Fundamentals: Gulf stream stopping?

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- CommentAuthordjh
- CommentTimeJul 26th 2023 edited
I see there's a piece in the Grauniad about the Gulf Stream collapsing sooner rather than later https://www.theguardian.com/environment/2023/jul/25/gulf-stream-could-collapse-as-early-as-2025-study-suggests

The article it's reporting on - https://www.nature.com/articles/s41467-023-39810-w - uses some apparently heavy duty statistical techniques to suggest it will collapse in 2050-2057 or so but with error bounds that suggest it could happen as early as 2025. Given the importance of the Gulf Stream for the UK climate, it makes me wonder whether the government have any contingency plans to deal with the massive increase in heating energy demand that will result? (Always assuming we've just reached net zero by 2050 of course )
- CommentAuthorDoubting_Thomas
- CommentTimeJul 26th 2023
One thing I've seen several commenters pointing out in response to this article is that it isn't actually the Gulf Stream itself, rather the AMOC which is an offshoot - the analogy I saw was comparing a major motorway with a rural side road in terms of volumes of water displaced.

That said, it will affect the UK regardless (but perhaps the US etc. will be unaffected) and is a terrifying prospect, so your point above still stands.

Notably in the US there's been a shift from denialism towards 'Climate Nationalism' lately where states squabble over who gets federal aid and there's increasing resentment towards government in general.

I suspect as this reaches our shores, the idea of contingency plans or forward planning of any type will have been replaced by reactionary emergency measures instead.
- CommentAuthorWillInAberdeen
- CommentTimeJul 26th 2023
Various sources suggest that the climate of SE England in that scenario, would become similar to that of NE Scotland today.

I can reassure you it's very pleasant and liveable, especially this time of year. There are about 30% more HDD, so you'll want a heatpump with COP=4 instead of 3, shouldn't be a problem with the next generation.

I cannot reassure you about any of the other disastrous effects of such a collapse; heating houses will be the least of everyone's problems.
- CommentAuthordjh
- CommentTimeJul 26th 2023
Posted By: Doubting_ThomasOne thing I've seen several commenters pointing out in response to this article is that it isn't actually the Gulf Stream itself, rather the AMOC which is an offshoot - the analogy I saw was comparing a major motorway with a rural side road in terms of volumes of water displaced.
I think you have things reversed. The AMOC is the large thing - the overall cycle of flows that include individual currents such as the North Atlantic Drift (a.k.a. the Gulf Stream). What is being discussed is disruption/destruction of the AMOC.
- CommentAuthordjh
- CommentTimeJul 26th 2023
Posted By: WillInAberdeenThere are about 30% more HDD, so you'll want a heatpump with COP=4 instead of 3, shouldn't be a problem with the next generation.
There won't be time to install a new generation of heat pumps, even if one with such large gains were available at the right time. The issue is whether there is contingency of 30% in the generation and distribution capacity of the network. Plus of course all the other effects that follow from loss of the current as you say.
- CommentAuthorowlman
- CommentTimeJul 26th 2023
Posted By: djh
Posted By: Doubting_ThomasOne thing I've seen several commenters pointing out in response to this article is that it isn't actually the Gulf Stream itself, rather the AMOC which is an offshoot - the analogy I saw was comparing a major motorway with a rural side road in terms of volumes of water displaced.
I think you have things reversed. The AMOC is the large thing - the overall cycle of flows that include individual currents such as the North Atlantic Drift (a.k.a. the Gulf Stream). What is being discussed is disruption/destruction of the AMOC.

Believed by many to be caused principally by Greenland's ice cap melting.
- CommentAuthorDoubting_Thomas
- CommentTimeJul 26th 2023
Posted By: djhI think you have things reversed.

I was basing it on my (admittedly layman's) reading of this thread:

https://twitter.com/GlobalEcoGuy/status/1683956621465079809?s=20

Some excerpts:

"The Gulf Stream is a HUGE current on the surface of the North Atlantic Ocean, carrying about ~150 Sv of water. (1 Sv equals 1 million cubic meters of water per second.)

