Climate change or variability: What rules Arctic sea ice?

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

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

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

Summer predictions for Arctic sea ice

graph of estimates from the SEARCH sea ice outlook

Last week, an international group of researchers released their best estimates for Arctic sea ice extent over the summer melt season. The scientists are compiling their estimates so that they can better predict changes in Arctic sea ice. Credit: SEARCH Sea Ice Outlook

Average Arctic sea ice extent this May was the third lowest in the satellite record. Does that mean that ice extent will reach a new record low this summer? Or will it recover somewhat over recent years?

Last week sea ice scientists from around the world shared their best answers to those questions, in the June report of the Sea Ice Outlook. For the report, the researchers used a variety of methods to predict how sea ice will behave this summer, such as statistical methods or computer models. Continue reading

Sea ice and the Arctic coast

eroding coast and house in shishmaref, alaska

Like many villages along the Arctic coast, the Inupiaq village of Shishmaref, Alaska, is increasingly threatened by erosion, which is aggravated by the loss of sea ice and increased temperatures that lead to permafrost thaw. Credit: Shishmaref Alaska Erosion & Relocation Coalition

Why does it matter if the Arctic sea ice melts? We often hear about the global consequences: waning sea ice is expected to lead to even more climate warming. On a more immediate and local level, the loss of summer sea ice is already affecting the land and people near the Arctic Ocean. As the ice melts to reveal the open ocean underneath, fragile coastlines become vulnerable to bigger waves and storms. Continue reading