Newly discovered source of heat contributes to Antarctic melting

Sun-heated surface water contributes towards melting under ice shelves in Dronning Maud Land.

Researcher Tore Hattermann and electrician Johan Hustadnes have recently dug up data that have been stored in the Antarctic ice.

Researcher Tore Hattermann and electrician Johan Hustadnes have recently dug up data that have been stored in the Antarctic ice. Photo: Stein Tronstad / Norwegian Polar Institute

Doing research on the Fimbul Ice Shelf.

Doing research on the Fimbul Ice Shelf. Photo: Lars Henrik Smedsrud

The Fimbul Ice Shelf is within the Norwegian sector Dronning Maud Land in Antarctica.

The Fimbul Ice Shelf is within the Norwegian sector Dronning Maud Land in Antarctica. In November 2009 and 2010 expeditions were mounted to Antarctica to study mass balance within the Fimbul Ice Shelf and melting and circulation in the sea beneath the floating ice. New research results from this expedition have now become available.
  Photo: Elvar Ørn Kjartansson / Norwegian Polar Institue

About half of the melting of the Antarctic ice cap occurs on the underside of ice shelves – floating glaciers several hundred metres thick. Research recently published in Geophysical Research Letters shows that surface water heated by the sun is a crucial source of heat, and contributes to melting in the sea under the Fimbul Ice Shelf in Dronning Maud Land. It was previously known that hot water from the depths also causes the bottom of the ice shelf to melt.

“It came as a surprise to us that warm water from the surface plays such an important role for ice melting in Dronning Maud Land,” says the article’s first author, researcher Tore Hattermann from the Norwegian Polar Institute.
 

Tore Hattermann has been participating in field work at Fimbulisen for three years in a row; he and his colleagues have analysed two years’ worth of data collected from three rigs that were deployed in 2010. When glaciers in Antarctica melt, the sea level rises all around the globe, including the Arctic. Hattermann emphasises that knowledge about the melting of the ice cap is crucial for understanding and predicting changes in sea level.

– “If we wish to understand what will happen to the ice in Antarctica and the future climate, we must understand the interactions between the ongoing changes in the atmosphere and the melting that occurs hundreds of metres below the sea surface,” says Hattermann.

To date, very few measurements of sea temperature have been done under the Antarctic ice shelves. In some places in West Antarctica, there is extremely rapid melting owing to direct contact between the ice and warm water from the ocean depths. In East Antarctica, where the Fimbul Ice Shelf is located, the new measurements show that melting is limited because warm water is in contact with the ice only for part of the year.

The researchers surmise that the amount of warm water that comes in contact with the ice varies depending on the extent of sea ice and wind conditions along the coast of Dronning Maud Land. These new results provide important clues about the processes that control melting along the coast of Dronning Maud Land.

The study is part of the ICE-Fimbul Ice Shelf project and is being carried out by researchers from the Norwegian Polar Institute in collaboration with other research institutes from Norway and abroad.