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article imageESA's CryoSat sheds new light on Antarctica's largest glacier

By Karen Graham     Jan 27, 2020 in Science
Ice loss from Pine Island Glacier has contributed more to sea-level rise over the past four decades than any other glacier in Antarctica. Current models indicate that this will continue in the future but at conflicting rates.
Given the conflicting data in the computer projections for future ice loss, scientists from the University of Bristol turned to the European Space Agency's (ESA) CryoSat mission to help clarify the situation, according to Eurekalert.
The CryoSat is a satellite dedicated to measuring the thickness of polar sea ice and monitoring changes in the ice sheets that blanket Greenland and Antarctica. Flying at an altitude of just over 700 kilometers above the Earth, it reaches latitudes of 88° north and south, giving it maximum coverage of both the North and South Poles.
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ESA
CryoSat is equipped with a unique instrument called Synthetic Aperture Interferometric Radar Altimeter (SIRAL). SIRAL is the first sensor of its kind designed for ice, measuring changes at the margins of vast ice sheets and floating ice in polar oceans.
In a paper published in Nature Geoscience, Jonathan L. Bamber and Geoffrey J. Dawson, both with the Bristol Glaciology Center at the University of Bristol, Bristol, UK, describe how they used information from CryoSat to help clarify the situation.
Ice melt at the grounding line contributes to seawater and thus sea levels  but the larger effect is...
Ice melt at the grounding line contributes to seawater and thus sea levels, but the larger effect is to send more ice above it out into the water, where it also drives up sea level. When sea bottom behind the grounding line, under the ice, slopes downward going inland, it exacerbates the process, which can become unstable, perpetually pushing ice out to sea.
AntargticGlaciers.org.
They discovered that the pattern of ice loss is evolving in complex ways, both in space and time. They found that thinning rates were highest along the slow-flow margins of the glacier, while rates in the usually fast-flowing central trunk have decreased "by a factor of five" since 2007. This is the opposite of what was observed in 2010.
So what does this mean? The results suggest that further rapid migration of the glacier's grounding line (the point where the grounded ice meets the ocean) may not occur for several decades unless there is a major change in the role of the ocean in ice loss - such as the ocean getting warmer.
The scientist's report support model simulations that show the glacier will continue to lose load mass, but not at much greater rates than the present.
At the end of October 2018  the European Space Agency’s Sentinel-1 satellite observed the glacier ...
At the end of October 2018, the European Space Agency’s Sentinel-1 satellite observed the glacier letting go of a huge chunk of ice. The largest piece, named Iceberg B-46, spanned 226 square kilometers. It is visible here on November 7, 2018, as observed by Landsat 8.
NASA Earth Observatory
Lead author Prof. Jonathan Bamber said, “This could seem like a ‘good news story’, but it’s important to remember that we still expect this glacier to continue to lose mass in the future and for that trend to increase over time, just not quite as fast as some model simulations suggested."
“It’s really important to understand why the models are producing different behavior in the future and to get a better handle on how the glacier will evolve with the benefit of these new observations," he added. “In our study, we didn’t make projections, but with the aid of these new data we can improve model projections for this part of Antarctica.”
Tommaso Parrinello, ESA’s CryoSat mission manger, added, “In April, CryoSat will have been in orbit for 10 years, far exceeding its expected life. We continue to be proud of the contribution to science this extraordinary satellite mission is making.
More about Antarctica, Pine Island Glacier, cryosat mission, evolving patterns, Ice loss
 
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