For six weeks from September to November 2001, the Healy
tracked the Atlantic Layer, more often called the Gulf Streamthe warm, salty current that moderates the climate of communities in the North Atlantic, especially northern Europeas it enters the Arctic between Norway and Svalbard Island in the Eurasian Arctic.
Scientists know that currents driven by differences in temperature and salinity, called thermohaline currents, form a conveyor belt circulating into, through and out of the Arctic Ocean and through all the oceans of the world. A part of these ocean currents, the Gulf Stream Current dives beneath colder water and is held down in layers, but scientists know that the freshwater fluxes from the melting Arctic glaciers, the Greenland ice cap and salt-depleted sea ice can affect thermohaline currents. They believe that any change or discontinuity in the direction, velocity or volume of these currents will affect climate. That's why scientists envision the Arctic Ocean as a "switch" that can flip the global climate. If the Atlantic Layer slowed or diverted, the North Atlantic region would become cooler while the rest of the world warms up.
On board the bow of the Healy.
"Fresh water intrusions from melting glaciers and salt-depleted sea ice in the Arctic front may have such an impact," Martin said.
When sea ice melts, the sea level does not change. (Iced tea doesn't spill over the rim as ice cubes melt in a full glass.) On the other hand, if ice caps such as those covering the landmasses of Greenland and Antarctica were to disappear, "seas would rise dramatically," Martin said. "And since this would also represent a large infusion of fresh water, bio-chemical changes would be profound."
's science lounge, scientists frequently speculate on the impact of climate change on animal habitats. "We're pretty sure that the shrinkage of the Arctic ice capthe preferred home of the polar bearhas, to some extent, upset the feeding and reproductive regimes of this animal," Martin said.
Norwegian scientists have produced a model indicating that if present trends continue, the Arctic may be ice free in summers by mid-century. "Others say this doomsday prediction is baloney," Martin said. "The conservative side says change is natural. Is it natural or caused by us? Nobody is sure. But it's definite: they all agree that things are changing."
A report on Arctic warming published on November 1 in the American Meteorological Society's Journal of Climate
chillingly underscores the point that the perennial Arctic ice pack has shrunk. According to satellite data, the rate of warming in the Arctic between 1981 and 2001 was eight times the rate of warming over the last 100 years. During Arctic summers temperatures over sea ice increased by an average of more than two degrees Fahrenheit each decade. A team of Chinese scientists found that the thickness of the sea ice now averages 8.8 feet, down from an average of more than 15 feet in the 1980s.