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  • 1
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    Separating the influence of temperature, drought, and fire on interannual variability in atmospheric CO2 (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Global Biogeochemical Cycles 28 (2014): 1295–1310, doi:10.1002/2014GB004890.
    Description: The response of the carbon cycle in prognostic Earth system models (ESMs) contributes significant uncertainty to projections of global climate change. Quantifying contributions of known drivers of interannual variability in the growth rate of atmospheric carbon dioxide (CO2) is important for improving the representation of terrestrial ecosystem processes in these ESMs. Several recent studies have identified the temperature dependence of tropical net ecosystem exchange (NEE) as a primary driver of this variability by analyzing a single, globally averaged time series of CO2 anomalies. Here we examined how the temporal evolution of CO2 in different latitude bands may be used to separate contributions from temperature stress, drought stress, and fire emissions to CO2 variability. We developed atmospheric CO2 patterns from each of these mechanisms during 1997–2011 using an atmospheric transport model. NEE responses to temperature, NEE responses to drought, and fire emissions all contributed significantly to CO2 variability in each latitude band, suggesting that no single mechanism was the dominant driver. We found that the sum of drought and fire contributions to CO2 variability exceeded direct NEE responses to temperature in both the Northern and Southern Hemispheres. Additional sensitivity tests revealed that these contributions are masked by temporal and spatial smoothing of CO2 observations. Accounting for fires, the sensitivity of tropical NEE to temperature stress decreased by 25% to 2.9 ± 0.4 Pg C yr−1 K−1. These results underscore the need for accurate attribution of the drivers of CO2 variability prior to using contemporary observations to constrain long-term ESM responses.
    Description: This work was supported by the Department of Energy Office of Science Biological and Environmental Research Division, the National Science Foundation Decadal and Regional Climate Prediction using Earth System Models (EaSM) program (NSF AGS 1048890 and AGS 1048827), and NASA Carbon Cycle Science (NASA NNX11AF96G). G.K.A. acknowledges a NOAA Climate and Global Change postdoctoral fellowship. J.B.M. and E.J.D. thank NOAA's Climate Program Office's Atmospheric Chemistry, Carbon Cycle, and Climate (AC4) program for support
    Keywords: Carbon cycle ; Climate variability ; Drought ; Fire ; Terrestrial ecosystems ; Atmospheric CO2
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Climate forcing for dynamics of dissolved inorganic nutrients at Palmer Station, Antarctica : an interdecadal (1993–2013) analysis (2016)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 121 (2016): 2369–2389, doi:10.1002/2015JG003311.
    Description: We analyzed 20 years (1993–2013) of observations of dissolved inorganic macronutrients (nitrate, N; phosphate, P; and silicate, Si) and chlorophyll a (Chl) at Palmer Station, Antarctica (64.8°S, 64.1°W) to elucidate how large-scale climate and local physical forcing affect the interannual variability in the seasonal phytoplankton bloom and associated drawdown of nutrients. The leading modes of nutrients (N, P, and Si empirical orthogonal functions 1, EOF1) represent overall negative anomalies throughout growing seasons, showing a mixed signal of variability in the initial levels and drawdown thereafter (low-frequency dynamics). The second most common seasonal patterns of nitrate and phosphate (N and P EOF2) capture prolonged drawdown events during December–March, which are correlated to Chl EOF1. Si EOF2 captures a drawdown event during November–December, which is correlated to Chl EOF2. These different drawdown patterns are shaped by different sets of physical and climate forcing mechanisms. N and P drawdown events during December–March are influenced by the winter and spring Southern Annular Mode (SAM) phase, where nutrient utilization is enhanced in a stabilized upper water column as a consequence of SAM-driven winter sea ice and spring wind dynamics. Si drawdown during November–December is influenced by early sea ice retreat, where ice breakup may induce abrupt water column stratification and a subsequent diatom bloom or release of diatom cells from within the sea ice. Our findings underscore that seasonal nutrient dynamics in the coastal WAP are coupled to large-scale climate forcing and related physics, understanding of which may enable improved projections of biogeochemical responses to climate change.
    Description: U.S. National Science Foundation Grant Numbers: OPP-9011927, 9632763, 0217282, 0823101, GEO-PLR 1440435; NASA ROSES Grant Number: NNX14AL86G
    Description: 2017-03-17
    Keywords: Nutrient drawdown ; Phytoplankton bloom ; Climate variability ; Western Antarctic Peninsula ; Palmer LTER ; Biogeochemistry
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
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    Seasonal forcing of summer dissolved inorganic carbon and chlorophyll a on the western shelf of the Antarctic Peninsula (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 115 (2010): C03024, doi:10.1029/2009JC005267.
    Description: The Southern Ocean is a climatically sensitive region that plays an important role in the regional and global modulation of atmospheric CO2. Based on satellite-derived sea ice data, wind and cloudiness estimates from numerical models (National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis), and in situ measurements of surface (0–20 m depth) chlorophyll a (ChlSurf) and dissolved inorganic carbon (DICSurf) concentration, we show sea ice concentration from June to November and spring wind patterns between 1979 and 2006 had a significant influence on midsummer (January) primary productivity and carbonate chemistry for the Western Shelf of the Antarctic Peninsula (WAP, 64°–68°S, 63.4°–73.3°W). In general, strong (〉3.5 m s−1) and persistent (〉2 months) northerly winds during the previous spring were associated with relatively high (monthly mean 〉 2 mg m−3) ChlSurf and low (monthly mean 〈 2 mmol kg−1) salinity-corrected DIC (DICSurf*) during midsummer. The greater ChlSurf accumulation and DICSurf* depletion was attributed to an earlier growing season characterized by decreased spring sea ice cover or nearshore accumulation of phytoplankton in association with sea ice. The impact of these wind-driven mechanisms on ChlSurf and DICSurf* depended on the extent of sea ice area (SIA) during winter. Winter SIA affected phytoplankton blooms by changing the upper mixed layer depth (UMLD) during the subsequent spring and summer (December–January–February). Midsummer DICSurf* was not related to DICSurf* concentration during the previous summer, suggesting an annual replenishment of surface DIC during fall/winter and a relatively stable pool of deep (〉200 m depth) “winter-like” DIC on the WAP.
    Description: This research was supported by NSF OPP grants 0217282 to HWD at the Virginia Institute of Marine Science and 0823101 to HWD at the MBL.
    Keywords: Climate variability ; Antarctica ; Carbonate system
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
    Format: text/plain
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