MODELING DROUGHT TOLERANCE IN AMAZONIA WITH SiB3
Description:
The
Amazon region of South America plays a
significant role in global cycles of water, energy and carbon, yet it
is also
one of the most challenging biogeographical areas of the world to model
correctly. Numerous global climate models have problems with anomalous
die-back
of the Amazon rain forest variously attributed to inadequate
representation of
rainfall, faulty soil moisture dynamics or an inability to correctly
simulate
the drought tolerance of the vegetation. Such misrepresentation of the
Amazon
in global climate models can cause larger than observed excursions of
the
global carbon cycle. This poster explores soil moisture and drought
stress for Amazonia with the Simple Biosphere Model (SiB3) and
possible reasons and solutions to the rain-forest die back problem,
which
should lead to more reasonable estimates of carbon fluxes at the
ecosystem
scale.
Author's Names: L. Prihodko, A.S. Denning, and I. Baker
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MECHANISMS IMPACTING INTER-ANNUAL VARIATIONS IN REGIONAL C18OO ISOFLUXES: MODEL ESTIMATES WITH ...
Description:
Temporal
and spatial distributions of the δ18O value of atmospheric CO2
(dCa) can be used to constrain regional
ecosystem carbon exchanges and linkages between carbon and water cycling.
However, our understanding of the substantial observed temporal and spatial
variability in dCa is limited. Among many contributing
factors, seasonal and inter-annual variations in climate are likely to be
important. In this study we investigate the impact of dry climatic conditions
on the ecosystem-atmosphere C18OO isoflux.
We conducted this study in the
U.S. Southern Great Plains using five-year monthly-averaged precipitation δ18O
values (δp) from the
National Atmospheric Deposition Program (NADP) network, Mesonet meteorological
forcing, and MODIS-derived NDVI and land-cover characterization. These data are
used to force the isotope ecosystem model ISOLSM [Riley et al., 2002; Riley et al., 2003] at 10 km resolution across the region for relatively
drier (2003) and wetter (2004) years. The model has been calibrated and tested
in the dominant herbaceous vegetation types in the region [Biraud et
al., this issue].
Author's Names: W.J. Riley, C.J. Still, R. Vachon, J. Welker, et al
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Added on: 03-Aug-2005 Downloads: 22
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MARINE ECOLOGY, BIOGEOCHEMISTRY AND ATMOSPHERIC CO2 SIGNATURE FROM A 43-YEAR REANALYSIS IN A ...
Description:
We
have developed a multiple element (C, N, P, Si, Ca, Fe) biogeochemical model of
marine ecology that includes small, large and diazotrophic phytoplankton as
well as explicit ballast-driven sinking and remineralization of detrital
organic matter and cycling of dissolved organic matter. Phytoplankton growth is
described through a new formulation including co-limitation by N, P, Si, Fe and
light to reproduce broad observational trends.
Phytoplankton grazing is described through different power laws in the
closure terms for small and large phytoplankton to reproduce observed
augmentation of large phytoplankton with increasing production. Detritus
production is assumed to be a temperature dependent fraction of small and large
phytoplankton. This model has been imbedded in a 1-degree; global ice/ocean
general circulation model (MOM4) forced by a 43-year atmospheric reanalysis
forcing from the Common Ocean Reference Experiments (CORE) program to quantify
the relationship between food web structure, biogeochemical cycles and the
atmospheric CO2 signature on inter-annual timescales. Novel aspects
in the model structure are described, the impact of the formulation of
ecosystem structure on biogeochemical cycling are discussed, and results of the
atmospheric reanalysis forcing experiment presented. Of particular interest are
the dynamical roles played by equatorial ENSO variability and polar sea ice
dynamics on air-sea CO2 fluxes.
Author's Names: J.P. Dunne, R.A. Armstrong, A. Gnanadesikan, et al
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Added on: 28-Jul-2005 Downloads: 21
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MAN-INDUCED CHANGES IN C STORAGE DURING THE 20TH CENTURY: ENVIRONMENTAL AND GEOCHEMICAL RECORD
Description:
Despite
their relative small extension, wetlands are important as sources or sinks of
C. But, due to their intermediate position between land and permanent water,
they have been modified in the name of “health” or “productivity.” Such changes
have altered substantially their ability to store/produce C greenhouse gasses
but the main point is to establish until which point this changes are
“structural” (implying the intrinsic environmental mechanisms), and therefore
unrecoverable, or “casual” (implying not the environment processes but its
“external”–not directly implied in the C storage/emission- components), and
consequently recoverable. Temperate wetlands are strongly dependant on water
availability due to their position but, on the other hand, use to be occupied
by resistant species able to survive hard conditions. The example shown below
presents a case of intense human activity on a Mediterranean wetland that has
caused very intense changes in the flooded area but not so evident and
perdurable in the main ecological relations implied in the C cycle.
Author's Names: F. Dominguez-Castro, J.I. Santisteban, R. Mediavilla, et al
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Added on: 28-Jul-2005 Downloads: 35
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IMPACT OF THE SOUTHERN ANNULAR MODE ON THE SOUTHERN OCEAN CARBON CYCLE
Description:
The
Southern Annular Mode (SAM) is the
leading mode of intraseasonal to interannual variability over the entire
Southern Hemisphere, yet the impact of the SAM
on the Southern Ocean carbon cycle is largely unknown. We investigate the
impact of the SAM on surface wind,
sea surface temperature (SST), chlorophyll concentration, and sea ice
concentration on the basis of 8-day averaged satellite observations. We find that Southern Ocean circulation and
biogeochemistry react quite sensitively to this mode of variability,
potentially resulting in air-sea CO2 flux anomalies. Since variations
in atmospheric CO2 congruent with the SAM
are small, we hypothesize that the SAM
produces anomalous air-sea fluxes of both natural and anthropogenic CO2,
which act to compensate each other.
