Arctic Sea Ice : Forum

AGW in general => Science => Topic started by: sidd on October 06, 2016, 05:44:51 AM

Title: AMOC slowdown
Post by: sidd on October 06, 2016, 05:44:51 AM
Kelly et al. trace AMOC slowdown to Agulhas leakage.

doi:10.1002/2016GL069789

No role for salinity,  AMOC slowdown not due to freshening in the north, rather they see increased salinity from precipitation decrease. This is a new development, Ruth Curry saw the opposite earlier.
Title: Re: AMOC slowdown
Post by: johnm33 on October 06, 2016, 10:23:35 AM
I read that as coincident rather than causative/consequential.  I'm still looking for some work which convinces me that it's not the inertia of melt/arctic waters hugging the coast through Labrador/Newfoundland impeding the flow of the gulf stream across to the east. My thinking is that these two streams cause each other to back up, and when mixed to flow east slower. Most of the meltwaters from the Arctic and Greenland make their way south by this route.
Title: Re: AMOC slowdown
Post by: AbruptSLR on October 06, 2016, 11:55:43 AM
Per the linked reference: "In this period, increased ocean heat uptake has largely arisen from reduced heat loss associated with reduced winds over the Agulhas Return Current and southward displacement of Southern Ocean westerlies.":

S. S. Drijfhout, A. T. Blaker, S. A. Josey, A. J. G. Nurser, B. Sinha and M. A. Balmaseda, (2014), "Surface warming hiatus caused by increased heat uptake across multiple ocean basins" Geophysical Research Letters, DOI: 10.1002/2014GL061456

http://onlinelibrary.wiley.com/doi/10.1002/2014GL061456/abstract (http://onlinelibrary.wiley.com/doi/10.1002/2014GL061456/abstract)

Abstract: "The first decade of the twenty-first century was characterised by a hiatus in global surface warming. Using ocean model hindcasts and reanalyses we show that heat uptake between the 1990s and 2000s increased by 0.7 ± 0.3Wm−2. Approximately 30% of the increase is associated with colder sea surface temperatures in the eastern Pacific. Other basins contribute via reduced heat loss to the atmosphere, in particular the Southern and subtropical Indian Oceans (30%), and the subpolar North Atlantic (40%). A different mechanism is important at longer timescales (1960s-present) over which the Southern Annular Mode trended upwards. In this period, increased ocean heat uptake has largely arisen from reduced heat loss associated with reduced winds over the Agulhas Return Current and southward displacement of Southern Ocean westerlies."

See also:

http://www.reportingclimatescience.com/news-stories/article/heat-uptake-by-several-oceans-drives-pause-says-study.html (http://www.reportingclimatescience.com/news-stories/article/heat-uptake-by-several-oceans-drives-pause-says-study.html)


Also, for the important influence of the Agulhas Current on amplifying global temperatures see: Turney, C. S.M. and Jones, R. T. (2010), Does the Agulhas Current amplify global temperatures during super-interglacials?. J. Quaternary Sci., 25: 839–843. doi: 10.1002/jqs.1423.
Title: Re: AMOC slowdown
Post by: jai mitchell on October 11, 2016, 11:03:03 PM
Stefan Rahmstorf October 9th Iceland presentation of recent science confirming AMOC slowdown.

https://www.youtube.com/watch?v=EmiVhT5cHpw (https://www.youtube.com/watch?v=EmiVhT5cHpw)

Title: Re: AMOC slowdown
Post by: prokaryotes on October 12, 2016, 04:47:06 AM
Stefan Rahmstorf October 9th Iceland presentation of recent science confirming AMOC slowdown.

https://www.youtube.com/watch?v=EmiVhT5cHpw (https://www.youtube.com/watch?v=EmiVhT5cHpw)
Btw. made the same mistake, but per video info from University of Iceland on May 27th 2016 at the conference "The Past, the Future. How Fast, How Far? Threats Facing the Climate System"
Title: Re: AMOC slowdown
Post by: Gray-Wolf on November 24, 2016, 09:30:19 PM
http://www.tellusa.net/index.php/tellusa/article/view/31051 (http://www.tellusa.net/index.php/tellusa/article/view/31051)

Maybe another way of looking at things? The paper explores a strengthening of The N.A.D. due to melt?

To me warm will always search out cold so I was never keen of us ( here in the UK) seeing cooling whilst the rest of the planet bakes!!! ;)
Title: Re: AMOC slowdown
Post by: Cate on January 06, 2017, 01:46:31 PM
This piece mentions neither the AMOC or climate change, but I'm gonna stick it here anyway: there's curious warming of the ocean bottom on Canada's east coast. The person interviewed says they see no significant trends, however.

http://www.cbc.ca/news/canada/nova-scotia/water-waters-climate-change-dfo-oceans-fisheries-science-1.3922876 (http://www.cbc.ca/news/canada/nova-scotia/water-waters-climate-change-dfo-oceans-fisheries-science-1.3922876)

Department of Fisheries and Oceans Canada has published its sea conditions report for 2015---yes, 2015. 2016 report is yet to come. "Every year the department measures temperatures throughout the water column off Newfoundland and Labrador, the Gulf of St. Lawrence, the Scotian Shelf, the Gulf of Maine and the Bay of Fundy."

