SOURCE: NASA

DATE: June 19, 2019

SNIP: In the next 200 years, the ice sheet model shows that melting at the present rate could contribute 19 to 63 inches to global sea level rise, said the team led by scientists at the Geophysical Institute at the University of Alaska Fairbanks. These numbers are at least 80 percent higher than previous estimates, which forecasted up to 35 inches of sea level rise from Greenland’s ice.

The team ran the model 500 times out to the year 3000 for each of three possible future climate scenarios, adjusting key land, ice, ocean and atmospheric variables to test their effects on ice melt rate. The three climate scenarios depend on the amount of greenhouse gas emissions in the atmosphere in coming years. In the scenario with no reduction of emissions, the study found that the entire Greenland Ice Sheet will likely melt in a millennium, causing 17 to 23 feet of sea level rise.

Capturing the changing flow and speed of outlet glacier melt makes the updated ice sheet model more accurate than previous models, according to the authors. As ocean waters have warmed over the past 20 years, they have melted the floating ice that shielded the outlet glaciers from their rising temperatures. As a result, the outlet glaciers flow faster, melt and get thinner, with the lowering surface of the ice sheet exposing new ice to warm air and melting as well.

Each of the three emissions scenarios used in the study produced different patterns of ice retreat across Greenland. The least severe scenario showed the ice retreating in the west and north, while the moderate scenario showed ice retreat around the island, except for in the highest elevation areas. The most severe scenario, in which emissions continue to increase at their present rate, showed more than half of the model runs losing more than 99 percent of the ice sheet by 3000.

At its thickest point, the Greenland Ice Sheet currently stands more than 10,000 feet above sea level. It rises high enough into the atmosphere to alter the weather around it, as mountains do. Today, this weather pattern generates almost enough snowfall to compensate for the amount of naturally melting ice each year. In the future, however, melting and flow will thin the interior, lowering it into a layer of the atmosphere that lacks the conditions necessary for sufficient replenishing snowfall.