A huge chunk of ice is positioned under up slope pressure on top of a
basin that could undermine what retention exists. If as and when we
have a major collapse, this mass would surely be the first to cascade
into the ocean.
Present work is obviously beginning to uncover such high risk
situations that can and will happen in the future. The sheer mass of
ice is astounding. It gives us a sense of what happened when the
northern ice age ended. When did the Hudson Bay Ice mass float?
Antarctic is a living Ice Cap that is in no danger of ever
disappearing until the Antarctic Plate drifts north thirty degrees.
That is a very long time away.
Scientists
discover new site of potential instability in West Antarctic Ice
Sheet
by Staff Writers
Austin TX (SPX) May 21, 2012
The
newly discovered basin covers 20,000 square kilometers (7,700 square
miles), nearly the size of New Jersey, and is well below sea level,
nearly 2 kilometers (about 1.2 miles) deep in places.
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
WestAntarctic 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
WestAntarctic 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."
The
study's co-authors also included Duncan Young, research scientist
associate at the Institute for Geophysics.
The
study, published this week in the journal Nature Geoscience, was
carried out in a collaboration led by the University of Edinburgh
with the British Antarctic Survey and the Universities of Aberdeen,
Exeter and York, as well as The University of Texas at Austin.
"This
is a significant discovery in a region of Antarctica that at present
we know little about," said Professor Martin Siegert of the
University of Edinburgh, who led the project. "The area is on
the brink of change, but it is impossible to predict what the impact
of this change might be without further work enabling better
understanding of how the West Antarctic Ice Sheetbehaves."
The
seaward edge of the newly discovered basin lies just inland of the
ice sheet's grounding line, where streams of ice flowing toward the
sea begin to float.
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.
The
newly discovered basin covers 20,000 square kilometers (7,700 square
miles), nearly the size of New Jersey, and is well below sea level,
nearly 2 kilometers (about 1.2 miles) deep in places.
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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