US Person has posted often about the effects of global warming and it the dire effect the phenomenon is having on the world's climate system. One of the most worrisome possibilities is the attenuaition or even shutdown of thermohaline circulation. You may know part of that globe girding system as the Gulf Stream which flows northward from the equator and crosses the North Atlantic. Ben Franklin was aware of it, and even drew a somewhat inaccurate map. Basically the thermohaline circulation mixes the globe's ocean waters distributing energy in the form of heat and salt content, Warm surface currents like the Gulf Stream flow poleward where the seawater cools, becomes more dense, and sinks. Deep subsurface currents flow into the ocean's basins and upwells in the Southern Ocean. Some of the oldest water, with a transit time of 1000 years, up wells in the North Pacific:
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| south polar view |
This circulation pattern of cooler and warmer ocean water has significant effects on climate. In 2005 British researchers discovered that the northern Gulf Stream surface current
had declined by about 30% since 1957. Scientists at Woods Hole Oceanographic Institute have
measured freshening of North Atlantic seawater as the polar ice cap melts. These events, could in theory, alter the course of the Gulf Stream from its current path past the British Isles and Norway towards the Equator much in the way Benjamin Franklin depicted it in his map. An event like this would seriously impact the climate of Europe since it is generally thought that the Gulf Stream keeps norther Europe more temperate than its latitude would indicate. Lessening of the Atlantic's currents has been
correlated with extreme sea level rise. This chart demonstrates that global sea levels have been rising since measurements began in the 1880's and the trend is expected to accelerate due to anthropomorphic warming driving seawater expansion and ice sheet melting:
