Global Problem: Ocean Currents May Change as Surface Temperatures Equalize

“These two papers do point strongly to the fact that the overturning has weakened over the last 150 years.”?- Jon Robson, Researcher, University of Reading

The thermohaline circulation, which is also known as the “ocean conveyor belt,” is the driving force behind the mixing of ocean waters, distribution of nutrients and heat around the world.?The concern is that a heating world could affect how the circulation works, which could cause, harsher winters in Europe, or whole ocean food chains to break down among many other things.?Some studies seem to indicate that the Atlantic Ocean current has reached a more than 1000-year low others suggest that it is weaker than any time in the last 1600 years.?

The thermohaline circulation moves at 2 m/s and transfers 100 000 000 m3 of sea water per second.?When these waters move in to the area between Europe and Greenland they release their heat to the atmosphere, mostly in the form of evaporation.?The colder denser water sinks in mid-ocean waterfalls known as “chimneys” which are around 15 km wide and drop 4000m.?Some of this water enters the Arctic Ocean as the cold dense “Atlantic Water,” through the Fram Strait between Greenland and Svalbard.?

There is evidence that when glacial Lake Agassiz (which covered much of Canada from Quebec to Saskatchewan, and areas of Nunavut, James Bay, Hudson Bay and the US States of Minnesota and North Dakota) catastrophically drained into the Atlantic Ocean, the immense volume of fresh water likely stopped the thermohaline circulation.?Research indicates that when the lake drained into Hudson Bay 8200 years ago, it raised global sea level between 0.8-2.8 m.?The release of such a great volume of fresh water is thought to have triggered the “8200 year climate event” which cooled the Earth for between 200-400 years.?It may also be the basis for various flood myths.

Side Note 1:?The El Ni?o phenomenon is a preview of what a breakdown of the thermohaline system might look like.?The El Ni?o occurs when warm water from the Central Pacific Ocean moves east to the west coast of South America.?When this happens, it stops the flow of deep cold water rising from the ocean depths, which cuts off the nutrients that phytoplankton require.?Phytoplankton isn’t as productive in warmer, nutrient poor water, so they don’t grow very well.?Given that plankton and phytoplankton are the base of the ocean food chain, all of the other creatures that depend on them, directly and indirectly, in the food web, are also less productive.?The result is that the local fishery collapses.?El Ni?o also affects weather as far away as California, where above average precipitation can be expected during an El Ni?o event.?If the thermohaline circulation were to stop completely, we could expect El Ni?o scale events around the world.

Side Note 2:?The Gulf Stream is part of the “ocean conveyor belt” which transfers warm water from the Equator and Gulf of Mexico through the Caribbean Sea and moves it along the eastern coast of the United Stated towards Europe.?It is estimated that the Gulf Stream transfers 300 GWh/s to the atmosphere off the coast of Europe.?That is approximately the output of 1 000 000 nuclear power plants.?That flow of warm water is credited with increasing the temperature of Europe by about 6°C over sites in North America at the same latitude.?E.G., London, England and Calgary, Canada, are roughly at the same latitude, yet their climates are very different.

Looking at this from a positive perspective, even though the global ocean conveyor seems to be weakening, it is still flowing.?With some tweaking from geoengineering projects, we may be able to increase the strength of the current.?Then again, who’s to say that a new weather regime change won’t be for the better?