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.