Antarctica is Melting Faster Than Ever
It seems that every day scientists are telling us how climate change is causing the Antarctic ice sheet to melt, threatening to raise sea levels and drive the region's iconic penguins into extinction. And now, it appears that Antarctica, which was already rapidly disappearing, is melting faster than ever before.
During the past decade, Antarctica's massive ice sheet lost twice the amount of ice in its western portion compared with what it accumulated in the east, according to Princeton University researchers.
The researchers "weighed" Antarctica's ice sheet using gravitational satellite data and found that from 2003 to 2014, the ice sheet lost 92 billion tons of ice per year - that's more than five times the height of the Empire State Building.
Most of that ice loss came from West Antarctica, which is the smaller of the continent's two main regions. Since 2008, ice loss from West Antarctica's unstable glaciers doubled from an average annual loss of 121 billion tons of ice to twice that by 2014, the researchers found. Meanwhile, the ice sheet on East Antarctica - the continent's much larger and overall more stable region - thickened during that same time.
So how does that mean that Antarctica's melting is increasing? Although East Antarctica's sea ice extent is increasing, it's still only half the amount of ice lost from the west.
Based on their findings, the Princeton team believes that man-made climate change is to blame for this accelerated ice loss.
"We have a solution that is very solid, very detailed and unambiguous," co-author Frederik Simons said in a statement. "A decade of gravity analysis alone cannot force you to take a position on this ice loss being due to anthropogenic global warming. All we have done is take the balance of the ice on Antarctica and found that it is melting - there is no doubt."
"But with the rapidly accelerating rates at which the ice is melting, and in the light of all the other, well-publicized lines of evidence, most scientists would be hard pressed to find mechanisms that do not include human-made climate change," he added. (Scroll to read on...)
Previous studies of the Antarctic ice sheet used satellite data to measure the volume of ice loss. But the Princeton study is unique in that it instead measured the mass of ice, providing a more accurate picture of overall ice loss.
While it's important to know the volume of an ice sheet - or how much space it takes up - it can change without affecting the amount of ice that is present. Mass, on the other hand, changes when ice is actually redistributed and lost. To better understand the difference between measuring ice volume and mass, Simons compares it to a person weighing himself by only looking in the mirror instead of standing on a scale.
So the researchers used monthly data from the satellite mission GRACE, or the Gravity Recovery and Climate Experiment, which measures components in the Earth's mass system such as ocean currents, earthquake-induced changes and melting ice. With this unique approach, the research team showed that ice is melting from West Antarctica increasingly faster - more so than scientists had previously realized.
Overall, ice-loss rates from all of Antarctica increased by 6 billion tons per year each year during the 11-year study period. The melting rate from West Antarctica, however, grew by 18 billion tons per year every year, proving that it's much more unstable compared to other regions of the White Continent.
While all of this data is concerning, the fact that is most worrisome to researchers is that this massive and accelerating loss occurred along West Antarctica's Amundsen Sea, particularly Pine Island and the Thwaites Glacier. These areas have already experienced heavy ice loss. For example, an iceberg more than 2,000 square miles in size broke off from the Thwaites Glacier back in 2002.
Though you might assume that warming temperatures due to climate change are causing this massive ice loss, it's actually ocean currents that are the culprit. As the ocean warms, floating ice shelves melt and can no longer hold back the land ice. (Scroll to read on...)
Ocean waters around Antarctica have warmed steadily for the past 50 years, but in addition to that, the region's shallow seas are also heating up, more quickly than others.
The Weddell Sea, for example, was already warmer than other parts of the continent five decades ago. While researchers aren't exactly sure why warm water masses are rising into shallow seas, the point is that it could be a major contributor to sea level rise.
"The fact that West Antarctic ice-melt is still accelerating is a big deal because it's increasing its contribution to sea-level rise," explained first author Christopher Harig. "It really has potential to be a runaway problem. It has come to the point that if we continue losing mass in those areas, the loss can generate a self-reinforcing feedback whereby we will be losing more and more ice, ultimately raising sea levels by tens of feet."
The Antarctic ice sheet contains 70 percent of the world's freshwater, so if this massive slab were to completely melt, it threatens to raise global sea levels by a whopping 197 feet (60 meters).
It is no secret that Antarctica is in trouble because of climate change, and now scientists understand better than before just how endangered the southern continent's ice cap really is. Hopefully this unprecedented data can help us prepare for the future and what's to come as things continue to heat up.
The findings are described in more detail in the journal Earth and Planetary Science Letters.
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