EPOW - Ecology Picture of the Week

Pressure Ridges on the Arctic Ocean   ----->

Sea Ice Pressure Ridges, Beaufort Sea, Arctic Ocean, Alaska

Explanation:  This week we find ourselves a couple dozen miles out on the Arctic Ocean north of Alaska National Wildlife Refuge.  We have landed our helicopter on this ice block to study polar bears.  It is May and the sea ice is just beginning to crack.  

We cannot detect it, but the massive Beaufort Gyre currents are moving the entire ice sheet under our feet about one mile per hour.  As it does so, however, it forms openings or leads ("leeds") in the ice that either come back together and pile up huge ice blocks or refreeze into ridges of these wonderful ice sculptures.

These blocks form "pressure ridges" of ice out on the Arctic Ocean.  It is hazardous to move across them, as you can sink deeply into crevasses filled with powder snow or, more dangerously, you fall into open water in the wedges between the blocks.  

When the sea ice cracks and forms leads, it also provides access to the surface for a variety of Arctic sea mammals including bearded seals, beluga whales, narwhal whales, bowhead whales, polar bears, eider ducks, and others.