What is Unique About the Polar Regions?

Why are the North and South Poles so cold? Are there differences between the two poles? What other factors make weather at the Poles so unique?

Both the North and South Poles are affected by a polar vortex. The polar vortex is a persistent large-scale cyclonic circulation pattern in the mid- to upper- troposphere and stratosphere, centered over the pole. The Arctic polar vortex is not symmetrical and features an elongated area of low pressure, called a trough, which extends over eastern North America.

Still frames from the NASA video about the polar vortex

In the Arctic, there are a number of semi-permanent patterns of high and low pressure that affect weather. Three areas of high pressure influence weather in the Arctic. The Siberian High is an intense cold anticyclone centered over eastern Siberia that is strongest during the winter. It is the cause of frequent cold outbreaks over eastern Asia.

Semi-permanent High Pressure Areas

The Beaufort High is a region of high pressure commonly centered over the Beaufort Sea. It, too, is strongest in the winter. The last region of semi-permanent high pressure is the North American High, which is a weaker pattern that covers most of North America during the Arctic winter.

Semi-permanent Low Pressure Areas

Two semi-permanent low-pressure areas are Arctic weather makers. The Aleutian Low is the source of many strong cyclones and is most intense in winter. The Icelandic Low, centered between Iceland and Greenland, reaches its greatest strength in winter. It weakens and breaks up in summer. It is a source of strong cyclonic activity. As other cyclones approach these two semi-permanent air masses, they slow down and intensify, which results in extended periods of stormy, unsettled weather in the region.

Aleutian Low over the north Pacific Ocean, and Icelandic Low over the north Atlantic Ocean.

Shorter episodes of low-pressure conditions also affect weather in the Arctic. These polar lows are small, in comparison to the semi-permanent Aleutian and Icelandic lows. The smaller polar lows are usually only several hundred kilometers in diameter and typically possess strong winds. They form beneath cold upper-level troughs when frigid Arctic air flows southward over warm open water. They develop rapidly, reaching their peak strength in 12-24 hours, and are of short duration, lasting only 1-2 days.

These lows dissipate quickly, especially after making landfall. Several may co-exist or develop in rapid succession. Satellite photos reveal a characteristic spiral or comma-shaped cloud pattern, often with an inner eye like that of a hurricane, prompting them to be called "Arctic hurricanes," although they rarely possess winds of hurricane strength.

Arctic Oscillation

The Arctic is also affected by the Arctic Oscillation, which refers to opposing atmospheric pressure in the northern middle and high latitudes. This pattern is marked by two phases. The negative phase is characterized by relatively high pressure over the poles and low pressure at the mid-latitudes.

The positive phase features low pressure at the poles and high pressure at the mid-latitudes. This phase brings ocean storms farther north, resulting in wetter weather in Alaska and Scandinavia, and drier conditions in the western United States. The positive phase also makes the United States east of the Rocky Mountains warmer than usual, and brings colder conditions to Greenland and Newfoundland. The Arctic Oscillation has generally been in this positive phase since the 1970s.

Comparing North Pole to the South Pole

In comparing the North Pole to the South Pole, we can reach the following conclusions:

  • The North Pole is in the middle of the Arctic Ocean. As a result, the sea ice often allows oceanic heat to dissipate and become more of a factor in its influence on climate. This is expecially true where there are cracks or leads in the ice that allow this oceanic heat to dissipate more rapidly.
  • Weather conditions at the South Pole, in the middle of the continental glacier, with high albedo, low heat conductivity, lower heat capacity, high elevation, and little marine influence, are even more extreme.