Sea ice in the Arctic Ocean: Role of shielding and consumption of methane

Sources and sinks of methane, one of the most important greenhouse gases, have attracted intensive attention due to its role in global warming. We show that sea ice in the Arctic Ocean regulates methane level through two mechanisms, shielding of methane emission from the ocean, and consumption of methane. Using a static chamber technique, we estimated that the methane flux from under-ice water was 0.56 mg(CH4) m(-2) d(-1) on average in central Arctic Ocean, relatively higher than that in other oceans, indicating considerable methane storage in this region under sea ice. Average methane flux on under-ice water was higher than that above sea ice, which suggests that sea ice could limit methane emission. In addition, negative fluxes on sea ice suggest that there are methane consuming processes, which are possibly associated with both photochemical and biochemical oxidation. Our results provide a general understanding about how sea ice in Arctic affects regional and global methane balance. (C) 2012 Elsevier Ltd. All rights reserved.