Antarctica is a special place, no matter how you look at it. It’s the highest, driest, coldest, and windiest continent, for starters. One way that it’s very special is its position, squatting right on the south end of the Earth.
To begin with, the seventh continent is in the middle of its own lithospheric plate, completely isolated from other continents. It was part of Gondwanaland throughout the Paleozoic, stuck together with Africa, South America, Australia, and India. But then during the Jurassic that supercontinent slowly broke up over a hundred million years, until Australia split from it and left Antarctica alone, beginning in the Eocene about 50 million years ago. You can follow the history at the Paleomap Project site.
Ever since that time, the ocean has surrounded it on all sides, turning around it in a great westward current. Antarctica has gotten colder and colder, cooling the rest of the planet along with it. Over the years, it has accumulated a gigantic layer of ice to a height of 3,000 meters. That huge central mound stands up nearly halfway through the atmosphere, so like a bald-headed man with no hat, it loses heat directly to outer space. The cold air that results flows right off the ice cap by gravity, picking up speed as it goes, until the resulting katabatic winds roar off the continent’s edge onto the sea.
The cold winds freeze the seawater, building up immense areas of solid pack ice every Antarctic winter. The water left behind is saltier and, because salty water is denser than the rest of the ocean, it sinks and slowly moves northward on the seafloor to the rest of the world.
Throughout most of geologic time, the Earth has had a warmer and more equable climate than today. Large areas of the continents were covered by shallow seas, where the limestones and shales and coal measures we see today were laid down. Antarctica has been keeping the world cool lately, though, and by piling up more and more ice, it has drawn down the level of the sea. I’m grateful for that, because I like dry land.
Antarctica is not really responsible for the ice ages we’ve been living through for the past few million years, though. For that, you might blame Panama, which rose out of the water about 3 million years ago and cut off the Atlantic from the Pacific Ocean. Now we have a complicated setup, involving Greenland with its ice cap and currents in the north Atlantic Ocean, that seems to switch back and forth between a cold-climate state and a warmer state, where we are today.