Greenland’s ice sheet is melting at a much faster rate than expected according to a new study released Monday in Nature Climate Change. Data from satellites led the study to conclude that Greenland is likely to develop more lakes “that speed up melt,” which would add as much as 20 feet to sea levels.
Greenland’s ice sheet covers an area over three times the size of Texas, approximately 656,000 square miles. If the oceans rise by 20 feet, the damage to coastal communities could be extensive. According to the Guardian, supraglacial lakes—lakes caused by melting glaciers and snow—will spread further inland, causing a cascade effect of more melting. Previously, melted ice from Greenland was expected to contribute “eight inches to global sea levels by 2100.” The new reports indicate this figure might be significantly too low.
The supraglacial lakes have a two-part impact on the melting of the ice sheet. Firstly, they absorb more of the sun’s heat, accelerating snow and ice melt. Amber Leeson, the lead researcher from the University of Leeds’ School of Earth and Environment, says, “Supraglacial lakes can increase the speed at which the ice sheet melts and flows, and our research shows that by 2060 the area of Greenland covered by them will double.”
Secondly, the lake water drains through fractures in the ice and then, once it reaches the ice sheet base, it acts like a lubricant and causes melting ice to “slide more rapidly into the ocean.” Leeson notes, “When the ice sheet is thinner, it is at a slightly lower elevation and at the mercy of warmer air temperatures than it would have been if it were thicker, increasing the size of the melt zone around the edge of the ice sheet.” Previously, the lakes were kept to a 62-mile-wide band around Greenland’s coast. It was too cold for lakes to form at higher elevations. Increasingly warmer temperatures will cause the lakes to spread up to 68 miles further inland by 2060, Leeson says, doubling the area they currently cover.
Why does this matter? Greenland’s ice sheet covers 81 percent of Greenland Island, according to NASA. The slab would stretch from Key West, Florida to Portland, Maine and cover the distance from Washington, D.C. to Indianapolis. It is also very thick, about 1.6 miles, and contains eight percent of the earth’s fresh water. NASA’s Earth Observatory site notes, “A sea level rise of only two to three feet—the high end of current plausible scenarios for the next 20 years—would create serious global problems: increased coastal erosion, salt water encroachment, loss of barrier formations (islands, sand bars, and reefs), and increased storm surge damage.”
Leeson adds, “The location of these new lakes is important; they will be far enough inland so that water leaking from them will not drain into the oceans as effectively as it does from today’s lakes that are near to the coastline and connected to a network of drainage channels. In contrast, water draining from lakes farther inland could lubricate the ice more effectively, causing it to speed up.”