Plumbing leaks in melting Antarctic contributes to rising sea levels

Stan Beer
Friday, 16 February 2007 13:12

Science - Climate

Antarctica, which holds about 70% of the world's fresh water in its ice, is leaking water into the ocean through a vast system of lakes and water ways beneath the ice, causing the sea level to rise, according to scientists using data from NASA satellites.

Scientists have discovered more than 145 subglacial lakes, a smaller number of which composes the "plumbing system" in the Antarctic.

A team of scientists led by research 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 nearly a half- mile of solid ice below filled and emptied.

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. This web of waterways acts as a vehicle for water to move and change its influence on the ice movement. Moving back and forth through the system's "pipes" from one lake to another, the water stimulates the speed of the ice stream's flow a few feet per day, contributing to conditions that cause the ice sheet to either grow or decay. Movement in this system can influence sea level and ice melt worldwide.

Ted Scambos of the National Snow and Ice Data Center in Colorado; and Laurence Padman of Earth and Space Research in Oregon; observed water discharging from these under-ice lakes into the ocean in coastal areas. Their research has delivered new insight into how much and how frequently these waterways "leak" water and how many connect to the ocean.

The study included observations of a subglacial lake the size of Lake Ontario buried under an active area of west Antarctica that feeds into the Ross Ice Shelf. The research team combined images from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA's Aqua satellite and data from the Geoscience Laser Altimeter System (GLAS) on NASA's Ice Cloud and Land Elevation Satellite (ICESat) to unveil a multi-dimensional view of changes in the elevation of the icy surface above the lake and surrounding areas during a three-year period. Those changes suggest the lake drained and that its water relocated elsewhere

"There's an urgency to learning more about ice sheets when you note that sea level rises and falls in direct response to changes in that ice," Fricker said.