Tag Archives: earth rotation

Petermann Ice Island Seen from International Space Station

Ron Garan aboard the International Space Station just send this photograph of Petermann Ice Island PII-A down to earth as reported by Jason Major.

Petermann Ice Island PII-A on July-25/26, 2011 as seen by MODIS/Terra and the International Space Station

While the detailed photo indicates that the ice island was about as close to the coast as it is long, it has since moved offshore and to the south. The ice island is on its way to clear the similar sized island of Belle Isle in the middle of a channel that separates Labrador in the north from Newfoundland in the south. The distance from the coast is not all that relevant, but the water depth is. Classical physical oceanography says so and I urge you to watch this MIT movie.

In a nutshell: The rotating earth limits large-scale flows, such as those that propel the ice island, to move in ways that seem to make no sense. More specifically, if there is a tiny change of the bottom depth, then the flow at all depths, and this includes the surface, will want to go around this obstacle to stay with the depth it started at. It is very hard to move water from water 200 meters deep such as on continental shelves to water 2000 meters deep such as further offshore. There are exceptions to this rule, of course, but they involve other forces that usually, but not always, are small.

It is so much fun to watch and predict where this ice island will move next, especially if one can be proven wrong so easily. “The proof of the pudding is,” as Cervantes has Don Quixote say so wisely, “in the eating.”