Is the Gulf Stream slowing down?

[Thomas II]

What would be the effects and dangers of a breakdown of the Gulf Stream System?

 

[bilby]

It has been modeled: https://courses.seas.harvard.edu/climate/eli/Courses/misc/201209-Mallorca/Sources/2-THC/from-EPS131/1h-vellinga-wood-THC-collapse-Hadley-model.pdf

In the first five decades after the collapse surface air temperature response is dominated by cooling of much of the Northern Hemisphere (locally up to 8C, 1–2C on average) and weak warming of the Southern Hemisphere (locally up to 1C, 0.2C on average). Response is strongest around the North Atlantic but significant changes occur over the entire globe and highlight rapid teleconnections. Precipitation is reduced over large parts of the Northern Hemisphere. A southward shift of the Intertropical Convergence Zone over the Atlantic and eastern Pacific creates changes in precipitation that are particularly large in South America and Africa. Colder and drier conditions in much of the Northern Hemisphere reduce soil moisture and net primary productivity of the terrestrial vegetation. This is only partly compensated by more productivity in the Southern Hemisphere. The total global net primary productivity by the vegetation decreases by 5%.

(my bold).

This particular paper examined the effect of an arbitrary large injection of fresh water to the North Atlantic, just to see how the stopping of the Thermohaline Circulation would effect the wider climate. The impacts are pretty dramatic and last about a century - but of course, that recovery assumes that the initial arbitrary cause was not sustained, and the model in question doesn't account for changes in vegetation distribution, nor for changes in atmospheric CO₂, both of which would likely have significant further impacts.

Whether such an injection of fresh water is a plausible event, or whether other (more plausible) events or chains of events might lead to a similar catastrophe, is not clear to me, and I haven't studied it in depth. However i do recall seeing some discussion of the rapid loss of the Greenland ice-cap that might produce effects similar to those discussed by this paper.

Certainly those parts of NW Europe currently warmed by the Gulf Stream could see some really nasty changes. Most European Union cities are a long way further north than the major Canadian population centres, and would see very harsh conditions for which they were never designed.

 

[J842P]

This particular paper examined the effect of an arbitrary large injection of fresh water to the North Atlantic, just to see how the stopping of the Thermohaline Circulation would effect the wider climate.

Don'tcha mean affect.

 

[bilby]

This particular paper examined the effect of an arbitrary large injection of fresh water to the North Atlantic, just to see how the stopping of the Thermohaline Circulation would effect the wider climate.

Don'tcha mean affect.

Your write. Eye due.

 

[StoneRoad]

I don't think the Gulf Stream is so much slowing down, as altering course a little in the short term. A large and sustained addition of meltwater - ie fresh - would probably have serious longer term results (as in the model quoted).
Larger affects in the short term to the weather / climate tend to result from alterations to the medium altitude airflows. Hence the bad winter weather in the UK !

 

[bilby]

I don't think the Gulf Stream is so much slowing down, as altering course a little in the short term. A large and sustained addition of meltwater - ie fresh - would probably have serious longer term results (as in the model quoted).
Larger affects in the short term to the weather / climate tend to result from alterations to the medium altitude airflows. Hence the bad winter weather in the UK !

Don'tcha mean effects?

 

[Jobar]

I have recently been watching a lot of YT videos on the possibility that the Younger Dryas extinction event, when the mammoths and sabertooths vanished, was caused by an impact on the ice sheet over the present site of the Great Lakes.

[YOUTUBE]https://www.youtube.com/watch?v=Aw5chtNWzo8[/YOUTUBE]

One of the results of that impact was the melting and release of a truly enormous flood of fresh water into the Atlantic; that seems to have shut down the Gulf Stream and extended the last glaciation by roughly a thousand years.

Though I doubt the much slower melting of the Greenland sheet would have anything like that severe an effect (not affect ), still there may be some cause for concern.
[YOUTUBE]https://www.youtube.com/watch?v=oAkL34Yu12A[/YOUTUBE]

 

[Thomas II]

https://www.washingtonpost.com/news/energy-environment/wp/2018/04/23/one-of-the-most-worrisome-predictions-about-climate-change-may-be-coming-true/?noredirect=on&utm_term=.36b5ecc64788