Tricky business

I read this afternoon of a possibility that global warming might do something unpleasant to the Gulf Stream, that is to say the part of something called the Atlantic Meridional Overturning Circulation which keeps the British Isles and Ireland (no longer part of the British Isles) green and pleasant. Something unpleasant which would mean that our climate, along with that of large chunks of Europe would become much more like that of Canada across the water, that is to say much colder.

I suppose this means that, given that the planet as a whole is getting hotter, some parts must be getting a lot hotter.

See references 1 and 2.

In reference 1, the caption to the first of the maps above reads: '(1) The shallow upper leg of the Atlantic Meridional Overturning Circulation carries warm, salty water northward [editor's note: the black terminal dot on the arrow seems to have landed on the wrong bit of current]. (2) The warm currents heat up the surrounding air and land, helping to create temperate weather over Western Europe. (3) The surface waters become cooler and denser as they near the Arctic, driving the currents deep below the surface and helping to propel the system. (4) The deep, cool waters run back down the Atlantic'. In the rather smaller and surprisingly different version in reference 2, the second of the maps above, they add some helpful arrows, so the flow on the lower blue stretch runs from left to right, that is to say towards the east.

My topological version of  the two versions of AMOC being included above, versions which one might have thought would be quite different from a modeling point of view. I put it all down to journalistic license in boiling a complicated story down to something the punters can manage. And I associate from the second version to a gravity feed central heating system.

While Bing tells me that the Antarctic Circumpolar Current flows to the east, just to the north of the East Wind Drift which flows to the west. And the waters follow the winds. Perhaps it is no wonder that the Southern Ocean is a bit rough on sailing boats.

No doubt it all keeps very big computers in business.

References

Reference 1: Climate change: The Atlantic’s vital currents could collapse. Scientists are racing to understand the dangers: So far, the efforts to observe the currents directly show they're weirder and more unpredictable than expected - James Temple, MIT Technology Review - 2021.

Reference 2: Factsheet: Risk management of climate thresholds and feedbacks: Atlantic Meridional Overturning Circulation (AMOC) - Met Office - 2019.