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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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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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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NEW COUPLED CLIMATE-CARBON SIMULATIONS WITH THE IPSL MODEL: FROM VALIDATION WITH ATMOSPHERIC ...
Description: We have developed a
Climate-Carbon coupled model based on the IPSL OAGCM and on two biogeochemical
models, ORCHIDEE for the continent and PISCES for the ocean, to investigate the
coupling between climate change and the global carbon cycle. We have performed
four climate-carbon simulations over the 1860-2100 period in which atmospheric
CO2 is interactively calculated. They are :
§
A control coupled
simulation with no anthropogenic emissions.
§
A coupled
simulation with anthropogenic emissions.
§
A coupled
simulation with anthropogenic emissions including non-CO2 greenhouse
and sulfate aerosols.
§
An uncoupled
carbon simulation with the same anthropogenic emissions as second simulation
but for which atmospheric CO2 change has no impact on climate.
Compared to the first IPSL
Climate-Carbon coupled model [Dufresne,
et al., 2002], the simple carbon models have been replaced by IPSL advanced
ocean and land biogeochemical models, respectively PISCES and ORCHIDEE. CO2
is transported in the atmosphere and compared with observations. Comparison
with satellite data is also done. We then analyze the coupled and uncoupled
simulations, highlight the importance of the climate change both on the oceanic
and biosphere sink and estimate the climate-carbon feedback. The results are
also compared to the outputs of other models participating in the C4MIP
inter-comparison project. Finally, off-line simulations are carried out to
perform sensitivity tests (fire, dynamics of land and ocean ecosystems, soil
respiration) in order to identify the key processes which govern the simulated
response.
Author's Names: P. Cadule, P. Friedlingstein and L. Bopp
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Added on: 27-Jul-2005 Downloads: 183
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OBSERVED RELATIONSHIPS BETWEEEN LARGE-SCALE ATMOSPHERIC VARIABILITY AND THE CARBON CYCLE
Description:
Various patterns of large-scale
climate variability have exhibited trends over the past few decades. These
patterns of variability are known to have contributed substantially to recent
trends in, for example, surface temperatures and precipitation. However, it is
less clear to what extent the climate impacts of these patterns extend to the
carbon cycle. Here we summarize the observed relationships between monthly and
daily mean variations in concentrations of atmospheric carbon dioxide and the
dominant pattern of variability in the extratropical circulations, the
so-called Northern and Southern Hemisphere Annular Modes. The observed
relationships are compared with results derived from surface flux estimates
from the Atmospheric Tracer Transport Model Intercomparison Project (TransCom).
Author's Names: A.K. Hawes, and D.W.J. Thompson
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OBSERVED RESPONSE OF THE CO2 GROWTH RATE TO CLIMATE VARIATIONS
Description:
The world is moving in a direction of managing the carbon
cycle in order to limit the forcing of earth's climate by CO2 as
well as to limit acidification of the oceans.
We may expect limitations on emissions, sequestration of carbon and
enhancements of natural sinks. It would
be important to be able to observe and quantify the impact of any such measures
on the growth rate of CO2. Until now it has been difficult to
quantify changes of the growth rate of CO2 with confidence due to
the large year to year variations that are caused by climate variations. A statistical method has been developed to
predict the growth rate of CO2 based on observed variations of
climate parameters.
Author's Names: Pieter Tans
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Added on: 08-Aug-2005 Downloads: 24
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ON THE NATURE AND CAUSES OF YEAR-TO-YEAR VARIABILITY IN THE CARBON CYCLE
Description:
Monthly time series of atmospheric carbon dioxide (CO2),
the relative amount of carbon-13 in CO2 (13C), hydrogen
(H2) carbon monoxide (CO), and methane (CH4) are examined
and related to each other and to an index of the status of ENSO. Making use of simple 12-month running mean
and difference filters isolates the year-to-year variability in the concentrations
and apparent sources of these constituents.
Author's Names: J.L. Russell and J.M. Wallace
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Added on: 04-Aug-2005 Downloads: 25
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ON THE SENSITIVITY OF OCEAN BIOGEOCHEMISTRY AND AIR-SEA CO2 FLUX TO CLIMATE DRIVEN VARIATIONS ...
Description:
A
coupled Biogeochemistry-Ecosystem-Circulation (BEC)
ocean model is used to examine the sensitivity of ocean biogeochemical cycling
and air-sea CO2 exchange to variations in mineral dust deposition
from the atmosphere. Mineral dust
deposition estimates from four different climate regimes are used to force the
ocean model. Our estimated climate-induced
changes in dust deposition to the oceans significantly modify phytoplankton
community composition, and global-scale rates of nitrogen fixation, export
production, and air-sea CO2 flux. Dust driven variations in air-sea CO2
exchange exceeding 1 PgC/yr are of similar magnitude to present net oceanic
anthropogenic uptake. Dust deposition
directly modifies rates of export production and CO2 flux over large
regions where iron is the primary growth-limiting nutrient. Dust deposition also indirectly influences
these rates by modifying the rates of nitrogen fixation in the tropics and
subtropics where nitrogen is the primary limiting nutrient. Initially the direct pathway dominates the
ocean biogeochemical response to dust variations, but over multi-decadal
timescales the indirect response may be equally important. Our predicted decrease in mineral dust
deposition over the next century would significantly slow oceanic uptake of CO2
and act as a positive feedback mechanism for the ongoing global warming.
Author's Names: J. K. Moore, S. C. Doney, K. Lindsay, and N. Mahowald
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PERSISTENCE OF NITROGEN LIMITATION OVER TERRESTRIAL CARBON UPTAKE
Description: Because
vegetation growth in the Northern Hemisphere is typically nitrogen-limited,
increased nitrogen deposition could have attenuating effect on rising
atmospheric CO2 by stimulating the accumulation of biomass. Given
the high carbon to nitrogen ratios and long lifetimes of carbon in wood, a most
significant effect of nitrogen fertilization is expected in forests. Forest
inventories indicate that the carbon content of northern forests have increased
concurrently with increased nitrogen deposition since the 1950s [Spiecker et al.,
1996]. In addition, variations in atmospheric CO2 indicate a
globally significant carbon sink in northern mid-latitude forest regions [Schimel et al.,
2001]. It is unclear however, whether elevated nitrogen deposition or other
factors are the primary cause of carbon sequestration in northern forests. We
argue that the elevated nitrogen deposition is unlikely to enhance vegetation
carbon sink significantly because of its differentiating effect on the carbon
sequestration capacity of uneven aged forests and climatic limitations on
carbon sequestration in the Northern Hemisphere. We estimate the potential of
forests with lifted nitrogen limitation to decelerate CO2
concentrations rise in the atmosphere and therefore to mitigate climate
warming. We also outline areas of the Northern Hemisphere which are most
sensitive to increased nitrogen deposition.
Author's Names: G. Churkina, M. Vetter, and K. Trusilova
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POTENTIAL VARIATIONS IN THE O-17 TO O-18 RELATION OF WATER AND ICE SAMPLES
Description: It is generally assumed
that the variations of O-17 and O18 contents of water samples are closely
related. In literature there are different relations described, for instance
the Craig relation that assumes O-17 to vary half compared to O-18. O-17 of
water can be determined from the measured ...
Author's Names: M. C. Leuenberger
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Added on: 01-Aug-2005 Downloads: 18
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