Ancient thermokarst and gas hydrate in the Kara Sea

Outline Here we study numerous cupshaped structures, discovered under the seafloor in the South Kara Sea. These structures (we call them Ushape structures) occur in the bedrocks and reach up to 100 m deep. We reckon that they are ancient analogs of modern thermokarst landscapes, common for yedoma (permafrost) regions in the Arctic. We suppose that similarly to modern thermokarst, Ushape structures may preserve a significant amount of organic carbon. Therefore, they constitute a discrete shallow carbon po