Thawing coastal and subsea permafrost and collapsing shallow methane hydrates could potentially add carbon dioxide and methane to the atmosphere this century, yet there is presently poor understanding of these systems and processes. We need to increase our understanding of the sizes of vulnerable pools of old organic matter and methane, of release processes and of the fate processes of released carbon components in order to better predict the trajectory of future remobilization and potential releases to the ocean and the atmosphere.

The aims of SWERUS-C3 were to investigate the present and historical connections between climate, cryosphere and carbon (C3) in the East Siberian Arctic Ocean (figure 1). Several sub-projects have focused on the sources, mechanisms and magnitudes of the methane released from the subsea permafrost, shelf hydrates and slope hydrates.

The investigations were focused to the inaccessible East Siberian Arctic Shelf and upper slope systems (figure 2) as this is the location of (1) majority of coastal ice complex deposit, known as Yedoma, draping thousands of km of coastline; (2) >80% of the World’s subsea permafrost; (3) 80% of the World ocean shallow hydrates, and (4) an underlying “petroleum megapool” that may contribute to methane releases through a failing subsea permafrost lid.

A wide breadth of state-of-the-art techniques were employed to continuously monitor and observe the composition of the sediments, the seawater and the overlying atmosphere.  Additionally, 57 oceanographic stations were taken during Leg 1 of SWERUS-C3 (figure 2).

The expedition was successfully executed and all desired study areas and system components were observed and sampled.  Analyses of these observations and collected samples will likely provide new fundamental insights of the climate-cryosphere-carbon system interactions in an absolute key region of the Earth System – the East Siberian Arctic Ocean.