Three polar bears
Changes to sea ice influence the Arctic's local weather, climate and ecosystems -- and also polar bears, seen here from an icebreaking ship that passed though the Northwest Passage this summer during an eight-day series of meetings to discuss Arctic science. Credit: Ronald Kwok/NASA
While satellites provide accurate and expansive coverage of ice in the Arctic Ocean, the records are relatively new. Satellites have only monitored sea ice extent since 1973. To extend the record, JPL scientist Ronald Kwok and Drew Rothrock of the University of Washington, Seattle, recently combined the high spatial coverage from satellites with a longer record from Cold War submarines to piece together a history of ice thickness that spans close to 50 years. Analysis of the new record shows that since a peak in 1980, sea ice thickness has declined 53 percent. The study, published online August 6 in Geophysical Research Letters, shows that the current thinning of Arctic sea ice has actually been going on for quite some time.

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