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article imageAntarctica is shedding ice at an accelerating rate

By Karen Graham     Jun 14, 2018 in Science
The melting of Antarctica is accelerating at an alarming rate, with about 3 trillion tons of ice disappearing since 1992, an international team of ice experts said in a new study.
A new climate assessment called the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) found a startling rise in sea level. In a major collaborative effort, the ESA, NASA, and scientists from around the world have revealed ice losses in Antarctica have tripled since 2012.
Andrew Shepherd from the University of Leeds in the UK and Erik Ivins from NASA’s Jet Propulsion Laboratory (JPL) led a group of 84 scientists from 44 international organizations in the research that gives us the most complete picture to date of the changes going on with the Antarctic ice sheet.
The new assessment was published in the journal Nature on June 13, 2018, and reveals that prior to 2012, when the last complete assessment of the Antarctic ice sheet was done, the continent was losing 76 billion tons of ice a year.
Since that time, the new assessment shows that since that time, Antarctica has been losing ice three times as fast. Between 2012 and 2017, Antarctica lost 219 billion tons of ice a year, raising sea levels by 0.6 millimeters (0.12 inch) a year.
This information, along with the previous assessment done in 2012, is key to understanding how climate change is affecting the most remote part of the planet, and in understanding the effects of the changes in the Antarctic ice sheet and the rise in sea levels.
Prof. Shepherd said, “We have long suspected that changes in Earth’s climate will affect the polar ice sheets. Thanks to the satellites that our space agencies have launched, we can now track their ice losses and global sea-level contribution with confidence.
The SENTINEL-1 mission is the European Radar Observatory for the Copernicus joint initiative of the ...
The SENTINEL-1 mission is the European Radar Observatory for the Copernicus joint initiative of the European Commission (EC) and the European Space Agency (ESA).
ESA and NASA satellite data
Space agencies have been flying satellites over Antarctica since the 1990s, and Europe has an unbroken record of satellite observations dating back to 1992. The research team used data from ESA and NASA satellites as well as computer modeling in their assessment.
The data gleaned from satellites, like the ESA's CryoSat and the Copernicus Sentinel-1 mission were particularly useful. These satellites can measure changes in the height of the ice sheets and the speed the sheets move toward the sea. There are specific missions that have the ability to weigh the ice sheet by sensing changes in the pull of gravity as they pass overhead.
The goal for IMBIE was to condense all the available information into a single narrative, according to the BBC, that would give us a clear picture of what is going on in Antarctica.
ESA’s Director of Earth Observation Programmes, Josef Aschbacher, added, “CryoSat and Sentinel-1 are clearly making an essential contribution to understanding how ice sheets are responding to climate change and affecting sea level, which is a major concern."
With the launch of CryoSat-2  ESA s so-called Ice Mission  data of unprecedented precision is now av...
With the launch of CryoSat-2, ESA's so-called Ice Mission, data of unprecedented precision is now available on the rate of sea and land ice melting.
Antarctica's three distinct regions
Glaciologists usually talk about Antarctica having three distinct regions, primarily because they behave a little bit differently from each other. West Antarctica has been of particular concern because of its marine-terminating glaciers - the focus of the IMBIE assessment.
The assessed ice sheet losses in West Antarctica have climbed from 53 billion to 159 billion tons per year over the full period from 1992 to 2017.
The Antarctic Peninsula encompasses the finger of land that points up to South America. Ice sheet losses in this region have risen from seven billion to 33 billion tons annually. Research has shown this region's ice melt is the result of the collapse of floating ice shelves that had been sitting in front of glaciers.
Once the ice shelves collapsed, the ice they had been holding back was able to move forward toward the sea at a faster rate.
Antarctica s glaciers carry ice from the interior of the continent to the ocean. This NASA illustrat...
Antarctica's glaciers carry ice from the interior of the continent to the ocean. This NASA illustration shows where the ice is moving fastest; areas in red have the fastest flow, followed by those in pink and purple.
NASA Goddard Space Flight Center
East Antarctica, which is actually the greater part of the continent, is the only region that has shown some growth. There is a reason for this. Most of this region does not sit on the ocean itself - so it collects its snow and is not subject to the same melting forces seen in the other two regions.
Even so, East Antarctica's gains are very small when looking at the bigger picture - running at about five billion tons a year.
Ice edge of Pine Island Glacier on January 26  2017. The iceberg is at the upper right in the image....
Ice edge of Pine Island Glacier on January 26, 2017. The iceberg is at the upper right in the image. Note the cracks, evidence of additional calving to come.
NASA Earth Observatory
Eric Rignot, from NASA’s Jet Propulsion Laboratory, added, “Measurements collected by radar satellites and Landsat over the years have documented glacier changes around Antarctica at an amazing level of precision, so that we have now a very detailed and thorough understanding of the rapid changes in ice flow taking place in Antarctica and how they raise sea level worldwide.”
Dr. Pippa Whitehouse from Durham University was quoted by the BBC. "At the moment, we have projections going through to 2100, which is sort of on a lifetime of what we can envisage," she said.
Talking about the rise in sea levels, Dr. Whitehouse adds, "And that is not only going to impact people who live close to the coast but actually when we have storms - the repeat time of major storms and flooding events is going to be exacerbated."
More about Antarctica, west of continent, Esa, NASA, Climate change