Model vs Model: Is the North Atlantic Current Collapsing?

Essay by Eric Worrall

h/t Dr. Willie Soon; 12,900 years ago the North Atlantic Current failed, likely due to the emptying of an enormous glacial lake. This catastrophic lake failure is believed to have disrupted ocean currents, which led to an abrupt return to ice age conditions which lasted for over a thousand years.

The glacial lake which caused this calamity no longer exists, but the remote possibility global warming could trigger a new ice age is a favourite scenario of climate alarmists.

Article Published: 

Interbasin and interhemispheric impacts of a collapsed Atlantic Overturning Circulation

Bryam Orihuela-PintoMatthew H. England & Andréa S. Taschetto 

Nature Climate Change (2022) Cite this article

Abstract

Climate projections suggest a weakening or collapse of the Atlantic Meridional Overturning Circulation (AMOC) under global warming, with evidence that a slowdown is already underway. This could have significant ramifications for Atlantic Ocean heat transport, Arctic sea ice extent and regional North Atlantic climate. However, the potential for far-reaching effects, such as teleconnections to adjacent basins and into the Southern Hemisphere, remains unclear. Here, using a global climate model we show that AMOC collapse can accelerate the Pacific trade winds and Walker circulation by leaving an excess of heat in the tropical South Atlantic. This tropical warming drives anomalous atmospheric convection, resulting in enhanced subsidence over the east Pacific and a strengthened Walker circulation and trade winds. Further teleconnections include weakening of the Indian and South Atlantic subtropical highs and deepening of the Amundsen Sea Low. These findings have important implications for understanding the global climate response to ongoing greenhouse gas increases.

Read more: https://www.nature.com/articles/s41558-022-01380-y

Of course, all these problems go away if what is actually happening is cyclical natural variation.

The evolution of the North Atlantic Meridional Overturning Circulation since 1980

March 2022

Nature Reviews Earth & Environment 3(4)

DOI:10.1038/s43017-022-00263-2

Authors: , Laura Jackson, Arne Biastoch, Martha W. Buckley, Damien Desbruyères, Eleanor Frajka-Williams, Ben I. Moat, Jon Robson

Abstract

The Atlantic Meridional Overturning Circulation (AMOC) is a key component of the climate through its transport of heat in the North Atlantic Ocean. Decadal changes in the AMOC, whether through internal variability or anthropogenically forced weakening, therefore have wide-ranging impacts. In this Review, we synthesize the understanding of contemporary decadal variability in the AMOC, bringing together evidence from observations, ocean reanalyses, forced models and AMOC proxies. Since 1980, there is evidence for periods of strengthening and weakening, although the magnitudes of change (5–25%) are uncertain. In the subpolar North Atlantic, the AMOC strengthened until the mid-1990s and then weakened until the early 2010s, with some evidence of a strengthening thereafter; these changes are probably linked to buoyancy forcing related to the North Atlantic Oscillation. In the subtropics, there is some evidence of the AMOC strengthening from 2001 to 2005 and strong evidence of a weakening from 2005 to 2014. Such large interannual and decadal variability complicates the detection of ongoing long-term trends, but does not preclude a weakening associated with anthropogenic warming. Research priorities include developing robust and sustainable solutions for the long-term monitoring of the AMOC, observation–modelling collaborations to improve the representation of processes in the North Atlantic and better ways to distinguish anthropogenic weakening from internal variability. The Atlantic Meridional Overturning Circulation (AMOC) has a key role in the climate system. This Review documents AMOC variability since 1980, revealing periods of decadal-scale weakening and strengthening that differ between the subpolar and subtropical regions.

Read more: https://www.researchgate.net/publication/358935843_The_evolution_of_the_North_Atlantic_Meridional_Overturning_Circulation_since_1980

Laura has been writing about cyclical variation for quite a while.

