- Until now, Arctic ice models have only had data going back to 1979. While accurate, they lack historic context. A new project adds over a hundred years of data to current models.
- The study used historic records kept by a precursor to the U.S. Coast Guard, the U.S Revenue Cutter Service. These records have been digitized by a team including citizen scientist volunteers.
- The records confirm what scientists have believed: the Arctic is experiencing historic thinning due to man-made global warming.
It's a regular refrain: Ice in the Arctic is thinning. Scientists are able to say so with certainty because the region has been monitored by satellites since 1979. But the Arctic, of course, has existed for much longer than our orbital eyes in the skies. Gauging the full spectrum of its loss would allow scientists to better contextualize what's happening today. So scientists at the University of Washington, who operate a leading tool for gauging Arctic ice, have expanded Arctic sea ice volume back more than a century.
“This extends the record of sea ice thickness variability from 40 years to 110 years, which allows us to put more recent variability and ice loss in perspective,” says Axel Schweiger, a sea ice scientist at the UW’s Applied Physics Laboratory, in a press statement.
To make the estimates, Schweiger and his team had to mix modern data with the old-school. The team used both cutting-edge computer simulations and hand-written historic observations dating back to the early 1900s aboard precursors to modern U.S. Coast Guard ships. Going back 110 years only further confirmed what scientists currently believe: Arctic ice is rapidly thinning.
“The volume of sea ice in the Arctic Ocean today and the current rate of loss are unprecedented in the 110-year record,” Schweiger says.
Today scientists use models like the University of Washington’s Pan-Arctic Ice Ocean and Modeling System, or PIOMAS, to observe what's happening with Arctic ice daily. PIOMAS combines weather records with satellite imagery of ice coverage in order to compute ice volume, and then cross-checks that against any other observations of thickness.
But in the early days of the 20th century, direct measurements of Arctic ice were infrequent. The U.S Revenue Cutter Service, formed after the Revolutionary War by Alexander Hamilton, was designated as one of the nation's earliest armed customs enforcement agencies. After the Civil War, the USRCS ships began passing through the Arctic once a year, every year, starting in 1879.
In what's called the Old Weather program, teams from the University of Washington, the National Oceanic and Atmospheric Administration and the National Archives, and citizen scientist volunteers have been digitizing old Cutter Service logbooks, which are filled with historic climate observations.
“In the logbooks, officers always describe the operating conditions that they were in, providing hourly observations of the sea ice at that time and place,” said co-author Kevin Wood, a researcher at the Joint Institute for the Study of the Atmosphere and Ocean. In open water, the logbook might read “steaming full ahead” or “underway.” When faced with ice, officers might write “steering various courses and speeds,” another way of saying that the ship was navigating through a field of ice floes. If a boat ended up trapped within the ice, the log might read “beset.”
The Old Weather records have not been officially incorporated into PIOMAS yet, but the UW team has run spot checks comparing the model and the early Cutter Service observations. They hold up.
“This is independent verification that the model is doing the right thing,” Schweiger said. The record will be able to provide greater context for the Arctic's weather, ranging from storms to thinning.
“The observations that we have for sea ice thickness and variability are so limited,” Schweiger said. “I think people will start analyzing this record. There’s a host of questions that people can ask to help understand Arctic sea ice and predict is future.”
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