Related articles

UN delivers warning on the catastrophe of climate change
Carbon dioxide rate is at highest level for 650,000 years
Now it is up to the world's political leaders to deliver more than hot air
Climate change reduces ocean food supply, threatening marine ecosystems
Arctic summer sea ice falls below normal for fifth year, despite a cool August
Rapid changes in Arctic sea ice
Melting permafrost methane emissions: The other threat to climate change
Ice bubbles reveal biggest rise in CO2 for 800,000 years
A disaster to take everyone's breath away
3 degrees: Chief scientist warns bigger rise in world's temperature will put 400 million at risk
Survey detects significant Antarctic ice mass loss
Greenland ice loss doubles in past decade, raising sea level faster
Global warming: Severe glacial reduction in southern Alaska
Environment in crisis: 'We are past the point of no return'
World is at its hottest since prehistory
2004 fourth warmest in over a century
Antarctic Peninsula glaciers surge when ice shelf breaks up

Home > Environmental Issues > Global warming > Article

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

View larger image

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.  "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.

In recent years, scientists have discovered more than 145 subglacial lakes, a smaller number of which composes this "plumbing system" in the Antarctic.

The research team 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 unveiled 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.

Images left: From December 2003 to December 2005, the MODIS satellite captured these two images showing a draw down of water in a subglacial lake (left) and the rise of water in the same subglacial lake (right). Color coded ICESat tracks across both images indicate rises and falls in the elevation of the lake's water.
Image credit NASA

View larger images

Copyright © 2007 TerraNature Trust. All rights reserved.

home | sponsors | latest news & events | join - donate | contact information | projects
volunteer activities | about us | site map | environmental issues | New Zealand ecology