The Heat Is Online

Antarctic Thaw Moves Inland

Snowmelt in Antarctica Creeping Inland Sept. 24, 2007


Antarctica's once fringe-thawing is moving well inland, say scientists who have studied water-sensitive microwave satellite data spanning the years 1987 to 2006.


The worst melting happened in the summer of 2004-2005, with snow and ice melting in unlikely places, the researchers report.


"2005 was an extreme event," said Marco Tedesco of NASA's Goddard Space Flight Center. Records of surface temperatures confirm that it was an unusually warm year at the bottom of the world, as well as one of the warmest years on record for Earth.


Water melt was spotted as far as 500 miles inland and at elevations of more than 5,500 feet in the Transantarctic Mountains, Tedesco told Discovery News.


The secret to detecting melting ice from space is looking for the marked increase in natural microwave emissions from water, Tedesco explained. Day or night, water naturally cools by emitting infrared and microwave energy.

"When the liquid water appears it jumps up," said Tedesco of the microwave emissions. One day it's not there, the next day it is, he said.

The Special Sensor Microwave Imager onboard satellites from the Defense Meteorological Satellite Program provided the data. The report on the melting is being published in the Sept. 22 issue of Geophysical Research Letters.

As for what this melting means for the rest of the planet, it depends, Tedesco said. Melting far inland in Antarctica most likely just refreezes, so it does not directly add to the oceans and raise sea level.

"The multibillion-dollar question is whether it will contribute to sea level rise," said Antarctic researcher Mahlon "Chuck" Kennicutt of Texas A&M University. "The real question is: What does this do?"

In Greenland, melt pools seen atop glaciers are thought to drain through cracks in the ice to the base of glaciers, said Kennicutt. There the water lubricates and speeds up the flow of ice to the sea, which contributes to sea level rise.

It's not at all clear if this is the sort of thing that might be going in Antarctica  which is a far bigger landmass with ice much farther from the sea.

Until now, global warming has been seen to cause rapid polar ice melting mostly in the Arctic and on the Antarctica Peninsula, which is less isolated than continental Antarctica. But recent research has shown that instead of being buried by solid ice, Antarctica has a gigantic subglacial liquid water system.

The dynamics of such a system could mean the continent's ice may be a lot more capable of sudden changes when conditions are ripe, which probably isn't very often.

"Thats another major question: Is the climate in Antarctica getting ready for a major shift?" Kennicutt said. "Its too early to tell."