Category Archives: Arctic sea ice

An Arctic hurricane?

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This satellite image from November 8 shows the hurricane-like storm that hit Western Alaska earlier this month. Credit: NASA Earth Observatory image created by Jesse Allen, using data obtained from the Land Atmosphere Near real-time Capability for EOS (LANCE).

On November 8 and 9, a strong storm hit the Western Alaska coast, bringing blizzard conditions, storm surge of up to 10 feet and wind gusts as fast as 93 miles per hour. Along the Western Alaskan coastline, towns and villages prepared for the worst. “Up here, cities are much more sparse, but a storm like this still impacts the people that live there,” said Kathleen Cole, an ice forecaster at the National Weather Service. Damage reports after the storm indicated extensive flooding, wind damage to buildings, as well as power outages, which led to many evacuations to higher ground and to shelters with generator power. Some reports referred to the storm as a “blizzicane,” or an Arctic hurricane. What was unusual about this storm—and was there any connection to changes in the Arctic climate? Continue reading →

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

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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 →

Climate change or variability: What rules Arctic sea ice?

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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 →

Getting beneath the ice

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Researchers can measure ice thickness by drilling holes in the sea ice. But the method is not a practical way to measure thickness over the millions of square miles of Arctic sea ice. Image courtesy of Martin Hartley

NSIDC reports ice extent, a two-dimensional measure of the Arctic Ocean’s ice cover. But sea ice extent tells only part of the story: sea ice is not all flat like a sheet of paper. While freshly formed ice might not be much thicker than a few sheets of paper, the oldest, thickest ice in the Arctic can be more than 15 feet thick—as thick as a one-story house. Scientists want to know not just how far the ice extends, but also how deep and thick it is, because thinner ice is more vulnerable to summer melt. Continue reading →

Heading towards the summer minimum ice extent

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Figure 1. This graph shows Arctic sea ice extent for spring and summer months. Light blue indicates the ice extent this year, dark blue shows ice in 2010, and green indicates ice extent during 2007, which was the record low year for Arctic sea ice. The gray line shows the 1979 to 2000 average ice extent, while the gray area around the gray line shows the standard deviation range for the data, which represents the range of normal variability. Credit: NSIDC

So far this summer, Arctic sea ice has been melting at a record pace. Satellite data, which go back to 1979, show that ice extent is currently lower than it was at the same time in 2007, the year that went on to shatter all previous records for low ice extent in September, the end of the melt season (Figure 1). It is not yet clear if the ice will hit a new record low this September. But whether or not the ice extent sets another record, Arctic sea ice is continuing its long-term decline, a trend that researchers say is related to warming temperatures in the Arctic.

This time of year, we receive a lot of questions about the upcoming sea ice minimum. What is it and why does it matter? Continue reading →