CLIMATE-INDUCED CHANGES IN OCEAN CO2 UPTAKE MEDIATED BY CHANGES IN THE SUPPLY OF IRON-BEARING DUST
Description:
The effect of changes in iron supply to the ocean on
CO2 uptake is examined. Dust deposition fields from a dust model
driven by output from a future climate simulation of a coupled general
circulation model (GCM) were used as input to an ocean GCM with an embedded
ecosystem model. In simulations using dust produced in a future climate the
primary productivity of the ocean increased by 56% compared to simulations
using dust from the present climate. The sinking particle flux of carbon at 100
m depth increased by 46%. The net air-to-sea flux of CO2 was 4.1
PgC/y greater in the future dust simulation. Most of these changes occurred in
the Equatorial Pacific Ocean, where the model ecosystem was iron-limited with
present-day dust inputs but which received a large increase in the dust
supplied from the Amazon
Basin. These
perturbations to the marine biogeochemical system are large compared to other
potential climate effects that have been observed in the model. Although these
results are preliminary, they could form a large negative feedback on global
warming.
Author's Names: I.J. Totterdell, J. Gunson and S. Woodward
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CLIMATE VARIABILITY IN THE PACIFIC NORTHWEST, USA AND THE IMPACT ON CARBON EXCHANGE IN AN ...
Description: Long-term micrometeorological measurements
(1998-2004) show high interannual variability in the atmosphere-ecosystem
exchange of carbon for a Pacific Northwest
coniferous old-growth forest. Earlier
work [Wharton et al. 2004] has shown that net ecosystem exchange of carbon (NEE)
in this forest is highly sensitive to any perturbations in climate, and in
particular, in precipitation and temperature anomalies. Here we present results
from the ACASA (Advanced Canopy Atmosphere-Soil Algorithm) model to investigate
NEE as it relates to various climate forcings, including a shift in precipitation
pattern and increase in air temperature.
Author's Names: S. Wharton, R.D. Pyles, M. Falk, E. González, and K.T. Paw U
Filesize: 71.00 Kb
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CLIMATE –CARBON CYCLE FEEDBACK ANALYSIS, RESULTS FROM THE C4MIP MODEL INTERCOMPARISON
Description:
Ten coupled climate-carbon cycle models were forced by
historical and SRES A2 anthropogenic emissions of CO2 for the
1850-2100 time period to study the coupling between climate change and the
carbon cycle. Each model ran two separate simulations in order to evaluate the climate-carbon
cycle feedback. All models agree that future climate change will reduce the
efficiency of the Earth system to absorb the anthropogenic CO2. A
larger fraction of CO2 will stay in the atmosphere if climate change
is accounted for. By the end of the 21st
century, this ranges between 20 ppm and 200 ppm depending on the model, the
majority of the models lying between 50 and 100 ppm. All models simulate a
negative sensitivity for both the land and the ocean carbon cycle to future
climate. However there is still a large uncertainty on the magnitude of these
sensitivities. Also, the majority of the models attribute most of the changes
to the land. Finally, most of the models locate the reduction of land carbon
uptake in the tropics. However, the attribution to changes in net primary
productivity versus changes in respiration is still subject to debate amongst
the models.
Author's Names: P. Friedlingstein, P. Cox, R. Betts, L. Bopp, et al
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CLIMATE AND DISTURBANCE EFFECTS ON GROSS ECOSYSTEM FLUXES ASSESSED BY MODEL-DATA FUSION
Description:
We
implement a model-data fusion method to determine the gross flux components
contributing to the net ecosystem exchange of a Ponderosa pine forest in Oregon. This site-level
investigation represents a test-run of the method, which will later be applied
to all of Oregon and north California.
Author's Names: J.M. Styles, B.E. Law, D. Turner, W. Cohen, and G. Whitley
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CARBON-CLIMATE SYSTEM FEEDBACKS TO NATURAL AND ANTHROPOGENIC CLIMATE CHANGE
Description:
A new three-dimensional global coupled carbon-climate model is
presented in the framework of the Community Climate System Model (CSM-1.4). A
1000-year control simulation has stable global annual mean surface temperature
and atmospheric CO2 with no flux adjustment in either physics or
biogeochemistry. At low frequencies (timescale > 20 years), the ocean tends
to damp (20-25%) slow, natural variations in atmospheric CO2
generated by the terrestrial biosphere. Transient experiments
(1820-2100) show that carbon sink strengths are inversely related to the rate
of fossil fuel emissions, so that carbon storage capacities of the land and
oceans decrease and climate warming accelerates with faster CO2
emissions. There is a positive feedback between the carbon and climate systems,
so that climate warming acts to increase the airborne fraction of anthropogenic
CO2 and amplify the climate change itself. Globally, the
amplification is small at the end of the 21st century in our model because of
its low transient climate response and the near-cancellation between large
regional changes in the hydrologic and ecosystem responses.
