simulation of drier-than-present conditions in the
western United States when extensive pluvial lake systems
prevailed in basins that are now dry; the simulation of
post-glacial warming at high northern latitudes much earlier
than is recorded by the data; and the inability of GCMs to
simulate positive snow and ice mass balances in northern
Canada at times when the observations indicate that ice sheets
began to grow. In each case, the inclusion of feedback from
the changes in vegetation or hydrology that would accompany
the simulated climate changes reduces the mismatch between the
simulations and observations.
>>>>>>>>>>>>>>>>>>>>
PALEOCLIMATIC CHANGE DURING HOLOCENE PERIOD
OF BENGAL BASIN (CALCUTTA), INDIA
N. C. Barui1 and S. Chanda2
1Department of Botany, Raja Rammohun Roy College,
Nangulpara - 712406, West Bengal, India
2Department of Botany, Bose Institute, 93/1, Acharya Prafully
Chandra Road,
Calcutta - 700009, India
During the Metro Railway Project work a series of sections
were exposed in different parts of Calcutta. The fresh peat
samples were collected from five different locations from
north of Calcutta at various depths reflecting two to three
peat layers sandwiched between sandy clay zones of different
thickness. Some peat samples were also collected at different
locations from the exposed vertical sections of the western
side of the river Hooghly in connection with the brick klins.
The Radio Carbon datings of all the samples at different
depths ranges from 2640 F1 150 YBP to 7030 F1 150 YBP,
confirming the Holocene age of the deposits. The samples were
palynologically investigated. The dominant pollen typesrecovered from the deposits were Heritiera, followed by
Excoecaria Avicennia, Sonneratia, Nipa, Phoenix, Suaeda,
Barringtonia, Bruguiera, Acanthus, etc., most of which were
typical mangroves. Pollen grains of grasses (both wild and
cultivated types) along with some fresh water elements and
fern spores such as Acrostichum, Stenochlaena, were also
recorded in large quantities. The fossil pollen assemblages
indicated the existence of a swampy halophytic vegetation in
the diagrams in and around Calcutta about 7030 years ago from
today, which to some extent express similarities with the
present day vegetation of the Sundarbans the largest mangrove
complex of the world situated about 100 km south of Calcutta.
Fromthe results it may be inferred that the migration of the
forest towards south was probably induced by the continued
river silting, tectonic movement, biotic factors and increased
population.
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A MODELLING SYSTEM FOR ORGANIC CARBON DYNAMICS
IN SOIL PROFILES DURING THE HOLOCENE
P. Becker-Heidmann1, R. Schipmann1, R. Lehfeldt2
1Institut f1r Bodenkunde, Universit4t Hamburg,
Allende-Platz 2, 20146 Hamburg, Germany
2Wasser- und Schiffahrtsdirektion Nord,Hindenburgufer 247, 24106 Kiel, Germany
During the last years, the dynamics of soil organic carbon has
become a major research target also in climate change studies,
because it may help to find the "missing sink" of annually 2
Gt in the global carbon balance. Contrarily to the complexity
of the subject, the modelling approaches have been rather
simple so far. Soil organic carbon is still more or less a
black box in global models.
Our modelling system is based on soil profiles with
distinguished depth and horizon dependent processes and
parameters, accounting not only for decomposition but also for
vertical translocation processes. Main variables are carbon
content, EB13C and 14C age of the soil layers. Output variables
are also carbon, EB13C and 14C of gaseous emissions and
percolation losses to the groundwater. The list of parameters
contains texture (particle size distribution), pH, temperature
and soil moisture and can easily be extended if necessary. The
boundary conditions include EB13C and 14C of the carbon input.
The system is programmed in C++ under Unix operating system
and OSF/Motif with an interactive graphical user interface.
Depth distributions of variables and parameters are visualized
in interactive windows. For sensitivity analysis, the input
data as well as the parameters and boundary conditions can be
modified by drag and drop mouse actions. The system is
designed as a module for a global "Community Terrestrial
Biosphere Model" which will be coupled to a global climate
model, both developed within the common BMBF funded climate
research project "Trace gas cycles". Therefore, all
intermediate modelling are logged into files which can be used
by the other modules.
An extensive data base of thin layer-wise sampled soil
profiles containing carbon, EB13C, 14C age, pH, texture and other
data provides the test data for the different models and
parameter sets. These soils have developed in Northern Germany
after the last glaciation.
ASSESSING VARIABILITY AND TRENDS IN ARCTIC SEA ICE
DISTRIBUTION USING THE SATELLITE DATA
Gennady I. Belchansky, Ilia N. Mordvintsev and Gregory
K.Ovchinnikov
Institute of Ecology and Evolution problems, Russian Academy
of Sciences,
Leninskey prospect 33, Moscow 117071, Russia
Monitoring of the sea ice cover in polar regions is essential
for the understanding of regional and global climate
processes. Results of numerical investigations show that
Arctic sea ice affects the polar climate by regulating the
exchange of heat, moisture, and momentum between the ocean and
atmosphere and is a potential early indicator of global
climate change. A number of studies have suggested that
changes in the global average air temperature might be
detectable by observing changes in the extents of the polar
sea ice covers . One sensitive region in the context of global
change is the Barents-Kara Seas and adjacent parts of the
Arctic Ocean. Documenting variations in the annual minimum ice
extent and concentration is important for establishing
baseline data, for understanding historical periodicity,and
for investigating long-term trends.
However, long-term trends derived from ice maps are fixed
estimates without variance .This report presents some results
of estimating the efficiency of Kosmos-1500, 1766, 1869 and
Okean-1,2,3 polar-orbiting satellite data (RM-08-passive
microwave radiometer, SLR- side-looking radar, and
MSU-M-multispectral optical system) and ALMAZ SAR satellite
data for investigating variability in sea ice distribution in
the Barents Kara seas and adjacent parts of the Arctic Ocean
and documenting variations in annual minimum sea ice extent,
concentration, and comparable analysis of results based on sea
ice database.A combined system takes advantage of different
sensitivities of different sensors to different surface types,
high resolution of SAR data, good temporal resolution and
large scale cover of SLR, RM-08 and MSU-M data. The sea ice
extent was studied for a set sea-ice classification schemes
produced using developed regional-scale remote sensing
database, a multi-thematic geographical database and a
problem-oriented data processing system.Kosmos and Okean
satellite image data were used to estimate confidence
intervals for the 1974-1994 map-derived ice-trends in the
Barents and Kara Seas.Results from the 1974-1993 period were
combined with ice extension data reported by Vinje(1991) to
examine longer-term trends over a 28-year period, 1966-1993.
Trends in the annual minimum sea ice extent determined by
three criteria(absolute annual minimum, minimum monthly-mean,
and the extent at the end of August) were investigated for the
Barents and western Kara Seas and adjacent parts of the Arctic
Ocean during 1966 to 1994. Four definitions of sea ice extent
were examined based on thresholds of ice concentration: > 90%
, >70% , > 40% and > 10% (E1, E2, E3, and E4,
respectively).Trends and sea ice concentration were studied
using ice maps produced by the Russian Hydro-Meteorological
Service (1974-1994) , Kosmos and Okean satellite imagery
(1984-1994), ALMAZ SAR satellite data and data extracted from
published literature. During 1984-1994, an increasing trend in
the extent of minimum sea ice cover was observed in the
Barents, Kara, and combined Barents-Kara Seas, for all ice
extent definitions. Root-mean-square differences between
Hydro-Meteorological sea ice maps and satellite-image sea ice
classifications for coincident areas and dates were 15.5 % ,
19.3 % , 18.8 % , and 11.5 % , for ice extensions E1-E4,
respectively. The differences were subjected to Monte-Carlo
analyses to construct confidence intervals for the 20-year
ice-map trends. With probability p 3D 0.8,the average 20-year
change in the minimum monthly-mean sea ice extent (followed in
brackets by the average change in the absolute annual minimum
ice extent) was between 30-60% [19-71%], 29-61% [15-67 %],
31-63% [18-69%] and 18-48% [7-55%] in the Barents sea;
(-24)-(-4) % [(-25)-(12) %], (-27)-(-9) %
[(-34)-(-4)%],(-32)-(-15)%[(-39)-(-9)%] and (-33)-(-15)%
[(-38)-(-8)%] in the western Kara sea; and (-3)-19%[(-8)-29
%],(-4)-18%[(-11)-26 %], (-6)-16%[(-11)-24)%] and
(-7)-15%[(-12)-24%] in the combined Barents and Kara Seas, for
sea ice concentration E1-E4 respectively. Including published
data from 1966-1983, the trend in minimum monthly-mean sea ice
extent for the combined 28-year period showed an average
increasing of 11.8% in the Barents Sea and of 47.4% reduction
in the western Kara Sea, and sea ice extent at the end of
August showed an average reduction of 4.7% in the Barents Sea.
>>>>>>>>>>>>>>>>>>>>
ALKANES AS GEOMARKERS OF RIVERINE INPUT IN MARINE SEDIMENTS
A.N. Belyaeva
P.P.Shirshov Institute of 0ceanology, Russian Academy of
Sciences
23 Krasikova Street, 117218 Moscow, Russia
New indicative properties of sedimentary n-alkanes in relation
to riverine input were obtained for Russian Arctic Seas and
Amazon river - sea system by means of multivariate statistical
processing ( principal component analysis, cluster and
discriminant analyses) of GC data.
Calculated parameter P which is the linear combination of each
sedimentary alkane content multiplied on weight coefficient
varied from -0.175 in the East Siberian Sea to -0.070 in the
Laptev Sea and to -0.007 in the Chukchi Sea, but it has a
positive value for the Barents Sea ( 0.275). Thus, this
parameter is meaningful for type ranging of Arctic Seas by
bottom sediment alkane composition and provides the advantage
of estimation of unknown interrelations between organic matter
composition and its accumulation conditions in sediments. In
regard of riverine organic matter input to the Arctic bottom
sediments the reversed relation between calculated parameter P
and riverine particulate load is of most importance.
