Some Antarctic Ice Is Forming from Bottom
ScienceDaily (Mar. 3, 2011) — Scientists working in the remotest part of Antarctica have discovered that liquid water locked deep under the continent's coat of ice regularly thaws and refreezes to the bottom, creating as much as half the thickness of the ice in places, and actively modifying its structure. The finding, which turns common perceptions of glacial formation upside down, could reshape scientists' understanding of how the ice sheet expands and moves, and how it might react to warming climate, they say.
The study appears in this week's early online edition of the journal Science; it is part of a six-nation study of the invisible Gamburtsev Mountains, which lie buried under as much as two miles of ice.
Ice sheets are well known to grow from the top as snow falls and builds up annual layers over thousands of years, but scientists until recently have known little about the processes going on far below. In 2006, researchers in the current study showed that lakes of liquid water underlie widespread parts of Antarctica. In 2008-2009, they mounted an expedition using geophysical instruments to create 3-D images of the Gamburtsevs, a range larger than the European Alps. The expedition also made detailed images of the overlying ice, and subglacial water.
"We usually think of ice sheets like cakes--one layer at a time added from the top. This is like someone injected a layer of frosting at the bottom--a really thick layer," said Robin Bell, a geophysicist at Columbia University's Lamont-Doherty Earth Observatory and a project co-leader. "Water has always been known to be important to ice sheet dynamics, but mostly as a lubricant. As ice sheets change, we want to predict how they will change. Our results show that models must include water beneath." The Antarctic ice sheet holds enough fresh water to raise ocean levels 200 feet; if even a small part of it were to melt into the ocean, it could put major coastal cities under water.
Article continues: http://www.sciencedaily.com/releases/2011/03/110303141551.htm