Structure and transport of Atlantic water north of Svalbard from observations in summer and fall 2018

The transport of warm Atlantic waters north of Svalbard is one of the major heat and salt sources to the Arctic Ocean. The circulation pathway and the associated heat transport influence the variability in the Arctic sea ice extent and the onset of freezing. We present observations obtained from research cruises and autonomous underwater glider missions in summer and fall 2018 to describe the hydrographic structure, volume transport rates and circulation patterns of the warm boundary current between 12E and 24E north of Svalbard.

A composite section is constructed along a representative, average bathymetry across the shelf break, using all available observations in order to obtain the hydrographic structure and the absolute geostrophic transport of the boundary current. The Atlantic water volume transport reaches a maximum of 3.0 ± 0.2 Sv in October, with an intraseasonal variability of 1 Sv. During summer and late fall, we observed Atlantic water flowing eastward (a counter current), in the outer part of the section away from the shelf break, in the Sofia Deep. The intensity of the Atlantic water counter current and the Atlantic water boundary current are very sensitive to the wind stress curl: we observed a near doubling of the volume transport in less than a week.

The composite section also reveals a bottom-intensified current flowing parallel to the boundary current, between the 1500 m and 2000 m isobaths. A composite of all historical data collected in the region, constructed identical to our observations, support the presence of the bottom intensified current.