Is the Gulf Stream running out of steam?
I recently read an article saying that the Gulf Stream was slowing down. This would be bad news for France and the UK, I thought. This part of the world still enjoys mild winters. For example Edinburgh is at the same latitude as Moscow and doesn’t get nearly as cold.
What powers the Gulf Stream? In short, it’s three giant pumps. The Gulf Stream is part of a global system called the Thermohaline Circulation. In Greek, this means temperature (thermo) and salinity (haline). Cold water is heavier than warm water so it sinks. Salty water is heavier than fresh water so it sinks. The three giant pumps are the three deep water formation places shown on the map. There, water sinks because it is cold and because when sea ice forms, some salt is left behind so the water gets saltier. All this cold salty water sinks fast. It is replaced by warm(er) surface water and it feeds the deep cold water currents.
The trouble is that global warming slows this down in two ways:
1- The polar regions warm faster than the rest, which means less temperature gradient.
2- The Greenland and Antarctic ice sheets melt pretty fast, which means lots of fresh water and less salt.
It sounds weird, but global warming could mean colder winters in France and UK. What does this mean for the Northern Rivers? Apparently “more frequent and intense El Niño events due to associated shutdowns of the Kuroshio, Leeuwin, and East Australian Currents”.(*)
References:
* Excellent article on the possible failure of the thermohaline circulation
https://en.wikipedia.org/wiki/Shutdown_of_thermohaline_circulation
Picture:
https://en.wikipedia.org/wiki/Thermohaline_circulation
Ocean currents
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