Recent slowing of Atlantic overturning circulation as a recovery from earlier strengthening

May 2016
Nature Geoscience 9(7)
DOI:10.1038/ngeo2715
Authors: Laura Jackson, Kenneth Andrew Peterson, Christopher David Roberts, , Richard A. Wood

Abstract

The Atlantic meridional overturning circulation (AMOC) has weakened substantially over the past decade. Some weakening may already have occurred over the past century, and global climate models project further weakening in response to anthropogenic climate change. Such a weakening could have significant impacts on the surface climate. However, ocean model simulations based on historical conditions have often found an increase in overturning up to the mid-1990s, followed by a decrease. It is therefore not clear whether the observed weakening over the past decade is part of decadal variability or a persistent weakening. Here we examine a state-of-the-art global-ocean reanalysis product, GloSea5, which covers the years 1989 to 2015 and closely matches observations of the AMOC at 26.5° N, capturing the interannual variability and decadal trend with unprecedented accuracy. The reanalysis data place the ten years of observations-April 2004 to February 2014-into a longer-term context and suggest that the observed decrease in the overturning circulation is consistent with a recovery following a previous increase. We find that density anomalies that propagate southwards from the Labrador Sea are the most likely cause of these variations. We conclude that decadal variability probably played a key role in the decline of the AMOC observed over the past decade.

Read more: https://www.researchgate.net/publication/303502652_Recent_slowing_of_Atlantic_overturning_circulation_as_a_recovery_from_earlier_strengthening

The reason I don’t lose any sleep over the North Atlantic scenario is the scale of the disturbance likely required to trigger such a collapse. The last collapse, 12,900 years ago, was believed to have occurred when the ice wall holding Lake Agassiz broke.

Lake Agassiz was gigantic, 170,000 square miles of fresh water which covered much of North America, much larger than any modern lake. When the ice wall gave way, a deluge of fresh water suddenly dumped into the ocean, triggering large scale ocean current changes.

Right now, in today’s world, there doesn’t seem to be any comparable trigger. There are no vast bodies of fresh water like Lake Agassiz, whose abrupt collapse could cause an ocean current disturbance of a magnitude comparable to what happened 12,900 years ago.

Of course, the apparent lack of plausible causation doesn’t stop climate alarmists from playing with their models, and publishing scary global warming causes ice age scenarios.

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Tom Halla
June 7, 2022 6:09 pm

Anyone using RCP8.5 does not care about plausibility.

H.R.
Reply to  Tom Halla
June 8, 2022 3:14 am

Or their own credibility.

Mark BLR
Reply to  Tom Halla
June 8, 2022 4:11 am

Anyone using RCP8.5 …

Both the Jackson et al papers are “reviews” of AMOC behaviour in the recent past, and do not refer to any RCP “pathway” (unless I missed something ???).

The Orihuela-Pinto et al paper doesn’t use RCP 8.5 (see my separate post “below”) … it’s MUCH worse than that !

While your observation is correct, it is “off topic” for this article.

Forrest Gardener
June 7, 2022 6:12 pm

The alternative interpretation of the catastrophic results delivered using models is that the models are FUBAR. I’ll wager good money that none of the catastrophists has ever even thought of that interpretation.

I’d suggest verifying the models before relying on them but I am preaching to the choir.

Dave Fair
Reply to  Forrest Gardener
June 7, 2022 6:35 pm

I’m sure that some CliSciFi practitioners have worried about that interpretation. Any such thought, though, would be quickly blocked off cognitively in response to the hysteria engendered by the threat to the governmental gravy train.

Reply to  Forrest Gardener
June 8, 2022 7:29 am

Working with EM models extensively (which are much simpler than climate models), I can concur the need for model validation. Without validation, it is just an interesting coloured picture.

ex-KaliforniaKook
Reply to  Forrest Gardener
June 8, 2022 5:09 pm

OH, [‘m pretty sure they’ve thought of them being FUBAR. I’ve worked with a lot of models during my career that I knew were FUBAR. Anyone who has worked with software development models know they can be tweaked for any conclusion – good, bad, or ugly. We still had to use them to estimate how much a software development program should cost.based on SLOCs, past contractor history, contractor rates, etc.

What the Government wanted they got. And they deserved the surprise when the stuff hit the fan.

Frederick Michael
June 7, 2022 6:31 pm

Bill Nye raised this possibility in his debate with Richard Lindzen on the Larry King show.

Richard shot this down hard.

