AEOLIAN INPUT OF BIO-AVAILABLE IRON TO THE OCEAN
Description:
Atmospheric
deposition of mineral dust aerosols supplies the essential nutrient of iron to
the ocean. However, only the readily soluble
iron is available to biological uptake while the insoluble iron precipitates to
the ocean bottom. Here we present a
global model simulation of Aeolian iron input to the ocean, considering
hematite dissolution in mineral dust aerosols catalyzed by nitric and sulfuric
acids. Our model suggests that atmospheric
deposition of soluble iron to the oceans is much larger than previous model
results in high nitrate low chlorophyll (HNLC) regions.
Author's Names: S.-M. Fan, W. J. Moxim, and H. Levy II
Filesize: 482.29 Kb
Added on: 05-Aug-2005 Downloads: 69
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ANALYSIS, INTEGRATION AND MODELING OF THE EARTH SYSTEM: INTEGRATING HUMAN PROCESSES WITH ...
Description: There is a growing recognition that the Earth itself
is a single system within which the biosphere is an active component. Human
activities are now so pervasive and profound in their consequences that they
affect the Earth at a global scale in complex, interactive and apparently
accelerating ways. The new IGBP project, Analysis, Integration and Modeling of
the Earth System (AIMES) is charged with integrating human processes with Earth
system processes.
Author's Names: K.A. Hibbard and D.S. Schimel
Filesize: 12.08 Kb
Added on: 29-Jul-2005 Downloads: 49
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ASSESSMENT OF WINTER FLUXES OF CO2 AND CH4 IN BLACK SPRUCE FOREST SOILS OF CENTRAL ...
Description:
This
research was carried out to estimate the winter fluxes of CO2 and CH4
by the concentration
profile method (indirect) and the chamber method (direct) at black spruce
forest soils of central Alaska during the winter 2004/5. The average winter
fluxes of CO2 and CH4 by the indirect and direct methods
were 0.24±0.06 (SE; standard error) and 0.21±0.06 gCO2-C/m2/d,
and 21.4±5.6 and 21.4±14 µgCH4-C/m2/h, respectively. The fluxes estimated by two methods are not a
significant difference based on a one-way ANOVA with a 95% confidence
level. The winter CO2 flux
corresponds to 30% of the annual CO2 emitted from Alaskan black
spruce forest soils. The average winter
emissions of CO2 and CH4 were 49±13 gCO2-C/m2
and 4.5±3.0 mgCH4-C/m2, respectively. This suggests that the winter emissions of CO2
and CH4 are an important part of the annual carbon budget in
seasonally snow-covered terrain.
Author's Names: Yongwon Kim, Masa Ueyama, Noriyuki Tanaka, et al
Filesize: 50.11 Kb
Added on: 01-Aug-2005 Downloads: 65
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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
Filesize: 25.84 Kb
Added on: 29-Jul-2005 Downloads: 130
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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
Filesize: 92.29 Kb
Added on: 27-Jul-2005 Downloads: 44
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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
Filesize: 84.50 Kb
Added on: 04-Aug-2005 Downloads: 41
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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
Filesize: 71.47 Kb
Added on: 03-Aug-2005 Downloads: 46
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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
Added on: 08-Aug-2005 Downloads: 54
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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
Filesize: 71.56 Kb
Added on: 28-Jul-2005 Downloads: 47
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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
Filesize: 48.86 Kb
Added on: 08-Aug-2005 Downloads: 50
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