Diving Deep In Polar Waters
Although both the Arctic and the Antarctic conjure up visions of frozen desolation, below the ice and water surface lie regions of staggering abundance. Possibly the most challenging of all marine environments, the polar regions offer many surprises for the intrepid diver.
Frozen Environment
Polar waters are found in the regions around the Arctic and Antarctic, though the precise lines of demarcation are blurred. Where polar waters start and temperate waters end varies between the poles. For the Arctic it is the 50A�F (10A�C) above-water July temperature boundary, while for the Antarctic it is seen as the line of the Antarctic Convergence, a zone where cold Antarctic waters sink below warmer northern currents.
Both the Antarctic and Arctic have quite consistent water temperatures, because the low angle of the sun and the reflective qualities of the ice minimize the impact of solar radiation. The temperature of the water hovers around an extremely chilly 32A�F (0A�C), only just above the freezing point for seawater, which is 29A�F( 1.8A�C). However, although they may seem similar, the Antarctic and Arctic are actually quite different in terms of their physical geography and marine ecosystems.
The Antarctic is an isolated continent covered largely in ice: its nearest land masses are over 600 miles (1,000 km) away, and the entire continent is circled by an ocean current. The Antarctic Circumpolar Current is extremely significant, as it essentially cuts the Antarctic waters off from warmer waters farther north. The Arctic, by contrast, is mainly an area of ocean covered in a thick layer of ice, bordered by the land masses of North America. Europe, and Asia, and as such its waters are affected by temperature changes, land runoff, and shallow coastal currents.
Life on the Ice
The adaptations that have evolved in animal life to tope with extreme polar environments are remarkable. There is a tendency toward gigantism – a larger body size keeps the relative body surface area to a minimum, and therefore the effects of heat loss through die skin are pronounced. Fish have a high body fat content, and mammals have blubber and fur to insulate them, while behavior such as migration in the winter months means the worst conditions are avoided. The most extraordinary adaptations exist, perhaps, in the fish and invertebrates of polar waters: many have special “antifreeze”‘ proteins in their blood to keep it liquid at low temperatures.
