Methane release from open leads and new ice following an Arctic winter storm event

Abstract

We examine an Arctic winter storm event, which led to ice break–up, the formation of open leads, and the subsequent freezing of these leads. The methane (CH4) concentration in under–ice surface water before and during the storm event was 8–12 nmol L−1, which resulted in a potential sea–to–air CH4 flux ranging from +0.2 to +2.1 mg CH4 m−2 d−1 in open leads. CH4 ventilation between seawater and atmosphere occurred when both open water fraction and wind speed increased. Over the nine days after the storm, sea ice grew 27 cm thick. Initially, CH4 concentrations in the sea ice brine were above the equilibrium with the atmosphere. As the ice grew thicker, most of the CH4 was lost from upper layers of sea ice into the atmosphere, implying continued CH4 evasion after the leads were ice–covered. This suggests that wintertime CH4 emissions need to be better constrained.