Based on cluster analysis the difference between alkane
composition of the sediments from Amazon River itself and
estuarine sediments was found in the fraction n-C14 - n-C17
which increased from 3-13% in the river sediments to 18-25% in
the estuarine sediments. Since alkane n-c17 is the most
significant component in this fraction such changes could be
induced by increased primary productivity in the river - sea
mixing zone relatively to the river water.
The comparison of alkane composition of North Dvina River and
Amazon River sediments revealed the surprising similarity of
sand sediments of these rivers quite independent from the
different climatic zones. The sands from the both rivers
appeared to be closely situated in the separate cluster which
differed from the clusters of river or estuarine muds by de-
creased content of alkanes C29 - C35. Most probable
explanation of obtained similarity could be significant
differentiation processes of alkanes during sedimentation and
accumulation in sediments. Sorption could play the leading
role in differentiation.
In order to elucidate the significance of sorption process in
the formation of alkane composition of various grain size
sediments 87 alkane spectra of terrigeneous Arctic and
Antarctic shelf sediments were analyzed by discriminant
analysis. The results of this study evidenced that the grain
size and bulk organic carbon content of sediments are of
primary importance for sorption which is markedly influence on
alkane composition.
In conclusion, sedimentary alkane composition contains
information on the main source input which could be revealed
on the basis of interrelationship between alkane constituent
rather than separate biomarker alkanes. Moreover, the
quantitative parameters obtained by multivariate statistics
seems to be the means for assessment of riverine particulate
load to marine sediments and so they could be useful for
attributing sediments from modern estuarine areas and
paleodelta environment.
>>>>>>>>>>>>>>>>>>>>
INTERACTION BETWEEN POLAR ENVIRONMENT AND SOURCE-SPECIFIC
SEDIMENTARY LIPIDS IN THE KARA SEA
A.N. Belyaeva1, G. Eglinton2
1P.P. Shirshov Institute of Oceanology,
RAS23 Krasikova Street, 117218 Moscow, Russia
2University of Bristol Cantock's Close, Bristol BS8 1TS, UK
In order to study the influence of polar environmental
controlling factors onto accumulation of source-specific
lipids in the bottom sediments 15 samples on the transect from
the Ob River mouth to the northern part of the Kara Sea have
been analyzed for molecular lipid composition. Since the Kara
Sea is distinguished from other Arctic Seas by the most inten-
sive riverine runoff (about 1350 km3 per year) terrestrial
derived lipids predominate over autochtonous ones in alkane,
fatty acid and fatty alcohol patterns. However, terrestrial
imprint as well as the spatial distribution of lipids of
primary plankton or bacterial origin in sediments are not
uniform along the transect. The relative importance of various
source lipids in the surface sediments appeared to be related
to sedimentation process rather than to variations in primary
productivity or to the distance from the Ob River. Therefore,
high terrestrial signal in sedimentary lipids in the river -
sea mixing zone is correspondent to high organic carbon flux
measured by means of sedimentary traps (Lisitzyn et al.,
1994). Maximum accumulation of plankton derived lipids in
surface sediments has been found in the area of low primary
productivity but it was closely related to the highest flux of
autochtonous detritus produced preferentially by zooplankton
(Lebedeva, Shushkina, 1994).
The importance of bacterial organic matter transformation in
the polar organic carbon cycle is still open for discussion.
On the basis of tentative calculations of organic carbon cycle
in the Barents Sea (Belyaeva et al., 1989) the reduced rate of
organic matter degradation in the water column and surface
sediments resulted from low bacterial activity. The low
bacterial biomass in the Kara Sea water (up to ten mg per m3)
(Mitskevich, Namsaraev, 1994) seems to confirm the hypothesis
of low bacterial activity in the polar environment. However,
bacterial derived fatty acids averaged at 9.5% of total acids
in the Kara Sea sediments and that value is of the same range
as corresponding values for the southern Bohai Sea (Bigot et
al., 1989).The enhanced bacterial imprint has been registered
near the Ob River mouth similarly to high bacterial lipid
content of the Lena River estuary (Laptev Sea) (Peulve et al.,
1993). Bacterial fingerprint in the Kara Sea sediments was
supported also by alkane patterns. These data evidenced that
Arctic estuarine areas are distinguished by intensive
bacterial organic matter transformation and the overall
distribution of bacterial sedimentary lipids is not suppressed
in the Kara sea in relation to low environmental temperature.
Of notice is the fact that accumulation of bacterial lipids in
sediments does not reflect the bacterial cell number in the
water column but it seems to be resulted in the activity of
more abundant bacteria associated with the surface of
particulate matter (Lisitzyn et al., 1994).
In conclusion, the accumulation of source-specific lipids in
the Kara Sea sediments is controlled by two main environmental
factors including the terrestrial organic matter input and by
biogenic heterotrophic processes that incorporate zooplankton
and bacteria activity. The significance of phytoplankton
organic matter input is decreased relatively to the next stage
of trophic chain.
>>>>>>>>>>>>>>>>>>>>
APPLICATION OF MULTIFRACTAL ANALYSIS
TO INTERPRETATION OF SEDIMENTARY LIPID PATTERNS
A.N.Belyaeva, S.S. Ivanov
Institute of Oceanology, RAS,
23, Krasikova Str., 117218, Moscow,Russia
The objective of the presented approach is to obtain a few
number of general parameters characterizing the GS-MS
chromatogram of sedimentary lipids instead of several hundreds
of values of concentrations of recorded individual components.
Multifractal analysis allows to emphasize the influence of
minor recorded peaks and obtain intrinsic regularities
governing the distribution that are hardly seen in the
original data.
We studied fifteen GC-MS spectra of bottom sediment samples
from the Kara Sea. Concentrations Ci were regarded as a
probabilistic measure distributed over a set of components.
For each moment q of distribution scaling exponent tau(q) and
dimension D(q) were computed, describing multifractal scaling
behavior. D(0) gives geometric dimension of the supporting set
(in our case D(0)3D1), D(1) presents the informational
dimension of the measure itself, and the correlation dimension
D(2) defines scaling propertie s of the squared values. These
three dimensions give much for understanding of internal
structure of the measure and degree of its multifractality.
Legendre transform allows to pass from (tau-q) coordinates to
(f-alpha) system and construct function f(alpha), indicating
singularities of initial data.
We have found the correlation between different fractal and
multifractal parameters of lipid spectra of bottom sediments
along the transect from the Ob River mouth to the north of the
Kara Sea. These data appear to be closely related to
sedimentary organic matter genesis analysed by means of
biomarkers of plankton and terrestrial primary origin. For
example, decrease of informational dimension consistent with
the increased accumulation of plankton derived organic matter
in sediments was definitely stated. In contrast, the increased
input of terrestrial organic matter leads to opposite changes.
Moreover, we obtained a number of additional evidences of
interrelation of fractal parameters with other indicative
lipid constituents promising for detection of diagenetic
organic matter transformation. These results could be applied
for various geochemical problems and, in particular, for
assessment of various sources and mechanisms of organic matter
preservation and accumulation in marine environment.
>>>>>>>>>>>>>>>>>>>>
VERTICAL EXCHANGE AND REDFIELD RATIOS
ALONG NEUTRAL SURFACES
J. Bendtsen1 and G. Shaffer1,2
1Department of Geophysics, Niels Bohr Institute for
Astronomy,
Physics and Geophysics, University of Copenhagen,
Haraldsgade
6,
2200 Copenhagen N, Denmark
2Born Institute for Ocean and Climate Studies, Holma
4235,
45400 Brastad, Sweden
Vertical transport of a tracer due to small scale turbulence
and associated diapychnal advection can be estimated from the
vertical curvature of potential temperature, salinity and the
tracer. Vertical transports calculated this way can be
projected upon and averaged along neutral surfaces (neutral
surfaces are those surfaces in the ocean interior along which
lateral mixing takes place preferentially). Such mean
transports can be used to correct estimates of
remineralization ratios obtained calculated by analysis of
ocean chemical data projected along neutral surfaces (eg
Anderson and Sarmiento 1994). Traditionally, vertical exchange
has been assumed to be negligable in such analyses.
Our method has been applied to GEOSECS data from the South
Atlantic, Indian and tropical Pacific oceans. When the
correction for vertical exchange is included, estimates of
-O2:P remineralization ratios in the upper part of the main
ocean thermocline turn out to be significantly lower than
those of the traditional method.
References:
Anderson L. A. And J. L. Sarmiento (1994) "Redfield ratios of
reminaralization determined by nutrient data analysis", Global
Biogeochemical cycles, vol 8, No 1, 65 - 80.
>>>>>>>>>>>>>>>>>>>>
The physical climate subsystem and climate change.
Lennart Bengtsson
Max Planck Institute for Meteorology
Bundesstrasse 55
D-20146 Hamburg
Abstract.
The climate system constitutes a complex interaction between the atmosphere, the oceans an the land surfaces and incorporates physical, chemical and biological aspects. On shorter time scales the climate system is essentially controlled by physical and dynamical processes, which in its principal form has been known since the end of the last century. Our empirical knowledge of the system though, with the exception perhaps of the atmosphere, is still rather poor and massive observational improvements are certainly required. Nevertheless, significant improvements are being made and it has been possible to study the coupled atmospheric/ocean system in reasonable details, in spite of the great difficulties to describe the sources and sinks of energy, momentum and water vapour in terms of the resolvable variables, as well as having the computational capabilities to numerically do this with a realistic accuracy.
The lecture will describe where we stand at the moment, illustrate some of the many achievements and discuss some of key issues which presently are pursued by the scientists. Examples of such issues are to better understand the predictability of the climate system, the problem of coupling the fast climate components, such as the atmospheric, with time scales of days and weeks, with the much slower ocean processes with time scales streching beyond decades and centuries.
Presently, intense work is going on within the framework of climate change, to couple the physical part of the climate system to the chemical aspect of the system, and to incorporate into this, the interaction with the biospheric processes at land and in the sea. The close scientific interaction between previously largely separated scientific groups has not only created a sound foundation for a joint scientific program for climate change, but also provided important techniques for model improvements, such as the calculation of chemical tracers for the measurement of the the exchange processes in the atmosphere, the land and in the oceans and between these media.