It comes from the tropics along the North American coast, and then heads from Cape Cod towards Ireland.

...A small branch of the Gulf Stream (the "North Atlantic Drift") heads towards the Norwegian and Greenland Seas, which is the small piece that connects the Gulf Stream to the AMOC system.

That's it. The Gulf Stream and the AMOC are only connected by the North Atlantic Drift.

Think of a super highway of warm water going in a big loop around the Atlantic. That's the Gulf Stream.

A small "side road" of water (about 10% of the Gulf Stream) heads north -- like an exit -- towards the far north, off the coast of Norway & Greenland.

That the NA Drift.

A bad analogy, maybe, but you can consider:

- The Gulf Stream is a superhighway of warm water circulating around the North Atlantic

- A small road (the North Atlantic Drift) branches off, heading north

- And this goes to a third, smaller road, where the AMOC begins

If the AMOC collapses -- but there is no direct evidence of this -- it would be a serious issue for that region. But the larger Gulf Stream circulation would continue operating, largely as before."
- CommentAuthorWillInAberdeen
- CommentTimeJul 27th 2023 edited
The research is being (wilfully?) misreported though. The researchers are actually looking at whether there will be warning signals before some change occurs in the ocean currents. Not whether there will be any change at all (which is already widely accepted).

They think that the signals are saying 'tipping point around 2057', but (of course) they're quite uncertain how to decode what the signal might actually be saying. Their 2-SD uncertainty range is 2025-2095 - so only a 2.5% chance (1 in 40) that this signal should best be decoded as 'tipping by 2025'. There's a whole load more uncertainty whether this signal is actually right, wrong, or irrelevant in the first place, as other scientists pointed out, this is normal because climate science is difficult.

The press of course reported this as 'scientists say gulf stream could collapse in 2025' because that sounds a lot more sensational.

Had they quoted the usual 3-SD uncertainty band, the press would have to report 'gulf stream might already have stopped in 2009' or 'not until 2114' which wouldn't be as sensational.

That kind of talking-up-doom to sell papers is unhelpful IMO as it feeds sceptics who use the uncertainty the other way. There's quite enough real climate disasters to report on this year without twisting possible-maybe-futures.

I agree with the PM that maths should be better taught, so people don't get suckered by that kind of (mis)reporting.

2057 is far enough away to fit many generations of heatpumps (or fusion-hydrogen boilers or whatever). Not long enough to prepare for other profound effects of gulf stream changes.
- CommentAuthordjh
- CommentTimeFeb 12th 2024
Another paper published about this:

https://www.science.org/doi/10.1126/sciadv.adk1189

"One of the most prominent climate tipping elements is the Atlantic meridional overturning circulation (AMOC),
which can potentially collapse because of the input of fresh water in the North Atlantic. Although AMOC collapses
have been induced in complex global climate models by strong freshwater forcing, the processes of an AMOC tip-
ping event have so far not been investigated. Here, we show results of the first tipping event in the Community
Earth System Model, including the large climate impacts of the collapse. Using these results, we develop a physics-Â
based and observable early warning signal of AMOC tipping: the minimum of the AMOC-Âinduced freshwater
transport at the southern boundary of the Atlantic. Reanalysis products indicate that the present-Âday AMOC is on
route to tipping. The early warning signal is a useful alternative to classical statistical ones, which, when applied
to our simulated tipping event, turn out to be sensitive to the analyzed time interval before tipping."
- CommentAuthorfostertom
- CommentTimeFeb 12th 2024
Just reading about the "Younger Dryas, which occurred circa 12,900 to 11,700 years BP, was a return to glacial conditions which temporarily reversed the gradual climatic warming after the Last Glacial Maximum, which lasted from circa 27,000 to 20,000 years BP" (from Wiki).

Apparently the warming was interrupted by the 'sudden' release of vast quantities of glacier meltwater from north central North America, which re-stopped the Gulf Stream which was just getting into its stride. Mean world temperature at that point was 5C below present - not a lot, to create an ice age, just like 1.5C above is already creating havoc.

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