A geothermal "hot spot" deep under the Greenland ice sheet is combining with global warming to cause the three kilometre thick slab of ice to melt from below as well as from above.
The melting at the bottom of the ice has caused the formation of a river network with water acting as a lubricant in some areas to help speed up the flow of ice into the North Atlantic .
This is the first confirmation that a geological process deep in the Earth can exert such influence over glacial movement and water release from the ice sheets, said Dr Alan Vaughan, a research associate at Trinity College Dublin.
“It adds uncertainty to what happens as we warm the Earth,” said the structural geologist. “We have to take that into account if we want to predict what will happen in Greenland as the planet warms.”
The hot spot is nothing new and formed as much as three million years ago, says Dr Vaughan, who is co author of a research report published on Monday in Nature Geoscience.
What is going on three kilometres down at the base of the ice sheet has grown in importance given climate change.
“It is as if Greenland was riding over a blowtorch to cause the melting,” he said.
The research team, led by Dr Irina Rogozhina of the GFZ German Research Centre for Geosciences, has measured the size of the hot spot as 1,200km by 400km.
“It has meant that hotter material is at a shallower layer so more heat is passed to the underside of the ice sheet,” Dr Vaughan said.
The ice is melting much faster at the top of the ice sheet, but the bottom of the sheet is of interest because of the action of water at the base.
“There is a big sub-glacial river system and this is increased in the areas of increased heat flow,” he said.
It in turn speeds up the flow of ice towards the coast and into the ocean where it has the potential to raise sea level.
The hot spot has been there for millions of years but was hidden from researchers by the kilometres of ice above it. It has now been defined by the research team and it helps explain the slightly faster transport of ice towards the coast from some areas in the middle of Greenland.