>>>>>>>>>>>>>>>>>>>>
THE UK TIGER PROGRAMME - NATIONAL THINKING AND GLOBAL MODELLING
M. Beran
TIGER Programme Office, Wallingford, UK
TIGER (Terrestrial Initiative in Global Environmental
Research) provides the major focus in the UK for research into
the many ways in which the land surface is implicated in earth
system processes in general and climate change processes in
particular. Around 300 scientists in over 100 projects direct
their research towards problems of carbon cycling, trace
greenhouse gases, the energy and water budget, and impacts on
ecosystems.
Within each of these four components of the TIGER programme
one finds a hierarchy of research building from process
studies in the laboratory, through field observations, up to
modelling at landscape, continental and global scales. This
paper reports on recent findings of the programme with a
particular focus on those large-scale activities closest to
the concerns of GAIM. These include carbon cycle models at
regional and global scales, a contribution to a global trace
gas transport model, continental scale hydrological models,
and descriptions of regional ecosystem and global vegetation
models. In each case these have been formulated to accomodate
future climate and CO2 changes, and in some cases also
incorporate parallel land cover changes forced by man's other
activities.
>>>>>>>>>>>>>>>>>>>>
SIMULATING CLIMATE/VEGETATION FEEDBACK:
AN INVESTIGATION OF THE EFFECTS OF
VEGETATION CHANGE ON A DOUBLED-CO2 CLIMATE
R. A. Betts1, P. M. Cox1 and F. I. Woodward2
1Hadley Centre for Climate Prediction and
Research,
UK Meteorological Office, Bracknell,
Berkshire RG12 2SY, UK
2Department of Animal and Plant Sciences,
University of Sheffield,
Sheffield S10 2TN, UK
Vegetation has a major effect on the fluxes of radiation,
sensible heat, moisture, momentum and biogeochemicals between
the atmosphere and the surface; it therefore has an important
influence on climate. Since the distribution of different
forms of vegetation is largely determined by climate, it
follows that changes in vegetation may act as a feedback
mechanism in the processes of climate change.
At present, most General Circulation Model (GCM) simulations
of climate change have not yet included vegetation feedback,
since they contain fixed representations of land surface
properties. The aim of the work described in this paper is to
make make a quantitative study of this feedback, using the
Hadley Centre GCM asynchronously coupled with the Sheffield
University Dynamic Global Vegetation Model (DGVM). The DGVM
predicts global vegetation in terms of Leaf Area Index (LAI),
Net Primary Productivity (NPP) and stomatal conductance, in
response to climate data provided by a GCM simulation with CO2
at a constant level. The three quantities predicted by the
DGVM can then be used to derive the vegetation characteristics
required as parameters in a further equilibrium GCM
simulation. This process can be repeated until the iterations
cause no further change, to give the equilibrium vegetation.
This paper describes the use of this method to simulate the
effects of vegetation feedback on climate change induced by a
doubling of CO2. The above procedure is carried out with a
doubled-CO2 GCM, starting with the vegetation predicted by the
DGVM for present-day conditions. The difference between the
first and last of the GCM climates can then be interpreted as
the contribution of the vegetation feedback to the climate
change due to doubling CO2. This result will be presented
here.
>>>>>>>>>>>>>>>>>>>>
RECORD ON THE CHANGE OF HOLOCENE CLIMATE IN THE LATERITIC
ZONES OF WEST BENGAL, INDIA BY POLLEN ANALYSIS
K. Bhattachaya
Department of Botany, Visva Bharati University
Santiniketan. 731 235.. INDIA.
Pollen analytical investigations to trace Holocene
vegetational history and climate of the lateritic zones of
West Bengal, India have been made. Judging from the above
study it reveals that natural forest constituents of tropical
broad-leaved elements existed in all parts of the area during
Holocene period. The main components of the vegetation are
comprised of the elements like
Shorea-Madhuca-Buchanania-Terminlia along with some other
tropical elements. The uniformity in distribution of
non-arboreals between the Holocene and present day vegetation
may be due to their high adaptive value. Palynological
application of Hierarchical cluster analysis of 16 sub-surface
samples also provide informations regarding past vegetational
environment. Two dendograms have been plotted for arboreal and
non-arboreal dendogram pollen taxa. From the arboreal
dendogram it is established that Shorea and Terminalia show
highest positive correlation in the minimum distance of 0.70.
When the distance increases upto 0.74 there is an association
of Shorea, Terminalia, Anacardium and Buchanaria. Among
non-arboreals Acanthaceae, Scrophu- lariceae and Polygonum are
in one cluster with a minimum distance value of zero. From the
above study it is evident that the association of tropical
broad-leaved elements still persists in some restricted parts
of the investigated area. The above elements perhaps got
extinct from most parts due to biotic interference and other
ecological factors.
>>>>>>>>>>>>>>>>>>>>
MODERN ANTHROPOGENIC INFLUENCE
ON GLOBAL CHANGE OF Si CYCLE
E.Bocharnicova, V.Matichenkov
Institute of Soil Science and Photosynthesis RAS, 142292,
Pushchino, Russia
Si is of a primary importance for plants and microorganism.
Without thes element the growth of plant impossible. The
silicon concentration in the ocean limits the plankton
population. Human activity results in a change in the natural
element cycling by removing elements and modification of
moving sense. The soil-plant system is base for the main
terrestrial trophic chains. It is precisely in soil, a great
amount of silicon is involved into biological circulation. A
main negative influence of human activity on the silicon cycle
and natural balance is observed in the soil-plant system. An
estimated 27.5 million tons of Si are removed with crop
harvest (by comparison, 18 million tons of P is "harvested").
Different cultures very in Si accumulation and removal. Our
calculations and literature data showed that the with each
harvest from 20 to 250 kg of Si ha-1 may move from the soil.
For example, about 100 kg of Si ha-1 is taken up by sugarcane
and as many as 250 kgof Si ha-1 by rice.
Plants adsorb silicon only in low molecular form (monosilicic
acid). But monosilicic acids amount in the soil is usually
small usually (from 1 to 200 kg Si ha-1 in the upper horizon).
Consequently, crop-bearing soils have a negative balance of
mobile silicon compounds and plants may exhibit in short Si
supply. Silicon deficient in the soils results in destroing
soil minerals to supplement plant-available Si. That destroys
silicon equilibrium in the soil and has negative consequences
namely increased susceptibility of plants to disease and
insects attacs, changes in plant elemental composition,
worsing physical-chemical soil properties - cementation,
increased of soil density, decreased soil ability to adsorb
nutrients and water. An estimated 9,0 million tons of Si are
removed from natural cycle annualy when forests are cut down.
All this silicon is irreversibky lost for the soil-plant
system.
Another global change of the silicon cycle by human activity
is connected with mining and concentration of ore. World
industry involves 1011 tons of rock minerals every year which
contain only 1% of ore and 40 to 80% of SiO2. A great part of
metal industry wastes is presented by various silicates which
aren't utilized today. Many of these wastes don't contain any
pollutant substances but they occupy a great area. By this
means human activity interfer with the nature silicon cycle
and silicon substabce is increasing every year. It is
necessary the silicon factor to be included in various models
and data incomparison, because the change of silicon status in
the soil-plant system has a great impact on plant
productivity, geochemical and biogeochemical reactions in soil
and natural waters. Silicon problem is not taken into account
numerouse errors in biogeochemical model simulations and
management of natural resources are possible.
>>>>>>>>>>>>>>>>>>>>
BIOGEOGRAPHIC AND CLIMATIC EVOLUTION OF THE COASTAL PLAIN
OF THE GULF OF BENIN FROM THE PLEISTOCENE TO THE
SUBACTUAL ERAS (WEST AFRICA)
M. Boko
Laboratoire de Climatologie UNB/DGAT,
BP 03-1122, Cotonou, Benin
The fringing coastal of Benin is one of the regions of West
Africa of which the dynamics during the Quaternary and the
Subactual Eras is marked by the major climatic and biogeo-
graphic events.
Thanks to many sediments facies allow to reconstitute this
evolution .
Although divarications exist yet about the agreement between
the dynamics of the regional paleoenvironments and the well
known events of global scale (glaciations and interglacial
ages), we may retain some fundamental facts.
FromInchirian Age to Tafolian Age (35,00 to 2,00 BP), humid
and dry phrases occurred by returns, in variable duration,
corresponding respectively to transgressions and recessions of
sea.
Coastal sand ridges have been formed during the last part of
the Tafolian Age, after the sea retreat which had uncovered
the coastal plain and stretched the course of coastal rivers.
This period marked the settlement of the first stands of the
mangrove vegetation (3,700 to 2,600 BP), the apparition of oilpalm tree (2,800 BP) and stands of Lophira lanceolata (2,500
to 1,400 BP).
The first traces of human activity had appeared belatedly in
the form of accumulations of shells (1,070 BP).
A slight sea recession occurred between 400 and 300 BP (1,500
A.D.) and provoked the disappearing of the mangrove vegetation
and the apparition of fresh water swampy forests round the
pre-coastal lakes deprived of sea water.
This evolution may explain the current dynamics of the coastal
zone of the Gulf of Benin, mainly the hydrologic continent-
ocean exchanges, and its biogeographic aspects.
Key-Words: West Africa, Gulf of Benin, paleoenvironment,
trangession, recession, sand ridges, mangrove,
lakes, swampy forests.