Retired_Engineer_Jim
June 7, 2022 6:47 pm

Has anyone actually measured metrics of the AMOC and compared them to historical data in a trusted database? Just a rhetorical question.

paul courtney
Reply to  Retired_Engineer_Jim
June 9, 2022 12:07 pm

Mr. Jim: That’s the very first thing the CliSci’s did!! Unfortunately, the results were non-conforming, so they had to toss all that and go elsewhere. Tree rings! But only after very careful, science-driven selection process to remove a whole bunch of non-conforming trees. You know what they say, science advances one dead tree at a time. Or something.

ATheoK
June 7, 2022 6:59 pm

Back in school, we were taught that the first sentence of the first paragraph were of supreme importance in conveying our thoughts and information.

Their, Orihuela-Pinto et al, first sentence of their first paragraph?

Climate projections suggest a weakening or collapse of the Atlantic Meridional Overturning Circulation (AMOC) under global warming”

Even the waffle words have waffle words underpinning their lack of science.

Their last sentence of their abstract is similarly crippled?

These findings have important implications for understanding the global climate response to ongoing greenhouse gas increases”

Isn’t it amazing that implications can be “important”?
Keep in mind that their “implications” are only “important” for “understanding”…

One gets the notion these characters are trying to refute Laura Jackson et al’s March 2022 paper. Where speed of rebuttal is paramount over research, data, science, observations and hard work.

Dan Kennedy
Reply to  ATheoK
June 7, 2022 7:17 pm

I live just south of Lake Agassiz , nice digs actually. Glad it drained, cleaned the crap out of the Minnesota, and the ole’ Miss is a nice afternoon cruise. Every now and then you need a douche.

ozspeaksup
Reply to  Dan Kennedy
June 8, 2022 3:14 am

thought I d read that it or another lake nearby was refilling and taking land/homes?

Chris Hanley
Reply to  ATheoK
June 7, 2022 8:36 pm

Confirmation bias on stilts, they look for trends in data that supposedly support their a prior belief and then extrapolate them.

RickWill
June 7, 2022 7:19 pm

Right now, in today’s world, there doesn’t seem to be any comparable trigger. There are no vast bodies of fresh water like Lake Agassiz, whose abrupt collapse could cause an ocean current disturbance of a magnitude comparable to what happened 12,900 years ago.

The Strait of Gibraltar sits in an interesting location in the Atlantic circulation.

The salt plume from the Mediterranean extends across a substantial portion of the mid Atlantic indicating it has a significant influence on subsurface conditions in the Atlantic.
comment image

Changes in flow through the Strait of Gibraltar would alter conditions in the Atlantic. Whether these changes could have enough influences to alter heat transport substantially in the Atlantic is a question that would be difficult to answer.

The Southern Ocean Oscillation is not well understood but recent works indicates that salinity plays a role in switching the mode. And we know the different modes have global consequences. It is not a stretch to think that salinity changes in the Atlantic due to “breathing” of the Mediterranean through the Strait of Gibraltar could have consequences for land abutting the North Atlantic.

The surface of the Mediterranean will reach 30C in the current precession cycle and will become a convergence zone for mid level moisture from the Atlantic as deep convection sets in. That will mean outflows will strengthen.

Michael ElliottMichael Elliott
Reply to  RickWill
June 7, 2022 8:26 pm

Never mind, what bad happenings forecast will magically go away if only we do what our “”Betters”” Tell us what to do.

Michael VK5ELL

RickWill
Reply to  Eric Worrall
June 8, 2022 3:07 am

Good try, but this didn’t happen last time the Mediterranean was wet.

The flip side of the Mediterranean being wet during the boreal summer monsoon when precession has the northern hemisphere pointing at the sun in June is that the NH land masses are at their coldest when atmospheric water is at its maximum during the boreal winter.

Last time that condition occurred the air was dust laden and glaciers began to melt. The three previous precession cycles resulted in the glaciers expanding during the cooling cycle of the boreal winters. That condition started 500 years ago and will peak in 9.500 years from now.

The current phase of NH land masses accumulating ice is in the very early stages.

billtoo
June 7, 2022 9:13 pm

all those poor fish

anthropic
Reply to  billtoo
June 7, 2022 11:56 pm

That’s the end of California honey, where bees are fish.

