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
Filesize: 22.54 Kb
Added on: 02-Aug-2005 Downloads: 17
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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
Filesize: 53.59 Kb
Added on: 01-Aug-2005 Downloads: 18
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FUTURE EVOLUTION OF THE TERRESTRIAL CARBON CYCLE CONSTRAINED BY CURRENT OBSERVATIONS: RESULTS ...
Description:
In a Carbon Cycle Data Assimilation System (CCDAS) one
infers the values of the parameters controlling the function of a process model
using various observations. One can then calculate quantities of interest from
the optimized parameters and the model. One can also calculate the
uncertainties on the parameters and propagate these to uncertainties of the
calculated quantities. In Rayner et al. [2005] we assimilated atmospheric
observations over two decades, into a terrestrial model and calculated fluxes
over this period. Here we extend this work by calculating the response of the calibrated
terrestrial biosphere to a GCM simulation of future climate. Using this
combination we are able to comment on the fate of terrestrial carbon pools and
fluxes under climate change, calculate the uncertainties of the response, and
determine which parameters in the model are responsible for this uncertainty.
We include an extra parameter that scales the climate change signal from the
GCM projection. We thus extend the sensitivity and uncertainty analysis to
include the climate sensitivity.
Author's Names: P. Rayner, M. Scholze, P. Friedlingstein, et al
Filesize: 12.32 Kb
Added on: 03-Aug-2005 Downloads: 19
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THE MID-LATITUDE WESTERLIES, ATMOSPHERIC CO2 AND CLIMATE CHANGE DURING THE ICE AGES
Description:
An idealized general circulation model is constructed
of the ocean’s deep circulation and CO2 system that reproduces the
main features of glacial-interglacial CO2 cycles, including the
tight correlation between atmospheric CO2 and Antarctic
temperatures, the lead of Antarctic temperatures over CO2 at
terminations, and the shift of the ocean’s 13C minimum from the
North Pacific to the Atlantic sector of the Southern Ocean. The model is based
on a new idea about the nature of the glacial-interglacial cycles in which the
driving force is independent of the orbital forcing and is not in the ocean.
The key to glacial-interglacial transitions, we claim, is a relationship
between the mid-latitude westerly winds, atmospheric CO2, and the
mean state of the atmosphere. Cold glacial climates seem to have
equatorward-shifted westerlies, which allow more respired CO2 to
accumulate in the deep ocean. Warm climates like the present have
poleward-shifted westerlies that flush respired CO2 out of the deep
ocean.
Author's Names: J.R. Toggweiler, J.L. Russell, S.R. Carson
Filesize: 12.05 Kb
Added on: 04-Aug-2005 Downloads: 19
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DGVMII – QUANTIFYING UNCERTAINTIES IN THE FUTURE LAND-ATMOSPHERE EXCHANGE
Description: In recent years attention has focused on the
role of terrestrial biosphere dynamics in the climate system, and the
possibility of large land-atmosphere carbon cycle feedbacks under human-induced
future climate warming. During the 1990s rapid development of Dynamic Global
Vegetation Models (DGVMs) led a growing community to soon recognize the need
for model evaluation and intercomparison. In Cramer et al. 2000 six DGVMs were
run using identical forcing data based on the HadCM2 GCM climatology
(1860-2100) and the IS92a emission scenario.
Author's Names: S. Sitch, W. von Bloh, P. Ciais, P. Cox, et al
Filesize: 18.83 Kb
Added on: 04-Aug-2005 Downloads: 19
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SYNERGISM OF TERRESTRIAL CARBON CYCLE FEEDBACKS IN SIMULATIONS OF FUTURE CLIMATE CHANGE
Description: This paper examines two key feedbacks that
operate between the terrestrial carbon cycle, atmospheric carbon dioxide (CO2)
and climate: the positive carbon cycle-climate feedback and the negative CO2
fertilization feedback. Both feedbacks
affect strongly the growth rate of future atmospheric CO2, and
interact in such a way that the effect of one is notably modified in the
absence of the other.
Author's Names: H.D. Matthews
Filesize: 76.93 Kb
Added on: 16-Sep-2005 Downloads: 19
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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
Filesize: 91.32 Kb
Added on: 29-Jul-2005 Downloads: 20
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THE EFFECTS OF NITROGEN ADDITION ON THE BELOWGROUND CARBON CYCLE IN TEMPERATE FORESTS AND DESERT
Description: Human activities such as fossil fuel and
fertilizer-use have doubled the amount of biologically active nitrogen entering
ecosystems each year [Vitousek et al.,
1997]. N is the limiting nutrient in many ecosystems
and N availability has been shown to affect plant, root, and soil
respiration. For several temperate
forests, experimental addition of N is associated with a decline in soil CO2
efflux [Bowden et al.,
2004; Burton et al., 2004; Nohrstedt et al., 1989; Swanston et al., 2004]. This decline
could be due to either (1) decreased allocation of C to root metabolism and
growth because N demand of plants can be met with less energy expended
belowground, or (2) decomposition rate due to changes in leaf or root tissue
chemistry, or to changes in the decomposer community. In contrast, the few studies of more water
limited systems do not show decreased soil respiration fluxes [Schaeffer et
al., 2003; Verburg et al., 2004], which could reflect hydrologic control of
belowground C allocation.
Author's Names: N.S. Nowinski, S.E. Trumbore, E.B. Allen, et al
Filesize: 18.62 Kb
Added on: 03-Aug-2005 Downloads: 20
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THE INFLUENCE OF THE NAO ON THE CONTINENTAL SHELF PUMP ON THE NORTHWEST-EUROPEAN SHELF
Description:
Using a coupled 3D
hydrodynamic-biogeochemical model system for the Northwest-European shelf we
simulated the years 1993-96, which exhibit an extremely strong transition from
a NAOI-high to a NAOI-low regime. The induced temperature-shift had two
consequences for the carbon budget of the North Sea:
Firstly it increased the CO2 solubility and secondly it destabilized
the water column in spring 1996. The latter effect was the precondition for
mixing events which brought new nitrogen for primary production into the upper
layer. Consequently the air-sea flux was 540 Gmol C a-1 in 1996, the
NAOI-low year, and it was 203 Gmol C a-1 in 1995, the year with the
highest NAOI.
Author's Names: J. Paetsch, W. Kuehn, A.V. Borges, Y. Bozec, et al
Filesize: 16.39 Kb
Added on: 03-Aug-2005 Downloads: 20
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DOES THE POSITION OF THE SOUTHERN OCEAN WESTERLY WINDS REPRESENT A NEGATIVE FEEDBACK ON ...
Description:
Increasing ocean stratification associated with global
warming has been posited to serve as a positive feedback on global warming,
reducing the oceanic uptake of anthropogenic carbon dioxide. We suggest that a
poleward shift of westerly winds combined with future increases in atmospheric
carbon dioxide may drive an increase in the CO2 uptake in the
Southern Ocean, representing a negative feedback on atmospheric anthropogenic
CO2.
Author's Names: J.L. Russell, K. Dixon, A. Gnanadesikan, et al
Filesize: 15.22 Kb
Added on: 04-Aug-2005 Downloads: 20
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