Greenland is covered in ice because it lies at high latitudes, where the mean temperature is below freezing. The Greenland Ice Sheet is a massive body of ice that covers much of the island and is approximately 3 kilometers (1.8 miles) thick. It is the second largest ice sheet in the world, after the Antarctic Ice Sheet, and contains approximately 7% of the world's fresh water.

The Greenland Ice Sheet was formed during the last ice age, which ended about 11,700 years ago. During the ice age, the climate was cooler than it is today, and the ice sheet grew to its current size. As the climate has warmed since the ice age, the ice sheet has started to melt, but this melting has accelerated in recent years due to human-induced climate change.