FOR the first time, satellites have peered down through a few kilometres of Antarctic ice to measure the heat radiating up from the Earth鈥檚 crust under the icy continent. This heat map will help us understand how ice sheets and glaciers move as the ice melts at their base. It may even uncover subglacial lakes and volcanoes.
Cathrine Fox Maule of the Center for Planetary Science in Copenhagen, Denmark, and her colleagues created the map with the help of magnetic field measurements taken by the Oersted and CHAMP satellites. Above a certain temperature most rocks undergo a change from non-magnetic to paramagnetic. So the magnetic state of the rocks below the ice reveals how temperature varies with depth.
The heat map covers all of Antarctica at a resolution of about 300 kilometres. Team member Michael Purucker of NASA鈥檚 Goddard Space Flight Center in Greenbelt, Maryland, says that hotspots on the map suggest the presence of a previously unknown active volcanic region under the ice, just inland from the Ronne ice shelf, one of Antarctica鈥檚 many ice sheets. If the volcanoes were to erupt, they could 鈥渃ause cataclysmic failure of a local part of the ice sheet鈥�, Purucker says. New satellites planned for launch in 2009 could watch for such changes.
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