Ice thickness, its spatial extent, and the fraction of open water within the ice pack can vary rapidly and profoundly in response to weather and climate. Sea ice typically covers about 14 to 16 million square kilometers in late winter in the Arctic and 17 to 20 million square kilometers in the Antarctic Southern Ocean. On average, the seasonal decrease is much larger in the Antarctic, with only about 3 to 4 million square kilometers remaining at summer's end, compared to approximately 7 million square kilometers in the Arctic. Over the past several years, Arctic minima have been only 4 to 6 million square kilometers. These maps provide examples of late winter and late summer ice cover in the two hemispheres.