Cyclones

A cyclone, also called a low or depression, is a weather pattern consisting of a region of low air pressure some 1000 kilometers to 2000 kilometers in diameter around which air circulates counterclockwise in the Northern Hemisphere. This counterclockwise motion is due to the Coriolis force: air moving toward the low-pressure center of the depression is deflected to the right in the Northern Hemisphere. In a cyclone, air ascends near the center of the low, and the weather tends to be stormy, with precipitation.

Cyclones in the Arctic

Winter cyclones in the Eurasian Arctic occur most frequently in the Barents and Kara Seas region. An average of six cyclones pass through the southern Barents Sea, and five through the southern Kara Sea in any winter. On average, four cyclones pass through the southern East Siberian Sea and the lower course of Kolyma river in each of the winter months. Cyclones can bring in warm air, causing rapid warming and melting even in the middle of winter. Over the North American Arctic, the highest frequency of cyclones occurs east of Greenland in association with the Icelandic Low. Cyclones are also common in Baffin Bay.

The summer distribution of air pressure and cyclones is different from that of winter. With more uniform temperatures over the northern parts of the Atlantic and Pacific oceans, summer cyclones tend to be weaker than their winter counterparts. The semipermanent Icelandic and Aleutian Lows weaken. In July and August, only one or two cyclones move to the arctic seas from the northern Atlantic. On the other hand, more cyclones move towards the pole from the midlatitudes of Siberia and Canada. The number of cyclones in the Chukchi Sea in July can be as high as six, and in the East Siberian Sea up to four or five.