The ocean beneath the Fimbul Ice Shelf is cold

The measurements that was done the borehole through the Fimbul Ice Shelf last Sunday shows that the water under the ice shelf is very close to the freezing point. The relatively warm deep water found over the continental slope does not seem to penetrate into the cavity beneath the ice shelf.

Instruments attached to the cabel

Ole Anders Nøst attaches temperature sensors to the cable as it is lowered into the borehole. Photo: Lars Henrik Smedsrud

This situation seems to be stable, suggesting that the melting under the ice shelf does not increase. This also indicates that the existing models for exchange between the ice shelf cavity and the open should be improved.

We observed a roughly 50 meter deep layer of water with temperatures very close to the freezing point, about -2.05 degrees, just beneath the ice shelf. The highest observed temperature was about -1.83 degrees close to the bottom. The temperatures are very similar to temperature data collected by elephant seals in 2008 and by British Antarctic Survey using an autosub below the ice shelf in 2005.

We collected three profiles from the underside of the ice to the seabed at 653 meters below sealevel. No trace of the relatively warm deep water that upwells over the continental slope was found. It will be exciting to see if this is the situation all year round, says Ole Anders Nøst.

Models of the ocean circulation in the area show warm deep water flowing in under the ice shelves. As this is not observed, the models are most likely wrong and should be improved. This is an important step towards an understanding of the processes under the Fimbul Ice Shelf.

It was Sunday December 6th that the Fimbul expedition from the Norwegian Polar Institute hot water drilled their first hole in the Fimbul Ice Shelf, Dronning Maud Land, Antarctica. They observed temperature profiles in the ocean beneath and lowered down permanent instrumentation that will monitor the ocean circulation and ice temperatures in the years to come. 

The expedition also includes a group of glaciologists which at the moment is on a traverse further south on the ice shelf. They measure parameters like snow accumulation and ice velocities as well as ice shelf basal melting. When these data is combined with the oceanographic data the researchers hope to come up with a good estimate of the mass balance of the ice shelf.