Subsurface floats in the Filchner Trough provide the first direct under-ice tracks of the circulation on shelf

• Published in: Ocean science 2024-10, Vol.20 (5), p.1267-1280
• Main Authors: Sallée, Jean-Baptiste, Vignes, Lucie, Minière, Audrey, Steiger, Nadine, Pauthenet, Etienne, Lourenco, Antonio, Speer, Kevin, Lazarevich, Peter, Nicholls, Keith W
• Format: Article
• Language: English
• Subjects: Bottom water; Circulation; Cold; Cold flow; Continental shelves; Deep water; Depth profiling; Drifters; Floats; Heat; Hydrography; Ice cover; Ice formation; Ice sheets; Ice shelves; Icebergs; Inflow; Land ice; Mooring; Ocean circulation; Sampling methods; Sciences of the Universe; Sea ice; Shelf dynamics; Subsurface drifters; Temperature; Tracks (paths); Warm water; Water; Water masses; Water temperature
• ISSN: 1812-0792; 1812-0784; 1812-0792
• DOI: 10.5194/os-20-1267-2024

Bottom water formation in the Weddell Sea and mass loss from the Filchner–Ronne Ice Shelf are tightly linked by the supply of Warm Deep Water to the continental shelf. Heavy sea ice cover and icebergs restrict ship access and upper-ocean measurements by moorings, compelling us to try new sampling methods. We present results from the first dedicated under-sea-ice float experiment tracking circulation on the continental shelf of the eastern Weddell Sea. Seven Apex profiling floats were deployed in 2017 at three different locations on the eastern Weddell Sea continental shelf, targeting the inflowing modified Warm Deep Water (mWDW), as well as the outflowing Ice Shelf Water (ISW). The floats capture a warm mWDW regime with southward inflow over the eastern continental shelf and a cold ISW regime with a recirculation of ISW in the Filchner Trough throughout the 4 years of observations. We provide the first Lagrangian in situ confirmation that the mWDW flowing onto the continental shelf follows two pathways: the eastern flank of the Filchner Trough and a small trough on the shallow shelf farther east. In the present circulation regime, this warm water is blocked from reaching the ice shelf cavity due to the presence of the thick ISW layer inside the Filchner Trough. The floats' trajectories and hydrography reveal the dynamically active front, flow reversal, and eddying motion between these two water masses along the eastern flank of the Filchner Trough.