hot spot under west Antarctica

151208134632_1_540x360.jpg-The topography of West Antarctica below the ice sheet as viewed from above, looking toward the Antarctic Peninsula.  Much of West Antarctica is a basin that lies below sea level (blue), although it is currently filled with ice, not water.  West Antarctica was stretched and thinned as it moved away from East Antarctica, forming one of the world’s largest continental rift systems.    Credit: Bedrock Consortium    

Lloyd helped deploy research seismometers across the West Antarctic Rift System and Marie Byrd Land in the austral summer of 2009-10.  He then returned in late 2011 and snowmobiled more than 1,000 miles, living in a Scott tent, to recover the precious data.

The recordings the instruments made of the reverberations of distant earthquakes from January 2010 to January 2012 were used to create maps of seismic velocities beneath the rift valley.  An analysis of the maps was published online in the Journal of Geophysical Research: Solid Earth.

This is the first time seismologists have been able to deploy instruments rugged enough to survive a winter in this part of the frozen continent, and so this is the first detailed look at Earth beneath this region.

Not surprisingly, the maps show a giant blob of superheated rock about 60 miles beneath Mount Sidley, the last of a chain of volcanic mountains in Marie Byrd Land at one end of the transect.  More surprisingly, they reveal hot rock beneath the Bentley Subglacial Trench, a deep basin at the other end of the transect.   https://www.sciencedaily.com/releases/2015/12/151208134632.htm?trendmd-shared=0

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-Mount Sidley, at the leading edge of the Executive Committee Range in Marie Byrd Land, is the last volcano in the chain that rises above the surface of the ice.  But a group of seismologists has detected new volcanic activity under the ice about 30 miles ahead of Mount Sidley in the direction of the range’s migration.  The new finding suggests that the source of magma is moving beyond the chain beneath the crust and the Antarctic Ice Sheet. Credit: Doug Wiens

“Most mountains in Antarctica are not volcanic,” Wiens says, “but most in this area are.  Is it because East and West Antarctica are slowly rifting apart?  We don’t know exactly.  But we think there is probably a hot spot in the mantle here producing magma far beneath the surface.”

“People aren’t really sure what causes DPLs,” Lough says.  “It seems to vary by volcanic complex, but most people think it’s the movement of magma and other fluids that leads to pressure-induced vibrations in cracks within volcanic and hydrothermal systems.”

Will the new volcano erupt?  “Definitely,” Lough says.  “In fact because of the radar shows a mountain beneath the ice I think it has erupted in the past, before the rumblings we recorded.

Will the eruptions punch through a kilometer or more of ice above it?  The scientists calculated that an enormous eruption, one that released a thousand times more energy than the typical eruption, would be necessary to breach the ice above the volcano.

On the other hand a subglacial eruption and the accompanying heat flow will melt a lot of ice.  “The volcano will create millions of gallons of water beneath the ice — many lakes full,” says Wiens.  This water will rush beneath the ice towards the sea and feed into the hydrological catchment of the MacAyeal Ice Stream, one of several major ice streams draining ice from Marie Byrd Land into the Ross Ice Shelf.  By lubricating the bedrock it will speed the flow of the overlying ice, perhaps increasing the rate of ice-mass loss in West Antarctica.      https://www.sciencedaily.com/releases/2013/11/131117155609.htm

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“We have now added a view of the climate changes at the end of another ice age, for comparison, and we found that the patterns were different,” said co-author Professor Eelco Rohling, from the University of Southampton and ANU.

“At the end of the last ice age (or glaciation), rapid melting of the Northern Hemisphere ice sheets and major climate changes did not occur at the same time.  At the end of the ice-age before last, 135,000 years ago, a rapid collapse of the Northern Hemisphere ice sheets into the North Atlantic Ocean suppressed ocean circulation, and caused global climate impacts.

“The North Atlantic cooled while the Southern Ocean warmed.  The latter destabilised Antarctic land ice, causing a continuation of melting that eventually drove sea level rise to several metres above the present,” he said.   https://www.sciencedaily.com/releases/2015/06/150610131444.htm

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A team of British climate scientists comparing today’s environment with the warm period before the last ice age has discovered a 65% reduction of Antarctic sea ice around 128,000 years ago.  The finding is an important contribution towards the challenge of making robust predictions about the Earth’s future climate.   https://www.sciencedaily.com/releases/2016/08/160816084738.htm

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