"Scientists have struggled to explain what is causing the most intriguing aspect of the recent trend: the warming of ocean bottom water, which is not influenced by surface weather events.
Hebert said the latest theory is based on model results that see the Gulf Stream moving northward and intersecting with the tail of the Grand Banks.

"That is stopping the cold Labrador Sea water from coming around the tail of the Grand Banks," he said. "That's where we normally get the cold water that refreshes the [Scotian] Shelf. That hasn't been rhappening.

"And what we are seeing is the warm slope water getting onto the shelf, sort of pumping more warm salty water, year after year, and the shelf will slowly change its conditions."

Title: Re: AMOC slowdown
Post by: budmantis on January 07, 2017, 04:53:50 PM
The linked article asserts that a significant enough warming in the arctic could potentially cause the AMOC to stagnate and shut down.

http://www.huffingtonpost.com/entry/atlantic-ocean-current-collapse-warning_us_587031f3e4b02b5f8588fa35?f02haoyl8e6xq1tt9 (http://www.huffingtonpost.com/entry/atlantic-ocean-current-collapse-warning_us_587031f3e4b02b5f8588fa35?f02haoyl8e6xq1tt9)

Extract: The Atlantic Meridional Overturning Circulation (AMOC) transports warm water from the tropics to the North Atlantic and helps regulate climate and weather patterns all over the world. As it releases the warmth into the air, the cooling water sinks and flows back to the tropics to repeat the process. But researchers fear that as the air in the north warms significantly due to climate change, the AMOC won’t be able to transfer its warmth to the atmosphere and the great circulatory engine of the ocean could stagnate and shut down. 
Title: Re: AMOC slowdown
Post by: AbruptSLR on January 09, 2017, 11:09:49 PM
The linked reference concludes that:

"We propose that such centennial-millennial productivity/climate variability in the NW Pacific and sequence of sub-stadial/interstadials in the EAM from the LGM to EH are a persistent regional features, synchronous with the Greenland/North Atlantic short-term changes. We speculate that such climate synchronicity was forced also by changes in Atlantic meridional overturning circulation coupled with Intertropical Convergence Zone shifting and the northern westerly jets reorganization." 

Where: EAM = East Asian Monsoon, LGM = Last Glacial Maximum and EH = Early Holocene.

This paleo-evidence of the synchronicity of the ITCZ, the AMOC and the northern westerly jets implies to me that the Earth's climate sensitivity is higher than consensus science currently acknowledges:

Gorbarenko et. al. (2016), "Centennial to millennial climate variability in the far northwestern Pacific (off Kamchatka) and its linkage to East Asian monsoon and North Atlantic from the Last Glacial Maximum to the Early Holocene", Clim. Past Discuss., doi:10.5194/cp-2016-102

http://www.clim-past-discuss.net/cp-2016-102/cp-2016-102.pdf (http://www.clim-past-discuss.net/cp-2016-102/cp-2016-102.pdf)

Title: Re: AMOC slowdown
Post by: GeoffBeacon on January 10, 2017, 09:39:09 PM
How do short term climate forcing agents (like methane and black carbon) contribute to the danger of triggering a tipping point in the Gulf Stream System? I’ve just found Centuries of thermal sea-level rise due to anthropogenic emissions of short-lived greenhouse gases by Ramanathan et. al. (http://www.pnas.org/content/early/2017/01/03/1612066114.short)

Seems relevant but I haven’t yet paid to access it. The “significance” includes:

Quote
Our study shows that short-lived GHGs contribute to thermal expansion of the ocean over much longer time scales than their atmospheric lifetimes. Actions taken to reduce emissions of short-lived gases could mitigate centuries of additional future sea-level rise.
A bit from the abstract:

Quote
For example, at least half of the TSLR due to increases in methane is expected to remain present for more than 200 y, even if anthropogenic emissions cease altogether, despite the 10-y atmospheric lifetime of this gas. Chlorofluorocarbons and hydrochlorofluorocarbons have already been phased out under the Montreal Protocol due to concerns about ozone depletion and provide an illustration of how emission reductions avoid multiple centuries of future TSLR. We examine the “world avoided” by the Montreal Protocol by showing that if these gases had instead been eliminated in 2050, additional TSLR of up to about 14 cm would be expected in the 21st century, with continuing contributions lasting more than 500 y.

Any thoughts?
Title: Re: AMOC slowdown
Post by: GeoffBeacon on January 10, 2017, 09:46:58 PM
Correction: That paper was by   Kirsten Zickfeld, Susan Solomon, and Daniel M. Gilford
Title: Re: AMOC slowdown
Post by: jai mitchell on January 11, 2017, 05:29:07 PM
The linked reference concludes that:

"We propose that such centennial-millennial productivity/climate variability in the NW Pacific and sequence of sub-stadial/interstadials in the EAM from the LGM to EH are a persistent regional features, synchronous with the Greenland/North Atlantic short-term changes. We speculate that such climate synchronicity was forced also by changes in Atlantic meridional overturning circulation coupled with Intertropical Convergence Zone shifting and the northern westerly jets reorganization." 

