Ancient thermokarst and gas hydrate in the Kara Sea

Outline Here we study numerous cup-shaped structures, discovered under the seafloor in the South Kara Sea. These structures (we call them U-shape 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, U-shape structures may preserve a significant amount of organic carbon. Therefore, they constitute a discrete shallow carbon po