Climate" The climate proved little more than one continuous blizzard the year round;a hurricane of wind roaring for weeks together, pausing for breath only at odd hours. " Douglas Mawson, The Home of the Blizzard  Antarctic weather is something to reckon with. At its most benign, the temperature will hover around zero (perhaps even a few degrees higher if you are on the coast), and with no wind it may even seem warm enough for people to strip off and sunbathe. Under these conditions visibility may be excellent as there is no haze or pollution, although the glare from the sun and the reflection from snow and ice can quickly result in snow blindness unless dark glasses are worn continuously. But don't get too relaxed: the weather can change dramatically in the space of a few hours -- usually for the worse. The air in Antarctica is extremely dry. The low temperatures result in a very low absolute humidity (the amount of water vapor contained in a given volume of air), which means that dry skin and cracked lips are a continual problem for scientists and expeditioners working in the field. The extreme cold also means large quantities of water vapor are lost from the lungs, making it necessary to drink frequently to replace the lost fluid. The low absolute humidity also rapidly dries out building timber, contributing to a very high fire risk on Antarctic research stations.
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TemperaturesLike the northern polar regions, Antarctica experiences dramatic seasonal effects that result from the earth's 23.5° tilt from the vertical axis. This means that for many weeks during mid-summer (November to February south of the equator!), it is light around the clock. In mid-winter (June and July) there is a corresponding period of continual darkness when the sun never rises.Yet the Antarctic is much colder than the Arctic for a variety of reasons, even though both poles receive very little direct radiation from the sun. Remember that there is about eight times more ice in the Antarctic than in the Arctic region. This is because the Arctic is primarily an ocean, and water is better than land at storing the summer heat and moderating the winter cold. A second reason is the reflection of shortwave radiation. The open sea reflects only 5 per cent of this radiation, while exposed land returns 15 per cent to 35 per cent. Compare that with Antarctica's year-round snow cover, which reflects nearly 80 per cent of the incoming radiation into the atmosphere. Heat is simply not retained in Antarctica to the degree which it is in the Arctic. Except for the Antarctic Peninsula, which extends much further north than the rest of the continent, there is no part of the Antarctic which has a mean temperature above 0°C in any month of the year. To no great surprise, the lowest temperature ever recorded on earth was in Antarctica, at the Russian station at Vostok in July 1983, when the thermometer recorded minus 128.6°F (89.6 °C below freezing point). At this temperature steel will shatter and water will explode into ice crystals. At the South Pole winter temperatures average around minus 70°F. Remember too that temperatures decrease with altitude as well as with latitude. Much of Antarctica has very high average altitude of 7500 feet (2300m), which is an additional reason for its being so cold. Return |
Blizzards Although Antarctica has more fresh water than any other continent, it also receives the least precipitation. The mean annual equivalent of only 2 inches (5cm) of rainfall, lower than the precipitation in many desert areas, descends each year as snow or ice crystals. When it does snow in Antarctica, and if there are also strong winds, then the most ferocious conditions prevail -- blizzards.
A severe blizzard may last for a week at a time with visibility reduced to a
few feet and winds blasting at over 100 knots. While blizzards may carry
freshly fallen snow they are more frequently composed of drift snow that is
picked up by the violent winds. Eight or ten blizzards a year are not
uncommon to coastal areas, and they bring any human outdoor activity to a
standstill. Blizzards often cause severe damage to buildings and can bury
structures under many feet of drift snow. Wind packed drift snow will form
fields of small hard ridges known as sastrugi which resemble frozen
waves and can make surface travel very rough.
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The Windiest Continent High winds combined with low temperatures make Antarctica an inhospitable place for humans, and Antarctica is the windiest continent on earth. Very strong winds can blow throughout the year, sometimes reaching speeds of about 200 miles an hour (320 km). Antarctica's coastal areas are often the windiest because of the cold dense air that flows down off the ice-cap under the influence of gravity. These extremely regular and very strong winds are known as Katabatic Winds (katabasis is Greek for descent) and their speed and direction is controlled by the shape of the icecap. The most famous site for Katabatic Winds is Cape Dennison at Commonwealth Bay, where Sir Douglas Mawson's Australian Antarctic Expedition recorded the annual mean wind speed average as 44 mph (67 kmph).
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| Photography ©Jonathan Chester, Extreme Images | © 1995 Terraquest. All Rights Reserved. |
Around the coast windy and clouded conditions often prevail. Low cloud
cover over snow usually leads to a condition known as a "white-out"
during which no visual points of reference exist. Navigation under these
conditions is exceedingly difficult and a compass is essential. If surface
vehicles are operated regularly in places prone to white-outs and blizzards,
the regular routes will be marked by fuel drums or metal tagged canes that
can be picked up by radar. It is very easy to become disoriented in a
white-out so flying becomes impossible, and at sea navigation becomes
difficult. The Air New Zealand plane that crashed into Mount Erebus in 1979
was the victim of errors in navigation and a white-out.