Physical Oceanography

Filchner Overflow

The plume of cold, dense Ice Shelf Water flowing out from the Filchner Ronne Ice Shelves in the southwestern Weddell Sea, Antarctica, and over the sill of the Filchner Depression was discovered in 1977 by Arne Foldvik and Tor Gammelsrød, both researchers from GFI.

Elin Darelius

Main content

The outflow descends the continental slope and contributes to the formation of Antarctic Bottom Water, a watermass found at the bottom of most of the world’s ocean. The overflowing Ice Shelf Water (ISW) has a temperature below the surface freezing point (-1.9C) and it is hence potentially super cooled, meaning that it would freeze to ice if it was raised to the surface.  Since cold water is more compressible than warm (the thermobaric effect), the low temperature of the ISW helps it descend the continental slope to the bottom of the slope.

Current and temperature records from moorings deployed in the plume region show high mesoscale variability and intense oscillations with periods between 1.5 and 6 days, likely related to eddies formed in the plume. Eddies are often observed to be generated in dense plumes, and they will affect e.g. plume mixing and descent rate.  

Part of the Filchner Overflow is steered downslope by a submarine ridge crossing the continental slope.

The dense overflow is now continuously monitored by a mooring at the sill.

Elin Darelius
Svein Østerhus
Ilker Fer
Tor Gammelsrød

Projects: WEDDELL