Science & Climate Definitions

What Is an Ice Shelf?

The Ross Ice Shelf is the largest ice shelf in Antarctica, spanning nearly 372 miles long and stands between 50 and 160 feet above the surface of the water. (Getty Images)
Ice shelves are part of the ocean, so they don’t affect sea level rise in and of themselves. They are constantly moving from a solid to a liquid already. But ice shelves buttress all the glacial ice on land. Think of them like a wall blocking all the ice on land from flowing into the ocean. If you take the ice shelves away, gravity starts pulling all the other ice to the ocean.

How Are Glaciers Formed?

A man stands on the water’s edge at the foot of the massive vertical face of the Spencer Glacier in Alaska. (Getty Images)
Glaciers are comprised of snow and ice, compressed into large masses. Glaciers form as snow remains in a single place long enough to transform into ice. Glaciers advance and recede, meaning they flow, like a very slow moving river. Glacier size varies, with some growing as large as dozens or even hundreds of miles long.

Most glaciers are located in polar regions like Antarctica, Greenland and the Canadian Arctic.

What's the Difference Between a Glacier and an Ice Shelf?

Unlike ice shelves, glaciers are land-based. While glaciers are defined as large sheets of ice and snow on land, ice shelves are technically part of the ocean.

What Is Happening to Ice Shelves?

Ice shelves have always melted, but in an era of warming polar environments, it’s now happening at a faster rate. Most melting happens where the ice meets the ocean and largely goes unnoticed – until an ice shelf collapses, an increasingly frequent occurrence over the past decade.
Ice calving, also known as glacier calving, happens when large ice chunks break from the edge of its larger mass. It is considered a form of ice abelation or ice disruption and is normally caused by the expansion of the ice around it. (Getty Images)
All across polar landscapes, glaciers are advancing faster, which causes true sea level rise. Removing the ice shelves doesn’t make sea level rise in itself, but it’s removing a key protection for the glaciers that are advancing rapidly, which really would affect sea level rise.


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