Where: EAM = East Asian Monsoon, LGM = Last Glacial Maximum and EH = Early Holocene.

This paleo-evidence of the synchronicity of the ITCZ, the AMOC and the northern westerly jets implies to me that the Earth's climate sensitivity is higher than consensus science currently acknowledges:

Gorbarenko et. al. (2016), "Centennial to millennial climate variability in the far northwestern Pacific (off Kamchatka) and its linkage to East Asian monsoon and North Atlantic from the Last Glacial Maximum to the Early Holocene", Clim. Past Discuss., doi:10.5194/cp-2016-102

http://www.clim-past-discuss.net/cp-2016-102/cp-2016-102.pdf (http://www.clim-past-discuss.net/cp-2016-102/cp-2016-102.pdf)

This is a very (VERY) complex paper!  could you give your ideas on how it implies higher sensitivity?  Is it a function of the meltwater lensing you have been discussing as implicated by the Hansen paper?  Or is it a combination of other effects?

I am finding some really difficult translations between paleoclimate studies and current impacts simply due to the incredibly rapid warming and scale changes we are experiencing.  It is so very difficult to compare previous conditions to today!

Thank you for posting it, this is incredibly valuable (which is why I am asking!)
Title: Re: AMOC slowdown
Post by: AbruptSLR on January 11, 2017, 10:06:41 PM
This is a very (VERY) complex paper!  could you give your ideas on how it implies higher sensitivity?  Is it a function of the meltwater lensing you have been discussing as implicated by the Hansen paper?  Or is it a combination of other effects?

I am finding some really difficult translations between paleoclimate studies and current impacts simply due to the incredibly rapid warming and scale changes we are experiencing.  It is so very difficult to compare previous conditions to today!

Thank you for posting it, this is incredibly valuable (which is why I am asking!)

Such matters are complex (think interacting Lorenz attractors).  So to be as simple as possible (& to focus on the primary interaction mechanism): as the thermohaline (say due accelerated WAIS loss as cited by Hansen) slows down, heat accumulates along the equator, particularly in the Equatorial Pacific Ocean; which causes both the ITCZ to move poleward and also advects heat through the atmosphere towards the poles (thus impacting the polar atmospheric jet-streams).

Edit: See the influence on high climate sensitivity of the warming of the Equatorial Pacific in the middle panel of the first attached image (with ECS near 5C).

Edit2: Also see the last three related images: (a) the first shows multiple mechanisms associated with the ENSO/ITCZ; (b) Deep convection near the Equatorial Pacific expanding ITCZ zone and moving the associated clouds poleward; and (c) A strong El Nino advecting (atmospheric bridge) atmospheric energy from the equator directly to the poles.
Title: Re: AMOC slowdown
Post by: jai mitchell on January 12, 2017, 06:08:30 PM
Thanks ASLR,

I am finding that the rates of changes is moving so much more rapidly now that the models are unable to keep up, the paleoclimate analogies are useless and local climate impact predictions understate the rates of changes by decades or more.   For example, if the current West Coast El Nino winter (in a NON El Nino year!) is a function of last year's water vapor pulse and as a result of perceptible reductions in high-temp coal combustion operations (iron, older less efficient power production closures) then we are seeing indications of what the climate SHOULD be at 490 ppm CO2e forcing rates.

remember, the Chinese smokestacks that don't have wet scrubbers exhaust superheated CO2 that rises rapidly to the upper troposphere.  not like our scrubbed smokestacks.  the use of scrubber technology rapidly reduces the upper tropospheric loading of this SO2 to near zero since the emissions of remaining SO2 are much cooler.

These emissions also have an effect on AMOC circulation rates.

see: http://journals.ametsoc.org/doi/full/10.1175/JAS-D-12-0331.1 (http://journals.ametsoc.org/doi/full/10.1175/JAS-D-12-0331.1)
http://onlinelibrary.wiley.com/doi/10.1002/jgrc.20178/full (http://onlinelibrary.wiley.com/doi/10.1002/jgrc.20178/full)
Title: Re: AMOC slowdown
Post by: bbr2314 on January 12, 2017, 10:08:56 PM
Thanks ASLR,

I am finding that the rates of changes is moving so much more rapidly now that the models are unable to keep up, the paleoclimate analogies are useless and local climate impact predictions understate the rates of changes by decades or more.   For example, if the current West Coast El Nino winter (in a NON El Nino year!) is a function of last year's water vapor pulse and as a result of perceptible reductions in high-temp coal combustion operations (iron, older less efficient power production closures) then we are seeing indications of what the climate SHOULD be at 490 ppm CO2e forcing rates.

remember, the Chinese smokestacks that don't have wet scrubbers exhaust superheated CO2 that rises rapidly to the upper troposphere.  not like our scrubbed smokestacks.  the use of scrubber technology rapidly reduces the upper tropospheric loading of this SO2 to near zero since the emissions of remaining SO2 are much cooler.