>>>>>>>>>>>>>>>>>>>>
BIOTIC AND ABIOTIC FACTORS OF THE CARBON SYSTEM
COMPONENTS VARIABILITY IN THE NORTH ATLANTIC
P. V. Boubnov
Institute of Oceanology of Russian Academy of
Sciences,
Laboratory of Biochemistry and Hydrochemistry,
24 Krasikova Street, Moscow, 117851, Russia
The problem of the carbon cycle in the ocean is now one of the
most actual problems of modern oceanography. This is connected
with the permanent increase of the CO2 concentration in the
atmosphere, caused by industrial activity, which can exert
significant effect on global climate. Maps of the inorganic
carbon forms distribution in the upper layer of the North
Atlantic, based on analysis of big massive of hydrochemical
data, were built to show reguliarities of the carbon cycle in
the North Atlantic. Two principal factor groups of the
inorganic carbon forms distribution were singled out: biotic
and abiotic. The most significant abiotic factor is the
temperature changes. Production and destruction of the organic
matter are the principal biotic factors. The variabilities of
the CO2 and total inorganic carbon due to the temperature
changes were calculated. The differences between the real and
temperature variabilities of the CO2 and total inorganic
carbon
can be interpreted reliably as the biotic factors effect.
Variability values, caused by biotic factors are in good
agreement with the primary production in the upper layer. The
values of the biotic CO2 variability are 0.02-0.04 gC/m3 year
in the central part of the North Atlantic, increasing up to
0.07-0.08 gC/m3 year near Africa and South America shores and
reaching 0.10-0.15 gC/m3 year in areas of high primary
production near Island and Greenland shores. The maximum
biotic CO2 variability - 0.2 gC/m3 year is observed near the
bank of Newfoundland. The primary production values exceed the
in-year CO2 variability, caused by biotic factors 5-15 times
in
average. It is due to the CO2 ocean-atmosphere exchange and
vertical movement of water masses. The values of biotic
variability of the total inorganic carbon exceed the primary
production values, because the total inorganic car- bon is
included in other biochemical processes. Maps of the CO2 and
Ctot. variabilities make possible to show areas with different
biochemical activity in the ocean.
>>>>>>>>>>>>>>>>>>>>
INFERRED SOURCES AND SINKS OF CO2 USING
2-D AND 3-D ATMOSPHERIC TRANSPORT MODEL
P.Bousquet1, P.Ciais2, M.Ramonet1, P.Monfray1, Y.Balkanski2
1Centre des Faibles Radioactivits, Laboratoire mixte
CNRS-CEA,
B3timent 709/LMCE, CESaclay, 91191 Gif-sur-Yvette Cdex,
France.
2Laboratoire de Modlisation du Climat et de l'Environnement,CE Saclay, B3timent 709, 91191 Gif-sur-Yvette Cdex, France.
Owing to atmospheric sampling network, modeling spatial and
temporal variations of CO2 in the atmosphere is a valuable
approach to describe the distribution of the surface fluxes.
However, modeled atmospheric transport is a potentially
important source of uncertainty in the diagnostic of the CO2
sources in sinks.
CO2 and Carbon-13 measurements from 50 sites of the NOAA/CMDL
global air sampling network and from the CSIRO network were
used as an input for a 2-D model of atmospheric transport a,b
(CMDL, Boulder), run in an inverse mode. The information given
by carbon-13 lead to partition oceanic and terrestrial CO2
fluxes, in 20 latitude bands b. In order to estimate how
sensitive this result is to atmospheric transport, we have
used the net fluxes predicted by the 2-D study as an input of
a 3-D atmospheric transport model c (MPIM, Hambourg). The 3-D
concentration fields of CO2 simulated in that manner are then
inverted again with the 2-D model. Differences between both
sets of fluxes reflect distinct transport features between the
two models, that we further analyse here.
Using the 3-D transport model, we found no significant
difference in the amplitude of the strong northern-mid
latitude terrestrial sink as predicted by the 2-D analysisb
(3.5 11.8 GTC for 1992). However, there are differences in
meridional transport across the ITCZ, which we quantify in
terms of CO2 fluxes. Also we employed two sets of input fluxes
for the 3-D model: one partionned between land and ocean and a
second which is zonally distributed. We discuss the
sensibility of North/South gradient predicted by the 3-D model
to these two longitudinal distributions.
a. Tans, P., T.J. Conway, and T. Nakazawa, Latitudinal
distribution of sources and sinks of atmospheric carbon
dioxyde derived from surface observations and an atmospheric
transport model. Journal of Geophysical Research, 1989, 94.
b. Ciais, P., et al, Partitioning of ocean and land global
uptake of CO2 as inferred by deltaC13 measurements from the
NOAA/CMDL global air sampling network. Journal of Geophysical
Research, 1994, 100.
c. Heimann, M., and C.D. Keeling, A three dimensional model of
atmospheric CO2 transport based on observed winds: 2. Model
description and simulated tracer experiments, In Aspects of
Climate Variability in the Pacific and Western Americas,
edited by D.H. Peterson, American Geophysical Union,
Washington DC, 1989.
>>>>>>>>>>>>>>>>>>>>
CLIMATIC CHANGES IN BULGARIA DURING THIS CENTURY
T.G. Boyadjiev
Bulgarian Society for Soil Science,
Zona B5, Blok 3, ap. 44, 1303 Sofia, Bulgaria
The change of climate in Sofia has been observed and recorded during this century. Temperature data for the period from 1887 to 1930 were compared with these of the period from 1931 to 1970 (for the precipitation data the latter period is from 1931 to 1985). Changes of maximum temperature values were observed and recorded during the mentioned periods.
It was found out that temperature had risen averagely by 0.5C per year and warming up has been better manifested during the autumn and winter months than spring and summer ones. Weather warming has been accompanied by slight drought (15 mm average annual for the period), especially in August, September and October.
Absolute temperature peaks vary in wide range between the two periods (up to 11 - 12.7C), while the average minimum and maximum temperature differences are insignificant (up to 1.6C).
The following zones can be differentiated on the territory of Bulgaria depending on the temperature changes in the period from 1931 to 1970 compared with the ones between 1887 and 1930:
- zone in which the temperature for the period from 1931 to 1970 is higher than the temperature between 1887 and 1930 and this temperature rise includes all months (Sofia);
- zone in which for the former time range the temperature rose in winter and spring months and dropped in summer and autumn (Karnobat, Vratza);
- zone in which temperature rose in winter and dropped in the remaining months (Tzarevo, Stara Zagora, Pleven);
- zone in which the temperature during the 1931-1970 period was lower than the 1887-1970 period and this temperature decline includes all months (Lom, Chepelare).
TSSI (Temperature Stress Severity Index), MSSI (Moisture Stress Severity Index) and CSSI (Climate Stress Severity Index) were computed at representative weather forecast stations in these zones, as well as the duration of the vegetation period. F. Newal mathematical model was used for this purpose. It is applied in defining water thermal soil regimes in the American soil taxonomy system.
>>>>>>>>>>>>>>>>>>>>
ABSTRACT
Oceanic radiocarbon: Separation of the natural and bomb components
Wallace S. Broecker, Stewart Sutherland, and William Smethie
Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York
Tsung-Hung Peng1
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge,
Tennessee
Gote Ostlund
Institute of Marine Science, Rosenstiel School of Marine and Atmospheric
Sciences, University of Miami, Miami, Florida
Abstract. An improved method has been developed for the separation of the
natural and bomb components of the radiocarbon in the ocean. The
improvement involves the use of a very strong correlation between natural
radiocarbon and dissolved silica. This method is applied to radiocarbon
measurements made on samples collected during the Geochemical Ocean
Sections Study (GEOSECS), Transient Tracers in the Ocean (TTO) and South
Atlantic Ventilation Experiment (SAVE) expeditions. On the basis of this
new separation we provide not only an estimate of the global inventory of
bomb 14C at the time of the GEOSECS survey but also the distribution of
bomb radiocarbon along four thermocline isopycnals in each ocean. We also
document the evolution of the bomb 14C inventory and penetration along
thermocline isopycnals in the North Atlantic Ocean between the times of the
GEOSECS (1972-1973) and TTO (1980-1982) surveys and in the South Atlantic
Ocean between the times of the GEOSECS (1973) and SAVE (1987-1989) surveys.
In addition, we show that the bomb tritium to bomb 14C ratio (expressed in
the tritium unit (TU) 81 units/100 ) for waters entering the thermocline of
the northern hemisphere is about 9 times higher than for those entering the
southern hemisphere thermocline. This contrast offers long-term potential
as an indicator of inter-hemispheric transport of upper ocean waters.
>>>>>>>>>>>>>>>>>>>>
DEFINING THE OCEANIC TRANSITION ZONE
C. W. Brown and W. E. Esaias
NASA/Goddard Space Flight Center Oceans and Ice Branch,
Code 971 Greenbelt, MD, 20771, USA
One proposed technique to calculate oceanic primary
productivity from satellite-derived estimates of phytoplankton
biomass requires that the oceans be divided into
biogeographical zones, each with its own unique physiological
characteristics. The oceanic Transition Zone, a region located
between the oligotrophic subtropical gyres and the eutrophic
subpolar gyres, represents a distinct biogeographical regime.
The criteria used to define the geographic limits of the
Transition Zone will determine its spatial extent and
consequently impact the estimates of global primary
productivity. Defining the boundaries of the Transition Zone
will also provide a means to track its position over time and
ascertain the seasonal and interanual variability of the
location of this important ecotone. However, no definitive
criteria exists to identify the boundaries of the Transition
Zone from a biological perspective.
We evaluated several methods and criteria to delimit oceanic
Transition Zones. The Transition Zone of the Atlantic and
Pacific Oceans were located by identifying discontinuities in
the meridional distribution of CZCS pigment concentrations and
AVHRR sea-surface temperatures in monthly composites. Gradient
analysis, the moving split-window technique, and
autocorrelation were applied to the imagery. Threshold values
were selected and the areal extent of the Transition Zones
resulting from several criteria applied to each method were
compared over an average annual cycle.
