Cooling and Freshening of the West Spitsbergen Current by Shelf‐Origin Cold Core Lenses. Issue 11 (19th November 2018)

• Record Type: Journal Article
• Authors: Koenig, Zoé; Meyer, Amelie; Provost, Christine; Sennéchael, Nathalie; Sundfjord, Arild; Beguery, Laurent; Athanase, Marylou; Gascard, Jean‐Claude
• Is Part Of: Journal of geophysical research. Volume 123:Issue 11(2018)
• Page Start: 8299
• Page End: 8312
• Publication Date: 2018-11-19
• Subjects: glider -- West Spitsbergen Current -- Arctic Ocean -- cooling and freshening -- lenses -- shelf/slope exchanges; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2018JC014463
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: 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 10‐km diameter) of cold (less than 3.8 °C) and fresh (less than 35.2 g/kg) waters in the core of the WSC, coming from the shelf and contributing to its cooling and freshening. Data show 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 onto the shelf in winter. Weak and/or northerly winds allow modified Atlantic Water 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. Plain Language Summary: The West Spitsbergen Current (WSC), which flows northward along the western Svalbard slope, carrying warm, high‐salinity Atlantic Water (AW), is a main source of heat and salt to the Arctic Ocean. It cools and freshens as it flows northward. We present observations from a SeaExplorer glider deployed in July 2017 for 14 days in the WSC around 79°N. They document small lenses (less than 10 km) of cold and fresh waters from the shelf in the core of the WSC (about 250‐m depth). Water from the Svalbard shelf cascades to the bottom of the slope. Cold and fresh lenses detached from the bottom of the slope. The presence of these lenses from the shelf is related with the wind regime. Strong southerly winds cause upwelling of the warm AW onto the shelf in winter. Weak and/or northerly winds allow modified AW on the shelf to cascade down the slope, leading to lenses of colder and fresher water protruding into the WSC. If lenses were common, they could be contributing significantly to the cooling and freshening of the WSC. Key Points: A SeaExplorer glider made six sections across the West Spitsbergen Current (WSC) at 78.5‐79 degrees north in the Arctic Cold and fresh small‐core lenses originating from the Svalbard shelf, observed in the core of the WSC contribute to the cooling of the WSC Shelf waters flow to bottom of the slope through diapycnal displacement and detached in lenses through isopycnal displacement