These emissions also have an effect on AMOC circulation rates.

see: http://journals.ametsoc.org/doi/full/10.1175/JAS-D-12-0331.1 (http://journals.ametsoc.org/doi/full/10.1175/JAS-D-12-0331.1)
http://onlinelibrary.wiley.com/doi/10.1002/jgrc.20178/full (http://onlinelibrary.wiley.com/doi/10.1002/jgrc.20178/full)

I wonder if the pulses of their emissions can be timed to be worse with the coldest outbreaks over China? In that, as temperatures plummet, heating requirements increase and so does automobile use, provoking a pollution-related response that is significantly worse than normal? This would evidently amplify the cold outbreaks (or weaken who knows, one or the other I suppose) as the winter drags on, abating as solar input increases again in the spring.
Title: Re: AMOC slowdown
Post by: AbruptSLR on January 13, 2017, 05:10:43 PM
Thanks ASLR,

I am finding that the rates of changes is moving so much more rapidly now that the models are unable to keep up, the paleoclimate analogies are useless and local climate impact predictions understate the rates of changes by decades or more. 

jai,
I believe that the paleo-record has value for helping to calibrate ESMs if Lorenz attractors and masking factors (like paleo dust) are considered in the calibration.  Once the models are appropriately calibrated to the best paleo data that we have, then looking to the future, we need to extrapolate probable Earth System responses that likely will exceed those within the paleo-record, but which conform to physics of a chaotic system with Lorenz attractors and ratcheting of quasi-static equilibrium system states (see the attached image for ENSO driven ratcheting).

As we both understand how complex state-of-the-art ESMs (like ACME), I will not pretend that I can appropriately account by hand for all of the feedbacks and interactions; which a good portion of my over 10,000 posts focus on (including carbon cycle feedbacks, natural and anthropogenic aerosol forcing & feedbacks, albedo flips, ice-climate feedbacks, ENSO/PDO interactions, etc. etc.); nevertheless, to add a very small amount of complexity to my Replies #12 & #2, with continued global warming one can expect more Agulhas Current leakage; which per the linked reference means that one can expect the AMOC to continue slowing; which should work synergistically with Hansen's ice-climate feedback to accelerate global warming beyond levels currently assumed.


Kathryn A. Kelly, Kyla Drushka, LuAnne Thompson, Dewi Le Bars & Elaine L. McDonagh (25 July 2016), "Impact of slowdown of Atlantic overturning circulation on heat and freshwater transports", Geophysical Research Letters, DOI: 10.1002/2016GL069789

http://onlinelibrary.wiley.com/doi/10.1002/2016GL069789/abstract (http://onlinelibrary.wiley.com/doi/10.1002/2016GL069789/abstract)

Best,
ASLR
Title: Re: AMOC slowdown
Post by: AbruptSLR on January 13, 2017, 10:22:54 PM
jai,

With regards to the use of paleoclimate data and strange attractors to constraint ECS, see the linked article that indicates that using this approach clearly indicates that ECS is likely higher than commonly assumed:

A.S. Von der Heydt and Peter Ashwin (2016), "State-dependence of climate sensitivity: attractor constraints and palaeoclimate regimes", arXiv:1604.03311v1

http://arxiv.org/pdf/1604.03311v1.pdf (http://arxiv.org/pdf/1604.03311v1.pdf)
or
https://arxiv.org/pdf/1604.03311v2.pdf (https://arxiv.org/pdf/1604.03311v2.pdf)

Abstract: "Equilibrium climate sensitivity is a frequently used measure to predict long-term climate change. However, both climate models and observational data suggest a rather large uncertainty on climate sensitivity (CS). The reasons for this include: the climate has a strong internal variability on many time scales, it is subject to a non-stationary forcing and it is, on many timescales, out of equilibrium with the changes in the radiative forcing. Palaeo records of past climate variations give insight into how the climate system responds to various forcings although care must be taken of the slow feedback processes before comparing palaeo CS estimates with model estimates. In addition, the fast feedback processes can change their relative strength and time scales over time. Consequently, another reason for the large uncertainty on palaeo climate sensitivity may be the fact that it is strongly state-dependent. Using a conceptual climate model, we explore how CS can be estimated from unperturbed and perturbed model time series. Even in this rather simple model we find a wide range of estimates of the distribution of CS, depending on climate state and variability within the unperturbed attractor. For climate states perturbed by instantaneous doubling of CO2, the sensitivity estimates agree with those for the unperturbed model after transient decay back the attractor. In this sense, climate sensitivity can be seen as a distribution that is a local property of the climate attractor. We also follow the classical climate model approach to sensitivity, where CO2 is prescribed and non-dynamic, leading to CS values consistently smaller than those derived from the experiments with dynamic CO2. This suggests that climate sensitivity estimates from climate models may depend significantly on future dynamics, and not just the level of CO2."


