Heterogeneous CO<sub>2</sub> and CH<sub>4</sub> content of glacial meltwater from the Greenland Ice Sheet and implications for subglacial carbon processes
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Published:2021-04-01
Issue:3
Volume:15
Page:1627-1644
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ISSN:1994-0424
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Container-title:The Cryosphere
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language:en
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Short-container-title:The Cryosphere
Author:
Pain Andrea J., Martin Jonathan B., Martin Ellen E., Rennermalm Åsa K., Rahman ShailyORCID
Abstract
Abstract. Accelerated melting of the Greenland Ice Sheet has
increased freshwater delivery to the Arctic Ocean and amplified the need to
understand the impact of Greenland Ice Sheet meltwater on Arctic greenhouse
gas budgets. We evaluate subglacial discharge from the Greenland Ice Sheet
for carbon dioxide (CO2) and methane (CH4) concentrations and
δ13C values and use geochemical models to evaluate subglacial
CH4 and CO2 sources and sinks. We compare discharge from southwest
(a sub-catchment of the Isunnguata Glacier, sub-Isunnguata, and the Russell
Glacier) and southern Greenland (Kiattut Sermiat). Meltwater CH4
concentrations vary by orders of magnitude between sites and are saturated
with respect to atmospheric concentrations at Kiattut Sermiat. In contrast,
meltwaters from southwest sites are supersaturated, even though oxidation
reduces CH4 concentrations by up to 50 % during periods of low
discharge. CO2 concentrations range from supersaturated at
sub-Isunnguata to undersaturated at Kiattut Sermiat. CO2 is consumed by
mineral weathering throughout the melt season at all sites; however,
differences in the magnitude of subglacial CO2 sources result in
meltwaters that are either sources or sinks of atmospheric CO2. At the
sub-Isunnguata site, the predominant source of CO2 is organic matter
(OM) remineralization. However, multiple or heterogeneous subglacial
CO2 sources maintain atmospheric CO2 concentrations at Russell but
not at Kiattut Sermiat, where CO2 is undersaturated. These results
highlight a previously unrecognized degree of heterogeneity in greenhouse
gas dynamics under the Greenland Ice Sheet. Future work should constrain the
extent and controls of heterogeneity to improve our understanding of the
impact of Greenland Ice Sheet melt on Arctic greenhouse gas budgets, as well
as the role of continental ice sheets in greenhouse gas variations over
glacial–interglacial timescales.
Funder
National Science Foundation
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Water Science and Technology
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