‘We might be seeing the beginning of a large-scale destabilisation,’ scientist warns

Part of the Greenland ice sheet could soon cross the point of no-return after which the rate of melting outpaces the rate of snow fall, scientists have warned.
Scientists analysing arctic data said the situation could soon reach a tipping point and warned that they urgently need to understand how the effects of melting affect each other.
The Greenland ice sheet contains enough water to raise the global sea level by seven metres, a change which would displace millions of people.
Losing it is expected to add to global warming and disrupt major ocean currents, monsoon belts, rainforests, wind systems and rain patterns around the world.
However, the researchers said their data is not as comprehensive as they would like, meaning they cannot make solid conclusions.
Dr Niklas Boers, from Potsdam Institute for Climate Impact Research in Germany, said: “We might be seeing the beginning of a large-scale destabilisation but at the moment we cannot tell, unfortunately.
“So far, the signals we see are only regional, but that might simply be due to the scarcity of accurate and long-term data for other parts of the ice sheet.”
He explained how an ice sheet can only maintain its size if the loss of mass from melting and calving glaciers is replaced by snow falling onto its surface.
The warming of the Arctic disturbs this mass balance because the snow at the surface often melts away in the warmer summers.
Melting will mostly increase at the lower altitudes, but overall, the ice sheet will shrink from a mass imbalance.
As this happens, a positive feedback mechanism kicks in – meaning as the ice sheet surface lowers, its surface is exposed to higher average temperatures, leading to more melting and the process repeats until the entire ice sheet is gone.
Beyond a critical threshold, researchers say, this process can not be reversed because, with reduced height, a much colder climate would be needed for the ice sheet to regain its original size.
Dr Boers, and his colleague Dr Martin Rypdal from the Arctic University of Norway, have found the data shows that the critical threshold has at least regionally been reached due to the last 100 years of accelerated melting.
They add an increase in melting will possibly be compensated, at least partly, by more snowfall as precipitation patterns over the ice sheet will change due to the changing ice sheet height.
However, if the Greenland ice sheet as a whole moves into accelerated melting there will be severe consequences for the entire planet.
Dr Boers added: “We need to monitor also the other parts of the Greenland ice sheet more closely, and we urgently need to better understand how different positive and negative feedbacks might balance each other, to get a better idea of the future evolution of the ice sheet.”
The research has been published in Proceedings of the National Academy of Sciences of the United States of America (PNAS).
Additional reporting by SWNS