It’s going to be a hot Canada Day in Dawson – forecasts call for 25º C – and it would be an amazing day to be out on the Arctic Ocean if I was just a little bit closer to that locale.
But cooling can happen through the mind, right? A contemplation of ice hummocking, a specific phenomenon that occurs only in the polar oceans, might provide more mental air conditioning than staring at the tray of ice cubes in my freezer.
Much of the sea ice in the Arctic Ocean is several years old. Ice formations will change dramatically as they are chucked around by wind, currents, pressure ridges from ice floes pushing into each other, or the movement of ice rafts – an ice topograhpy that occurs when ice cakes ride overtop of each other.
Hummocking happens with old sea ice when pressure forces sections of ice upwards into small hills. The broken ice hills can be weathered or fresh; they can be unstable when ice-breaking ships pass through the sea. At the time of its formation, hummocked ice is similar to rafted ice; the major difference is that hummocked ice, because of its thickness, requires more pressure to form heaps and ridges.
A floeberg happens when a large hummock or a group of hummocks freeze together and separate from any other ice surroundings to float solo. Floebergs protrude up to 5 metres above water level.
And last but not least: what the heck is a bummock! Whoever named the opposite of a hummock must have had a sense of humour. A bummock is the counterpart to a hummock – a downward projection from the underside of an ice field. I couldn’t locate any photos of these but if you’re cooled down enough now to do some web-searching, feel free to send any photos my way.
Sources: Canadian Ice Service website (http://ice-glaces.ec.gc.ca); Aerographer/Meteorology training manual (http://www.tpub.com/content/aerographer); Woods Hole Oceanographic Institution
meg walker 