Predicting sea level rise from Antarctic ice melt

Antarctica holds about 90 percent of the world's ice and 70 percent of the world's reservoir of fresh water.
Image NASA/Rotts

View larger image

The new discovery of lakes and rivers beneath Antarctic ice sheets raises very important questions about the rate of ice sheet flow into the ocean, and how much sea level might rise in a warmer world.

"We've found that there are substantial subglacial lakes under ice that's moving a couple of metres per day. It's the fast-moving ice that determines how the ice sheet responds to climate change" said NASA scientist Robert Bindschadler.

"We aren't yet able to predict what these ice streams are going to do" he said.

"We thought these changes took place over years and decades, but we are seeing large changes over months. The detected motions are astonishing in magnitude, dynamic nature and spatial extent," said Helen Fricker research team leader at the Scripps Institution of Oceanography.

Scientists find lakes and rivers beneath fast moving Antarctic ice that lubricate flow

16 February 2007

From 400 miles above the Earth, satellites have detected rises and falls in the surface of fast-moving ice streams on the Antarctic ice sheet.

Scientists have also used this extraordinary view to discover an extensive network of waterways deep beneath the ice stream that provide clues as to how "leaks" in the system impact sea level and the world's largest ice sheet.

A team led by geophysicist Helen Fricker of the Scripps Institution of Oceanography, La Jolla, California, detected for the first time the subtle rise and fall of the surface of fast-moving ice streams as the lakes and channels below a half-mile of solid ice filled and emptied.

The Antarctic ice sheet is the biggest potential contibutor to sea level rise, but the melting rate, especially the exponential effect, is still not known.

The research was presented at the annual meeting of the American Association for the Advancement of Science (AAAS), and published in the February 16 issue of Science.

"This exciting discovery of large lakes exchanging water under the ice sheet surface has radically altered our view of what is happening at the base of the ice sheet and how ice moves in that environment," said co-author Robert Bindschadler at NASA's Goddard Space Flight Center.

"NASA's satellite instruments are so sensitive we are able to capture an unprecedented three-dimensional look at the system beneath the thick ice sheet and measure from space changes of a mere 3 feet in its surface elevation. That is like seeing an elevation change in the thickness of a paperback book from an airplane flying at 35,000 feet."

The surface of the ice sheet appears stable to the naked eye, but because the base of an ice stream is warmer, water melts from the basal ice to flow, filling the system's "pipes" and lubricating flow of the overlying ice.

The Antarctic ice sheet in West Antarctica in 2005. Image courtesy of NASA, Ben Holt Sr