Antarctica’s climate is determined by its polar location. It should not be surprising, therefore, that Antarctica is the coldest continent. Mean temperatures in the interior during the coldest month (August) range from -40° to -70° C (-40° to -94° F) and in the warmest month (February) range from -15° to -45° C (5° to -49° F). The lowest environmental temperature ever recorded on Earth was -89.6° C (-129.3° F) at the Russian "Vostok" base on the inland ice cap.
Antarctica is also the windiest of the continents. Apart from global wind currents, Antarctica actually creates its own wind systems. Cold dense air essentially slides from the high interior ice fields towards the lower areas along the coasts. At the edges of the ice plateau the winds accelerate, thereby lifting and blowing clouds of snow high into the air. The strongest winds are habitually found on the long coastal slopes of Greater Antarctica. Some coastal areas endure almost constant strong winds, whereas other areas may be quite calm much of the time and then suddenly experience hurricane force winds as air rushes down through glacial valleys. These sudden and unexpected winds are called katabatic, or down slope, winds. Australian explorer Douglas Mawson established a base at Cape Denison in 1912 and recorded wind speeds for two years. This is reputed to be the windiest place on Earth, because the average wind speed during that time period was 72 kph (45 mph), and gusts of more than 240 kph (150 mph) were common.
Antarctica is also the driest continent. By definition, most of the continent qualifies as a desert. There is very little precipitation each year in the interior, and the vast amount of ice and snow that make up the polar ice cap has accumulated over millions of years. The mean annual accumulation for the entire continent amounts to less than 5 cm (2 in) of water equivalent, which is just slightly more than what the Sahara Desert receives. However, some coastal areas, particularly the west side of the Antarctic Peninsula, receive much more precipitation (the tip of the peninsula receives about 90 cm, or 35 in, of water equivalent each year).
As a ship sails southwards, it must cross a broad band of sometimes turbulent water affected by low pressure systems that circle the globe unimpeded by land at these latitudes. Somewhere between 50° and 60° S latitude, it will encounter a sharp drop in water temperature. If the weather is calm, there may be a sudden fog bank, a line of turbulence, and/or concentrations of feeding sea birds. This drop in temperature delineates the Antarctic Convergence, which completely surrounds the continent. During the time of year we visit these waters, throughout the southern Summer, the sea temperature may drop from 6°C to 2°C (43°F to 35°F) at the convergence. During Winter months the differences in sea temperatures may be as great as 10°C (18°F). The Antarctic Convergence (also called the Polar Front) is a natural boundary between the relatively warmer SubAntarctic Surface Water and the cold Antarctic Surface Water. The convergence is easily detected by a drop in sea temperature, and can often be detected visually in the Atlantic Ocean sector (but less so in the Pacific Ocean sector). The waters south of the convergence, as well as all land masses, is considered the Antarctic environment, and both climate and weather patterns can be quite different from what is encountered north of the convergence. The location of the convergence varies only slightly throughout the year, or from year to year, or even century to century.
In addition, scientists also refer to the Antarctic polar climate boundary, which is based on the 10°C (50° F) isotherm for the warmest month of the year (February). Using this as the definition for the Antarctic climate covers an area much less than that of the Antarctic Convergence, but still includes about 12 percent of the world’s surface within this zone. However, this definition for the Antarctic polar climate boundary is somewhat questionable, because it does not include all of the Antarctic continent. According to this view, the extreme northern tip of the Antarctic Peninsula is not part of the Antarctic polar climate region, which seems strange since like the rest of the continent, it is almost entirely covered with thick ice caps and glaciers.
Meteorologists define climate as the average weather for a particular region over a given period of time. The two main elements of climate are temperature and precipitation, and these are influenced by many factors, such as the latitude and/or altitude, amount of solar radiation, air pressure, wind patterns, mountain ranges, etc.
Antarctica's climate is usually categorized into three basic regions…
1). Peninsula. The Antarctic Peninsula extends well north of the Antarctic Circle, whereas all the rest of the continent is located south of the circle. It is generally both warmer and wetter than the rest of the continent, especially at the northern region, and often receives above-freezing temperatures and considerable amounts of rain (as opposed to just snow). Summer air temperatures are frequently well above freezing. One also encounters more life in the peninsula than any other region of the continent. This includes enormous populations of breeding sea birds, as well as numerous pinnipeds that haul out on peninsular shorelines. In addition, some areas contain considerable growths of plants and plant-like organisms. However, in spite of the milder conditions in the peninsula, it still endures severe snowstorms and gale force winds that can last for several days at a time, especially in the Winter.
2). Coastal zones. The Antarctic coastal zone, like the peninsular region, experiences milder temperatures and higher rates of precipitation than the majority of the continent. This zone also receives a significant tempering influence on temperatures brought on by the nearness of the ocean. In the Summer, the maritime effect can cause temperatures to rise above freezing, perhaps as high as 10°C (50°F). In the winter, coastal sea ice forms and causes dramatic cooling…dropping the temperatures to as low as -40 to -50°C (-40° to -58°F). The high precipitation in this zone, as much as one meter (39 in), falls mostly as snow, not rain, because most of the precipitation comes from winter storms.
3). Interior. The climate of the Antarctic interior is determined by several important criteria. First of all, the interior area receives the most indirect rays from the sun which makes it cooler, and in fact receives no sunlight at all for long periods during the Winter. Taking the ice cap into account, Antarctica is the highest continent. The ice dome covering most of Greater Antarctica reaches a height of 4,200 m (13,860 ft), while the ice plateau of Lesser Antarctica has an average height of about 2,000 m (6,600 ft). In fact, the South Pole is located 2,800 m (9,240 ft) above sea level on top of a layer of ice of about that same thickness (the underlying bedrock is almost at sea level). This very high altitude also adds to the very cold temperatures. The interior is affected by a general high pressure, so as one moves farther inland there is less of a maritime effect and therefore less moisture in the form of precipitation. Severe blizzards occur often here, but most of the wind-blown snow is simply snow that was previously deposited and later moved about. During the Summer, the interior receives almost continuous daylight and the average temperatures can rise to about freezing.
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