Climate: Polar

The Arctic

The limits of the Arctic are marked by the 10 °C isotherm of July (the warmest month of the year in the Northern Hemisphere). Another criterion is the boundary of 15 kcal cm-2 yr.-1 (kilocalories per square centimeter per year), or 62.7 kJ cm-2 yr.-1 (kilojoules per square centimeter per year). This zone corresponds to the transition between the taiga and tundra ecosystems, and its position fluctuates between 50 °N and 700 °N. In such a range, the influences of harsh climatic conditions extend over an area of almost 27 million km2 (square kilometers). The inner part of the region, delimited with the 50 °C isotherm of [Page 450]July, is called the high Arctic, with the landscape dominated by herbaceous and bare-ground tundra (with a majority of lichens and mosses) and polar desert.

The glacial mountains of Spitsbergen, Norway's most northern territory

Source: Morguefile.

Polar climates can be identified as either maritime or continental. In the Northern Hemisphere, the warm Norwegian Current of the Northern Atlantic provides significant energy fluxes into the adjacent polar land masses. The current flows along the Scandinavian coast and then continues far into the north. Mild maritime influences are observed up to the 80° latitude, and sea ice does not accumulate along most of the Norwegian and Svalbard coasts. Typically (e.g., the Bear Island on the Northern Atlantic), monthly average temperatures oscillate between −100 °C in February and 50 °C in July. In the coastal areas of the inner part of the Arctic Ocean, temperatures in winter drop down to about −300 °C due to the presence of sea ice, but in summer, the temperatures are still under the control of the open sea and reach 50 °C (e.g., Barrow in Alaska and Tiksi in the northeastern Siberian coast).

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