ESA Cryosat: West Antarctica continues to lose ice

West Antarctica continues to lose ice to the ocean and this loss appears to be accelerating, according to new data from Europe's Cryosat spacecraft.

The dedicated polar mission finds the region now to be dumping over 150 cubic km of ice into the sea every year.

It equates to a 15% increase in West Antarctica's contribution to global sea level rise.

Cryosat was launched in 2010 with a radar specifically designed to measure the shape of ice surfaces.

And the instrument's novel design, scientists believe, is enabling the European Space Agency satellite to observe features beyond the capability of previous missions.

The new study, presented here in San Francisco to the American Geophysical Union (AGU) Fall Meeting, confirms the usual suspects to be involved in the increased ice loss.

They are Pine Island, Thwaites and Smith Glaciers.

These major glaciers and their associated tributaries drain the interior of West Antarctica, taking its mass into the Amundsen Sea.

The ice near to their grounding lines - the places where the ice streams lift up off the land and begin to float out over the ocean - is now thinning by between four and eight metres per year.

"Interestingly, Smith Glacier is thinning fastest," said study leader Dr Malcolm McMillan from the UK's Nerc Centre for Polar Observation and Modelling (CPOM).

"It's smaller but its thinning rate is roughly double that of Pine Island or Thwaites, which tend to get all the headlines because they have such huge catchments," he told reporters.

In a recent major review of all satellite data, scientists concluded that ice losses from West Antarctica pushed up global sea levels by some 0.28mm a year between 2005 and 2010.

The new Cryosat data picks up from the end of that period, and suggests the contribution has risen still further.

Professor Andrew Shepherd from the University of Leeds, who led the West Antarctica study, said that part of the increase of ice loss could be due to faster thinning, but that part of it may also be down to CryoSat’s capacity to observe previously unseen terrain.

“Thanks to its novel instrument design and to its near-polar orbit, CryoSat allows us to survey coastal and high-latitude regions of Antarctica that were beyond the capability of previous altimeter missions, and it seems that these regions are crucial for determining the overall imbalance,” he said.

Mount Sidley West Antarctica: Volcano discovered smoldering under a kilometer of ice

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

It wasn't what they were looking for but that only made the discovery all the more exciting.

In January 2010 a team of scientists had set up two crossing lines of seismographs across Marie Byrd Land in West Antarctica.

It was the first time the scientists had deployed many instruments in the interior of the continent that could operate year-round even in the coldest parts of Antarctica.

Like a giant CT machine, the seismograph array used disturbances created by distant earthquakes to make images of the ice and rock deep within West Antarctica. There were big questions to be asked and answered.

The goal, says Doug Wiens, professor of earth and planetary science at Washington University in St. Louis and one of the project's principle investigators, was essentially to weigh the ice sheet to help reconstruct Antarctica's climate history.

But to do this accurately the scientists had to know how the earth's mantle would respond to an ice burden, and that depended on whether it was hot and fluid or cool and viscous.

The seismic data would allow them to map the mantle's properties.

In the meantime, automated-event-detection software was put to work to comb the data for anything unusual.

When it found two bursts of seismic events between January 2010 and March 2011, Wiens' PhD student Amanda Lough looked more closely to see what was rattling the continent's bones.

Was it rock grinding on rock, ice groaning over ice, or, perhaps, hot gases and liquid rock forcing their way through cracks in a volcanic complex?

Uncertain at first, the more Lough and her colleagues looked, the more convinced they became that a new volcano was forming a kilometer beneath the ice.

The discovery of the new as yet unnamed volcano is announced in the Nov. 17 advanced online issue of Nature Geoscience.

Read the full article here in www.phys.org