Climatology of Arctic

(from AMSA Report 2009)

One defining threshold of the Arctic environment that is often used is set by the 10°C July isotherm. This isotherm marks the southern Arctic boundary where the monthly mean temperature in July is below 10°C. This limit also closely corresponds to the northern limit of the treeline.

Because of the mix of landmasses, water and ice in the northern latitudes the isotherm pushes north above the Arctic Circle in all of Eurasia, but is south of the Arctic Circle in much of central and eastern Canada, southern Greenland and the Aleutian Islands. For example, the mean monthly July temperature at Honningsvag, Norway (latitude 70° 58’ N) is 10.3°C; at Murmansk, Russia (latitude 68° 58´ N) it is 13.4°C. However, at Inukjuak, Quebec, Canada on the east side of Hudson Bay (58° 27´N) the average July temperature is only 9.4°C; at Paamiut, Greenland on the south west coast (62° 00´ N) it is 5.5°C.

In January, mean temperatures everywhere within the Arctic Circle are all below 0°C, varying from about -5°C along the north coast of Norway to greater than -35°C in central Greenland, the northern part of the Canadian Archipelago and in northern Siberia. The average January temperature at the North Pole is estimated at between -30 and -35° C; however, this is difficult to know given that no permanent recording station exists at the pole. Over virtually all of the Arctic Ocean mean winter air temperatures are not as cold as they are in fringing continental land masses in Siberia, Alaska and Canada.

Precipitation, generally, is light within the Arctic at less than 250 millimeters per annum. Only along exposed coastal regions in southern Baffin Island, western Greenland and northern Scandinavia are amounts greater than this regularly experienced. The main component of the precipitation in the central and high Arctic is snow, but it too is light, at less than 25 centimeters per annum. Although light, snow tends to be blown in all regions and accumulates in drifts and around structures; in marine environments drifting snow accumulates along ice edges and other features on the sea ice creating considerable additional barriers to normal navigation. Almost all snow disappears nearly everywhere in the summer, except in glacier areas.

One of the factors explaining the climatic patterns and annual weather events in the Arctic is the distribution of high and low pressure systems through the year. In winter two semi-permanent low pressure areas set up in the region: one over Iceland and the North Atlantic extending into the Barents Sea, the other over the Gulf of Alaska in the North Pacific. In contrast, high pressure areas are established over Siberia and the Yukon in Canada. The pressure differences bring about frequent and intense cyclonic storms moving generally from west to east. In summer, the lows weaken, the Siberian high disappears and the Canadian high shifts north over the Canadian Archipelago. As a result, pressure gradients are less and cyclonic activity declines, providing a fairly benign Arctic marine environment for voyages and regional operations. By October, the winter configuration begins to take effect and storminess increases with declining temperatures.

Again, the seasonality of the polar environment, in this case the overall annual weather patterns over the Arctic Ocean, is a critical, strategic aspect for planning current and future marine transport systems throughout the Arctic basin.

Arctic Council, 2009, Arctic Marine Shipping Assessment (AMSA), Arctic Council.©