Thursday, August 9, 2012

Some icy bits

A different menace to shipping
I’ve been sitting at my desk with the view of the beautiful summer day on my island in the Pacific thinking about sea ice. The ice in Cumberland Sound is still delaying science work there. On top of real life ice woes, I’ve been reading about sea ice.

Sea ice is surprisingly complex. After a morning’s reading I’ve had to look up three terms I hadn’t run across before: lamella, nilas and breccia. But, if I take a step back, ice in the Arctic can be broken into four categories:

1 - Polar Ice Cap - this makes up about 70% of ice found in the Arctic Ocean. This ice stays year round, however it isn’t static. New ice is being included into the cap while older ice is carried away. Overall, the cap is rotating in a disjointed fashion clockwise.

2 - Pack Ice - Wind blew this type of ice into my path when I was up in the Beaufort Sea a few years ago. There was pack ice as far as I could see in every direction at a time when clear sea was expected. This ice is made up of floes, which are separate chunks of ice. About 25% of the Arctic Ocean is covered in pack ice.

3 - Fast Ice - No, it isn’t moving anywhere, in fact, it’s land fast. The ice extends to the bottom where it attaches. This ice type is seasonal, thickening to 1-2 m in winter while disappearing entirely in summer. As an aside, funky things can happen when pack ice and fast ice meet.

4 - Ice Bergs - These are mostly found in the North Atlantic and come from chunks of glaciers on Greenland and Elsemere Islands breaking (or calving) away. They then drift south becoming a menace to shipping.

Image is from here.

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