The ebb and flow of glacial lakes


The Quelccaya Glacier in Peru is the largest glacier in the tropics. This glacier provides water to the city of Lima and contributes to hydroelectric power. In the last fifteen years, it has retreated nearly 195 feet per year. The increasing presence of glacial lakes around it reflects its unprecedented recession. Photo credit: Edu Bucher (

People sometimes ask us what it means if the world’s glaciers melt because of warmer temperatures. As Earth’s climate warms, the fate of the world’s shrinking glaciers matters to people who depend on them for meltwater. An increase in glacial lakes may mean more water for the present but leaves many to wonder how reliable this source of water will be if glaciers continue to recede. But what are glacial lakes and how do they form? Are they a part of a normal, healthy glacier, or evidence of glacier decline? Continue reading

Arctic melt versus Antarctic freeze: Is Antarctica warming or not?

Photograph of a large tabular iceberg and sea ice near Antarctica

During the short austral summer, much of the sea ice surrounding Antarctica melts, often leaving only the large, tabular icebergs. Credit: NSIDC courtesy Andi Pfaffling

September 2012 was a record-setting month for both of Earth’s poles, but for different reasons: sea ice in the Arctic fell to a record low minimum extent after a summer of melting, while Antarctic sea ice froze to a record high extent during the South Pole winter. Is record Antarctic sea ice canceling out the losses in Arctic ice? And does the record in the south mean that Antarctica is not warming? Continue reading

Greenland’s glaciers and the Arctic climate

These before-and-after photographs show Petermann Glacier in July 2009, before the calving event, and again in July 2011. Photographs courtesy Jason Box (top), Alan Hubbard (bottom)

Last summer, a chunk of ice three times the size of Manhattan broke off Petermann Glacier in Greenland and floated out to sea. The calving left miles of newly open water in the deep Petermann Fjord, which had been capped in a thick layer of glacial ice. New research out this summer confirmed that it was likely the largest calving in the region since observations began in 1876. What does this event tell us about climate change in the Arctic? Continue reading