Polar Access Fund: Methane Cycling in the Beaufort Sea

Methane emissions in the Arctic region are expected to rise due to thawing permafrost and while they are increasingly studied on land, their marine counterpart is still understudied. The link between marine ecosystem changes, thawing of subsea permafrost and methane emission in the Arctic Ocean is currently insufficiently understood. A planned expedition to the Beaufort Sea on board the Canadian ice breaker R/V Amundsen offers the unique opportunity to collect samples from the water column as well as surface sediments and longer sediment cores (Holocene timescales). The Beaufort Sea shelf has one of the best constrained subsea permafrost distributions on the Arctic shelf and is the only large validated region of thick (> 500 m) subsea permafrost outside of Siberia. However, little is known about permafrost thaw rates below the seafloor and whether CH4 releases are directly related to permafrost distribution or thaw rates observed. A previous study in the Beaufort Sea suggested permafrost methane (differentiated from modern sources with specific radiocarbon, 14C, measurements) only contribute to ~10 % of the methane emitted at the surface of the Beaufort Sea. This observation can be explained by the activity of anaerobic and aerobic methanotrophes which significantly moderate fluxes of dissolved methane. As such it would be exciting to discover which bacterial community is responsible for the methanotrophic activity observed in the Beaufort Sea and how it varied in the Holocene.