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An important ice bridge tethering a large ice sheet to Antarctica fissured and threatened collapse this week, sending scientists and the United Nations into a panic. The Wilkins ice sheet, which is roughly the size of Connecticut, is attached to the continent's landmass elsewhere, but this ice bridge is thought to connect the northern portion, itself covering more than 1,400 square miles. This development is only the latest for the ice sheet, which has been under close observation for more than a year.
Scientists were first alerted that the area was in danger last March when more than 350 square miles of the sheet suddenly detached and broke up in the ocean, causing glaciologists to conclude "runaway disintegration" had begun. Before that, an ice sheet 8,500 square miles in size was released from elsewhere on the Antarctic Peninsula.
The first question this raises is usually about sea levels: will this cleaving ice eventually melt and flood the world's coastline? So far, the vast majority of ice that has separated from the continent has been floating sea ice, which, as anyone who has had ice cubes in a glass of water on a summer day knows, does not raise water levels when it melts. The fear is about the land-based ice that is exposed when the floating ice disappears. More than that, scientists worry that the latest melting is an ominous milestone, one that signals a rapidly approaching tipping point from which there may not be a return.
For now, however, the 25 mile ice bridge is holding, despite its ever-lengthening fissures. When it breaks, another large ice mass will be following close behind. If nothing is done to slow or halt global warming, the already shocking loss of ice from Antarctica will continue and, eventually, land-based ice will slide into the ocean. As Jane Ferrigno, leader of the USGS Antarctica study explained:
This continued and often significant glacier retreat is a wakeup call that change is happening? and we need to be prepared?Antarctica is of special interest because it holds an estimated 91 percent of the Earth's glacier volume, and change anywhere in the ice sheet poses significant hazards to society.
Hopefully, this is the last warning the world needs.
For more of the latest environmental news, watch Focus Earth: April 11, 2009: A Bee Mystery & an Antarctic Collapse.
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