Extract: “... the presence of variability on the attractor on a number of timescales means there are clear and non-trivial distributions of sensitivities, even for unperturbed climates. The distribution of sensitivities depends strongly on the background state as well as on the timescale considered. This suggests that it could be useful to think of the unperturbed climate sensitivity as a local property of the “climate attractor”. For a perturbed system (we have considered instantaneously doubled CO2) this is still useful once an initial transient has decayed. This transient will depend in particular on ocean heat uptake, though also on carbon cycle and biosphere processes that act on time scales roughly equivalent with the forcing time scale. If the climate system has more than one attractor, the perturbed system may clearly evolve to a completely different set of states than the original attractor – a situation that did not occur in the climate model used here. In less extreme cases, there may still be very long transients for some perturbations associated parts of the climate system that are associated with slow feedbacks.

Such perturbations (illustrated in Fig. 1b,d) are not normally applied in climate models used for climate predictions [IPCC, 2013], where climate sensitivity is derived from model simulations considering prescribed, non-dynamic atmospheric CO2. In our conceptual model, we have derived climate sensitivities from both types of perturbations and find that the classical climate model approach (section 2.2, Fig. 4f) leads to significantly lower values of the climate sensitivity than the perturbations away from the attractor with dynamic CO2 (section 2.3, Fig. 11a). This emphasises the importance of including dynamic carbon cycle processes into climate prediction models. Moreover, it supports the idea that the real observed climate response may indeed be larger than the model predicted one, because those models never will include all feedback processes in the climate system.“

Edit, see also:

A. S. von der Heydt, H. A. Dijkstra, R. S. W. van de Wal, R. Caballero, M. Crucifix, G. L. Foster,  M. Huber, P. Köhler, E. Rohling, P. J. Valdes, P. Ashwin, S. Bathiany, T. Berends, L. G. J. van Bree, P. Ditlevsen, M. Ghil, A. Haywood, J. Katzav, G. Lohmann, J. Lohmann, V. Lucarini, A. Marzocchi, H. Pälike, I. Ruvalcaba Baroni, D. Simon, A. Sluijs, L. B. Stap, A. Tantet, J. Viebahn and M. Ziegler Lessons on climate sensitivity from past climate changes, Curr. Clim. Change Rep. (2016), doi:10.1007/s40641-016-0049-3.


http://link.springer.com/article/10.1007/s40641-016-0049-3 (http://link.springer.com/article/10.1007/s40641-016-0049-3)


Abstract: "Over the last decade, our understanding of climate sensitivity has improved considerably. The climate system shows variability on many timescales, is subject to non-stationary forcing and it is most likely out of equilibrium with the changes in the radiative forcing. Slow and fast feedbacks complicate the interpretation of geological records as feedback strengths vary over time. In the geological past, the forcing timescales were different than at present, suggesting that the response may have behaved differently. Do these insights constrain the climate sensitivity relevant for the present day? In this paper, we review the progress made in theoretical understanding of climate sensitivity and on the estimation of climate sensitivity from proxy records. Particular focus lies on the background state dependence of feedback processes and on the impact of tipping points on the climate system. We suggest how to further use palaeo data to advance our understanding of the currently ongoing climate change."

Best,
ASLR
Title: Re: AMOC slowdown
Post by: nowayout on January 13, 2017, 11:12:14 PM
Slightly hidden in the pdf, but I think this catches it:

Quote
In this sense, climate sensitivity can be seen as a distribution that is a local
property of the climate attractor. 

Translation: In the end it's all about tipping points. Even climate sensivity.

On AMOC slowdown or collapse: If it is the freshwater intrusion from Greenland to cause it, we should carefully observe what is going on beneath the central Greeenland glaciers. There is enough space to collect sufficient amounts of freshwater. This would be a smaller tipping point, into the "wrong" direction. See Younger Dryas. The (Our) CO2 dynamics will only be stopped for a short time.

Generally: this (our!) relentless and still accellerating pollution of the earth with CO2 could be (and imho is) so strong that some attractors of the climate past that went effective could simply be overrun.

BAU implies this. Sorry.

Title: Re: AMOC slowdown
Post by: AbruptSLR on January 16, 2017, 09:01:01 PM
Further to my Replies #15 & #16 about multiple interacting climate attractors,the linked reference provides additional details about the oceanic and atmospheric interconnections between the Equatorial Pacific Ocean and the subpolar North Atlantic Ocean.

