What is causing Arctic sea ice decline?

The Arctic Ocean has lost more than 30 percent of its summer ice cover in the last thirty years. Scientists have long thought that climate change is to blame, but a new study provides more evidence for that idea. Credit: Patrick Kelley, U.S. Coast Guard. High Resolution Image

Readers sometimes ask us, “What are the reasons behind Arctic sea ice decline?” In summer months, ice extent has declined by more than 30 percent since the start of satellite observations in 1979. But is climate change really the culprit, or could other factors be contributing? Continue reading

The Arctic sea ice maximum

NSIDC scientists announced today that the Arctic sea ice cover has likely reached its maximum extent, marking the beginning of the melt season. (For details, see Arctic Sea Ice News & Analysis). What is the sea ice maximum and why does it matter?

The maximum ice extent marks the beginning of the melt season for Arctic sea ice. Leads, long cracks in the ice, begin to open up and the ice cover starts to melt as sunlight brings warmth to the Arctic. Credit: Angelika Renner

What is the maximum and when does it happen?
Arctic sea ice melts and regrows in an annual cycle, freezing throughout the winter months and melting in the spring and summer. The ice cover generally reaches its maximum extent sometime in late February or March. After that, ice melts through the summer, hitting a low point in early or mid-September. NSIDC scientist Walt Meier said, “The maximum marks the point when the Arctic shifts from a freezing period into the summer melting period.” Continue reading

Sea ice down under: Antarctic ice and climate

The sea ice cover surrounding the continent of Antarctica is on average thinner than Arctic sea ice, and more susceptible to winds. This photo, from a 2003 research cruise, shows the trail of open water left by a research ship. In the background, an iceberg towers above the thinner sea ice cover. Credit: Ted Scambos, NSIDC

The Arctic Ocean is not the only place with sea ice. The ocean surrounding the continent of Antarctica also freezes over each winter. But we don’t hear much about sea ice on the bottom of the planet. What’s happening to Antarctic sea ice and why does it matter?

One reason that we hear less about Antarctic sea ice than Arctic sea ice is that it varies more from year to year and season to season than its northern counterpart. And while Arctic ice has declined precipitously over the past thirty years of the satellite record, average Antarctic sea ice extent has stayed the same or even grown slightly. Continue reading

What’s in a number? Arctic sea ice and record lows

Arctic sea ice extent for September, 2011 was the second-lowest in the satellite record. However, other data sources showed that ice extent perhaps hit a new record low for several days in September. Credit: NSIDC/NASA Earth Observatory

Did Arctic sea ice reach an all-time record low this year—or not? Scientists at University of Bremen in Germany thought it was a new record, while data from NSIDC showed the sea ice at its second-lowest level. The two groups were examining data from two different satellite sensors. Why did the data differ—and if data can vary, does a record low really matter? Continue reading

Arctic sea ice and U.S. weather

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