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Captain Cook's Notes Describe Now-Vanishing Arctic Ice Wall

The meticulous records of Capt. James Cook, the intrepid British explorer famous for exploring Australia and the Hawaiian islands, have found a new and modern-day value: Helping climate change scientists understand the extent of sea ice loss in the icy Canadian Arctic, according to a new study.

Notes, charts and maps created by Cook and his crew during an Arctic expedition in August 1778 carefully documented the position and thickness of the ice barring the explorers' way. They were searching for a corridor that they thought would link the Pacific and northern Atlantic oceans and offer a new maritime trade route between Great Britain and the Far East.

Cook never found that route, known today as the Northwest Passage. But his observations and those of his crew provide the earliest recorded evidence of then-extensive summer ice cover in the Chukchi Sea. That part of the Arctic Ocean lies between Alaska and Russia. These records, when compared to modern observations of sea ice, indicate how dramatically Arctic ice cover has changed — particularly in recent years, according to study author Harry Stern, a researcher with the Polar Science Center at the University of Washington.

While Cook wasn't the first explorer to search for the Northwest Passage — nor was he the last — he was the first to chart the ice border that bisected the ocean north of the Bering Strait, Stern said in the study. Cook was also the first to attempt the approach from the Pacific side by traveling up the North American coast, Stern said.

At the time, finding this route — which would have expedited and strengthened trade with the Orient — was an especially urgent goal for Great Britain. In fact, the House of Parliament issued an act in 1745 offering a reward of up to 20,000 pounds (about $24,978 U.S.) for finding and mapping the passage, according to archives of the Royal Greenwich Observatory maintained by the University of Cambridge Digital Library.

Stern, who studies climate and Arctic sea ice, researched Cook's journey for an essay the climate scientist contributed to the book "Arctic Ambitions: Captain Cook and the Northwest Passage" (University of Washington Press, January 2015). As Stern studied the archival documents from the 1778 voyage, he realized he was looking at the very first detailed maps of the ice edge in the Chukchi Sea, he said.