L. Chafik, S. Häkkinen, M. H. England, J. A. Carton, S. Nigam, A. Ruiz-Barradas, A. Hannachi & L. Miller (21 October 2016), "Global linkages originating from decadal oceanic variability in the subpolar North Atlantic", Geophysical Research Letters, DOI: 10.1002/2016GL071134

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071134/abstract (http://onlinelibrary.wiley.com/doi/10.1002/2016GL071134/abstract)

Abstract: "The anomalous decadal warming of the subpolar North Atlantic Ocean (SPNA), and the northward spreading of this warm water, has been linked to rapid Arctic sea ice loss and more frequent cold European winters. Recently, variations in this heat transport have also been reported to covary with global warming slowdown/acceleration periods via a Pacific climate response. We here examine the role of SPNA temperature variability in this Atlantic-Pacific climate connectivity. We find that the evolution of ocean heat content anomalies from the subtropics to the subpolar region, likely due to ocean circulation changes, coincides with a basin-wide Atlantic warming/cooling. This induces an Atlantic-Pacific sea surface temperature seesaw, which in turn, strengthens/weakens the Walker circulation and amplifies the Pacific decadal variability that triggers pronounced global-scale atmospheric circulation anomalies. We conclude that the decadal oceanic variability in the SPNA is an essential component of the tropical interactions between the Atlantic and Pacific Oceans."
Title: Re: AMOC slowdown
Post by: jai mitchell on January 21, 2017, 12:21:15 AM
http://advances.sciencemag.org/content/3/1/e1601666?utm_campaign=toc_advances_2017-01-20&et_rid=17776844&et_cid=1116593 (http://advances.sciencemag.org/content/3/1/e1601666?utm_campaign=toc_advances_2017-01-20&et_rid=17776844&et_cid=1116593)

Overlooked possibility of a collapsed Atlantic Meridional Overturning Circulation in warming climate

Wei Liu et al.
Science Advances  04 Jan 2017:
Vol. 3, no. 1, e1601666
DOI: 10.1126/sciadv.1601666

Abstract:  Changes in the Atlantic Meridional Overturning Circulation (AMOC) are moderate in most climate model projections under increasing greenhouse gas forcing. This intermodel consensus may be an artifact of common model biases that favor a stable AMOC. Observationally based freshwater budget analyses suggest that the AMOC is in an unstable regime susceptible for large changes in response to perturbations. By correcting the model biases, we show that the AMOC collapses 300 years after the atmospheric CO2 concentration is abruptly doubled from the 1990 level. Compared to an uncorrected model, the AMOC collapse brings about large, markedly different climate responses: a prominent cooling over the northern North Atlantic and neighboring areas, sea ice increases over the Greenland-Iceland-Norwegian seas and to the south of Greenland, and a significant southward rain-belt migration over the tropical Atlantic. Our results highlight the need to develop dynamical metrics to constrain models and the importance of reducing model biases in long-term climate projection.
Title: Re: AMOC slowdown
Post by: AbruptSLR on January 22, 2017, 02:47:32 AM
To me the linked article by Neven entitled: "A new Arctic feedback (?)", clearly identifies a feedback mechanism that can contribute to the early collapse of the AMOC:

http://neven1.typepad.com/blog/2017/01/a-new-arctic-feedback-.html (http://neven1.typepad.com/blog/2017/01/a-new-arctic-feedback-.html)

Extract: "Yesterday this video was posted on Peter Sinclair's ClimateCrocks blog, showing an interview with Dr Jennifer Francis (Rutgers University) at the AGU 2016 Fall Meeting this past December:"
Title: Re: AMOC slowdown
Post by: logicmanPatrick on January 22, 2017, 07:12:00 AM
Double whammy!  AMOC slowdown means more heat transfer south, adding to global warming according to paleoclimate data.


Quote
The researchers believe the melting of the Greenland ice sheet weakened the Atlantic Meridional Overturning Circulation, or AMOC, a system of currents that usually brings warmer water from the tropics to the south. As it weakened, sea surface temperatures rose in the southern hemisphere, also contributing to warmer global temperatures.

“It was a double whammy,” Clark said. “Solar insolation warmed the northern hemisphere, a weakened AMOC warmed the south.”

Scientists zero in on global ocean temperatures during last interglaciation period  (http://oregonstate.edu/ua/ncs/archives/2017/jan/scientists-zero-global-ocean-temperatures-during-last-interglaciation-period)
Title: Re: AMOC slowdown
Post by: AbruptSLR on January 23, 2017, 07:22:17 PM
The linked reference indicate that current models likely do not accurately represent CO₂ ventilation from the equatorial Pacific (& Atlantic) Ocean(s) during periods of deglaciation.  The reference states: "In addition, both gradual and rapid deglacial radiocarbon changes in these Pacific records are coeval with changes in the Atlantic records.  This in-phase behavior suggest that the Southern Ocean overturning was the dominant driver of changes in the Atlantic and Pacific ventilation during deglacitions."  This does not bode well for our future.

