Compare the Poles: Weather
Antarctica |
The Arctic |
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The annual mean temperature at the |
The annual mean temperature at the |
Why are the Poles so cold?
Captain A.D. Colburn, right, crew member Bill Dunn, and others wield their ice mallets on Knorr's foredeck during the Labrador Sea cruise. Photo by George Tupper, WHOI.There are a number of reasons why the polar regions remains cold, even in summer. The primary reason is that the sun is low on the horizon all day. Thus, solar energy needs to pass through more atmosphere to get to the ground. In addition, the high reflectivity (albedo) of snow and ice surfaces means that very little of the energy that reaches the ground (or ocean, or ice) stays there. Therefore, the heat gained during the long summer days is small and highly dependent on topography and albedo. For instance, wet tundra and bare ground absorb more solar radiation than ice sheets.
In addition to being cold, the Arctic and Antarctic are also very dry. In fact, the Antarctic is the driest continent on Earth. This is due in part to the fact that colder air can hold less moisture than warm air. This is because the molecules of air are packed so tightly that it's as if the moisture has been squeezed out of it.
Why is Antarctica colder than the Arctic?
There are two key reasons why Antarctica is colder than the Arctic.
First, since Antarctica is a giant landmass, it receives very little heat from the ocean. In comparison, the Arctic's icy cover is relatively thin and it has an entire ocean underneath it. While the water is anything but warm, it usually stays around 30° F, which is often significantly warmer than the air above the ice. Some of this heat makes its way through the ice to the air, moderating temperatures somewhat. Also, even in winter areas of open water are present in the pack ice, allowing more ocean heat to escape into the air.
The second reason is elevation. As you go up in altitude, the air temperature decreases (by 6.5C for each 1 km). Since the average elevation of Antarctica is 2.3 km, the air is much colder compared to the Arctic Ocean, which is at sea level.
