The great ocean conveyor belt plays an extremely important role in shaping the Earth's climate. A slight disruption in it could destabilize the current and trigger an abrupt climate change. Climatologists at NOAA and NASA believe that as the Earth's atmosphere continues to heat from the effects of global warming there could be an increase in precipitation as well as an influx of freshwater added to the polar oceans as a result of the rapid melting of glaciers and ice sheets in the Arctic Ocean. They believe that large amounts of freshwater could dilute the Atlantic Gulf Stream to the point where it would no longer sink to the ocean depths to begin its return from the polar latitudes back to the equator.
Measurements taken over the past 40 years have shown that salinity levels within the North Atlantic region are slowly decreasing. What makes this so serious is that if cold water stopped sinking—which means the Gulf Stream would slow and stop—there would be nothing left to push the deep, cold current at the bottom of the Atlantic along, which is what ultimately drives the worldwide ocean current system today.
If this were to happen, the results would be dramatic. Western Europe and the eastern part of North America would cool off. Temperatures could plummet up to 8.3°F (5°C). This is about the same temperature as in the last ice age.
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