Preprints
https://doi.org/10.5194/tc-2020-208
https://doi.org/10.5194/tc-2020-208

  26 Aug 2020

26 Aug 2020

Review status: this preprint is currently under review for the journal TC.

Methane cycling within sea ice; results from drifting ice during late spring, north of Svalbard

Josefa Verdugo1,2, Ellen Damm1, and Anna Nikolopoulos3 Josefa Verdugo et al.
  • 1Alfred-Wegener-Institute, Helmholtz-Centre for Polar and Marine Research, Bremerhaven, 27570, Germany
  • 2University of Bremen, Faculty 2 Biology/Chemistry, Bremen, 28359, Germany
  • 3Institute of Marine Research, P.O. Box 1870 Nordnes, Bergen, 5817, Norway

Abstract. Summer sea ice-cover in the Arctic Ocean has declined sharply during the last decades, leading to changes in ice structures. The shift from thicker multi-year ice to thinner first-year ice changes the methane storage transported by sea ice into remote areas far away from the sea ice’s origin. As significant amounts of methane are stored in sea ice, minimal changes in the ice structure may have a strong impact on the fate of methane when ice melts. Hence, the type of sea ice is an important indicator of modifications to methane pathways. Our study is based on the combined sample analyses of methane concentration and its isotopic composition coupled with measurements of nutrient concentrations and physical variables performed on a drifting ice floe, as well as in the traversed water in late spring 2017, north of Svalbard. We report on different storage capacities of methane within first-year ice and rafted/ridged ice, as well as methane super-saturation in the seawater during the drifting time. We show that the ice type/structures determine the fate of methane during the early melt season and that methane released into seawater is a predominant pathway. Thereafter, the pathway of methane in seawater is subjected to oceanographic processes. We point to sea ice as a potential source of methane super-saturation in Polar Surface Water.

Josefa Verdugo et al.

 
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Josefa Verdugo et al.

Josefa Verdugo et al.

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Short summary
We show that the ice structures determine the fate of methane during the early melt season and that sea ice may act as a sink of methane when methane oxidation occurs in specific layers of thick and complex sea ice. In spring, when ice melt starts, sea ice methane-released into the ocean is the favored pathway. We suggest that changes in ice cover are thus likely to change the methane pathways in the Arctic Ocean and sea ice as a potential source of methane super-saturation in surface waters.