It is difficult to characterize one specific Arctic climate. Indeed, the Arctic encompasses different types of region where the climate can be rather different from one place to another.
Several factors can produce variations in climate, including latitude (more or less northwards), distance from coasts (it is generally colder inland), whether or not marine currents are present (like the Gulf Stream which warms the coasts of Scandinavia), altitude, or relief. Several climates can exist within the same region, Alaska for instance. Moreover, in the polar regions, the top-of-atmosphere radiative balance is negative, meaning that more heat is lost than gained. This effect is linked to loss of energy which can be explained by:
- The energy of the solar radiation is lost by a maximum amount in reaching the poles because there it crosses the atmosphere always at an oblique angle; therefore the nearer the poles, the longer its path. The quantity of energy received by a given surface area in the polar regions is therefore lower than that for the same area in the equatorial regions. This effect is moreover accentuated by the Earth’s curvature and axial tilt.
- The snow and ice also play a role. Whereas on average the Earth’s surface and atmosphere sends back 30% of the solar energy, this reflection is accentuated by the whiteness of the snow, which reflects 80% of the incident light back towards space.
These variables influence the Arctic climate. A climate characterized by the disparity of its seasons, the Earth’s tilt in relation to the Sun expressed in most of the region by the existence of seasons of highly variable length: winter lasts about 9 months (involving 6 months of polar night for the regions furthest north), summer is only1/3 as long whereas spring and autumn are like transition periods no longer than a few weeks. At Resolute in Canada (74°N), the period without frost is restricted to 9 days per year on average!
The Arctic climate may well be harsh, but it would be even more so if it did not enjoy the warmth carried in by the ocean and atmospheric currents from warmer regions. This makes the climate nonetheless “milder” than in the Antarctic.
For more information on the alternance of the polar day and night, See. opposite « annual light cycle »