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
In February, polar climate researchers gathered at the National Center for Atmospheric Research in Boulder, Colorado to discuss the newest updates to models of the Earth’s climate system. The researchers are working together to create better models of the Arctic and Antarctic climates, which will feed into larger models of the whole Earth that help scientists understand how climate will change in the future. What goes into a climate model, and what can scientists learn from models that they cannot learn from observations?
This image shows several aspects of climate, including sea ice, surface winds, and sea surface temperature. This image came from data simulated from NCAR’s Community Earth System Model. Credit: ©UCAR, image courtesy Gary Strand, NCAR
What’s in a model?
Computer climate models are based on scientists’ understanding of Earth’s climate. The models use mathematical relationships to try to quantify the relationships between parts of the climate system. If you tweak one factor in climate, how does the simulated climate system respond? Models that bring many factors together help scientists learn how the climate system works, and let them run simulations on Earth’s climate. They also allow scientists to assess how climate may be affected by present and future changes in greenhouse gases and solar forcing, and how much of a role natural variability plays. Continue reading
The Arctic Oscillation (AO) is a large-scale climate pattern that influences weather throughout the Northern Hemisphere. It alternates between a positive phase (left) and a negative phase (right). In its positive phase the AO tends to bring warmer weather to the middle latitudes, while in its negative phase, winter storms are more common in the Eastern United States and Europe. Credit: J. Wallace, University of Washington.
Last year, many scientists blamed the winter storms that blasted the Northeastern United States and Europe on the negative mode of a weather pattern called the Arctic Oscillation. This winter, the Arctic Oscillation started out in the opposite mode, which scientists connect to the warmer-than-average temperatures and unusually low snowfall over much of the U.S. The swings of the Arctic Oscillation also help control how sea ice moves in the Arctic Ocean, which is of great interest to climate scientists. Readers often write in to ask us about this powerful but mysterious climate phenomenon, and how it affects weather where they live. What is the Arctic Oscillation, and how does it affect Arctic sea ice and the rest of the Northern Hemisphere? Continue reading
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
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