Thursday, September 3, 2009

Weather in McMurdo

Negative 100 windchill yesterday, -91 today! Winterovers say its about the coldest weather all winter.

Antarctica is the highest, driest, and coldest continent. Snow accumulates continuously at the pole and is compressed gradually into a pancake ice sheet which is about 3miles thick at the pole and thins to nothign at the edges where it melts/breaks away. Like glass, even though it seems solid, ice flows. The weight of 3 miles of ice causes ice to flow outward from the zone of accumulation at the pole towards the edges of the ice sheet. Most ice caps and glaciers are wet-bottom; pressure causes a lubricating layer of meltwater to form beneath the glacier. Because Antarctica is so cold, it is covered in dry-bottom ice. Some scientists fear that global warming could convert Antarctic ice to the wet-bottom variety and accelerate flow and melting at the edges. The Antarctic ice sheet holds 61% of the world's freshwater.

South Pole is considered high elevation (9,186ft - note: the difference between 9186ft and 3 miles is due to the weight of the ice pressing the bedrock down- the ice is thicker than the elevation of the pole is high). Weather at the Pole tends to be calm, cold, and sunny. An enormous force is created by the Pole's altitude and the density of the cold air there which results in "Katabatic winds" ("downslope winds") which often exceed hurricane force at shore locations such as McMurdo. (Cold dense air warms as it travels downslope and in warmer regions can become hot and dry; another example of a katabatic wind is the Santa Anas fueling the fires in California. In Antarctica everything is so cold that the warming effect is negligible. It is very very dry here though). Pics from wiki.

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