Satellite observations since 1979 show that sea ice melted to its lowest extent in the satellite record, during August 2012 . As of this post date, the ice continues to melt, with two to three weeks left before the days shorten enough for the ice extent to begin to expand through the winter. Readers often write to us asking what such records really mean. How far from normal is this year’s record low, and how do scientists decide what is normal? Continue reading
Readers often ask us, “Why does your sea ice map show sea ice where there is none?” Sometimes our Daily Sea Ice Extent images show sea ice in a particular area, but when readers who live in those areas look out their windows, they see open water—or they even may see ice where our maps show open water. This occurs most frequently along rivers or near coasts. Why does this happen?
Ups and downs of passive microwave
These discrepancies are most often caused by the resolution of the satellite sensor. NSIDC relies on passive microwave sensors to compile daily sea ice maps. These sensors have the advantage of being able to see through the Arctic’s cloudy weather and capture surface data even during long, dark winters, making them ideal for tracking sea ice. The disadvantage, however, is that passive microwave sensors often have low spatial resolution. The sensors collect data in “footprints” that are up to 50 to 70 kilometers (31 to 44 miles) in diameter. Continue reading
In April, average ice extent in the Arctic Ocean was right near the long-term average for the month. Ice extent even reached a near-record high in the Bering Sea, and still remains above average for that region. Does this mean that the Arctic sea ice has stopped declining? Is it starting to recover?
Unfortunately, scientists say no—and they are not surprised to see such a short upward bump in ice extent. “This does not indicate that the Arctic sea ice is recovering,” said Marika Holland, a sea ice expert at the National Center for Atmospheric Research (NCAR). Instead, the higher ice extent this year compared to recent years likely just reflects different weather this winter compared to last winter. “Sea ice exhibits large natural variability due to year-to-year variations in weather,” she said. Continue reading
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
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