04 Jan 2023
04 Jan 2023
Status: this preprint is open for discussion.

Sudden, local temperature increase above the continental slope in the Southern Weddell Sea, Antarctica

Elin Darelius1, Vår Dundas1, Markus Janout2, and Sandra Tippenhauer2 Elin Darelius et al.
  • 1Geophysical Institute, University of Bergen and the Bjerknes Centre for Climate Research, Bergen, Norway
  • 2Alfred Wegener Institute, Bremerhafen, Germany

Abstract. Around most of Antarctica, the Circumpolar Deep Water (CDW) shows a warming trend. At the same time, the thermocline is shoaling, thereby increasing the potential for CDW to enter the shallow continental shelves and ultimately increase basal melt in the ice shelf cavities that line the coast. Similar trends, on the order of 0.05 °C and 30 m per decade, have been observed in the Warm Deep Water (WDW), the slightly cooled CDW derivative found at depth in the Weddell Sea. Here we report on a sudden, local increase in the temperature maximum of the WDW above the continental slope north of the Filchner Trough (25–40° W), a region identified as a hotspot for potential changes in the flow of WDW towards the large Filchner-Ronne Ice Shelf. A combination of new and historical Conductivity-Temperature-Depth profiles and mooring records show that, starting in late 2019, the temperature of the warm water core increased by about 0.1 °C over the upper part of the slope (700–2750 m depth). The increased temperature of the WDW is accompanied by an unprecedented (in observations) freshening of about 0.1 g kg-1 in the overlying Winter Water. Mooring records from the continental shelf further south, in the inflow pathway, do not show increased temperatures during the same period, suggesting that factors other than the WDW core temperature over the slope determine the variability in the heat content on the shelf.

Elin Darelius et al.

Status: open (until 01 Mar 2023)

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Elin Darelius et al.

Elin Darelius et al.


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Short summary
Antarctica's ice shelves are melting from below as ocean currents bring warm water into the ice shelf cavities. The melt rates of the large Filchner-Ronne Ice Shelf in the southern Weddell Sea are currently low, as the water in the cavity is cold. Here we present data from a scientific cruise to the region in 2021 and show that the warmest water at the upper part of the continental slope is now about 0.1 °C warmer than in previous observations, while the surface water is fresher than before.