The Antarctic Climate

Antarctica's location as the southernmost continent presents a unique situation in terms of weather and climate. The Antarctic polar climate boundary -- the 50° F (10°C) isotherm for the warmest month -- encompasses about 12 percent of the surface of the globe, an area twice as large as that of the Arctic. It includes all of the Antarctic continent except the extreme northern tip of the Antarctic Peninsula. In the interior regions, extremely low temperatures, several months of complete darkness, fierce winds and blowing snow combine to make life virtually impossible. On the Antarctic Peninsula, temperatures are milder, yet snowstorms and gale force winds can persist for days or weeks on end. Most of Antarctica is covered with vast areas of snow and ice which reflect about 75% of the incoming solar radiation. Winter temperatures are also influenced by latitude, elevation and by the shortage of sunlight during the Antarctic winter. In fact, the coldest temperatures are usually during late August before the return of the sun.

The Interior
The interior of Antarctica receives the most indirect rays from the sun which makes it cooler. For long periods in the winter it receives no sunlight at all. The interior has a very high altitude which adds to the very cold temperatures.
Because the interior of Antarctica is a land mass and far away from the ocean, it gets no warming effect from the water.The interior is characterized by extreme cold and light snowfall. Raging blizzards often occur, however, when winds pick up previously deposited snow and move it from place to place. Almost continuous daylight occurs during the southern hemisphere's summer and darkness during the southern hemisphere's winter. On the polar plateau, temperature is controlled by solar input, latitude and altitude. The annual average temperature is -50°C (-58°F). Winter temperatures drop quickly, then level out. Summer is short, from mid-December to mid-January, however, temperatures can reach a balmy -30°C (-22°F)! This is partly due to the increase in solar radiation, but also the surface of the ice is a little darker and, therefore, less reflective after the winter. A small accumulation of fresh snow at the onset of winter quickly restores the high surface albedo.

A common feature of the plateau is a temperature inversion. Temperature inversions occur when extremely cold, dense air settles near the surface with warmer temperatures at some distance above (normally, temperatures decrease with elevation). These inversions may only be 300 feet thick, but the temperature difference can be over 50°F in that short distance. The intensity of inversions is greater in winter when winds are lighter and there are fewer clouds.

Coastal Areas
The coastal areas of the Antarctic continent are characterized by somewhat milder temperatures and much higher precipitation rates, mainly occurring as snow. Annual precipitation amounts range from 20 to 40 inches (500 to more than 1,000 mm). The ocean has a tempering influence on coastal temperatures. Temperatures are maritime in the summer and can go as high as 9°C (48°F). In the winter, incoming solar radiation decreases, sea ice grows, and albedo increases, causing cooling at the coast. With the exception of the Antarctic Peninsula, coastal winter temperatures can drop to -40 to -50°C (-40° to -58°F). Annual mean temperatures range from ° to 14° F (- 15° to - 10° C).

Did you know?

In Antarctica, severe low temperatures vary with latitude, elevation, and distance from the ocean. East Antarctica is colder than West Antarctica because of its higher elevation. The Antarctic Peninsula has the most moderate climate on the continent. Antarctica can be classified as a true desert; in the interior the average annual precipitation (in water) is only about 50 mm (about 2 in).

Most precipitation in coastal areas falls as snow, but is highly variable depending on location. The bulk of the precipitation comes from the cyclonic storms that diverge into the interior from the ocean, mainly during the winter. Heavy snowfalls occur when these cyclonic storms pick up moisture from the surrounding seas. This moisture freezes and is deposited as snow as it moves inland. In areas which are farther north, long periods of continual sunshine occur during the summer, with sunrises and sunsets occurring during much of the rest of the year.

The Antarctic Peninsula
The Antarctic Peninsula extends much further north than the rest of the continent and is characterized by a warmer and wetter climate than the coastal areas, with above-freezing temperatures common. In many locations, especially at the northern end, rain is as common as snow. Here, life is more prevalent than any other region of the continent. Birds and marine mammals nest and breed on the rocky shores; while inland, pockets of vegetation are found, mostly in the form of grasses, lichens, and mosses. However, the peninsula also experiences some of the continent's strongest winds and fiercest storms. Sustained westerlies and gales can buffet the peninsula for days or even weeks on end, producing bone-numbing wind-chills and mountainous seas.