Why is Antarctica colder than the Arctic?

The Arctic is largely a frozen ocean surrounded by land, and the water beneath the sea ice moderates temperatures. Antarctica is a continent with an ice sheet averaging over 2 kilometres thick, giving it the highest average elevation of any continent, and air gets colder with altitude. It is also isolated by the Antarctic Circumpolar Current and strong winds that block warmer air. The lowest temperature ever measured on the ground, -89.2°C, was recorded at Vostok Station in 1983. The North Pole averages around -40°C in winter, while the South Pole averages around -60°C.