High-density salty, cold waters that sink into the water column from the Polar Regions power the ocean currents. This downward movement draws warm surface water from the equatorial regions to the poles and thus creates a current (the Gulf Stream being a notable example of this phenomenon). As the warm equatorial waters flow northward, they provide warmer waters and create milder climates along the Eastern Seaboard and Northern Europe. The cold, oxygen-rich polar water makes its way along the ocean’s depths to be eventually forced up by ocean upwellings to the surface in more temperate zones. As this stream of water rises up through the water column, it transports vast amounts of nutrients from the ocean floor. While organisms in the deep ocean rely on oxygen supplied from the sinking water, everything from blue whales to sea birds depend on the upwelling of the now-nutrient rich water for their existence.
Melting glaciers and sea-ice resulting from global warming have the potential to dump an enormous amount of freshwater into the North Atlantic, reducing these waters’ salinity and density. This water will not sink into the saltier water from the equatorial region, thus bringing the world’s ocean conveyor system to a halt. Aside from the obvious impacts on the ocean’s food chain and oxygen supply, the climatic changes that may develop from this scenario would have a dramatic effect on our environment. With a weakened, or absent, Gulf Stream, the Eastern Seaboard and Northern Europe will have much colder climates than they have now. Additionally, the normally cold Pacific coast may be locked in a perpetual warm, El Nino-type ocean pattern, resulting in the destruction of local fisheries as well as creating harsh weather conditions throughout the world.