Why is there so much Antarctic sea ice?


Photograph from a ship traveling through Antarctic sea ice

Even during the Antarctic summer, heavy sea ice conditions are not uncommon. This photograph of sea ice was taken from the British icebreaker, HMS Protector, on its way to assist a Norwegian cruise ship that had become stuck in sea ice in January 2013.
–Credit: Royal Navy Media Archive (http://www.flickr.com/photos/rn_topten/8443836559/in/set-72157632684027667)

In late December 2013, the Russian research vessel, Akademik Shokalskiy, became trapped in thick sea ice off the coast of Antarctica. After several research vessels and icebreakers attempted rescue, the 52 passengers were evacuated. Soon after, one of the rescue ships also became stuck in the ice. However, conditions eased and both icebound ships safely churned out to open water.

Research in polar regions is inherently risky, and these events show how easily weather and ice conditions can disrupt research missions and travel during the already short Antarctic summer. But why was there so much sea ice around Antarctica to begin with, and why was it so thick? Antarctic sea ice is ruled by very different systems than Arctic sea ice. The reasons behind this increase are complex, and several recent studies show that scientists are still trying to understand them. Continue reading

Core of climate history

Lou and the Ice Core Drill

Scientists take ice core samples in cold, windy, and forbidding environments. After drilling through solid ice to retrieve a core, initial measurements are taken before it is sent away for more in-depth analysis and storage. Photo credit: NSIDC courtesy Ted Scambos and Rob Bauer

People have asked how scientists know that today’s climate situation is unusual. Hasn’t the Earth undergone many cold and warm cycles before? Could this just be another? Buried in the world’s ice sheets is a long story of climate on Earth–and the contribution of atmospheric CO2 to warming or cooling. Scientists can access a unique and detailed look at the history of the Earth’s atmosphere through ice cores and start to understand the recent climate in context of past ones. Continue reading

Are icebreakers changing the climate?

On July 20, 2011, the U.S. Coast Guard Cutter Healy traveled through a break in the sea ice and melt ponds in the Arctic Ocean, during the NASA Impacts of Climate on Ecosystems and Chemistry of the Arctic Pacific Environment (ICESCAPE) mission, a field survey aimed at understanding the ecology of the Arctic Ocean. Credit: NASA/Kathryn Hansen

In summer months, icebreaking ships head north into the Arctic Ocean, tearing through the sea ice and leaving trails of open water in their wakes. Readers occasionally write in to ask us whether the trails left by these ships contribute to the melting of sea ice. 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

What about sea ice in winter?

Researchers take measurements of the physical properties of sea ice in Fram Strait, in the Canadian Arctic. Thinner sea ice melts away faster in the summer compared to older, thicker ice. Credit: Angelika Renner

Arctic sea ice has most likely frozen to its maximum extent for the winter. This event marks the turning point between winter and spring for sea ice, and may affect the amount of ice that will remain by end of summer. In early April, NSIDC scientists will talk about what this year’s maximum signifies for the upcoming summer. Meanwhile, readers are asking how the ice cover this year is different from the ice cover in years past.

Arctic sea ice grows each winter, hitting its annual maximum sometime in March. When the sun returns to the Arctic in the spring, the air warms up and the ice starts to melt. The ice retreats through the warmer summer months, hitting its lowest point sometime in September. Although scientists watch the sea ice year-round, they pay attention to the highest and lowest extents of the year as indicators of the overall health of the sea ice. Continue reading