Heterogeneous CO₂and CH₄Content of Glacial Meltwater From the Greenland Ice Sheet and Implications for Subglacial Carbon Processes

Authors

Andrea J. Pain, University of Florida
Jonathan B. Martin, University of Florida
Ellen E. Martin, University of Florida
Åsa K. Rennermalm, Rutgers University–New Brunswick
Shaily Rahman, University of FloridaFollow

Document Type

Article

Publication Date

4-1-2021

Department

Marine Science

School

Ocean Science and Engineering

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.

Publication Title

Cryosphere

Volume

15

Issue

3

First Page

1627

Last Page

1644

Recommended Citation

Pain, A., Martin, J., Martin, E., Rennermalm, Å., Rahman, S. (2021). Heterogeneous CO₂and CH₄Content of Glacial Meltwater From the Greenland Ice Sheet and Implications for Subglacial Carbon Processes. Cryosphere, 15(3), 1627-1644.
Available at: https://aquila.usm.edu/fac_pubs/18876