Category Archives: Climate Change

Greenland’s glaciers and the Arctic climate

Posted on by

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 →

Climate change or variability: What rules Arctic sea ice?

Posted on by

This photo, taken during the NASA ICESCAPE mission in summer 2011, shows melt ponds on the surface of Arctic sea ice. Weather patterns in the Arctic this summer have favored ice loss, leading to near-record low ice extent over most of the summer. New research is explaining how much ice loss is caused by variable conditions, and how much can be pinned on human-caused climate change. Credit: NASA/Kathryn Hansen

Arctic sea ice is near its annual low extent for the year. Will it reach a new record low? While many people are watching this year’s ice extent closely, the effect of climate change on ice extent in a single year is different than its effect in the long term. Arctic sea ice has declined more than 30 percent in summer since satellite measurements started in 1979. But from year to year, ice extent jumps up and down quite a lot. Continue reading →

When will the Arctic lose its sea ice?

Posted on by
sea ice and icebergs

Scientists expect the Arctic to lose most of its summer ice cover by the end of this century, and are working to determine when this might happen. Here, open water in Fram Strait, in the Canadian Arctic, is interspersed with chunks of sea ice. Credit: Angelika Renner

If you have been following the topic of Arctic sea ice, you have probably seen a few headlines warning that the Arctic is about to lose its summer ice cover. Although scientists agree that Arctic sea ice is declining, they have published several different estimates of when the last of the sea ice will melt in summer, leaving more ocean surface open to absorb heat and add to global warming. What is behind all these different predictions? Continue reading →

Arctic sea ice and U.S. weather

Posted on by

People sometimes wonder if the weather they are experiencing locally, such as the heavy snow that fell in February 2011 over the Northeastern U.S., is connected to decreasing Arctic sea ice. Scientists are exploring a possible connection. Credit: NASA Earth Observatory.

Over the 2010 to 2011 winter, news stories suggested a potential connection between a warming climate, low Arctic sea ice extent, and unusually cold weather this winter in the U.S. and Europe. What do scientists know about how sea ice affects the weather?

Scientists have been exploring a possible link, but the question is far from settled. It makes sense that changing sea ice conditions could affect weather in the Arctic and other parts of the world. During the colder months, sea ice insulates the relatively warm ocean from the colder atmosphere. As sea ice declines, more heat can escape to the atmosphere in the fall and winter, affecting wind patterns, temperature, and precipitation. Continue reading →

Arctic sea ice and the tipping point

Posted on by
lead in sea ice

A lead or large crack in the ice opens up in melting summer sea ice. A seasonally ice-free Arctic is likely some time in the future, and will mark the decline of the ice pack and its stabilizing effects on temperatures. Credit: NSIDC

As Arctic sea ice thins and becomes more vulnerable to melting in summer, the data trend indicates that we may eventually see ice-free summers. The question is when. Could it be sooner than we think, because the weakened ice cover has reached a point of no return? A new study suggests that, in fact, there may be no “tipping point.”

Scientists refer to a tipping point as a threshold after which a system changes irreversibly. For sea ice, a tipping point would mean losing so much ice that its heat-reflecting effects are severely diminished, leading to more and more ice loss. With this vicious cycle in place, ice could not recover to its previous summertime levels. After Arctic sea ice hit a record low in 2007, some scientists considered the possibility that sea ice has already passed this tipping point. Continue reading →