Scientists Discover New Site of Potential Instability in West Antarctic Ice Sheet

[OKIsItJustMe]

http://www.utexas.edu/news/2012/05/10/ice_sheet/

[font face=Serif][font size=5]Scientists Discover New Site of Potential Instability in West Antarctic Ice Sheet[/font]

May 10, 2012

[font size=3]AUSTIN, Texas — Using ice-penetrating radar instruments flown on aircraft, a team of scientists from the U.S. and U.K. have uncovered a previously unknown sub-glacial basin nearly the size of New Jersey beneath the West Antarctic Ice Sheet (WAIS) near the Weddell Sea. The location, shape and texture of the mile-deep basin suggest that this region of the ice sheet is at a greater risk of collapse than previously thought.

Team members at The University of Texas at Austin compared data about the newly discovered basin to data they previously collected from other parts of the WAIS that also appear highly vulnerable, including Pine Island Glacier and Thwaites Glacier. Although the amount of ice stored in the new basin is less than the ice stored in previously studied areas, it might be closer to a tipping point.

"If we were to invent a set of conditions conducive to retreat of the West Antarctic Ice Sheet, this would be it,” said Don Blankenship, senior research scientist at The University of Texas at Austin's Institute for Geophysics and co-author on the new paper. "With its smooth bed that slopes steeply toward the interior, we could find no other region in West Antarctica more poised for change than this newly discovered basin at the head of the Filchner-Ronne Ice Shelf. The only saving grace is that losing the ice over this new basin would only raise sea level by a small percentage of the several meters that would result if the entire West Antarctic Ice Sheet destabilized."

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Two features of the basin, which is entirely below sea level, are particularly worrisome to scientists: First, like a cereal bowl, its edges slope down steeply. If the grounding line begins to retreat upstream, seawater will replace it and more ice will begin to float. The study's authors predict that this positive feedback mechanism would sustain retreat of the ice sheet until eventually all of the ice filling the basin goes afloat. Second, the bed of the basin on which the ice rests is smooth. There are few big bumps, or "pinning points," to hold back sliding ice.

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http://dx.doi.org/10.1038/ngeo1468

[font size=5]"If we were to invent a set of conditions conducive to retreat of the West Antarctic Ice Sheet, this would be it,”[/font]

[XemaSab]

1. Any expectations on when this will happen?

'Cause if I know one thing...

[happyslug]

2. The West Antarctic Ice Sheet has been "unstable" since the collapse of the North American Ice Sheet,

The North American Ice Sheet (Proper name:the Laurentide Ice Sheet) melted about 20,000 years ago and was the most recent cause of world wide sea level rise, a rise that increase how much sea water comes in contact with the West Antarctic Ice Sheet (Which is grounded BELOW sea level).

Saying that, The West Antarctic Ice Sheet is theory should have collapsed centuries ago, but it has not. Thus the ice sheet is hanging on, but can give at any spring (i.e March 1 to April 15, the Ice Shelves that surround the West Antarctic Ice Sheet, retreat from September to about March 23 every year. by the first day of Spring in the Northern Hemisphere (First day of Autumn in the Southern Hemisphere) the Ice Shelves are at their smallest and thus provide the least protection to the Ice Sheets. Thus the time for the break up of the West Antarctic Ice Sheet is March to mid April (and most probably March 15 to April 1st).

Definitions:
ICE SHELVES: Ice that is FLOATING on water. The water the ice in an Ice Sheet would replace if melted, equals to the water the ice is displacing as it floats on the water. Thus the melting of an Ice Shelf will have little to no affect on world wide sea levels. Through a lost of Ice Shelves make the Ice Sheets more exposed to warm temperatures thus may be the key to why the West Antarctic Ice Sheet has NOT collapsed over the last 20,000 years.

ICE SHEET: Ice that is GROUNDED, i.e. laying on ground, including the sea floor. An Ice Sheet CAN exist BELOW Sea level (as it does in the West Antarctic Ice Sheet). An Ice Sheet does displace some of the water it has pushed out of its way, but it can contain more water as ice then it is displacing. In the case of the West Antarctic Ice Sheet it is Grounded on the sea floor, its ice content exceeds what water it is displacing. If the West Antarctic Ice Sheet breaks up and FLOATS (and thus becoming an Ice Shelve or an Iceberg) this would displace enough water to raise world wide sea levels 15-20 feet. Thus the West Antarctic Ice Sheet is called the "Godzilla" of global warming.

Thus, the West Antarctic Ice Sheet can collapse any year and your guess is as good as mine. On the other hand, it will be close to the First day on the Northern Spring (about March 23) which is also the Southern first day of Autumn. Outside guess March 1 to April 15, mostly likely March 15 to April 1st. Thus we can estimate the time of year of the Collapse, but not the year.

[OKIsItJustMe]

3. c 2100?

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In a related paper published simultaneously in the journal Nature, computer models reveal that the Weddell Sea region may experience warmer ocean conditions at the end of the 21st century, which could provide the trigger for ice sheet change.

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