Bowhead whales now ply the Northwest Passage: study

Bowhead whales are starting to regularly travel across the Northwest Passage for the first time in about 10,000 years, says a new study by scientists in Greenland and the United States. (FILE PHOTO)

(updated Sept. 23)

This year there are likely more bowhead whales than boats or ships trying to travel the increasingly ice-free Northwest Passage.

The Northwest Passage is now connecting bowhead whales from two populations, one from the Bering Sea and the other from Baffin Bay, which have been separated by sea ice for about 10,000 years, says scientists from Greenland and the United States.

Their study, called “the Northwest Passage opens for bowhead whales,” published Sept. 21 in the Biology Letters journal, relates how satellite tracking has shown that bowhead whales from West Greenland and Alaska enter the ice-filled channels of the Canadian High Arctic during summer.

But now they’re meeting in the middle of Northwest Passge: in August 2010, two bowhead whales from West Greenland and Alaska entered the Northwest Passage from opposite directions and spent approximately 10 days in the same area around Viscount Melville Sound, “finally documenting overlap between the two populations.”

Bowhead whales bones on elevated beaches in Nunavut’s High Arctic islands show that in the past bowhead whales did occupy the Northwest Passage, although few remains exist from Coronation Gulf, the study notes.

The bowhead bones suggest that 11,000 to 8,500 years ago there was enough open water in the channels for bowhead whales to travel between the Atlantic and the Pacific oceans.

Satellite tagging suggests bowhead whales from the the Bering–Chukchi–Beaufort population and the Baffin Bay–Davis Strait stock are doing that again.

For the study, bowhead whales have been tagged with satellite transmitters near Disko Island in West Greenland since 2000 and in Alaska since 2006.

The first evidence that bowhead whales move at least partially into the Northwest Passage was obtained in 2002 when a 12 metre-long (40-foot) bowhead whale tagged in West Greenland moved as far west as 93 degrees W. in the Northwest Passage in late September and early October. The bowhead whale finally returned east and headed out into Baffin Bay before moving south to winter in the Hudson Strait.

Four years later in 2006, a 14 m (45-foot) bowhead whale tagged near Point Barrow, Alaska was tracked north of Banks Island and along the coast into the Northwest Passage in early October, reaching 800 km from the position of the bowhead whale from 2002.

In both 2002 and 2006, the Northwest Passage was blocked by dense sea ice that apparently prevented whales from moving through the passage.

But in 2010, the Northwest Passage was largely free of sea ice by Aug. 10 and the two more bowhead whales moved into the Northwest Passage from opposite directions.

Both bowhead whales ended up in Viscount Melville Sound for more than two weeks that September, within 130 km of each other (less than 48 hours of travel for a bowhead whale).

The whales crossed each other’s paths in the Parry Channel in September, 2010 before each returned home.

“It is not known what attracted the whales to this area, given the region has relatively low marine production in autumn compared with other known bowhead whale feeding areas,” the study says.

The four bowhead whales that entered the Northwest Passage in from 2002 and 2006 were all males, “perhaps indicating a more exploratory behaviour by males,” it suggests.

Their movements confirm previous observations that bowhead whales range widely and can travel long distances during the open water season, as much as 1,000 km in less than a week, the study says.

As for why the bowhead whales are now in the Northwest Passage, that’s connected to the reduction in ice cover there and throughout the Arctic.

“The recent reduction of sea ice extent in August in the Arctic has probably facilitated greater access to the area and will ultimately allow for exchange through the Passage,” the study says.

The “plug” of ice which used to block their travel through McClintock Channel may now be less dense, it suggests.

Whalers in Russia are said to have harpooned Atlantic bowheads in the past — so it’s possible that some bowhead whales have always travelled through the Northwest Passage when possible, but that may increase.

“Given recent rates of sea ice loss, climate change may eliminate geographical divisions between stocks of bowhead whales and open new areas that have not been inhabited by bowhead whales for millennia,” the study says — and the Arctic Ocean could become a kind of corridor between the two oceans for marine mammals.

Bowhead whales are not the only whales which have been sighted recently in the Northwest Passage — belugas have been spotted further into the Parry Channel than previously, and this past August pods of narwhals made a surprise appearance in Cambridge Bay.

But these new travels across the Northwest Passage may also prove lethal to whales and marine mammals.

In 2009, a team of U.S. scientists documented the first transmission of a seal-killing virus from the Atlantic Ocean to a population of Pacific sea otters in Alaska — a suspected sign that melting Arctic sea ice was not only altering animal ranges but also opening new pathways for pathogens.

Those findings, detailed in the journal Emerging Infectious Diseases and published by the U.S. Centers for Disease Control and Prevention, indicated that the deadly phocine distemper virus – which killed 30,000 harbour seals in one 2002 outbreak in Northern Europe, and has affected populations on Canada’s Atlantic coast — was passed between seal species across Northern Canada or Arctic Eurasia before infecting the otters in Alaska’s Kachemak Bay.

with files from Postmedia News