Tom in Florida
Reply to  anthropic
June 8, 2022 5:10 am

Have you never head of Bumble Bee tuna?

Old Man Winter
Reply to  anthropic
June 8, 2022 6:49 am
Joe
June 7, 2022 9:28 pm

Obviously oil is collapsing, spamming low quality noise articles won’t change that.

Saudi combined e.png
Julien
June 7, 2022 10:07 pm

Hahaha if the AMOC slows down the Arctic Sea Ice will hardly melt further. The Ice Free Arctic will be yet another failed prediction from the Alarmists.

FOAF
June 7, 2022 11:13 pm

“Global warming could trigger a new ice age”

I … just … can’t … even …

Old Man Winter
Reply to  FOAF
June 8, 2022 6:40 am

Don’t let the fear of a potential crisis go to waste!

https://wattsupwiththat.com/2019/07/24/that-70s-climate-crisis-show/

Stuart Hamish
Reply to  Old Man Winter
June 9, 2022 8:02 am

” What scientists are telling us now is that the threat of an ice age is not as remote as they once thought ” .. The coiffured, confident Stephen Schneider waltzing along in his funky bell-bottom’s converted to become a high priest of the global warming movement within just a few years after this In Search Of episode …. Then John Holdren , Paul Ehrlich and the other jeremiahs …..Almost as if the 70’s global cooling crisis never happened

Coeur de Lion
June 8, 2022 2:16 am

I’m privileged to be able frequently to drive along the French N10 from Poitiers to Angouleme. It’s a magnificent freeway and UNTOLLED therefore has a multitude of huge roaring twelve wheel artics shipping Spanish foodstuffs to Paris citizens. None were battery driven. Saw one electric car. Squeaky squeaky, dwarfed, irrelevant.

Reply to  Coeur de Lion
June 8, 2022 7:35 am

12 wheel? In North America, We call them 18 wheelers. They often have more than 18.

Rxc
Reply to  Jeff in Calgary
June 8, 2022 2:13 pm

12 wheels, much bigger than the ones in the US. 2 + 4 on the tractor, and 2 rows of 3 on the trailer

ozspeaksup
June 8, 2022 3:12 am

eyup
aus media picked up on it asap of course and ran scare stories that wed have continual la nina and floods like this yr after 2 laninas in a row(and the first was a bit of a fizzer anyway) see the enso meters had it move a smidge towards the neutral zone again too;-)

BallBounces
June 8, 2022 4:00 am

“Here, using a global climate model”.

Oldseadog
June 8, 2022 4:14 am

But a week ago it was reported here that a paper by P. Gosselin on 29th.May says that the N. Atlantic Current has increased recently.

So the science still isn’t settled.

Ewin Barnett
June 8, 2022 4:21 am

“…but does not preclude a weakening associated with anthropogenic warming.“. Or weakening of our ideology.

June 8, 2022 4:45 am

The hilarious thing about the North Atlantic current (the AMOC) is that both weakening and strengthening of this circulation – both cause warming!

Weakening AMOC causes warming:

https://www.nature.com/articles/s41586-018-0320-y

Strengthening AMOC causes warming:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL078719

Mark BLR
June 8, 2022 4:46 am

From the “Discussion and summary” section of the Orihuela-Pinto et al paper :

Our study investigates the potential climatic impacts and global atmospheric teleconnections of an AMOC shutdown.

The results presented here have been derived from a single model set-up under pre-industrial conditions … Future work should examine how the impacts of an AMOC shutdown are further modulated under more complex scenarios, such as in past climate eras or in the future under a range of increasing greenhouse gas concentration scenarios.

NB : They did not check what happens under RCP 8.5, or indeed any other IPCC “pathway”, so what did they actually simulate in order to “shutdown” the AMOC ?

From the “Experimental design” paragraph of the “Methods” section of the paper :

… the AMOC-off runs are identical, only with a constant surface freshwater forcing of 1 Sv applied over the North Atlantic (50°N to 70°N). This meltwater anomaly represents a strong idealized forcing, as also used in previous studies, intended to trigger the AMOC to collapse within a few decades, equivalent to melting 1% of Greenland per year.

