There are two warnings about melting ice and rising oceans: one is by land, the other, by sea. But it’s ice sheets on land, not icebergs in the ocean, that are the biggest contributors to sea level rise.

Land ice includes mountain glaciers and ice sheets, covering Greenland and Antarctica. These giant blocks of ice are melting and the water is flowing rapidly into the oceans. Think of it like adding water to an already full glass – it soon overflows. But melting sea ice behaves differently. Axel Schweiger is a researcher at the University of Washington.

Schweiger: “Melting sea ice has no impact on sea level rise because it’s already floating in the ocean.”

Like a glass of ice water. As it warms, the ice in the glass melts, but the total volume of water does not change. However, melting sea ice does contribute to climate change. That’s because white sea ice reflects the sun. So when it melts, the dark open ocean now absorbs sunlight and heats up, raising global temperatures, which in turn cause glaciers and ice sheets on land to melt further. Globally, sea levels have risen four to eight inches since the last century and will continue to rise as the ice melts, putting coastal communities worldwide at risk.

Reporting credit: ChavoBart Digital Media.

Photo: The Antarctic Ice Sheet covers an area larger than the U.S. and Mexico combined. This photo shows Mt. Erebus rising above the ice-covered continent. (Ted Scambos & Rob Bauer) Courtesy of the National Snow and Ice Data Center, University of Colorado, Boulder.

More Resources

All About Sea Ice

A Tour of the Cryosphere (includes an audio version)

Arctic vs. Antarctic

Melt of Key Antarctic Glaciers ‘Unstoppable’

Stronger Winds Explain Puzzling Growth of Sea Ice in Antarctica

Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise

NASA Mission Takes Stock of Earth’s Melting Land Ice