Cooling of the West Spitsbergen Current: AUV-based turbulence measurements west of Svalbard

The role of turbulence is critical in the redistribution of heat and salt throughout the global ocean, and in boundary currents of the high-latitude oceans in particular. In the Arctic Ocean, warm, saline waters of Atlantic origin, which are carried northwards by the West Spitsbergen Current (WSC), are the largest source of oceanic heat carried into the Arctic Eurasian basin, and may have a significant impact on the rate of sea ice decline. While the rapid down-stream cooling of the WSC around its entry point into the Arctic Ocean is well-known, the processes by which this heat flux occurs are still an area of active research. During a cruise to the Svalbard region in July 2010, a Hydroid REMUS 600m AUV, equipped with a forward-mounted microstructure package, was used to quantify the level of turbulent mixing within and across the shoreward edge of the WSC. The microstructure-equipped AUV was used to measure horizontal profiles of water properties and turbulence parameters while a more-conventional, vertically free-falling microstructure profiler was used to conduct complementary transects of vertical profile measurements across the edge of the WSC. In this study we evaluate the resulting measurements and compare the views of the upper ocean derived from similar sensors mounted on two very different platforms: one view assembled from conventional vertical profiles and the second from horizontal, AUV-based profiles. We discuss the impact of mixing on the cooling of the WSC and the capacity of these platforms to resolve small-scale variability in both the vertical and the horizontal.