The Greenland Ice Sheet (GIS) has a volume of roughly 2.85 million cubic kilometres.

1 cubic km of ice (or water) masses roughly 1 Gt.

According to NASA (direct link) the GIS has seen melting of roughly 275 Gt of ice per year since 2002 (in what looks at first sight to be a linear manner ?).

“1% of Greenland per year” ~= 28,500 Gt/year.

275 Gt isn’t “1% per year”, it’s (just under) 0.01% per year.

The “Oh my $DEITY were all gonna diiiiiiiiiiie ! ! !” narrative is (currently) off by only two orders of magnitude … good enough for “Climate Science” work (and their “friends” in the media) …

– – – – – – – – – –

PS : I first came across the Orihuela-Pinto et al paper in an article on the Grauniad website, which included a link to a “With Sharing Token, but cannot download the PDF file” version of the paper, but they closed the comments section before I could post my “findings” there.

Mark BLR
Reply to  Mark BLR
June 9, 2022 9:02 am

It turns out that most of the main text of the AR6 WG-I report translates GIS melt into “equivalent GMSLR” numbers instead.

I finally managed to find a graph for “Greenland ice sheet mass change (to 2100)” in Gt (panel b of Figure 9.17, which can be found on page 1256 of the “Final” version of the WG-I report released last month), which is copied below.

A reminder of what the Orihuela-Pinto et al paper actually “simulated”, from the start of the “Model set-up and experimental design” section of the paper :

The Community Earth System Model (CESM) v.1.2 global climate model is used to perform two sets of experiments (Methods); the first ensemble set is based on a pre-industrial control simulation (AMOC-on) wherein the AMOC exhibits a realistic modern-day overturning circulation (Fig. 1; Methods), while the second set is derived from runs perturbed by meltwater so that the AMOC collapses (AMOC-off).

They compared the characteristics of various “teleconnections” between those two “ensemble sets”, especially ENSO.

– – – – –

OK, so their “perturbed by meltwater so the AMOC collapses” state was entered in “a few decades” of simulated time by melting “1% of Greenland per year”, i.e. 28,500 Gt/year.

Figure 9.17(b) has a “zero line” set to (roughly ?) 2015, and most of the “worst-case” SSP5-8.5 model run lines seem to have a “break point” around 2075 (TBC) …

The worst individual model run shows 100,000 Gt of “mass change” between 2015 and 2199 (85 years), i.e. ~1176 Gt/year … that’s a lot (over 24 times) less than 28;500 Gt/year !

Roughly 60,000 Gt of those 100,000 is lost from 2075.
60,000 Gt / 25 years = 2400 Gt/year … which is still 11.875 times less than 28,500 Gt/year …

The median (or “50%” or “most likely” …) loss for the “worst-case” SSP5-8.5 ensemble, according to the IPCC, is 40,000 Gt by 2100 … which means we should “realistically” multiply the above numbers by 0.4 to avoid being accused of “hysteria” or “fear-mongering” or “cherry-picking an outlier” …

– – – – –

The paper documents what one model says “will” happen to ENSO (amongst other teleconnections) after an AMOC collapse has occurred.

The conditions specified by the paper’s authors in order to enter their “AMOC-off” state “within a few decades” are completely unrealistic.

Screenshot_AR6-Final_Figure-9-17-a-b_GIS.png
Ari Okkonen
June 8, 2022 5:42 am

Yes, it is very likely that temperatures will drop in the near future. However, it is not catastrophic and not related to changes of CO2 or other emissions of our society.

North Atlantic Sea Surface Temperature (NASST) does not show any deviation from its traditional development that is determined by 1. linear recovery from Little Ice Age (LIA) and 2. Atlantic Multidecadal Oscillation (AMO). Recovery from LIA is linear warming c.a. 0.3°C/100 years. AMO’s effect seems to be c.a. 66 year sine shaped cycling of 0.37°C peak to peak. Moreover, short term fluctuations of +/- 0.13 °C can be seen in yearly averages. No significant effect of recently raised atmospheric CO2 content can be detected.

