Episodic Bottom Warming, Mixing and Temperature Variability on the Laptev Sea Shelf

This contribution highlights the strong temperature variability and the unique hydrographic nature of the Laptev Sea shelf, based on a multi-year mooring record (2007-2014) and satellite imagery. This Arctic shelf is a key region for river runoff, sea ice formation and export and includes submarine permafrost and methane deposits, which emphasizes the need to understand the thermal variability near the seafloor. Recent years were characterized by early ice retreats and a warming near-shore environment. However, a warming trend was not observed on the deeper shelf until year-round under-ice measurements recorded unprecedented warm bottom waters of +0.6°C for several months in winter 2012/2013. Conditions leading to the bottom water warming included winds favorable for early ice retreat coupled with an offshore transport of warm Lena River water and mixing by winds and tides. Based on our recent records, we discuss the processes that dominate the hydrographic variability on this Arctic shelf. A particular emphasis will be put on mixing mechanisms, spatial variability in stratification and mixing across the shelf, as well as transport of shelf-modified waters across the Eurasian continental slope.