Author's Names: S.C. Doney. K. Lindsay, I. Fung, and J. John
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CARBON-CLIMATE INTERACTIONS: RESULTS FROM THE CSIRO GLOBAL CLIMATE MODEL
Description:
Using
the CSIRO global climate model (CCAM)
coupled with a terrestrial carbon cycle model, we carried out two simulations
using the protocol of C4MIP (Coupled Carbon Cycle Climate Model Intercomparison Project) Phase I to study the
influences of increasing atmospheric CO2 concentration and changes
in sea surface temperature over the last 100 years on CO2 between
atmosphere and 11 biomes. It was found that the inter-annual variation of net
ecosystem prediction of global terrestrial biosphere is significantly
correlated to the variation of land surface temperature from 1980 to 1999, and
the increase in net ecosystem production can be largely explained by the
increase in net primary production from CO2 fertilization from 1970
to 1999 in our model. The response of net ecosystem production to CO2
fertilization is strongest in tropical rainforest and not significant in
tundra. Our estimates of net ecosystem production of global terrestrial
biosphere in 1990’s agree well with the results from an inversion study by
Allison et al. [this volume].
Author's Names: Y.P. Wang, E.A. Kowalczyk, and R.M. Law
Filesize: 55.91 Kb
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CARBON, WATER AND LAND USE IN THE WESTERN GREAT PLAINS: MANAGEMENT IMPACTS ON LOCAL AND REGIONAL ...
Description:
This
research investigates how land use in the shortgrass steppe of eastern
Colorado impacts short
and long-term water, carbon and energy dynamics. A large and
homogeneous area of Conservation
Reserve Program (CRP) grassland near Briggsdale, Colorado, was selected
for this
experiment and divided into three 40 hectare plots. An open-path eddy
flux
system was established in each plot and measurements made during a
baseline
comparison prior to land use transformation.
The three treatments include an un-grazed grassland (control), a
moderate intensity grazing treatment, and a dry-land agricultural
rotation
(winter wheat-hay millet; considered optimal for this low rainfall area
of Colorado). We report on the trajectories of carbon,
water and energy fluxes in theses three land use systems and analyze
how
altered carbon storage and water use efficiency may impact short-term
land
surface-atmosphere interactions, as well as long-term source-sink
relationships, water conservation, productivity and sustainability.
Author's Names: N.P. Hanan, T.C. Peterson, and C.A. Williams
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CANOPY UPTAKE OF ATMOSPHERIC NITROGEN AT A CONIFER FOREST: ENHANCED PHOTOCHEMICAL EFFICIENCY ...
Description: A field study at the Niwot conifer forest
within
the footprint of an AmeriFlux tower site used fluorometry (chlorophyll
fluorescence) to identify a mechanism by which canopy uptake of
atmospheric/anthropogenic N deposition may influence photosynthesis
and net ecosystem
exchange (NEE). Correlation of daytime NEE with canopy N uptake (CNU)
had suggested a linkage. Strongly differing N additions were
spray
applied (simulating wet deposition) to spruce branches. Photochemical
efficiency was markedly enhanced in N-treated branches under high light
with a
concomitant reduction in foliar photodamage and/or in PAR-induced
foliar heat dissipation. Photosynthesis
and NEE enhancement were statistically related to CNU.
Author's Names: H. Sievering, T. Tomaszewski, and R. Boyce
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BIOGEOCHEMICAL CHANGES IN SUBTROPICAL AND SUBPOLAR MODE WATERS: A MINER’S CANARY FOR CLIMATE ...
Description: Long-term observations of carbon, nutrients and oxygen
in upper thermocline waters, such as subtropical and subpolar mode waters, have
revealed substantial interannual to decadal variations. While part of this
variability can be ascribed to internal ocean and ecosystem dynamics as well as
large-scale climate phenomena (like ENSO,
NAO or the PDO), we presently do not know to which extent this variability is
influenced by anthropogenic climate change. As a first step to answer this
detection question, the impact of natural variability on biogeochemical
properties in thermocline waters must be understood and quantified. This
permits us then to accurately describe the natural "noise" against
which an anthropogenic change needs to be detected. Subtropical and subpolar
mode waters may be ideally suited to look at this task since they tend to
respond sensitively to climate variations, integrate short-time scale
variations over time, and hence exhibit maximum signal to noise ratio. We investigate the role of mode water
formation and spreading on interannual to decadal accumulation and release of
nutrients and carbon by analyzing results from model runs with the Upper Ocean
Model [Danabasoglu and McWilliams 2000] coupled
to the ecosystem model of Moore et al.
[2002]. We compare results from a run forced with NCEP reanalysis data for the
period from 1948 to present with a climatological control run. To better
isolate the mechanisms forcing these biogeochemical changes, we compare our
results also to a set of experiments in which we manipulate the wind stress
forcing and sea surface temperature fields of the model locally.
Author's Names: H. Brix and N. Gruber
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ATMOSPHERIC CO2, CARBON ISOTOPES, THE SUN AND CLIMATE CHANGE OVER THE LAST MILLENNIUM
Description: The records of atmospheric CO2 and of NH surface temperature
covering the past millennium hold information on the strength of the
sensitivity of the global carbon cycle to climate changes. This sensitivity is
defined as the change in atmospheric CO2 in response to a given
change in NH temperature in units of ppm K-1. The magnitude of the
sensitivity is estimated for modest (< 1 K) temperature variations from
simulations with the Bern Carbon Cycle Climate model driven with solar and
volcanic forcing over the last millennium and from simulations with the range
of C4MIP models over the industrial periods. The model results are broadly
compatible with the data-deduced range.
Author's Names: F. Joos, S. Gerber, S.A. Müller, R. Muscheler
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