>>>>>>>>>>>>>>>>>>>>
MIXED LAYER PULSE RESPONSE FUNCTION AND
OCEANIC TRACER UPTAKE
M. Bruno, F. Joos
Climate and Environmental Physics, Physical Institute,
University of Bern, SidlerstraE1e 5, CH-3012 Bern, Switzerland
Program in Atmospheric and Oceanic Sciences, Princeton
University,
Princeton, NJ, USA
Text nur auf Papier (LaTex)
>>>>>>>>>>>>>>>>>>>>
ABSORPTION OF ANTHROPOGENIC 12C, 13C AND 14C
BY THE OCEAN: AN OCEAN GCM SIMULATION
K. Caldeira1, P. B. Duffy1 and G. H. Rau1,2
1Global Climate Research Division, Lawrence
Livermore
National Laboratory, 7000 East Ave., Livermore, CA
94550, USA
2Institute of Marine Sciences, University of Santa
Cruz, CA
95064, USA
We have developed an inorganic carbon cycle model that
computes steady-state concentrations of total inorganic 12C,
13C
and 14C. This model is based on a detailed calculation of the
speciation of total dissolved inorganic carbon and the
fractionation of carbon isotopes that occur during air-sea gas
exchange. Furthermore, we are now developing an ocean carbon
cycle model that incorporates biological transport of carbon
and carbon isotopes. These models are coupled to a version of
the GFDL ocean general circulation model that incorporates (1)
a dynamic sea-ice model and (2) the Gent-McWilliams
parameterization for the impact of isopycnal eddies on
advection and diffusion in the ocean.
We will present results of our three-dimensional simulations
of the penetration of anthropogenic carbon, and carbon
isotopes, into the ocean, from pre-industrial times, through
the bomb era, to the present. Our calculations produce
three-dimensional fields for the perturbation to 12C, 13C and
14C
concentrations as a function of time. We will present results
from our inorganic carbon cycle model. If available, we will
also present results from our organic carbon cycle model.
These calculations are directly relevant to the estimation of
oceanic CO2 absorption.
Measurement and modeling of oceanic [#183#CO2], 13C/12C and
14C/12C may serve to narrow uncertainties in predicted oceanic
absorption of anthropogenic CO2. Furthermore, the ability to
predict and simulate the penetration of the fossil-fuel carbon
and bomb 14C into the oceans are potential tests of ocean
general circulation and carbon cycle models. Such model
results should be useful in helping to guide measurement
efforts, as measurement efforts could be focused where models
suggest the signal should be strongest.
This work was performed under the auspices of the U.S.
Department of Energy by the Lawrence Livermore National
Laboratory under Contract No. W-7405-Eng-48.
>>>>>>>>>>>>>>>>>>>>
A STATISTICAL APPROACH TO SCALING BIOGEOCHEMICAL
FLUXES IN THE OCEAN USING SATELLITE DATA
J. W. Campbell, G. M. Weiss, and S. R. Gaudreau
Ocean Process Analysis Laboratory
Institute for the Study of Earth, Oceans, and Space
and Department of Earth Sciences
University of New Hampshire
Durham, New Hampshire 03824, USA
Satellite remote sensing measurements will play a key role in
scaling biogeochemical fluxes to the global ocean. The spatial
resolution of many ocean satellite sensors lies between that
of global-scale models and local-scale measurements used to
parameterize models. Global-scale models typically have
resolution elements on the order of 1-4 degrees in latitude
and longitude (100-500 km spatial resolution). Processes
within the models are often parameterized with in-situ data
collected at much smaller scales (e.g., point measurements
made from a ship or time series data at a mooring).
Small-scale measurements, however, cannot be scaled up readily
to obtain large-scale average properties. This is largely a
consequence of the high small-scale variance and nonlinear
nature of ecological and biogeochemical processes in the
ocean. The use of spatial means as input in nonlinear models
does not result in the mean of the modeled property. In order
to represent these processes in global Earth systems models,
one must properly account for variability at scales ranging
from the local to the global.
In this paper, we will demonstrate how statistical information
potentially derived from satellite measurements is needed to
properly extend local-scale flux equations to global and
annual scales. By way of illustration, we will focus
specifically on the flux of CO2 between the ocean and
atmosphere to demonstrate how certain statistical facts and
artifacts might lead to significant underestimation of the
carbon flux. Undersampling leads to underestimation when the
variables being sampled are highly skewed (a statistical
fact). Spatial and temporal variability in nonlinear
biological and physical processes, if not properly modeled,
can bias model results (a statistical artifact). A statistical
approach is needed to account for the effects of the
small-scale variance in scaling local models to the global
scale.
We will describe a statistical approach based on results of
our NASA-sponsored research for the past 3 years. In this
work, we have studied spatial and temporal patterns of
variability in phytoplankton pigments, photosynthetic rates,
and ocean optical properties, and have recommended methods for
averaging satellite data over spatial scales of order 10-100
km. The methods we have recommended will help avoid problems
associated with scale. By knowing statistical properties of
the sub-scale variability, one can predict large-scale spatial
means of derived fluxes. Specific examples will be presented
to illustrate how the spatial distributions of phytoplankton
pigment concentration, surface photosynthetic available
radiation, mixedlayer temperature, and wind speed, all derived
from satellite measurements, are required to scale models of
biogenic carbon flux to the world's ocean.
>>>>>>>>>>>>>>>>>>>>
INTEGRATIVE MONSOON DYNAMICS
P. Carl
Institute of Physics, Humboldt University
Hausvogteiplatz 5-7, D-10117 Berlin, Germany
Regional climate and environmental change dynamics are
accessible with sufficient certainty only in a global context.
Their long-term comprehension appears to be crucially
dependant upon the existence and safe identification of
dynamic regimes of operation of the Earth system. The climate
subsystem offers natural oscillators which fundamentally
contribute in shaping respective global `architectures'.
Monsoon dynamics, with its sensitive but dynamically stable
`active-break' cycles, rises to fame as such an oscillator -
perhaps the most important natural one. Critical transitions
between climate regimes of different functionality are
essential to a `monsoon hypothesis' derived in connection with
a first comprehensive in-depth analysis of the dynamic system
of a General Circulation Model (GCM).
Deliberate use is being made of a very economic, coarse
resolution (12 lat x 15 lon) two-layer tropospheric GCM which
turned out to be a kind of `regime model' in that it
accentuates the low-dimensional character of the global
system`s dynamics. Thrown into relief against the seasonal
cycle by bifurcations, an oscillatory monsoon regime at the
30-60 days timescale develops for both summer and winter.
Detailed studies are concerned with the GCM`s summer monsoon
attractor which is organized as an interhemispheric coupled
oscillator phenomenon, apparently at the highest possible
coupling strength. Tropical/extratropical interactions carried
by shifts and intensity changes of the major tropospheric jets
(`jet shifting oscillator' - JSO) are inherent to this strong
coupling. The dynamics born in this architecture of the
model`s monsoon system enables it to simulate both large Asian
precipitation systems and midlatitude intraseasonal
temperature and precipitation profiles at least qualitatively
correct.
It is important to note that `climate change' events detected
on the intraseasonal attractors of the model`s summer monsoon
are found to be accompanied by common spectral shifts, of the
(four) coupled oscillators, which preserve their rational
frequency relationships. As far as the model climate is
concerned, influences external to atmospheric dynamics
encounter these selection rules and come into effect if they
are capable of triggering such a common oscillator shift.
After decoupling (and extinction) of the JSO at monsoon
retreat, the (atmospheric!) model exhibits a Southern
Oscillation (SO) attractor at a much lower coupling strength.
This might explain the greater irregularity of the SO, as
compared with the monsoon activity cycle. Timescales of
relevance to ENSO found in seasonal simulations using the same
model include both a quasi-biennal oscillation (QBO) and a
longer term modulation of about 6.2 years. Specific monsoon
retreat trajectories are blamed for phase locking of ENSO to
the annual cycle.
The systems analytic interpretation of a GCM`s phase space
trajectories supports an approach to global change via climate
analogs. An integrative, universal response of the model`s
monsoons to different forcings, grasped with the term degree
of monsoon excitation, is found to link regional to global as
well as intraseasonal to palaeoclimatic scales. A `monsoon
climate' bifurcation is encountered if the (intraseasonal)
onset and retreat bifurcations merge at some critical forcing.
The study illustrates the potential of monsoon dynamics both
to trigger abrupt climate change and to cause long-term
instability of the planetary-scale hydrological cycle.
`Survival' of Mei-Yu and/or (non phase-locked) ENSO regimes
after loss of the oscillatory, interactive monsoon climate are
fundamental to the latter aspect of past global climate
change.
GREENLAND AND ANTARCTIC CH4 RECORDS AND THEIR IMPLICATIONSWITH PAST CLIMATIC CHANGES
J. Chappellaz and D. Raynaud
CNRS Laboratoire de Glaciologie et Gophysique de
l'Environnement
BP 96, 38402 St Martin d'HAres Cedex, FRANCE
This presentation aims to discuss the state of the art of
methane measurements from both Greenland and Antarctic ice
cores, in terms of information on the CH4 cycle, past climatic
changes and phase relationship between climatic parameters
obtained from ice cores.
Methane, as a radiatively active trace gas, is of large
interest for the understanding of past climatic conditions.
During the most recent years, increasingly detailed profiles
of atmospheric methane have been obtained from ice cores of
both hemispheres, covering time periods from the preindustrial
era to the penultimate climatic cycle (back to 250,000 yrs
BP). Apart from the recent anthropogenic increase, the most
stricking feature observed in the methane profiles is the
general coherency between CH4 and climate changes. In
particular, the new Greenland CH4 results from the GRIP and
GISP2 drillings reveal that abrupt Greenland climate changes
during the last glaciation and deglaciation are paralleled by
similar methane variations. Methane is in phase (F1 200 years)
with Greenland temperature changes during the deglaciation.
However, some differences appear between the two signals over
the Holocene and in the middle of the last glaciation. Changes
of up to 15% characterize the Holocene methane profile, with a
clear minimum of concentration around 6 Kyr BP, whereas the
temperature signal remains stable. Also, between 40 and 8 Kyr
BP, slow temperature changes have no analogy in the methane
profiles.
