February 25 – Glacial Progress

Today’s Factismal: The Grand Pacific Glacier has retreated more than 68 miles since 1794, making it the fastest retreating glacier in the world.

What’s slightly smaller than Connecticut, filled with mosquitoes and tourists, and was established in 1925? It Glacier Bay National Park in Alaska. This huge wildlife preserve is home to bears, seals, whales, bald eagles, and lots and lots of glaciers; as of the last count, there were more than 50 different glaciers in the park.

The Great Pacific Glacier with Mt. St in the background (My camera)

The Grand Pacific Glacier with Mt. St. Elias in the background (My camera)

But there used to be just one big glacier there. Known to the local Tlingit as Xáatl Tú, or “Among the Ice”, Glacier Bay was once dominated by the Grand Pacific Glacier, which stretched nearly 100 miles from Canada’s St. Elias Mountains down to the ocean at Icy Straight Point in Alaska. The point got its name from the constant stream of icebergs that were “calved” off of the glacier. So many icebergs fell off that by 1879 the glacier had retreated 48 miles, leaving behind several smaller glaciers in side valleys. By 1916, the Grand Pacific Glacier had shrunk another 17 miles and left behind yet more feeder glaciers. Today, the Grand Pacific Glacier is just one-quarter of its original length.

Glacier dynamics made simple

Glacier dynamics made simple

The glacier has gotten shorter because it has been losing ice into the ocean faster than it gains snow in the mountains. 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.

A new ice berg is born

A new ice berg is born

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 “ice bergs”. These bergs range in size from smaller than a doghouse to larger than the state of Rhode Island! And it is the bergs that worry most climate scientists; once the ice berg is in the water, it raises the sea level just a little much as ice raises the level of water in a glass. And there is enough ice on top of Antarctica to raise the sea level by nearly 100 feet, which would be enough to drown most of the world’s coastlines and turn more than half of the world’s population homeless.

The ice floating in front of the glacier has already raised sea level

The ice floating in front of the glacier has already raised sea level

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 ISee Change and post something in the almanac?

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s