New data on global warming; thinning polar ice cap

By Marsha Walton
source: CNN

Tuesday, May 10, 2005 Posted: 2019 GMT (0419 HKT) CNN) -- One outcome of global warming could be a dramatic cooling of Britain and northern Europe.

Scientists now have evidence that changes are occurring in the Gulf Stream, the warm and powerful ocean current that tempers the western European climate.

Without the influence of the Gulf Stream and its two northern branches, the North Atlantic Drift and the Canary Current, the weather in Britain could be more like that of Siberia, which shares the same latitude

Cambridge University ocean physics professor Peter Wadhams points to changes in the waters of the Greenland Sea. Historically, large columns of very cold, dense water in the Greenland Sea, known as "chimneys," sink from the surface of the ocean to about 9,000 feet below to the seabed. As that water sinks, it interacts with the warm Gulf Stream current flowing from the south.

But Wadhams says the number of these "chimneys" has dropped from about a dozen to just two. That is causing a weakening of the Gulf Stream, which could mean less heat reaching northern Europe. The activity in the Greenland Sea is part of a global pattern of ocean movement, known as thermohaline circulation, or more commonly the "global conveyor belt."

Wadhams presented his findings at a meeting of the European Geosciences Union in Vienna, Austria, last month.

When Wadhams began his studies of Arctic Sea ice more than 30 years ago, there was not a focus on a warming of the region or the ice becoming thinner. His research aboard British Royal Navy submarines began as a way to use new tools, such as sonar, to study this harsh region of the planet.

"Initially the idea was just to map what the ice thickness distribution was," Wadhams said. "You cannot measure it with satellites, and to drill through it is difficult," he said.

But year after year, a dramatic pattern emerged.

"We discovered the ice was getting rapidly thinner. It has thinned by 40 percent in the past 20 years," said Wadhams.

Wadhams and other scientists say the slowing of the Gulf Stream could contribute to other severe effects on the planet, such as the complete melting of the Arctic ice cap in the summer months. That could eliminate the habitat and lead to the extinction of Arctic wildlife, including the polar bear. Current predictions indicate that could happen as early as 2020 or as late as 2080.

Scientists are getting other information about the disappearing ice cap from Alaskan Inuits. They report changes in where and when certain species of fish have been found, and in populations of seals and polar bears.

Other oceanographers stress that Wadhams' findings are one piece of a very complex earthly puzzle.

Terrence Joyce, senior scientist in the department of physical oceanography at Woods Hole Oceanographic Institution in Massachusetts, says it's important not to get alarmist, but instead to keep up a wide array of research.

For a dramatic climate change to take place, "A whole bunch of pieces have to fit together. Certainly this is one of them. We need to keep paying attention, and people are doing that," he said.

Woods Hole is conducting research that measures the path and temperature of some parts of the Gulf Stream.

Such a dramatic climate change would not take place in five days, but rather several years, said Joyce.