13 December 2014 Pressure Ridges

Journal

Each winter, temperatures in the Antarctic drop so low that the top of the ocean freezes into a solid mass of ice about 2m (6 feet) thick! This is called Sea Ice, and it pushes up against continental Antarctica, extending the coastlines by 20 or more miles!!

Sea Ice Extent — These Sea Ice maps from NASA show the difference in the extent of ice between September (left) and February (right). You can read more about Sea Ice variability at http://earthobservatory.nasa.gov/Features/SeaIce/page4.php Photo Credit: NASA maps by Jesse Allen, based on AMSR-E data from the National Snow and Ice Data Center.

Neverending Sea Ice — Although we are in prime melting season, when looking out over the Sea Ice, there is still no end in sight! Photo credit: Yamini Bala

At the same time, in the interior of the continent, snow falls and accumulates, rarely melting, since temperatures are so low. As the snow piles up higher and higher, it gets heavier and heavier, pressing down in the middle, causing snow to freeze into ice, and forcing ice to flow outward toward the sea.

Ice Flow Diagram — Snow from the middle of the continent pushes down and, once frozen, ice flows out toward the edges of the continent. Image Credit: adapted from a drawing by Erin Pettit

When the outbound glacial ice runs into the inbound Sea Ice, there is a crash of epic proportions, which results in something called a "pressure ridge." Pressure ridges are basically like mini ice mountains, since mountains form when two plates collide and are forced upward.

How a pressure ridge forms — This diagram shows how two separate masses of ice that flow toward each other collide to form a pressure ridge. Image credit: By Lusilier (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

A few days ago, we went out to the coastline near Scott Base to explore the pressure ridges that had formed there.

I had never thought that ice alone could be so gorgeous, but the ridges create some beautiful and interesting formations that were well worth the visit.

Here are some of my favorites: