A new study finds that the accelerating retreat and thinning of Greenland’s glaciers that began 20 year ago is speeding the ice sheet toward total meltdown.
Excerpt from this story from InsideClimate News:
The Greenland Ice Sheet managed to withstand the warming brought by the first 150 years of the industrial age, with enough snow piling up each winter to balance the ice lost to spring and summer melting. But, according to a new study, that all changed 20 years ago.
Starting in 2000, Greenland’s glaciers suddenly began moving faster, their snouts rapidly retreating and thinning where they flow into the sea. Between 2000 and 2005, that acceleration led to an all-but irreversible “step-increase” of ice loss, scientists concluded in the new research, published this week in the journal Nature Communications Earth & Environment.
If the climate were to stop warming today, or even cool a little, Greenland’s ice will continue to melt, said Ohio State University Earth scientist Ian Howat, co-author of the research paper. “Glacier retreat has knocked the dynamics of the whole ice sheet into a constant state of loss,” he said. “Even if we were to stabilize at current temperatures, the ice will continue to disintegrate more quickly than if we hadn’t messed with the climate to begin with.”
When all Greenland’s ice melts, it will raise sea level by 20 feet. That could take 10,000 years, but jolts to the climate system like the glacier acceleration in the early 2000s, combined with the effects of the growing spread of ice-darkening algae and black carbon, the amount of meltwater saturating of the snow atop the ice or changes in ocean currents flowing near the glaciers could speed that up by thousands of years, Howat said. When a tongue of ice breaks free from its seafloor anchor, the flow of the glacier above it accelerates.
Melting ice is the main cause of sea level rise, and Greenland contributes the most meltwater to the ocean. With millions of people threatened by the rising ocean, the rate of sea level rise in the coming decades is critical for planning seawalls and other defenses, or deciding to abandon some coastal areas for higher ground. The Fourth National Climate Assessment estimates sea levels will rise 1 to 4 feet by 2100. The new study warns that accelerating melting could push the ocean toward the higher end of that range.
