Polar desert snow

Q: My father-in-law explained to me how there is no snow or precipitation in the Arctic and Antarctic. At least that's what he says. Then, where did the snow and ice lying all over the place come from, I ask him? Please tell him. Also, does fresh water or saltwater make up the icebergs and the ice masses?  Mark, Quitman, Georgia

Maritime antarctica. Photo courtesy of Lyubomir Ivanov and Wikipedia.

A: Polar snow and ice comes from precipitation falling from polar skies. It snows and even rains there though both polar regions are deserts. The snow and ice accumulate over the years because, each year, at least some of the new fall fails to melt or evaporate.

The Arctic gets about 8 to about 16 inches (20 -41 cm) of water (rain or melted snow) each year. Dry Antarctic gets only 5 inches (13 cm) and most of that falls along the coast. The inland Antarctic Plateau — the world’s largest and coldest desert — receives only 2 inches (5 cm).

For comparison, the Sonoran Desert of Arizona and Mexico gets between 4 to 12 inches (10 - 30 cm) of moisture. A desert gets less than 10 inches (25 cm) of precipitation.

Not all polar precipitation comes from clouds. The Antarctica Plateau is so dry and so far inland that ice crystals fall from the clear sky — not clouds, writes Jack Williams in his fascinating book, The Complete Idiot’s Guide to the Arctic and Antarctic.

Fresh water makes up the icebergs and ice floes because ice crystals expel salt as water freezes. Sometimes, though, the temperature drops fast enough that the freezing sea traps pockets of brine in the ice. The brine normally seeps out of the ice in a year. Old sea ice, consequently, is pure enough to drink.

Further Surfing:

USA Today: Science in Earth’s cold regions

WonderQuest: Freezing salty water

(Answered Jan. 9, 2004; updated Sep. 28, 2007)

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