Natalie E. Umling & Robert C. Thunell (2017), "Synchronous deglacial thermocline and deep-water ventilation in the eastern equatorial Pacific", Nature Communications, doi:10.1038/ncomms14203

http://www.nature.com/articles/ncomms14203 (http://www.nature.com/articles/ncomms14203)
Title: Re: AMOC slowdown
Post by: bbr2314 on February 04, 2017, 01:47:04 AM
(https://pbs.twimg.com/media/C3t6L-QVMAITgVN.jpg:large)
Title: Re: AMOC slowdown
Post by: bbr2314 on February 04, 2017, 01:50:15 AM
I think the 1/17 anomaly map above clearly shows the area primarily effected so far. This anomaly has accumulated year over year since at least 2012 (looking at HYCOM maps) and has steadily worsened (immediately SE of Greenland and SW of Iceland).

It seems that when combined with the ice-free Atlantic side of the Arctic this winter, the result of the AMOC mess + vast areas of newly open water = significantly more snowfall over high elevations in Europe and Northern Africa, explaining the cold anomalies in those regions. Perhaps this is the mechanism that results in Saharan re-greening, because it certainly seems we could be heading that way based on these maps...!
Title: Re: AMOC slowdown
Post by: FishOutofWater on February 06, 2017, 04:43:32 AM
The isothermal deeply mixed area that is the source of Labrador sea mode water is larger than normal. Note that it is ringed by water that is warmer and saltier than normal. That probably indicates that deep water formation is chugging along this winter. There was a major slowdown in the MOC and the Gulf Stream in 2010. Warm water built up in the tropics in 2010 while the temperate and subpolar north Atlantic cooled. The SST pattern is very different now than 2010. It shows warm water moving across the temperate Atlantic at a good clip and up the coast of Norway towards the Arctic.

Note that the cool region has a negative Sea Surface Height anomaly. That means that it is dense. It is not a light cold fresh surface layer floating over warm salty water. The high density is an indication of mixing, that deep water formation is going on.
Title: Re: AMOC slowdown
Post by: johnm33 on February 06, 2017, 01:44:56 PM
This illustrates your point about ssh rather better
(https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/natspgssh_nowcast_anim30d.gif)
It's easy to see that the dense water exiting the arctic is passing both down the Denmark strait and over the Faroe ridge, the second of those then appears to flow around the ridge which indicates it's close to the bottom http://topex.ucsd.edu/marine_topo/jpg_images/topo4.jpg (http://topex.ucsd.edu/marine_topo/jpg_images/topo4.jpg) .
I'm thinking the major slowdown was the result of an increase in the flow of fresh[er] water out of the north, it's inertia keeping it against the coast, and when mixing with the oppositely inclined southern waters both slowed down and backed up, that now seems to be resolving leading to an accelerated flow of mixed southern and northern waters crossing the atlantic further south than the old gulf stream. Following this more circuitous route it arrives warmer and later and having increased in mass persists longer. An interesting feature of this new route, if this is what's happening, is that it more closely follows an arc around the north antlantic amphidromic point [@40w50n] and thus will be accelerated by tidal forces where before it passed through that area which would have mildly disrupted the flow.
The mixing
(https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/glfstrsst_nowcast_anim30d.gif)
(https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/natspgsst_nowcast_anim30d.gif)
Title: Re: AMOC slowdown
Post by: FishOutofWater on February 06, 2017, 03:33:30 PM
Melting of Greenland's ice cap and intense melting of Arctic sea ice may have added a large amount of fresh water to the subarctic seas in 2005 to 2010. There was also a slowdown of transport of water from the Indian ocean to the south Atlantic via Agulhas rings that may have had an effect if I remember correctly. The tricky thing about the south Atlantic is the substantial lag time with deep convection in the subpolar Arctic seas.

A large pulse of freshwater released from the Beaufort gyre helped with the brief sea ice recovery in 2013 and 2014.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fimages.dailykos.com%2Fimages%2F338395%2Fstory_image%2FWHOI_Beaufort_Figure-3-for-BG-FWC-results_432873.jpeg%3F1481589031&hash=fd88f84603a1904f89cb37c8cd70a1bb)

The Beaufort fresh water pulse may have slowed down the overturning circulation in 2013 and 2014. The cold dense anomaly may have formed as the water finally chilled and densified enough to begin mixing strongly again.

There are lag times in many of the processes involved with ocean dynamics so it's very tricky interpreting reports on the slowing of the THC because different investigators use different measures of THC activity.
Title: Re: AMOC slowdown
Post by: AbruptSLR on May 23, 2017, 09:35:33 PM
The linked reference indicates that the Younger Dryas may be due to a comet strike instead of a change in the AMOC:

 Martin B. Sweatman and Dimitrios Tsikritsis (2017), "DECODING GÖBEKLI TEPE WITH ARCHAEOASTRONOMY: WHAT DOES THE FOX SAY?", Mediterranean Archaeology and Archaeometry, Vol. 17, No 1, pp. 233-250,  DOI: 10.5281/zenodo.400780

http://maajournal.com/Issues/2017/Vol17-1/Sweatman%20and%20Tsikritsis%2017%281%29.pdf (http://maajournal.com/Issues/2017/Vol17-1/Sweatman%20and%20Tsikritsis%2017%281%29.pdf)

Abstract: "We have interpreted much of the symbolism of Göbekli Tepe in terms of astronomical events. By matching low-relief carvings on some of the pillars at Göbekli Tepe to star asterisms we find compelling evidence that the famous ‘Vulture Stone’ is a date stamp for 10950 BC ± 250 yrs, which corresponds closely to the proposed Younger Dryas event, estimated at 10890 BC. We also find evidence that a key function of Göbekli Tepe was to observe meteor showers and record cometary encounters. Indeed, the people of Göbekli Tepe appear to have had a special interest in the Taurid meteor stream, the same meteor stream that is proposed as responsible for the Younger-Dryas event. Is Göbekli Tepe the ‘smoking gun’ for the Younger-Dryas cometary encounter, and hence for coherent catastrophism?"

