Greenland is just one island. But its ice sheet has the potential to transform the entire planet. The Greenland ice sheet has existed for 2.4 million years and is 2.1 miles (3.4 kilometers) thick at its deepest point.
The whole thing weighs about half as much as Earth’s whole atmosphere, or 6 quintillion — or 6 with 18 zeros after it — lbs. (2.7 quintillion kilograms). If it melted entirely, sea level would rise by 24.3 feet (7.4 meters). In the 21st century, scientists use laser measurements of the height of the ice, measurements of the ice sheet’s total gravity and satellite photos to gauge changes in ice thickness. Scientists already knew that there was a lot more ice on Greenland in the 1970s and 1980s. And they’ve had precise measurements of the increase in melting since the 1990s. Now they know just how dramatically things have changed in the last 46 years.
To extend that record further into the past, the researchers divided Greenland into 260 “basins” of ice, which they studied individually using a combination of direct measurements of ice changes in satellite photos and sophisticated computer models of ice behavior. They found that between 1972 and 1980, Greenland actually gained roughly 100 trillion lbs. (47 trillion kg) of ice per year. The real mass loss, they found, started in the 1980s. Between 1980 and 1990, the island lost in the ballpark of 112 trillion lbs. (51 trillion kg) of ice per year. Between 1990 and 2000, it lost about 90 trillion lbs. (41 trillion kg) per year. Then, in the 2000s, things dramatically accelerated. Between 2000 and 2010, Greenland lost about 412 trillion lbs. (187 trillion kg) of ice per year. Between 2010 and 2018, the ice sheet lost roughly 631 trillion lbs. (286 trillion kilograms) of ice per year. Marco Tedesco is a professor in atmospheric sciences at the Lamont Doherty Earth Observatory of Columbia University. He monitors behavior of the cryosphere— the part of earth’s water system that is frozen. He says melting of this extent shouldn’t begin until May. “The first melt event was detected on April 7.
“Incoming solar radiation reached a value similar to ones we observed in August last year,” wrote Tedesco. That heats the ground even more. It’s a vicious cycle of positive feedback, indicating just how unstable — and delicate — the Arctic is.“I call this ‘melting cannibalism,” explained Tedesco. And it could get even worse, as it preconditions the ice to be more vulnerable to melting in the summer. When snow/ice on the ground melt, they form small pools of water. That changes how reflective the surface is a measure scientists refer to as “albedo.” Snow and ice have a very high albedo, meaning it reflects most of the incoming light that hits it. That’s why you have to wear sunglasses when you go skiing. Water, on the other hand, is a lot less shiny, which allows it to absorb more heat, a cyclical process on a local level and a driver of additional warming on the global level.
