Tuesday, April 7, 2009

Spring Sea Ice

It’s beautiful, glowing stuff. The light bends around its edges and in places appears to be coming from within. On the underside it is a gorgeous aquamarine. Many people curse it because it makes a long winter feel even longer. But if you choose your moment when the light is soft, or low in the sky, it is nature at its most radiant.

This is sea ice (also known as pack ice or drift ice) that forms in arctic waters and drifts south on the cold Labrador current each spring. It envelopes the coast of Labrador and the northeast coast of Newfoundland extending as much as 200 miles offshore. It is frozen sea water in contrast to icebergs which are frozen freshwater from the land. Newly formed sea ice is indeed salty but over time the salt leaches out and what remains is fresh enough to put in a rum and coke, my preferred winter libation.

Although many people have the impression that salt water doesn’t freeze, clearly it does but at a lower temperature than freshwater - about -2C or 29F. So sea ice develops in the winter months and melts in the summer months. Some of it in the high arctic may not completely melt before the onset of winter again. This is known as multi-year ice and it can grow to considerable thickness.

Sea ice is most prevalent in areas with cold ocean currents. Therefore, the east side of the Atlantic, which is influenced by the warm Gulf Stream, has almost no sea ice at latitudes that are much further north than those on the west side where sea ice is an annual event. Therefore shipping along the coast of Norway remains open throughout the winter whereas that along the coast of Labrador and the eastern Canadian arctic must shut down.
Ecologically sea ice is very important because it is the hunting platform for polar bears and the whelping surface for millions of harp seals. It also has a tremendous influence on the world’s climate. Because it has a bright, light surface, it reflects most solar radiation back into space thus keeping northern latitudes cold. Global warming trends are significantly reducing arctic ice cover exposing areas of darker water that absorb solar radiation. Hence the warming escalates. This is one of the reasons why the polar regions are the most sensitive to the global warming phenomenon.

For me as a photographer sea ice is a delight. I look forward to this time of year when the ice pushes into our inshore waters near my home. I like to walk slowly around its edges frequently changing my angle of view to see the effect of light. Exposure can be tricky since the mostly white surfaces will cause light meters, which want to render tones to a medium gray, to under-expose. If I’m trying to get a single image with an acceptable exposure, I’ll over-expose between 0.5 and 1.0 stops. But when I’m looking for good exposures in both dark and light areas (the background and water areas as well as the ice) I will bracket and then blend images together in a treatment called high dynamic range (HDR) processing. Sea ice and HDR make a very good marriage of subject and technique. Another great marriage is sea ice and rum...but I already said that.

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