Combined effect of LIA and AMO to NASST peaked year 2012. Short term fluctuations made the year 2016 apparently the warmest year of North Atlantic Sea Surface until the next warm phase of AMO. Now we are heading to cold times around 2040 whether we produce CO2 or not.

Increasing Carbon Dioxide Concentration in Atmosphere Has Negligible Effect on North Atlantic Sea Surface Temperature

Atlantic_SST_21_with_estimate.png
RevJay4
June 8, 2022 6:08 am

Models? Again? OMG! Another attempt by the alarmist cultists to stir up the masses over a nothingburger. And, no doubt, continue their academic funding to continue their faux research into something over which we, the puny humans, have no control.
Gotta give ’em an ‘A’ for the effort, but when your livelihood depends on taxpayer funding ya gotta keep publishing something. Even if it is fantasy.

Fred Z
June 8, 2022 6:21 am

Global Warming can stop and even reverse entropy! Tropical water warmed by the sun no longer wants to move, it wants to stay in the tropics! Laws of thermodynamics repealed by Biden and the American Congress!

Prjindigo
June 8, 2022 7:14 am

I have yet to see any proof that it didn’t “flow somewhere else” as opposed to ‘failed’. Until then ‘failed’ is a goddamned assumption and Umption is gonna refuse to be seen with its other half.

whiten
June 8, 2022 8:34 am

It is amazing how much these guys know about the long long past, about any thing then, in a very cared and detailed explanation, but know almost nothing about far certain, historical, and closer to date events,
like for example LIA… to the point that it requires a lot of effort from some of them weirdos to blatantly attempt to eliminate such climatic events from the history.

Weird!

cheers

Last edited 28 days ago by whiten
Eben
June 8, 2022 9:27 am

Somebody watched The Day After Tomorrow one time too many

Ulric Lyons
June 8, 2022 9:54 am

“In the subpolar North Atlantic, the AMOC strengthened until the mid-1990s and then weakened until the early 2010s, with some evidence of a strengthening thereafter; these changes are probably linked to buoyancy forcing related to the North Atlantic Oscillation. In the subtropics, there is some evidence of the AMOC strengthening from 2001 to 2005 and strong evidence of a weakening from 2005 to 2014.”

So a slower AMOC drives a warmer AMO, as from 1995. which is when the solar wind weakened from. With a negative NAO regime (1993)+1995-1999. a positive NAO regime 2000-2004, and a negative NAO regime 2005-2013, and returning generally positive again 2014-2018. Note the positive periods around and just after the sunspot cycle maximums, that’s handy for prediction.

comment image

Gary Pearse
June 8, 2022 4:11 pm

“The glacial lake which caused this calamity no longer exists”

Well, Lakes Winnipeg, Winnipegosis and Manitoba lie in the basin of former glacial Lake Agassiz. I was born on the bottom of the old lake. Mapping geology in northern Manitoba, I found a barchan which is a crescent-shaped sand dune in the middle of a Jack pine forest which marks a western shoreline of a shrinking Lake Agassiz remnant. The northern shore of the lake was the ice sheet. When it had melted back enough to give the water access to Hudson’s Bay the lake drained, but it was a staged draining. The lake dropped and stabilized for a few centuries, developed new beaches and then dropped again and so on.

Interestingly, a U of Manitoba engineering professor, a specialist in soil mechanics, discovered how to determine the thickness of the glacial ice sheets. When certain clay’s are compressed they remain compressed. If you want to determine what load had been applied, you put a cored sample in a triaxial compression apparatus. As you apply pressure, no change in reading occurs until you surpass the pressure that the sample had been subjected to (by the column of ice).

A practical application in engineering is the use of the sheep’s foot roller to compact clays for a highway base, or a foundation.

https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Ftse1.mm.bing.net%2Fth%3Fid%3DOIP.rAuAziOBUQ-74i9-TTahswHaFY%26pid%3DApi&f=1

June 10, 2022 3:06 pm

Is the North Atlantic Current collapsing?

No, just undergoing its normal cyclical change in strength.

https://ptolemy2.wordpress.com/2020/07/26/from-chaos-to-pattern-in-ocean-driven-climate/

Sage
June 11, 2022 2:34 pm

Test

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