Heterogeneous CO 2 and CH 4 content of glacial meltwater from the Greenland Ice Sheet and implications for subglacial carbon processes

Pain, Andrea J.; Martin, Jonathan B.; Martin, Ellen E.; Rennermalm, Åsa K.; Rahman, Shaily

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 (COinline-formula2) and methane (CHinline-formula4) concentrations and inline-formulaδ13C values and use geochemical models to evaluate subglacial CHinline-formula4 and COinline-formula2 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 CHinline-formula4 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 CHinline-formula4 concentrations by up to 50 % during periods of low discharge. COinline-formula2 concentrations range from supersaturated at sub-Isunnguata to undersaturated at Kiattut Sermiat. COinline-formula2 is consumed by mineral weathering throughout the melt season at all sites; however, differences in the magnitude of subglacial COinline-formula2 sources result in meltwaters that are either sources or sinks of atmospheric COinline-formula2. At the sub-Isunnguata site, the predominant source of COinline-formula2 is organic matter (OM) remineralization. However, multiple or heterogeneous subglacial COinline-formula2 sources maintain atmospheric COinline-formula2 concentrations at Russell but not at Kiattut Sermiat, where COinline-formula2 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.

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Pain, Andrea J. / Martin, Jonathan B. / Martin, Ellen E. / et al: Heterogeneous CO2 and CH4 content of glacial meltwater from the Greenland Ice Sheet and implications for subglacial carbon processes. 2021. Copernicus Publications.

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Rechteinhaber: Andrea J. Pain et al.

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