Lakes of meltwater can crack Greenland's ice and contribute to faster ice sheet flow

Closer inspection of the data revealed that the pressure of the water from the lake split open the ice sheet from top to bottom, through 980 meters (3,200 feet) of ice. This water-driven fracture delivered meltwater directly to the base, raising the surface of the ice sheet by 1.2 meters in one location. In the middle of the lake bottom, a 750-meter (2,400 foot) wide block of ice was raised by 6 meters (20 feet). The horizontal speed of the ice sheet--which is constantly in motion even under normal circumstances--became twice the average daily rate for that location.

“It’s hard to envision how a trickle or a pool of meltwater from the surface could cut through thick, cold ice all the way to the bed,” said Das. “For that reason, there has been a debate in the scientific community as to whether such processes could exist, even though some theoretical work has hypothesized this for decades.”

The seismic signature of the fractures, the rapid drainage, and the uplift and movement of the ice all showed that water had flowed all the way down to the bed. As cracks and crevasses form and become filled with water, the greater weight and density of the water forces the ice to crack open. As water pours down through these cracks, it forms moulins (cylindrical, vertical conduits) through the ice sheet that allow rapid drainage and likely remain open for the rest of the melt season.

Das, Joughin, and their field research team will be featured this summer during an online- and museum-based outreach project known as Polar Discovery (http://polardiscovery.whoi.edu). Their return research expedition to Greenland will be chronicled daily through photo essays, and the researchers will conduct several live conversations with students, educators, and museum visitors via satellite phone.

Funding for the research was provided by the National Science Foundation, the National Aeronautics and Space Administration, the WHOI Clark Arctic Research Initiative, and the WHOI Oceans and Climate Change Institute.

The Woods Hole Oceanographic Institution is a private, independent organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans’ role in the changing global environment.

Related Links:

Tracking an Ocean of Ice Atop Greenland
http://www.whoi.edu/oceanus/viewArticle.do?id=9126&sectionid=1001

Who is Sarah Das?
http://www.whoi.edu/hpb/Site.do?id=445

Who is Ian Joughin?
http://psc.apl.washington.edu/pscweb2002/Staff/joughin/joughin.html

Greenland’s Glaciers Pick Up Pace in Surge Toward the Sea
http://www.uwnews.org/article.asp?articleID=23320

Polar Discovery Online Expeditions
http://polardiscovery.whoi.edu/

Polar Research at WHOI
http://www.whoi.edu/page.do?pid=12295