The Petermann glacier in Greenland is the largest Arctic glacier, but it’s about to get quite a bit smaller.

Scientists say that an ice chunk around the size of Manhattan is about to fall off of the glacier, which they say has been disintegrating for years now.

It’s pretty common for chunks of ice to fall off the glacier, but the size of this one is what’s got environmental experts buzzing. The Manhattan-sized piece is 5 billion tons of ice; the same amount as half the glacier’s annual flow. This means it will be tough for snowfall and ice to make up for this lost piece throughout the winter season, in order to get the glacier back to its size.

Scientists studying the glacier say that warming oceans are definitely part of the problem: they speed up the break-up and thinning of the glaciers.

Environmentalists have said for years that melting glaciers are a sure sign of global warming, and now say that melting rates around the world are at a high.

If you want a chance to see those glaciers for yourself, make sure they stick around by doing what you can to stop global warming.