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Antarctica’s Many Distinctions Make for Severe Weather
Antarctica's weather patterns are fierce to say the least. This is the most inhospitable continent on Earth for several reasons, the most obvious of which is the cold temperatures. In fact, the coldest temperature ever recorded was here, at Vostok, on July 21, 1983. It was -129° Fahrenheit. A balmy 59° is the highest temperature ever measured; recorded both by those optimists at Hope Bay and the Vanda Station on January 5th, 1974.
During the winter, the average temperature is -30°Fahrenheit. A primer in the geography of Antarctica will explain why the physical features such as 98 percent of it covered in ice (4 kilometers thick in some places), average elevations well over a mile (making it the highest continent), and its circular continental shape contribute to making it the most hostile of environments in terms of weather.
Apart from being the coldest, it is also the driest continent, which is hard to grasp when you think of the vast expanses of deserts on many other continents. The fact that it is virtually bereft of fresh water resources and rain fall make it so; there is only an average of 150 mm of snowfall, which makes it a cold desert. The air above the continent has only 1/10 of the water vapor concentration that temperate latitudes have.
It’s also dark for six months out of the year, and in the interior, the angle of the sun is such that it gets little of its warming effects. Any discussion of Antarctica's unique weather patterns must necessarily include the legendary, varying, and punishing winds, which also give it the distinction of being the windiest place on Earth. So, for one more record distinguishing it as a leader among the world’s continents, winds were once recorded here moving at an astounding 16 feet per second.
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Antarctic Winds Shape its Weather
The winds play a predominant part in creating and shaping Antarctica’s weather; and you won’t find any other place that has so many distinct kinds of winds with intriguing names and characteristics. First off, it's the winds that make it colder, with that factor alone able to reduce temperatures by 10 degrees. Ferocious winds cause the blinding (and sometimes rather localized) blizzards that can reduce visibility to zero in a flash, and the deadly wind chill factors can kill a human in record time.
As you may know, differences in air pressure produce winds, which can be defined as the movement of air from areas of higher pressure to areas of lower pressure. Pressure differences are the result of changing temperatures. The unique circular shape of Antarctica, coupled with its position on the southern axis of Earth, means that the atmospheric circulation of air is consistent (for the most part) which makes for uniform weather patterns.
The most salient factor to understand about these patterns is that they're marked by a series of weather bands, and each band is known to have a particular set of conditions prevalent there. For each of the different winds that form Antarctica's weather patterns described below, we’ll explain their role in influencing conditions, and if they are specific to a part of the continent.
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The Polar Plateau's Light Winds
The Polar Plateau is located at the center of the East Antarctic Ice Sheet, and the average height is nearly a mile high above the surrounding seas of the continent. There's a mild slope in this polar region but no geological features interrupt the course of the mild winds generating from the high pressure system located there throughout the year which cause clearer, calmer days in the region. Occasionally, oceanic storms sometimes can break through and cause snow storms. The interior region of Antarctica only gets about two inches of snow compared to the one to two feet of snow that coastal storms initiate, especially during the winter.
Image courtesy of Image credit/Wikimedia Commons/Jim Waldron USNR
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Wild WesterliesA large band of strong Westerlies inhabit the space between the latitudes of 30°S and 65°S. These "Wild Westerlies" have more names, depending upon where they're at which include the "Roaring Forties", "Furious Fifties", and "Screaming Sixties". The names reveal a bit about their intensity. The warming effect from the ocean and its heat storing capabilities equate to milder weather on the coasts, especially in summer, although as mentioned, a lot more precipitation falls here.
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Katabatic winds are caused by heavy, cold air flowing downhill from the high elevations of the interior of the continent reaching speeds of up to 100mph as the result of gravity. Winds emanating from the interior travel over gentle slopes mostly, but where they encounter geological landforms like indentations, caverns, canyons, and channels in the landscape, they are changed into wind forced through a funnel, coming out with a force not unlike water over a waterfall. These descending, Katabatic winds flow down slope like inversion winds (described next) but are surface winds, reaching only roughly 1500 feet. There can be a quiet calm which is suddenly interrupted by Katabatics moving 40 mph and beyond to hurricane force almost instantaneously. They contribute to the localized blizzards caused by ground snow being swept up even when skies above this phenomenon are clear and no snow is falling from clouds.
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The fiercest and harshest Antarctic winds are formed by temperature inversions on the ice plateau of the high interior. The Polar Plateau has a constant source of wickedly cold air. Gravity forces this dense pool of air to settle in close to the ground, then it flows from the high continental interior down toward the coast, as a river would do. The Coriolis effect redirects inversion winds toward the west, which in turn creates the coastal easterlies.
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Antarctic Circumpolar Trough Winds
The Antarctic Circumpolar Trough is located between the latitudes of 60°S and 65°S. This area is a low pressure zone containing variable winds that flow from the west to east. This region is marked by fierce storms that sweep warm and moist air from the middle latitudes toward the south pole. Heavy clouds and precipitation are frequent and the storms can last for days. Usually there is a brief window of calm clearness before another snowstorm, and sometimes a coastal storm system ravages the area.
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The Coastal (Polar) Easterlies
In between the continent and the Antarctic Circumpolar Trough, there is a narrow band of easterly winds. The cold winds moving off the continent are deflected to the west because of the Coriolis effect. The weather here is usually clearer and calmer than conditions in the Antarctic Circumpolar Trough. Because the coast gets more direct sunlight, it is nowhere near as harsh as the Antarctic interior, which only receives indirect sunlight or none at all during the winter.
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Although the landscape is austerely breath-taking on the continent encapsulating the South Pole, Antarctica's weather patterns make it the most inhospitable place on Earth, especially the high desert of the interior. If you ever want to read about the most remarkable tale of survival and exemplary leadership in the face of insurmountable odds, read Shackleton's Incredible Voyage by Alfred Lansing. You will then become intimate with the climate of the frozen coastline of Antarctica and learn about explorers who navigated the most dangerous seas in the world in glorified life rafts to get themselves back to civilization after having their ship crushed by ice and being left stranded for years.
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