The Greenland ice sheet is melting much faster than previously thought, threatening hundreds of millions of people with flooding, and bringing much closer to some of the irreversible effects of climate change.
In Greenland, ice is lost seven times faster than in the 1990s, and the extent and rate of ice loss is much higher than predicted in the global climate research, according to the Intergovernmental Panel on Climate Change.
This means that sea level rise is expected to reach 67 cm by 2100, about 7 cm more than the IPCC’s main forecast. Such a rate of increase will lead to an annual flood risk of 400 million people, instead of the 360 million forecast by the IPCC by the end of the century.
The world has warmed by about 1 ° C in the past century, but the Arctic is well above this global average and warms up about twice as fast as the rest of the world.
In some places the rate of warming was astonishing. November in the Alaskan town of Utqiaġvik, formerly Barrow, is now 5.5 ° C warmer than in 1979. In summer 2019, an arctic heat wave in parts of Greenland reached temperatures that were 40 ° C above normal.
The Arctic is dominated by sea ice, unlike Antarctica, which is essentially a huge ice sheet on land. Since the sea and the atmosphere are warm, Nasa has shrunk sea ice by about 13% per decade since 1979. The bright white surface of the ice, known as albedo, gives way to the dark ocean, which means that sunlight is absorbed rather than reflected, thereby increasing the warming effect.
These “rapid” and “unprecedented” changes are changing the Arctic and threatening the traditional way of life, according to US government scientists in a 2019 report. The sea ice is younger, thinner, more fragile, and less extensive than hunting on ice makes it more difficult and dangerous. The marine ecosystem is shifting as warmer water forces fish species to retreat to northern waters.
What is a major challenge for Arctic communities is a blessing for the shipping industry, which can find its way around the region more easily. This task becomes even easier when the Arctic is ice-free in summer, which is expected in the 2040s.
An increase in sea level also increases the risk of storm surges when the stronger storms from the coastal regions of the global heating dough become more likely. This impact is likely to affect coastal regions around the world.
“These are not unlikely events or small impacts,” said Andrew Shepherd, a professor of earth observation at the University of Leeds, one of the study’s main authors. “[This impact] is happening and will be devastating to coastal communities.”
Greenland has lost 3.8 billion tons of ice since 1992, and the rate of ice loss has increased from 33 billion tons per year in the 1990s to 254 billion tons per year in the past decade. Greenland’s ice contributes directly to the rise in sea level as it melts as it rests on a large mass of land, unlike the floating sea ice that makes up much of the rest of the Arctic ice cap.
About half of Greenland’s ice loss was due to melting caused by surface air temperatures that have risen much faster than the global average in the Arctic, and the rest was due to the acceleration of ice flow from the glacier to the sea warming ocean.
The oceans have absorbed most of the excess heat generated by our current climate disruption and much of the carbon dioxide, but they are reaching the limits of their ability to do so. The rise in sea level is driven not only by melting ice, but also by the thermal expansion of the oceans as they warm up.
The extent and speed of ice loss surprised the team of 96 polar researchers who backed the results published on Tuesday in the journal Nature. The intercomparison exercise on the mass balance of the ice sheet comprised 26 separate surveys in Greenland from 1992 to 2018 with data from 11 different satellites and comparisons of volume, flow and gravity, which were compiled by experts from Great Britain, NASA in the USA and European space agency.
Erik Ivins of the Nasa Jet Propulsion Laboratory in California emphasized that the results – the most comprehensive study of the ice sheet in recent decades – were based on observations rather than computer models.
“While computer simulation allows us to project climate change scenarios, satellite measurements provide prima facie evidence,” he said.
The year with the highest ice loss was 2011 when 335 billion tons of ice were lost. Since then, the average rate has slowed from 2013 to 238 billion tons a year, but without the recent observations from this summer, which showed an even more widespread melting.
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