Climate of the Arctic

The climate of the Arctic is characterized by long, cold winters and short, cool summers. There is a large amount of variability in climate across the Arctic, but all regions experience extremes of solar radiation in both summer and winter. Some parts of the Arctic are covered by ice (sea ice, glacial ice, or snow) year-round, and nearly all parts of the Arctic experience long periods with some form of ice on the surface.

The Arctic consists of ocean that is largely surrounded by land. As such, the climate of much of the Arctic is moderated by the ocean water, which can never have a temperature below −2 °C (28 °F). In winter, this relatively warm water, even though covered by the polar ice pack, keeps the North Pole from being the coldest place in the Northern Hemisphere, and it is also part of the reason that Antarctica is so much colder than the Arctic. In summer, the presence of the nearby water keeps coastal areas from warming as much as they might otherwise.

There are different definitions of the Arctic. The most widely used definition, the area north of the Arctic Circle, where the sun does not set on the June solstice, is used in astronomical and some geographical contexts. However the two most widely used definitions in the context of climate are the area north of the northern tree line, and the area in which the average summer temperature is less than 10 °C (50 °F), which are nearly coincident over most land areas.

This definition of the Arctic can be further divided into four different regions:

Moving inland from the coast over mainland North America and Eurasia, the moderating influence of the Arctic Ocean quickly diminishes, and the climate transitions from the Arctic to subarctic, generally, in less than 500 km (310 mi), and often over a much shorter distance.

Due to the lack of major population centres in the Arctic, weather and climate observations from the region tend to be widely spaced and of short duration compared to the midlatitudes and tropics. Though the Vikings explored parts of the Arctic over a millennium ago, and small numbers of people have been living along the Arctic coast for much longer, scientific knowledge about the region was slow to develop; the large islands of Severnaya Zemlya, just north of the Taymyr Peninsula on the Russian mainland, were not discovered until 1913, and not mapped until the early 1930s.

Much of the historical exploration in the Arctic was motivated by the search for the Northwest and Northeast Passages. Expeditions in the 16th and 17th centuries were largely driven by traders in search of these shortcuts between the Atlantic and the Pacific. These forays into the Arctic did not venture far from the North American and Eurasian coasts, and were unsuccessful at finding a navigable route through either passage.

National and commercial expeditions continued to expand the detail on maps of the Arctic through the 18th century, but largely neglected other scientific observations. Expeditions from the 1760s to the middle of the 19th century were also led astray by attempts to sail north because of the belief by many at the time that the ocean surrounding the North Pole was ice-free. These early explorations did provide a sense of the sea ice conditions in the Arctic and occasionally some other climate-related information.