Greenland Ice Sheet Hits Highest Melting Rates in 350 Years, Study Shows
"These long-term records tell us we're in exceptional or unprecedented times."
In the wake of the apocalyptic findings of the fourth National Climate Assessment released on Black Friday 2018, damning evidence of humanity’s ability to trash the planet continues to accumulate. The most recent doom-laden factoid? After analyzing the last 350 years of ice melt, scientists know the Greenland ice sheet is melting faster than ever.
A study published in Nature on December 5 revealed the alarming news. Led by Luke D. Trusel, Ph.D., an assistant professor in the School of Earth and Environment at Rowan University, the team threaded together satellite and expedition data to produce the first continuous analysis of the entire ice sheet that spans over 300 years of melt and runoff.
“You could consider this a sort of warning from the climate system,” Trusel tells Inverse. “Do we heed the warning the climate is giving us? It’s a question we collectively need to grapple with.”
“Today’s Melt Rates Are Off the Charts”
The Greenland Ice Sheet, three times the size of Texas, covers an area of 1.7 million square kilometers (650,000 square miles). It’s also the leading source of new water being added to the oceans, reports Trusel.
“From a historical perspective, today’s melt rates are off the charts,” Sarah Das, a glaciologist at Woods Hole Oceanographic Institution and one of the co-authors on the study, says in a statement. “We found a 50 percent increase in total ice sheet meltwater runoff versus the start of the industrial era, and a 30 percent increase since the 20th century alone.”
These rates make for an exceptional quantity of meltwater. At peak runoff during the summer of 2012, the ice sheet lost more than 90 percent of its surface, dumping 600 gigatonnes of water into the ocean.
Satellite data gave the group of European and US scientists a pretty good idea of melt over the past few decades, but to go further back, the crew ventured to Greenland to collect ice cores, a vertical sample of ice removed from an ice sheet or glacier. The layers capture a record of the climate over the course of many seasons and years.
The team analyzed ice cores like this one to determine Greenland's past climate. This core, analyzed by Oregon State University, came from West Antarctica.
“Finding the right location was definitely a challenge,” says Trusel. “The goal was finding not too high of an elevation where it doesn’t melt at all, and not too low where it just runs off or is too icy and hard to interpret.”
The results of this study have implications beyond Greenland, too. Not only is Greenland melting faster than ever, but the effect of this melting will likely accelerate global climate change.
The Vicious Warming Cycle
Once melting rates start picking up, they cue a vicious cycle of acceleration. Sea ice can reflect roughly 50 percent of radiation back into space, but as this bright white ice and snow transform to dark ice or water, these patches absorb more heat from the sun. (Soot from forest fires will cause a similar response.)
Adding heat to the ocean makes water molecules increase in volume and energy, causing the ocean to expand — a process called thermal expansion. This open water only reflects 10 percent of radiation back to space as well, and the overall increase in heat makes it more difficult for ice to reform the following season. Melt and repeat.
"[Greenland] is a really beuatiful, austere place on the coastline but flat, white, and boring on the ice sheet," says Trusel.
If the entire Greenland ice sheet melted, it could add 7 meters (roughly 23 feet) of sea level rise to the globe. Extreme sea level rise puts cities like New Orleans, the already-flooded Venice, and Shanghai at risk, to name only a few.
Other than Greenland, glaciers, ice caps, and the continent of Antarctica — which is the largest single mass of ice on Earth — are the next potential contributors to sea level rise that scientists are keeping an eye on. Work in Greenland is far from complete, though, and Trusel hopes to make a return trip to under-sampled areas of the massive ice sheet.
“We know there’s regional changes going on,” says Trusel. “We could collect more ice cores and better understand how they’ve changed over recent decades. There’s more to understand.”
