15 November 1997
Somewhere below the surface of the western Arctic Ocean, a layer of warm water has been expanding and rising. No one is sure where its exact boundaries are. But wherever they are, one thing is certain: if it reaches the surface underneath the ice cap, it could rapidly melt the cap.
This, points out Wayne Grady in a new book, is « an entirely new phenomenon. The Arctic Ocean (is) warming up from below.’’ If the cap melts, « it would have a devastating effect’’ on how waters circulate through the Atlantic and Pacific Oceans, « and therefore (a devastating effect) on world climate.’’
Grady’s book chronicles a scientific expedition that crossed the top of the world in the summer of 1994 aboard two icebreakers — the Canadian Louis St. Laurent and the smaller U.S. Polar Sea.
It was a two-month journey, and Grady’s account in The Quiet Limit of the World: A Journey to the North Pole to Investigate Global Warming (Macfarlane Walter & Ross, Toronto, $29.95) is written in the relaxed and intimate style of a good travel writer.
He describes the day-to-day activities of the expedition, delivers capsule histories of arctic expeditions over the past 270 years, and interlaces his accounts with scientific observations and explanations that are easy to understand.
It adds up to an unusual accomplishment for scientific writing — a good read.
There are a lot of experiments described, but it’s the references to warm water seeping into the Canadian Basin that rivet the attention. To explain what’s going on, Grady suggests that we think of the Arctic Ocean as a double, stainless steel, kitchen sink, with the divider representing a range of undersea mountains that passes over the North Pole.
The right hand sink is the Eurasian Basin, the left hand sink is the Canadian Basin, and the dividing undersea mountain range is the Lomonosov Ridge.
The warm water layer comes from the Gulf Stream that flows northward between Greenland and Norway, enters the Barents Sea, and joins a current circling the Eurasian Basin in a counterclockwise direction.
When the current hits the Lomonosov Ridge, it forks. Some of its top waters flow over the ridge into the Canadian Basin; the remainder of the current continues counterclockwise, past the North Pole and out again into the North Atlantic.
Its all part of a grand pattern that takes warm water from tropical areas, cools it in the arctic and returns it.
Where waters from the Atlantic and Pacific meet in the arctic, they are different. In the past, they met near the Lomonosov Ridge. But in 1993, scientists aboard the Canadian icebreaker, the Henry Larsen, discovered that the meeting point had moved 600 kilometres away from the ridge and into the Canadian Basin. And it had brought warm water with it — 50 metres thick and, because it was saltier and heavier, lying 400 metres below the surface.
Scientists hypothesize that, as a result of global warming, the Gulf Stream is bringing more warm water than it used to into the Barents Sea. And much more warm water is slopping over the top of the Lomonosov Ridge.
The 1994 expedition, with Grady aboard, couldn’t find where the warm water layer ended. But it appeared to have covered about a third of the Canadian Basin. And it had risen from a depth of 400 metres to 200 metres.
The speed with which this warm water is moving out and up is scary. Even without melting from below, the ice cap is about 40 per cent thinner than it used to be.
This past fall a Canadian icebreaker, the Des Grosseillers, with a team of scientists aboard, deliberately locked herself into the ice in the Chukchi Sea, north of Alaska. She will drift with the ice pack toward the North Pole and the eastern arctic until next fall. One of the tasks set for her scientists is to find the warm front and to pinpoint what it’s doing, and why.
If you want to track what the Des Grosseillers scientists are finding, you can check their website at http://www.joss.ucar.edu/sheba/catalog/.
NEXT WEEK: Acting locally