Abstract
AbstractThe transport of warm Atlantic Waters north of Svalbard is one of the major heat and salt sources to the Arctic Ocean. The circulation pathways and the associated heat transport influence the variability in the Arctic sea ice extent, the onset of freezing, and marine ecosystems. We present observations obtained from research cruises and an autonomous underwater glider mission in summer and fall 2018, to describe the hydrographic structure, volume transport, and circulation patterns of the warm Atlantic Water Boundary Current between 12°E and 24°E north of Svalbard. The Atlantic Water volume transport reaches a maximum of 3.0 ± 0.2 Sv in October, with an intraseasonal variability of 1 Sv (1 Sv = 106 m3 s−1). During summer and late fall, we observed an Atlantic Water recirculation flowing westward (0.1–0.2 Sv) in the outer part of the section away from the shelf break. This counter current appears to be a part of an anticyclonic circulation in the Sofia Deep. The strength of the Atlantic Water recirculation and the Atlantic Water boundary current is very sensitive to the wind stress curl: The boundary current volume transport doubled in less than a week, corresponding to a transition from strongly negative (−10−6 N m−3) to strongly positive (10−6 N m−3) wind stress curl over the Sofia Deep. A previously unknown, deep bottom‐intensified current is observed to flow parallel to the boundary current, between the 1,500 and 2,000 m isobaths. Historical data in the region support the presence of the bottom‐intensified current.
Highlights
In a time of decreasing sea ice volume and increasing atmospheric and oceanic temperatures in the Arctic region, understanding the processes controlling the warm water inflow into the Arctic Ocean is becoming increasingly important (Carmack et al, 2015; Polyakov et al, 2017)
We present observations obtained from research cruises and an autonomous underwater glider mission in summer and fall 2018, to describe the hydrographic structure, volume transport, and circulation patterns of the warm Atlantic Water Boundary Current between 12°E and 24°E north of Svalbard
We presented the data as synoptic sections, composite sections, and depth‐averaged currents in order to resolve short‐term variability, intraseasonal variability, and general circulation
Summary
In a time of decreasing sea ice volume and increasing atmospheric and oceanic temperatures in the Arctic region, understanding the processes controlling the warm water inflow into the Arctic Ocean is becoming increasingly important (Carmack et al, 2015; Polyakov et al, 2017). The West Spitsbergen current (WSC), located on the eastern continental slope in Fram Strait (Figure 1a), is considered the major oceanic heat source to the Arctic Ocean (Aagaard et al, 1987). The AW distribution and circulation in Fram Strait are complex, including multiple branches and recirculation paths (Hattermann et al, 2016; Manley, 1995; Marnela et al, 2013; von Appen et al, 2016). The outer part of WSC recirculates, joining the East Greenland Current (Hattermann et al, 2016; Marnela et al, 2013; von Appen et al, 2016).
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