Ocean Forces Threaten Our Climate

The danger is that this fresh water might dilute the salty current of the Gulf Stream so much that it stops sinking down into the ocean depths near Iceland. If the Gulf Stream does stop, there will be nothing pushing the deep cold river at the bottom of the North Atlantic. As the Atlantic portion of the ocean conveyor belt grinds to a halt, then Europe could indeed freeze ‚ ironically, as a direct result of global warming.

Global Warming Kicks In

If that weren't enough, the ocean current specialists have just found something else to worry about. Global warming may interfere with not just the North Atlantic currents, but may disrupt the entire system of ocean currents ‚ affecting the entire world's weather.

Leading the new investigation is Wallace Broecker and his colleagues at Columbia University, New York. They start with evidence that the great ocean currents tend to make the climate in the Earth's two hemispheres change in opposite directions: when the north is hot, the south is colder ‚ and vice versa. In Europe, most of the past millennium (from about 1300 to 1800) was so cold that it has been dubbed 'The Little Ice Age'. Some researchers have blamed the Little Ice Age on a slowdown in the ocean current system that includes the Gulf Stream. But Broecker takes the analysis a stage further. At the same time, he says, the southern currents were stronger, and - in a mirror image of the Little Ice Age - the Antarctic region warmed up, perhaps by as much as 3 ^oC.

The link involves the ocean rivers that flow along the coast of Antarctica ‚ the deep cold currents flowing back from the South Atlantic, south of Africa and Australia. Cold, salty water off the Antarctic coast sinks down into the depths, adding its push to the interlinked system of ocean currents.

The perpetual chill of Antarctica helps to drive the ocean conveyor belt, as cold salty water sinks to join the deep current flowing from the Atlantic to the Pacific. But latest measurements show a slow-down in the sinking Antarctic waters.

photo - Sean Leslie

In his latest research, Broecker and his colleagues at Columbia University, New York, have just announced that the surface water near Antarctica is sinking at only a third of the rate it was a century ago.