The large CH4 changes observed over these various time scales
are thought to result from variations in the hydrological
budget over the continents, affecting the extent of wetlands,
the main natural source of methane. The comparison of CH4
changes, during the last deglaciation and during the Holocene,
with paleoclimatic data on the continents suggests that
low-latitude wetlands were mainly responsible for these
changes and that the role of high-latitude wetlands became
important after about 3 Kyr BP.
As methane has a long enough residence time in the atmosphere,
it can be used as a stratigraphic marker to correlate
Greenland and Antarctic ice-core signals. The use of the GRIP,
GISP2 and Vostok profiles allows us to depict the chronology
of Greenland and Antarctic climatic events during the last
deglaciation and their phase relationship with CH4, CO2 and
ice
volume changes. In particular, the start of the deglaciation
at Vostok appears to lead Greenland temperature, CH4 and CO2
increases, and ice volume decrease.
The comparison of CH4 signals over the Eemian period show that
the sequence of methane changes in the Vostok and Greenland
cores is different, suggesting that the Greenland core
stratigraphy has been altered. A tentative redating of this
part of the GRIP and GISP2 cores is proposed, based on the
combination of CH4 and EB18O of O2 signals of the Vostok core.
>>>>>>>>>>>>>>>>>>>>
CARBON FLUXES IN THE SUBTROPICAL NORTH PACIFIC OCEAN
J.R. Christian and D.M. Karl
School of Ocean and Earth Science and Technology, University of Hawaii 1000 Pope Road, Honolulu, HI, USA 96822
The subtropical oceanic gyres are the largest of the earth's ecological-biogeochemical provinces. They account for a large fraction of global ocean primary productivity and cross-thermocline carbon flux. The ecosystems of the subtropical gyres are dominated by a picophytoplankton-nanozooplankton food web that is poorly parameterized by existing ecosystem models. The relationship between new and primary production and particulate carbon flux to the deep ocean is similarly poorly understood. Because these vast regions of the world's oceans are generally undersampled, improved models of this ecosystem are of great importance in reducing uncertainties in models of the global carbon cycle.
The Hawaii Ocean Time Series (HOT) program has been sampling a hydrostation in the North Pacific subtropical gyre since 1988 and has generated a new understanding of seasonal and interannual variability of biological production in this ecosystem and its relationship to the global biogeochemical cycles of carbon, nitrogen, phosphorus and oxygen. Emerging models of this system show that many assumptions widely incorporated into models of ocean biogeochemistry are inappropriate in this ecosystem. Models incorporating size-specific rates of production and respiration for several phytoplankton and microzooplankton size classes can predict fluxes of carbon to the metazoa and to the bacteria and provide a framework for assessing confidence regions about estimates of processes that are difficult to measure directly. The six years of time-series data obtained to date will be used to estimate net community production and respiration, and statistical evidence will be presented that this ecosystem is a net exporter of reduced carbon.
>>>>>>>>>>>>>>>>>>>>
MODELLING NET ECOSYSTEM PRODUCTION
AND METHANE EXCHANGE IN NORTHERN WETLANDS
T. R. Christensen, J. Kaplan, A. Haxeltine, S. Sitch and
I. C.
Prentice
Global Systems Group, Department of Ecology, Lund
University,
Ecology Building, S-223 62 Lund, Sweden
Methane is an increasingly important greenhouse gas due to its
rising atmospheric concentration, caused mainly by
anthropogenic emissions. However, there are still significant
uncertainties concerning the magnitude and geographical
distribution of its natural atmospheric sources and sinks.
Relatively high early estimates of the contribution from
northern wetlands have been lowered. It is now generally
believed that about 35 Tg CH4/yr originates from wetlands and
tundra north of 50F8N. This represents about 20-25% of all
natural emissions.
A number of studies have shown a correlation between net
primary production (NPP) and methane emission. It has
similarly been suggested that net ecosystem production (NEP)
of wetland ecosystems across a range of latitudes can be used
as a predictor of methane flux. Although these relationships
may hold approximately for annual fluxes, they are incorrect
for seasonal cycles. Both NPP and NEP tend to be highest early
in summer; methane emissions are generally higher towards the
end of the growing season. Total heterotrophic respiration is
a better indicator of methane exchange. While still strongly
linked to NPP, heterotrophic respiration has a more correct
seasonal signal and is constrained appropriately by below-
ground conditions.
A modified version of the BIOME 2 model was used as basis for
an estimation of the global northern wetland contribution to
the atmospheric methane budget. The methane model builds on an
empirical quantitative relationship between total respiration
and methane emission in wetlands. The model has been validated
against observed NPP, respiration, net CO2 flux (NEP), and
methane emission rates at a number of northern wetland and
tundra sites. In order to compare with other global emission
estimates, the widely used Matthews and Fung digitised global
wetland mask was applied to extrapolate fluxes. We thereby
estimate total non-forested bog emission (> 50F8N) to be 10.4 F1
6.9 Tg CH4/yr. This is lower than most other recent estimates.
This estimate does not include forested bogs and
nonforested/forested swamps. Nevertheless, it clearly
conflicts with the total northern wetland figure of 30 Tg
CH4/yr (excluding 5 Tg from mesic tundra) that has been widely
used in recent attempts to model the global methane budget.
Unaccounted-for winter emission, and high emissions that are
localized both in time and space, may partly make up for the
"missing" methane source. However, there still seems to be a
significant lack in our understanding of natural atmospheric
methane sources and sinks, in particular at high northern
latitudes.
>>>>>>>>>>>>>>>>>>>>
TESTING THE ASSUMPTION OF WATER BALANCE LIMITS
CONTROLLING GLOBAL NPP: FROMTHE POTSDAM-95
MODEL INTER-COMPARISONS
G. Churkina and S.W. Running
NTSG, School of Forestry, University of Montana,
Missoula, MT 59812, USA
Phone: (406) 243-6311, Fax: (406) 243-4510,
Email: galina@ntsg.umt.edu
Terrestrial NPP is one of the most-modeled ecological parameters
at theglobal scale. Approaches to its modeling vary and are based
on differentsuites of parameters. Although most of the models
produce similar results atthe global scale, their abilities to predict
NPP at smaller scales differnotably. Inter-comparison of global NPP
models at smaller scale using acommonly-accepted assumption
about their possible behavior is effective inchecking their consistency.
In this study, as a criterion for model inter-comparison, we assume
thatwater is the primary limiting factor of NPP. Current theory and
empiricalanalysis tend to support this assumption for most of the
world92s uplandecosystems (Woodward 1987, Neilson et al. 1989;
Stephenson 1990). Exceptionsare high latitude systems, which are
energy limited. We compared global NPPmodels that were presented
at the 2nd NPP model workshop in Potsdam-95. Inorder to test if
water balance could be considered as the primary driver of NPP for
a model, a water balance coefficient was correlated with mean
annualNPP for each model. The water balance coefficient was
calculated as thedifference of precipitation and potential
evapotranspiration at each gridsell (0.5B0 x 0.5B0 grid) for the
whole globe on an annual basis. Potentialevapotranspiration was
a function of mean annual temperature and radiation.For
consistency with the model92s inputs, global data for precipitation
andtemperature were obtained from climate files by Cramer & Leemans
(1990,updated by Cramer in 1994). Also we gave an overview of the
correlationresults and made some suggestions for future
inter-comparisons of global NPPmodels.
Galina Churkina NTSG Phone: +1 (406) 243-4632
University of Montana Fax: +1 (406) 243-4510
Missoula,MT 59812 Email: galina@ntsg.umt.edu
>>>>>>>>>>>>>>>>>>>>
A THREE DIMENSIONAL MODELING STUDIES
OF O18 IN ATMOSPHERIC CO2
P. Ciais1 , P.P. Tans2, S. Denning3, J.W.C. White4,5,
M. Trolier2,4, J.A. Berry6, and P. Monfray7
1LMCE, CEA, L'Orme les Merisiers, Gif sur Yvette, France
2National Oceanic and Atmospheric Administration, CMDL,
Boulder, Colorado, USA
3Colorado State University, Department of Atmospheric
Sciences,
Fort-Collins, Colorado, USA
4University of Colorado, Institute of Arctic and Alpine
Research, Boulder, Colorado, USA
5University of Colorado, Department of Geological Sciences,
Boulder, Colorado, USA
6Carnegie Institution of Washington, Department of Plant
Biology,
Stanford, California, USA
7CFR, CNRS-CEA, Av. de la Terasse, Gif sur Yvette Cdex,
France
The recent development of complex models of terrestrial
ecosystems requires a validation of the CO2 fluxes exchanged
between plants, soils and the atmosphere. Direct flux measure-
ments can be made at a few location but they may prove
difficult to "scale up" to global scale. Conversely, tracers
in the atmosphere make it possible to derive useful
information on surface fluxes by modeling atmospheric
concentrations.
We present a new 3-D modeling study of the O18 isotope
composition in CO2 and discuss the implications regarding the
gross CO2 fluxes between land biosphere and atmosphere (GPP
and
total ecosystem respiration). We simulate the O18 composition
of atmospheric CO2 (expressed in d18O units) using the 3-D
transport model TM2 [Heimann, 1989], treating separately the
isotopic exchange of CO2 with leaves, soils, ocean and fossil
fuels. The isotopic fluxes on land are derived from the
interactive vegetation model SiB-2. Our simulations are
compared with new d18O flask measurements made at 50 sites of
the NOAA-CMDL global air sampling network. Constraints on the
latitudinal and seasonal distribution of GPP and total
ecosystem respiration are brought by the analysis of the
north-south gradients of d18O in CO2 as well as of the
seasonal
cycle at specific locations.
Denning, S., 1994, Investigations of the transport, sources
and sinks of atmospheric CO2 using a general circulation
model.
Heimann, M., and C.D. Keeling, A three dimensional model of
atmospheric CO2 transport based on observed winds: 2. Model
description and simulated tracer experiments, In Aspects of
Climate Variability in the Pacific and Western Americas,
edited by D.H. Peterson, American Geophysical Union,
Washington DC, 1989.
