Mining more than a century of sea ice observations, including from 19th century Yankee whalers and 20th century Arctic wildcatters, researchers at the University of Alaska Fairbanks have put together an expansive view of climate change that lets web surfers track the ice pack off Alaska for decades.
To create the play-by-play of diminishing sea ice, researchers relied on space-age data -- satellite images collected since 1979 -- plus decades of older information collected from ship decks, shorelines and airplanes.
A preliminary version of the map that was unveiled weeks ago dates back to 1953. But the map will ultimately stretch back to 1850 once it's fully launched on Feb. 18 with a webinar providing details for scientists or others who wants to call in, said John Walsh, a research professor and the project coordinator.
The research shows the dramatic effect of a warming planet.
"What stands out is that these last five or six summers are unique in the whole record in terms of ice retreat north of Alaska," said Walsh, with the Alaska Center for Climate Assessment and Policy at UAF. "In the past, there was an occasional year where the ice edge goes several hundreds of miles offshore." Those measurements were taken in September, when sea ice is at its minimum. But that didn't happen year after year, as it has lately. "This seven-year period is unprecedented in the 160 years of data we've got," Walsh said.
The map may be one of a kind for its breadth of data and interactive features. "That ability to navigate through time, I think, is unique," Walsh said.
The project drew on a variety of sources, including the reports from whaling ships. The lion's share of the work involved digitizing historical documents. Those documents will be available for download for anyone who wants to dig deeper into the data, Walsh said.
One long-running set of records came from ice yearbooks compiled by the Denmark Meteorological Institute dating back to the 19th century and lasting through 1956. The annual records include summer reports of the sea ice edge from scientific expeditions, mariners and coastal observers.
Also useful before satellite tracking began in 1979 are U.S. Navy overflights of the sea ice from Nome and Barrow starting in 1953, as well as aerial reconnaissance conducted by the Canadian Ice Service based in Ottawa.
Walsh, 65, had firsthand experience with one of the best sources of data. As a young man he worked for Sea Ice Consultants Inc., a company that for three decades starting in the 1950s developed ice charts for the Bering Sea and the U.S. Arctic Ocean for oil explorers and later, the buildup of the Prudhoe Bay oil fields.
The most memorable year was 1975, during the height of construction, when the ice clung to the coast nearly the entire summer and tugs and barges with supplies lingered outside Barrow waiting for a window in the sea ice to make the last leg of the trip to the oil patch, Walsh said.
Ice forecasters like Walsh helped the vessels find a two- or three-day opening, but the ice temporarily trapped a barge and the news made The New York Times.
"They finally got out, but it was nip and tuck," he said. "It was a pretty tense time in the forecasting office, because if you sent guys through and they got trapped in the ice you had real problems."
Those charts for the oil industry, assembled with firsthand observations from planes, provide a smaller but more reliable view of ice conditions than satellite, he said. That's because satellites have difficulty distinguishing between a wet ice surface and open water.
Walsh, who taught meteorology at the University of Illinois for decades, moved to Alaska in 2001. He said he'll likely retire from UAF in a couple of years.
"I look at this (project) as nice closure," he said.
Contact Alex DeMarban at firstname.lastname@example.org.