Lakes Beneath Antarctic Ice Sheets Initiate, Sustain Flow Of Ice To The Ocean
By David Sims, Institute for the Study of Earth, Oceans, and Space
February 28, 2007
Combined RADARSAT and ICESat images showing the Recovery Glacier Ice Stream
(arrows) and location of four new subglacial lakes (A, B, C and D) that
lie at the head of the stream. Photo: Chris Shuman and Vijay Suchdeo, NASA.
One of the planet's most remote and little-understood features may play
a crucial role in transporting ice from the remote interior of Antarctica
towards the surrounding ocean and therefore impact sea level rise and regional
and global climate change, according to a new research published in the
February 22 issue of the journal Nature.
A team of scientists led by geophysicists Robin Bell and Michael Studinger
from the Lamont-Doherty Earth Observatory at Columbia University, and including
UNH glaciologist Mark Fahnestock and colleagues from NASA and the University
of Washington, discovered four large, subglaical lakes and, for the first
time, linked these water bodies locked beneath miles of ice to fast flowing
ice streams in Antarctica.
The scientists found that four separate lakes appear to contribute to
the formation of an ice stream. Ice streams are large, fast-flowing features
within ice sheets that transport land-based ice and meltwater to the ocean.
One such stream, the Recovery Ice Stream, drains eight percent of the U.S.-sized
East Antarctic Ice Sheet. The Recovery basin, unexplored since 1966, funnels
an estimated 35 billion tons of ice into the Weddell Sea annually.
“It has been a puzzle to us why, in a few cases, ice streams reach
well into the interior of the large ice sheets,” said Fahnestock
of the UNH Institute for the Study of Earth, Oceans, and Space (EOS). Fahnestock
added, “These lakes at the head of the Recovery system provide a
Until about a year ago, not many people cared much about subglacial lakes,
according to Studinger of Columbia University. "That's changing, but
we're still only just beginning to understand how these lakes, sealed beneath
more than two miles of ice, have the potential to impact the rest of the
world," he said.
The scientists examined satellite radar images and high-resolution laser
profiles of the region for ice stream patterns and surface features indicating
the presence of subglacial lakes beneath the ice. Not only did they find
four new lakes, but they discovered that the lakes coincide with the origin
of tributaries of the Recovery Glacier. Upstream of the lakes, the ice
sheet moves at just 2 to 3 meters per year; downstream the flow increases
to nearly 50 meters per year. The scientists conclude that the lakes provide
a reservoir of water that lubricates the bed of the stream to facilitate
ice flow and prevent the base of the sheet from freezing to the bedrock.
Moreover, their work suggests that subglacial lakes could play a role
in and sea level rise as well as regional and global climate change. Meltwater
at the base of ice streams increases the flow of ice to the oceans, which
could, in turn, contribute to higher sea levels worldwide. In addition,
floods have been known to originate from the interior of the ice sheet
in the past, possibly from subglacial lakes. These sudden pulses of fresh
water could potentially interfere with nearby ocean currents that redistribute
heat and carbon dioxide around the globe, disrupting the Earth's finely
tuned climate system.
"It's almost as if the lakes are capturing the geothermal energy
from the entire basin and releasing it to the ice stream." said Bell. "They
power the engines that drive ice sheet collapse. The more we learn about
them, the more we realize how important they are."