>>>>>>>>>>>>>>>>>>>>
COUPLING VEGETATION INTO GLOBAL CHANGE MODELS
C. Ciret and A. Henderson-Sellers
Climatic Impacts Centre, Macquarie University
North Ryde, 2109, NSW, Australia
Human activities are producing measurable changes in many
major earth systems, including natural vegetation and the
atmosphere. Modelling the global earth system can help under-
standing the processes and their interactions involved in the
different subcomponents (e.g. ocean, cryosphere, atmosphere,
vegetation and soils), as well as the effects of human activi-
ties on the global system. This modelling task demands that
different types of models have to be linked together. In this
paper, global climate models (GCMs) and vegetation models are
linked in a "one way" mode (i.e. no feedback from the
vegetation model to the GCM is allowed) and the results are
compared with those obtained when the observed climate is
used. The aim of this study is to investigate the sensitivity
of the global vegetation models to the climates simulated by
the GCMs. This includes the analysis of the sensitivity of the
vegetation models to changes in the spatial resolution of a
GCM (i.e. CCM2 that has been run with different spectral
resolutions). In addition, the comparison of the vegetation
distributions obtained with simulated current climates and
with observed climate enables the evaluation of the ability of
the GCMs to simulate the bioclimatic variables required for
the prediction of natural vegetation. The two vegetation
models used are BIOME1 and a version of the Holdridge scheme
tuned to produce vegetation distributions that resemble those
from BIOME1. They are both global static models. The atmo-
spheric general circulation models (AGCMs) employed are the
National Center for Atmospheric Research's Community Climate
Models (CCM): CCM0, CCM1, CCM1-Oz, CCM2 and the Australian
Bureau of Meteorology Research Centre (BMRC) model. Some of
these AGCMs are coupled to ocean models and some are coupled
with a land-surface scheme (e.g. CCM1-Oz with the land-surface
scheme BATS). The horizontal resolutions vary, from coarse
(CCM0, CCM1) through medium (BMRC) to high (CCM2). The
agreement between the vegetation distributions obtained with
observed and simulated climate is poor: for more than 50 % of
the total land area, the vegetation is "incorrectlyr"
predicted when simulated climates are used. The results depend
on the GCM and on the vegetation model used, nevertheless the
range of results vary from about 55 % to 73%. The increase in
the resolution of CCM2 does reduce the discrepancies between
the vegetation distributions obtained with observed and
simulated climate. However, even when a relatively high
resolution version of CCM2 (i.e. T63) is used, the differences
between the vegetation distributions it "predicts" and that
produced using observed climate is still greater than 50 % of
the total land area. It appears also that the vegetation
models react differently to changes in horizontal resolution,
BIOME being more sensitive than Holdridge.
>>>>>>>>>>>>>>>>>>>>
THE GREEN SAHARA AT 6 KA B.P.:
RESULTS FROM AN INTERACTIVE ATMOSPHERE-BIOME MODEL
M. Claussen and V. Gayler
Max-Planck-Institut fuer Meteorologie
Bundesstr. 55, D-20146 Hamburg
Analysis of the climate simulation for 6 ky B.P. with the
Hamburg climate model ECHAM (carried by Stefan Lorenz, Univ.
Bremen, within the framework of the PMIP) reveals that 6 ky
B.P. global vegetation patterns closely resemble present-day
vegetation distributions. This is at variance with
reconstructions (e.g. Frenzel et al., Atlas of Paleoclimates
...) which suggest much more rain in the Sahara than today
with the potential of at least sparse vegetation. Here it is
demonstrated that the obviously unrealistic results from ECHAM
are due to the specification of present-day land-surface
patterns as surface boundary conditions (as was prescribed for
all PMIP runs).
The paleoclimate simulation has been repeated by coupling the
BIOME model of Prentice et al. (J. Biogeography, 1992) with
ECHAM (level 3). Earlier studies by Claussen (Clim. Res.,
1994) indicate that the combinded ECHAM-BIOME model is
sensitive to the initial distribution of land surface
conditions. It was found that under present orbital conditions
and SST distribution, (at least) two stable equilibria of
vegetation patterns are possible: one corresponding to
present-day sparse vegetation in the Sahel, the second with
savanna extending far into the southwestern part of the
Sahara. The former equilibrium is achieved by initializing the
climate-biome model with a vegetation distribution close to
the present-day one, the latter by initially prescribing a
green Sahara.
Similar is valid when simulating the climate with orbital
conditions of 6 ky B.P. During the Holocene optimum, almost
the entire Sahara becomes vegetated except for the Lybian
desert. Both experiments, present-day and 6 ky B.P. climate
simulations, corrobrate Charney's (Quart. J. R. Met. Soc.,
1975) hypothesis of a positive bio-geophysical feedback in the
Sahel. Moreover, they suggest that for paleoclimate
simulations, vegetation has to be integrated into the climate
model as a dynamic component.
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TOMS Results in Brazil
Maria Albertina Costa
Abstract
A scientific video were produced using monthly mean data from TOMS (Total Ozone Mapping Spectrometer) inside the nimbus 7 satellite, from 1989 to 1991 over Brazil. Spatial models were designed through the Geographyc Information System and Computer Graphyc. As a result it was observed higher ozone concentrations over the Southern and Western region and lower ozone concentrations over the Northern and Eastern region.
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TOP PREDATORS AS A GLOBAL BIOTIC MEASUREMENT
Authors are Steve Cousins, Pablo Ferreras, Noemi de la Ville
Ecosystems Group, IERC, Cranfield University, Cranfield,
Bedfordshire, MK43 0AL, England.
Abstract
There are theoretical and practical reasons for believing that a global count of remaining top predators is a direct summary measure of human impact on earth. The quantity of energy available to flow through the food web to 'primative' top predators has almost always been reduced by humans (hunting, agriculture, pollution). Estimates are made of the global abundance of major top predators in the assumed absence of humans, i.e. based on climatically derived vegetations, 2000 bp. These predator abundances are a baseline to compare to existing predator abundances. Global top predator count is a QUANTITATIVE measure of biota which complements the QUALITATIVE measure, global biodiversity, where the latter represents the number of types rather than the quantity of life on earth. Quantitative biotic measures may influence the conceptual framework of global modelling and biological conservation. >>>>>>>>>>>>>>>>>>>>
A GLOBAL VEGETATION MODEL USING PLANT FUNCTIONAL TYPES
W. Cramer, H. Bugmann and M. Plchl
Potsdam Institute for Climate Impact Research
P.O.Box 60 12 03, Telegrafenberg, D-144 12 Potsdam, Germany
The comparison of a range of global terrestrial ecosystem
models has shown that fundamental differences exist concerning
the models' capabilities to predict the dynamic response of
the biosphere to changes in climate and ambient CO2
concentration. We present a new, coupled model of global
vegetation structure and trace gas fluxes (the Potsdam Land
Atmosphere Interaction model, PLAI) that differs from previous
ones in considering plant functional types (PFTs) rather than
ecosystems. For the hypothetical case of climate-vegetation
equilibrium, PLAI predicts the composition of potential
natural vegetation (PNV) in terms of fundamental PFTs (e.g.,
trees with different leaf turnover times, or shrubs vs.
grasses), as well as the major biogeochemical processes
concerning the interaction of these plants with the atmosphere
(e.g., net primary productivity, NPP, or actual
evapotranspiration, AET). For the case of human-driven land
cover dynamics, PLAI also simulates the biogeochemical fluxes
for a prescribed mixture of PFTs.
The development of this model towards a dynamic global
vegetation model (DGVM) consists of a gradual inclusion of
processes on several levels of temporal resolution. Presently,
PLAI simulates diurnal and seasonal flux variations for the
case of long-term average climatic conditions. Realistic
weather fluctuations within the long-term means (dry/wet or
cold/warm periods within a year) and interannual variability
(dry/wet or cold/warm years) in the absence of a long-term
trend are features that are currently implemented and under
ongoing validation, using local time series of weather data,
as well as a globally applied stochastic weather generator.
Plausible performance for both cases will be required before
transient simulations are possible.
To progress towards realistic transient behaviour of the model
on the time-scale of decades to centuries, we present a
framework for application of patch-model derived rules for
establishment, competition and mortality of PFTs, and
ecophysiologically derived functions for their growth. The
first simulations will be initialized by conditions of the
equilibrium model, connected to a global land use data base.
At a later stage, the behaviour of the model under different
initial conditions will be tested as well as its response to
an interactive coupling with a general circulation model.
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AN ASSESSMENT OF DIFFERENT CLIMATE CHANGE SCENARIOS
FOR THE GLOBAL REDISTRIBUTION OF AGRICULTURAL LAND
W. Cramer1, M. Claussen2 & A. M. Solomon3
1Potsdam Institute for Climate Impact Research
P.O.Box 60 12 03, Telegrafenberg, D-144 12 Potsdam, Germany
2Max-Planck-Institute for Meteorology, Bundesstr. 55, D-20146
Hamburg, Germany
3USEPA Environmental Research Laboratory,
200 SW 35th Street, Corvallis, OR 97333, USA
The central purpose of this paper is to address the issue of
spatial scale in climate change impact scenarios. A problem
arises due to the gap between the coarse, often continent-wide
scales that general circulation models provide information for
and the much finer regional scales required for the simulation
of ecosystem processes. From the point of view of the
atmosphere, only land surface processes at the same resolution
as the climate model can be considered for feedback
simulations. From the point of view of the biosphere, however,
the atmospheric signal must be converted into scenarios at
finer scales if the sensitivity of ecosystems is to be
assessed in a realistic way. The assessment of the statistical
sensitivity of ecosystem change to a climate change signal
requires multiple numerical realisations of different climate
states. This paper uses a series of such realisations. One set
was derived from several general circulation models, and
another one from several time slices of one general
circulation model.
Cramer and Solomon (1993) estimated future redistributions of
potential agricultural land using scenarios derived from four
different general circulation models. Here, we reassess their
study using various realisations of present-day and future
climate simulated by the T42 general circulation model of the
Max-Planck-Institute for Meteorology (Hamburg, Germany). We
show that only the gain in potential arable land on Northern
latitudes constitutes a spatially coherent and statistically
significant signal driven by climate change. The variability
between different climate realisations, along with the lower
amplitude, in tropical and Southern hemisphere regions,
conceals any systematic trend in changing availability of
potential arable land.
