Cooling and freshening of the West Spitsbergen Current by shelf-origin cold core lenses
The West Spitsbergen Current (WSC) cools and freshens as it flows northward along the western Svalbard shelf. The cooling takes place at the ocean surface through interaction with the atmosphere, and also in subsurface. We present observations with high horizontal resolution (around 2 km) from a SeaExplorer glider deployed in July 2017 for 14 days in the WSC offshore Kongsfjorden around 79°N. They document small lenses (less than 10km diameter) of cold (less than 3.8°C) and fresh (less than 35.2g/kg) waters in the core of the WSC, coming from the shelf and contributing to its cooling and freshening. Data shows that water from the shelf cascades to the bottom of the slope and then detaches on the offshore side of the WSC core where it is baroclinically unstable. The presence of these lenses from the shelf can be related to the wind regime. Strong southerly winds cause upwelling of the warm Atlantic Water (AW) onto the shelf in winter. Weak and/or northerly winds allow modified AW formed by mixing with cold waters on the shelf to cascade down the slope, leading to lenses of colder and fresher water protruding into the WSC. If lenses are common in the WSC, they could be contributing significantly to its cooling and freshening especially in summer when the influence of the atmosphere on the cooling of the WSC is less important.