Author's Names: N.S. Lovenduski, N. Gruber, A. Hawes, and D.W.J. Thompson
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Added on: 01-Aug-2005 Downloads: 22
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IMPACT OF CO2, CLIMATE AND O3 ON FUTURE LAND-ATMOSPHERE CARBON EXCHANGE
Description:
In this study we evaluate the individual and combined impacts
of CO2, climate and Ozone on future terrestrial carbon storage using
the computationally efficient GCM analogue model coupled to the MOSES/TRIFFID
land surface carbon cycle model. Ozone is modelled to have a significant
detrimental effect on future plant productivity and hence terrestrial carbon
storage, opposing the enhanced production and terrestrial carbon storage
associated with elevated atmospheric CO2 concentrations.
Author's Names: S. Sitch, B. Collins, P. Cox, N. Gedney, D. Hemming, et al
Filesize: 22.92 Kb
Added on: 04-Aug-2005 Downloads: 20
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HOW RESILIENT MAY THE AMAZON RAIN FOREST CARBON BALANCE BE TO CLIMATE CHANGE?
Description:
The Amazon region represents a large
stock of biomass as well as a potentially important sink for additional
atmospheric CO2. Climate change, land-use changes and their
interaction present a risk to this role in the global carbon cycle. Both
positive and negative feedbacks exist in the system that can lead to resilience
but also to accelerated break-down of the carbon stocks and sinks. A set of
linked projects will investigate elements of these processes in the coming
years.
Author's Names: Bart Kruijt, Flavio Luizao, Antonio Nobre, et al
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HIGH RESOLUTION 13C MEASUREMENTS FROM THE EPICA DOME C ICE CORE
Description: Measurements of the isotopic
composition of carbon dioxide were performed on EPICA Dome C ice on 76
different depth levels covering the last 40’000 years. The time resolution is
in the order of 500 years for the last 18’000 years. For each depth level at
least two determinations were obtained. The d13C signals show different
trends during the last 18000 years that are anti-parallel to the CO2
concentration evolution as measured on the same ice core. However millennial
scale deviations from these trends are observed for at least three time
periods. The robustness and significance of these deviations are investigated
by Monte Carlo simulations performed with
different subsets of the measurements. The decreases of carbon isotopes could
be connected with observed step-like increases of the CO2 concentration.
Furthermore, a similar evolution as for stable carbon isotopes is visible for
detrended radiocarbon. We will discuss potential mechanisms responsible for the
trends as well as for the millennial scale deviations in carbon-13, including
changes in the thermohaline circulation as well as potential influences of a
changing 17O-18O relationship.
Author's Names: M. C. Leuenberger, M. Eyer, Serge Bogni, et al
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HAZARDS OF TEMPERATURE ON FOOD AVAILABILITY IN CHANGING ENVIRONMENTS
Description: Global
temperatures are predicted to increase from rising
levels of atmospheric carbon dioxide (CO2) and other greenhouse
gases. We conducted experiments in sunlit, controlled-environment chambers and
temperature-gradient greenhouses to determine effects of elevated temperature
and doubled CO2 concentration on pollination and yield of rice,
soybean, dry bean, peanut, and grain sorghum. Photosynthesis and vegetative
growth were more tolerant of increasing temperatures than reproductive
processes. Rice seed yields were optimum at 25°C mean daily temperature and
decreased with increasing temperature (typically about 10% decline for each 1°C
rise in temperature). Grain sorghum yield response to temperature was similar to
rice, but dry bean was more sensitive, and soybean and peanut were more
tolerant. Pollen viability followed a temperature response similar to seed
yield. Comparisons of 43 rice cultivars in temperature-gradient greenhouses
showed genetic variation in percent seed-set in response to a 4.5°C increase
above ambient temperatures in Florida.
Thus, there appears to be a range of adaptation of seed crops to temperature.
Elevated CO2 did not prevent high temperature decline in yield; in
dry bean it made pollination more sensitive to high temperature. In summary, global
warming will be a greater threat to crop seed yields than to photosynthesis and
vegetative growth. However, crop genetic improvements might ameliorate part,
but not all, of the high temperature hazards for seed yields and global food
security.
Author's Names: L.H. Allen, Jr, K.J. Boote, P.V.V. Prasad, J.M.G. Thomas, and J.C.V. Vu
Filesize: 28.20 Kb
Added on: 25-Jul-2005 Downloads: 174
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GREENHOUSE GAS CO2, CH4 AND CLIMATE EVOLUTION SINCE 650KYRS DEDUCED FROM ANTARCTIC ICE CORES
Description: Ice cores are unique archives of past climatic and atmospheric
conditions through the isotopic composition of the ice and the analysis of the
air bubbles trapped. In 1999 Petit et al published the reconstruction of the
Antarctic climate and atmospheric composition over the last 420 000 years from
the Vostok ice core. This record covered the last four glacial inter glacial
cycles back to the end of the marine interstadial 11 (MIS 11). It has revealed
the close relationship between the atmospheric part of the carbon cycle and the
climate. With CO2 concentration oscillating between 180 and 280 ppmv
during the last 4 climatic cycles. In
a similar way the methane concentration followed closely
temperature on glacial interglacial time scales, with millennial-scale
structures during glacial times which appear out of phased with Antarctic
temperature but, at least for the last glaciation, in phase with the Greenland rapid climatic oscillations, as revealed by the
GISP and GRIP ice cores.
Author's Names: J.M. Barnola, U. Siegenthaler, et al
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Added on: 27-Jul-2005 Downloads: 200
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