Part of Melting Greenland Ice Sheet May Reach a Tipping Point, Study Finds

Scientists say the melting of Central-Western Greenland ice sheet, the second largest ice formation in the world, may be reaching a tipping point, causing the thaw to accelerate as the body of ice destabilizes.

Accelerated melt. (Credit: TiPES/HP)

(CN) — Scientists estimate the melting of Central-Western Greenland ice sheet may be reaching a tipping point, causing the thaw to accelerate.

Even if the artic warming trend is reversed in the coming decades, the change may not be enough to save the massive ice sheet, which is a 660,000 square mile body of ice covering almost 80% of Greenland. It is the second largest ice formation in the world after the Antarctic ice sheet.

Data from the Jakobshavn drainage basin of the ice sheet reveals distinct evidence of the growing melt, according to Niklas Boers from the Potsdam Institute for Climate Impact Research in Germany and Martin Rypdal from the Arctic University of Norway. The pair of scientists have studied the melt rates and ice-sheet height changes during the last 140 years.

Analyzing reconstructions of height changes of the Central-Western Greenland ice sheet since 1880 compared to corresponding model simulations, Rypdal and Boers conclude that this part of the Greenland ice sheet is losing stability, the pair state in an article published Monday in the journal PNAS, as part of the Tipping Points in the Earth System project coordinated and led by the University of Copenhagen, Denmark, and the Potsdam Institute for Climate Impact Research, Germany.

“We might be seeing the beginning of a large-scale destabilization,” Boers said in a statement. “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.”

The instability that Boers and Rypdal discovered indicates that the critical threshold has been crossed regionally due to the last century of accelerated melting.

An ice sheet maintains its size only if the mass lost from melting and calving glaciers is replaced by snow falling on its surface. The Artic warming disturbs this balance since the surface snow often melts in warmer summers.

While melting tends to concentrate at lower altitudes, the overall ice sheet will shrink due to a mass imbalance. This triggers a positive feedback mechanism in which the surface of the ice is exposed to higher temperatures, leading to more melting, height reductions and mass loss.  Beyond a critical threshold, this process cannot be reversed because only a colder climate can restore the ice sheet to its original size.

While surface melt may be mitigated by snowfall increases as precipitation patterns over the ice sheet change due to the changing ice-sheet height, the change is unlikely to make a significant difference.

If accelerated melting occurs in the Greenland ice sheet, the global consequences would be severe. The mass equivalent of the melted Greenland ice sheet would raise global sea level by nearly 25 feet. In addition, the loss of the Greenland ice sheet would increase global warming due to decreasing albedo as well as disrupt major ocean currents, monsoon belts, rainforests, wind systems and precipitation patterns.

“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,” notes Boers.

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