A further limitation to the possibility of deriving scenarios
of ecosystem redistribution from general circulation models is
the inappropriate spatial resolution of the climate models.
Here, we demonstrate a procedure of combining a detailed
present-day surface climatology with the climate change signal
from the circulation model. We demonstrate that the method is
capable of producing detailed maps for present-day equilibrium
ecosystem distributions at resolutions between global
circulation models and detailed local weather generators.
Although based on present-day local weather features, we
conclude that the method is suitable for ecosystem
redistribution scenarios.
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The Importance of Tropical Ozone for the Chemistry of the Atmosphere: The Need for the Measurement Initiative ITOY, an IGAC Initiative
P.J. Crutzen
(Max Planck Institute for Chemistry, PF 3060, D55020
Mainz, Germany;
+49 6131 305458;email air@mpch-mainz.mpg.d400.de)
As one of the precursor gases of the OH radical, tropospheric ozone plays a key
role in the oxidation efficiency of the atmosphere. Despite its great importance
there still exist major gaps
in knowledge about the distribution of ozone especially in the tropics and subtropics.
To remedy this problem a proposal has been launched within the International
Global Atmospheric Chemistry (IGAC) Core Project of the IGBP to conduct
an intensive measurement campaign of ozone soundings over a period of +2 years
emphasizing the tropics and subtropics (ITOY International Tropospheric Ozone
Years).In this lecture the great importance of such an effort will be outlined.
Measurements have shown that
the tropics and subtropics contain both regions with very low (Pacific Ocean)
and very high (biomass burning influenced) ozone concentrations
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HALOCARBON AND ALKYL NITRATE DISTRIBUTION ALONG THE SOUTH-EAST COAST OF SOUTHERN AFRICA
A. C de Kock1, C. R Anderson2, and C Labuschagne1
1Department of Chemistry, Port Elizabeth Technikon, Private Bag X6011, Port Elizabeth, 6000
2Department of Geology, University of Port Elizabeth, PO Box 1600, Port Elizabeth, 6000
Photochemical processes in the troposphere are known to be influenced by a large variety of trace gases, such as halocarbons, hydrocarbons, ozone, and nitrogen oxides (NOx). Selected halocarbon and alkyl nitrate (RONO2) measurements were performed on ambient air samples taken on the south-east coast of southern Africa. The prevailing meteorological conditions determined whether the air mass sampled was of oceanic, rural continental or urban origin.
The alkyl nitrates quantified in this study were; 2-propyl, 1-propyl, 2-butyl, 1-butyl, 3-pentyl, 2-pentyl, 2-methyl-1-butyl, and 1-pentyl nitrate. Variability in absolute and relative RONO2 mixing ratios were observed on a synoptic time scale. These changes were directly related to the prevailing meteorological conditions. Air masses of an urban origin had significantly higher RONO2 mixing ratios and lower 2-propyl/2pentyl ratios as compared to those of rural continental or oceanic origin. In addition some seasonality was observed in mixing ratios, with higher RONO2 levels evident during winter and early spring and lower levels during summer.
The following halocarbons were identified and quantified in the ambient air samples; dibromomethane, bromodichloromethane, dibromochloromethane, chloroiodomethane, bromoform, 1,2-dibromoethane and hexachloroethane. Biogenic halocarbons observed in seawater samples were; bromodichloromethane, dibromomethane, chloroiodomethane, dibromochloromethane, and bromoform. Using known Henry's law constants, it was found that the seawater was super saturated with these compounds, with respect to their atmospheric concentrations. The biogenic halomethanes, such as bromoform and dibromomethane, exhibited far more variability in their atmospheric mixing ratios as compared to the relatively long lived anthropogenic species such as hexachloroethane. The mixing ratios of the petrol additive, 1,2-dibromoethane, were found to be directly related to local traffic. Under certain meteorological conditions, a correlation between the 1,2-dibromoethane and RONO2 levels was observed.
The results of this study show that the ocean is a major source of biogenic halocarbon species found in the marine troposphere. The alkyl nitrate levels measured for air masses of a marine origin was significantly higher than those predicted by model studies. This, together with the observed changes in relative and absolute concentrations of the alkyl nitrates, supports the hypothesis that long range transport plays a significant role in the distribution of alkyl nitrates in the remote troposphere. It would thus appear that trace gas variability in the coastal troposphere is strongly influenced by biogenic emissions and long range transport.
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#303
THE EVALUATION OF DYNAMICS OF SOIL CARBONATE BUFFER RESERVOIR DURING LAST 4ka
Vitaliy A. Demkin and Yaroslav G. Ryskov
Institute of Soil SCience and Photosynthesis RAS, 142292 Pushkino Moscow Region, Russia
Soil carbonates, being a buffer reservoir, are able either to accumulate or evolve CO2 into the atmosphere according to equation: CO2 + H2O + Ca2+ 3D CaCO3 thus controlling the content of CO2 in the atmosphere. We try to evaluate the dynamics of soil carbonate buffer reservoir using the carbonate supplies in a 2 m layers of paleosoils having the different ages. More than 200 paleosoils in archaeological monuments of the Bronze Age (III-II millennia B.C.) and the Middle Ages (XIII-XIV centuries A.D.) have been studied. The studies were carried out in steppe of Eurasia containing chernozems, chestnut and brown desert-steppe soils.
It has been established that in the Bronze Age paleosoils of all soil-geographic areas were characterized by surface occurrence of carbonates (5-7% CaCO3). For the last 30-40 centuries the carbonates migrated from the upper part of soil profile into the middle one (15-20% CaCO3). The average rate if carbonate leaching was 1 cm/100 years in chernozems and 0.4- 0.8 cm/100 years in chestnut and brown soils. CaCO3 migrated from 0-50 cm layer with the rate of 15-20 and 5-10 g/m annually. The carbonate accumulations in two meter thickness were very labile and depend on soil type, particle size of parent material, geomorphology and of carbonate supplies in soils. Thus, during recent 30-40 centuries, steppe soils did not were the sink of atmospheric CO2, but were the additional source of it.
This work was fulfilled under support of Russian Foundation for Fundamental Investigations, International Science Foundation "Cultural Initiative" and National Program "Global Change of Environment and Climate".
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PROGNOSTIC SIMULATION OF ATMOSPHERIC CO2 IN A
GENERAL CIRCULATION MODEL -
EFFECTS OF CORRELATIONS BETWEEN SURFACE FLUXES
AND TRANSPORT
A. S. Denning and D. A. Randall
Department of Atmospheric Sciences, Colorado State
University
Fort Collins, CO 80523 USA
The exchange of carbon dioxide (CO2) between the terrestrial
biosphere and the atmosphere has long been recognized as the
primary driver of the seasonal cycle of atmospheric CO2
concentration at large spatial scales. The physiological
processes responsible for this seasonal cycle are driven by
seasonal changes in solar radiation, temperature, and
available moisture at the land surface. Terrestrial CO2 flux
is
also coupled to physical forcing on the diurnal time scale.
These cycles in the physical forcing drive seasonal and
diurnal cycles in atmospheric circulations as well, which are
strongly correlated to the CO2 flux. Such correlations lead to
a nonuniform distribution of atmo spheric CO2 in the annual
mean even if there is no net annual storage or release of
carbon by terrestrial ecosystems.
We investigated the effects of these diurnal and seasonal
correlations by performing several multiyear prognostic
simulations of atmospheric CO2 concentration using the
Colorado
State University General Circulation Model (GCM) coupled to a
new version of the Simple Biosphere Model (SiB2). Our model
differs from most ecosystem models in that we calculate the
exchange of CO2 between the atmosphere and the land surface at
the atmospheric time step of six minutes, and thereby resolve
the diurnal cycle of the carbon flux. In addition, the model
simulates the diurnal evolution of low-level atmospheric
turbulence, which is a key determinant of vertical transport
of CO2. As a result, the simulated diurnal and seasonal
evolution of CO2 reproduced the limited observational data
much
better than any previous global simulation.
The coupled diurnal cycles of photosynthesis, respiration, and
boundary layer turbulence produced very strong spatial
gradients of annual mean CO2 over biologically productive
continental regions which are not detectable given the present
observational network. Expanding the network to include such
areas could significantly reduce the current uncertainty in
the global carbon budget. Correlations between vertical
transport and CO2 flux on the seasonal time scale produced a
meridional gradient in annual mean CO2 at the current
observational sites that was four times as strong as
previously simulated, implying a stronger net terrestrial
carbon sink than found in previous studies.
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INTERACTIONS BETWEEN GLOBAL HYDROLOGICAL AND CARBON CYCLES
R. Dickinson 1, L. Graumlich 2, and R. Bryant 2
Department of Atmospheric Sciences University of Arizona, Tucson, AZ 85721, USA
Tree Ring Laboratory University of Arizona, Tucson, AZ 85721, USA
The BATS land surface package is used for climate simulation with the NCAR CCM2 atmospheric GCM. We have extended BATS to include carbon fluxes by using empirical relationships relating carbon assimilation to stomatal functioning. Our approach differs from what has been done in SIB2 and other land models including carbon in that, rather than deriving stomatal functioning from modeled carbon dynamics, we generalize the existing stomatal parameterization for water so that it includes the assimilation of carbon. Our carbon model attempts to treat in detail various respiratory processes and the partitioning of photosynthate. We assume that as LAI increases, a smaller fraction of photosynthate is given to leaves; although plausible, there is a dearth of observations to quantify this assumption. However, we find that the results are sensitive to the detailed functionality of this dependence of partitioning on LAI. Our carbon model has long suffered from too slow spring growth of leaves at small LAI and a tendency to develop excessively large LAIs. These errors were corrected by changing the function we used for LAI dependence of partitioning to leaf.
With the current version of this model, we have carried out global simulations with the