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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 34 (2007): L10601, doi:10.1029/2006GL028790.
    Description: Air-water gas transfer influences CO2 and other climatically important trace gas fluxes on regional and global scales, yet the magnitude of the transfer is not well known. Widely used models of gas exchange rates are based on empirical relationships linked to wind speed, even though physical processes other than wind are known to play important roles. Here the first field investigations are described supporting a new mechanistic model based on surface water turbulence that predicts gas exchange for a range of aquatic and marine processes. Findings indicate that the gas transfer rate varies linearly with the turbulent dissipation rate to the inline equation power in a range of systems with different types of forcing - in the coastal ocean, in a macro-tidal river estuary, in a large tidal freshwater river, and in a model (i.e., artificial) ocean. These results have important implications for understanding carbon cycling.
    Description: This research was performed and the manuscript prepared with support from: the National Science Foundation (OCE-03-27256, OCE-05-26677, ATM 01-20569, and DEB-05-32075), the Office of Naval Research Young Investigator Program (N00014-04-1-0621), the Hudson River Foundation (010/02A), NOAA (NA03OAR4320179), the Marie Curie Training Site Fellowship (HPMFCT- 2002-01865), the NERC (NER/B/S/2003/00844), the David and Lucille Packard Foundation, and the LDEO Climate Center.
    Keywords: Air-sea gas exchange ; Turbulent dissipation rate ; Carbon
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 26 (2012): GB0E02, doi:10.1029/2012GB004299.
    Description: While much of the dissolved organic carbon (DOC) within rivers is destined for mineralization to CO2, a substantial fraction of riverine bicarbonate (HCO3−) flux represents a CO2 sink, as a result of weathering processes that sequester CO2 as HCO3−. We explored landscape-level controls on DOC and HCO3− flux in subcatchments of the boreal, with a specific focus on the effect of permafrost on riverine dissolved C flux. To do this, we undertook a multivariate analysis that partitioned the variance attributable to known, key regulators of dissolved C flux (runoff, lithology, and vegetation) prior to examining the effect of permafrost, using riverine biogeochemistry data from a suite of subcatchments drawn from the Mackenzie, Yukon, East, and West Siberian regions of the circumboreal. Across the diverse catchments that we study, controls on HCO3− flux were near-universal: runoff and an increased carbonate rock contribution to weathering (assessed as riverwater Ca:Na) increased HCO3− yields, while increasing permafrost extent was associated with decreases in HCO3−. In contrast, permafrost had contrasting and region-specific effects on DOC yield, even after the variation caused by other key drivers of its flux had been accounted for. We used ionic ratios and SO4 yields to calculate the potential range of CO2 sequestered via weathering across these boreal subcatchments, and show that decreasing permafrost extent is associated with increases in weathering-mediated CO2 fixation across broad spatial scales, an effect that could counterbalance some of the organic C mineralization that is predicted with declining permafrost.
    Description: Funding for this work was provided through NSF-OPP-0229302 and NSF-OPP-0732985. Additional support to S.E.T. was provided by an NSERC Postdoctoral Fellowship.
    Description: 2013-02-21
    Keywords: Arctic ; Bicarbonate ; Dissolved organic carbon ; Permafrost
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2022-05-26
    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 Global Biogeochemical Cycles 30 (2016): 629–643, doi:10.1002/2015GB005351.
    Description: Northern rivers connect a land area of approximately 20.5 million km2 to the Arctic Ocean and surrounding seas. These rivers account for ~10% of global river discharge and transport massive quantities of dissolved and particulate materials that reflect watershed sources and impact biogeochemical cycling in the ocean. In this paper, multiyear data sets from a coordinated sampling program are used to characterize particulate organic carbon (POC) and particulate nitrogen (PN) export from the six largest rivers within the pan-Arctic watershed (Yenisey, Lena, Ob', Mackenzie, Yukon, Kolyma). Together, these rivers export an average of 3055 × 109 g of POC and 368 × 109 g of PN each year. Scaled up to the pan-Arctic watershed as a whole, fluvial export estimates increase to 5767 × 109 g and 695 × 109 g of POC and PN per year, respectively. POC export is substantially lower than dissolved organic carbon export by these rivers, whereas PN export is roughly equal to dissolved nitrogen export. Seasonal patterns in concentrations and source/composition indicators (C:N, δ13C, Δ14C, δ15N) are broadly similar among rivers, but distinct regional differences are also evident. For example, average radiocarbon ages of POC range from ~2000 (Ob') to ~5500 (Mackenzie) years before present. Rapid changes within the Arctic system as a consequence of global warming make it challenging to establish a contemporary baseline of fluvial export, but the results presented in this paper capture variability and quantify average conditions for nearly a decade at the beginning of the 21st century.
    Description: National Science Foundation Grant Numbers: 0229302, 0732985; U.S. Geological Survey; Department of Indian and Northern Affairs
    Description: 2016-11-11
    Keywords: Arctic ; River ; Carbon ; Nitrogen ; Watershed ; Export
    Repository Name: Woods Hole Open Access Server
    Type: Article
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