January 6 – Crack Of Doom

Today’s factismal: When the iceberg at the Larsen C Ice Shelf breaks off, it won’t directly raise sea levels.

By now, you have probably seen the news reports. There is an iceberg about the size of Delaware that is getting ready to break off of the Larsen C Ice Shelf in Antarctica.  Because the iceberg is already floating in the water, when it breaks off, it won’t raise the sea level. But it is still important because the same thing has already happened at Larsen B in 2002 and Larsen A in 1995 which tells us what will happen next – nothing good.

Glacier dynamics made simple

Glacier dynamics made simple

Ice shelves like Larsen C form when glaciers reach the sea and spread out. And glaciers form when snow piles up in the mountains and compresses into ice under its own weight. This compression creates ice so pure that it turns blue! The ice then slowly creeps downhill, like fudge sliding down the side of a scoop of ice cream. The ice actually moves in several layers, like sheets of paper sliding over each other; if you look at the top of a glacier, you can often see these layers in the lines of rocks that have fallen onto the ice. Once a glacier meets a deep enough body of water, it starts to float. The stress at the end of the glacier causes pieces to break off; this is called “calving” and the pieces are called “icebergs”. These bergs can range in size from smaller than a doghouse to larger than the state of Rhode Island! And when the bergs break off, another part of the glacier flows downhill to replace it, raising sea level just a little.

Larsen B breaks up after the loss of a large ice berg

Larsen B breaks up after the loss of a large ice berg
(Image courtesy NASA)

Right now, the Larsen C ice shelf is holding back the glaciers that are uphill. But when it breaks apart like Larsen B and Larsen A did, it will uncork enough ice to raise the sea level around the world by nearly a foot! If that doesn’t sound so bad, remember that the total sea level rise since 1870 was just seven inches. Of course, this won’t happen overnight; instead, it will take perhaps as much as twenty years. But while the sea level rise will be slow, it will also be unstoppable. Places such as New Orleans, New York City, and the Netherlands will all be challenged by rising sea levels.

Ice on the west side of Antarctica, where it is being lost in record amounts (My camera)

Ice on the west side of Antarctica, where it is being lost in record amounts
(My camera)

Today climatologists are working to puzzle out the climate changes that are caused by people (anthropogenic climate change) from those caused by other things (changes in the amount of sunlight, changes in the cloud cover, etc.). If you would like to help in this effort, then why not join Old Weather? You’ll read logs from sailing captains and help identify weather.

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