Occurrence of Ice-Bonded Sediments in the Mackenzie Trough, Beaufort Sea

The Arctic continental shelves experienced subsea permafrost degradation because of the long-term warming and sea level rise since the Last Glacial Maximum (LGM), when the sea level was ~100 m lower than its present level. However, the current status of the subsea permafrost limit is not yet clearly defined due to a lack of evidence. New subbottom profiling and subsurface temperatures were acquired to examine the subsea permafrost limit on the eastern slope of the Mackenzie Trough during Korean Icebreaker R/V Araon expeditions in the summer of 2013 and 2014. We found anomalous subbottom acoustic features indicating ice-bonded sediments where cold bottom water and a subsurface with subzero temperature exists. The cold bottom water belongs to the Arctic halocline. We conclude that with help from cold Arctic halocline, ice-bonded sediments can exist at shallow water depths of <100 m. We argue that they are relict subsea permafrost from the LGM, but further investigation is required to clarify their origin. Our conclusion implies that ice-bonded sediments can occur at shallow water depths over the Arctic continental shelves and that their fate depends on the temperature change in seawater.