See also:

https://www.forbes.com/sites/trevornace/2017/04/30/ancient-stone-tablet-found-reveals-comet-impact-sparking-the-rise-of-civilization/#4a16ac9c7342 (https://www.forbes.com/sites/trevornace/2017/04/30/ancient-stone-tablet-found-reveals-comet-impact-sparking-the-rise-of-civilization/#4a16ac9c7342)
Title: Re: AMOC slowdown
Post by: TerryM on May 24, 2017, 11:25:26 AM
ASLR
The above is a reference to the Black Mat event in the '2017 open thread' found in "The Rest". I had found the connection a little tenuous, but different strokes.
One of many reasons for moving to Ontario was my hope that I could find some evidence of the comet here, close to where the largest piece may have hit ground ice.
Terry
Title: Re: AMOC slowdown
Post by: solartim27 on January 25, 2018, 05:16:09 PM
Here's a short article with an interesting description of how they determine the time frame of the melting ice sheet that would have disrupted the AMOC
https://phys.org/news/2018-01-freshwater-route-ice-rapid-cooling.html
Title: Re: AMOC slowdown
Post by: bbr2314 on February 19, 2018, 01:04:23 AM
Reading over this old paper, there are several interesting observations to be made 20 years after the fact based on climactic shifts since publication --

http://onlinelibrary.wiley.com/store/10.1029/96PA02711/asset/palo566.pdf?v=1&t=jdtfcebo&s=67abdc591afa463aca36853b7db2b23a66c8f983

1) It should be noted that the approximated warming since Younger Dryas is estimated at only 2C over Quebec/NE Canada. With annual temperatures in these regions now dropping, what decline from current levels would be sufficient to precipitate re-glaciation?

2) Approximated sea ice during the Younger Dryas differs very minimally from what was observed during the twentieth century across the Pacific front. However, the contrast with the Atlantic could not be starker, with ice estimated to have advanced on an annual basis to a rough boundary of Newfoundland -> Scotland.

I think the contrast between Pacific vs. Atlantic is something that we can expand upon now that we have another twenty years of observations. Most notably, salty Pacific water is now making its way well into the Arctic during wintertime, with the Bering front proving far less resilient than Barentz (after many years of what seemed to be the opposite).

This begins to beg the question: could the trigger behind an abrupt shift like the Younger Dryas be the failure of the peripheral seas to buffer the Arctic from ocean water? And whether this occurs solely from the Pacific side? And how long it would take/weather required for a saltwater push into Bering sufficient to cause a substantial release of freshwater into the Atlantic?

It seems possible that this summer we could see a months-long intrusion of Pacific water, which could dislodge a substantial portion of the freshwater halocline towards the Labrador Sea... combined with Greenland melt, we may have a potential tipping point coming up shortly...!
Title: Re: AMOC slowdown
Post by: CDN_dude on April 12, 2018, 12:14:13 AM
A new Washington Post article based on two interesting studies. https://www.washingtonpost.com/news/energy-environment/wp/2018/04/11/the-oceans-circulation-hasnt-been-this-sluggish-in-1000-years-thats-bad-news/?utm_term=.3ccd466288ac

Overall, main finding is that there has been a 15% slowdown in the AMOC since mid-20th C.

Direct links to the studies here https://www.nature.com/articles/s41586-018-0006-5.epdf?referrer_access_token=tm9E8fUFguAT3qTTze_EP9RgN0jAjWel9jnR3ZoTv0OdzeJ18XkImxSDnyYEEsE8kZxiCFQRHXUDVk7z88DZuCVSpNT526jCYc7AolNWO0q1VuAzrHmqVEhSpPio75PuDkbmnZMCM7UNkijPz7lF85lllre35b36xIR2bFKP-N8KD_GUVf7qEKH5RpZgKimkm5eaGY-9_iwbrfmXiiwSKC-h6dYZT5WJkAU7Qi4h8o_8yfGCnteJjUPRVV4rc19oLjmhua0qUJhEChUDiojei7F2Rf9Xzi1pD71prBBEvbMnQwuyUCWxUGnnHzldyJpPOVBceyPNMxR-gw0HYNpNm3i5htAMMGwB89h5OyrzzPxNlTq6kpZp624zwI3DVBqd&tracking_referrer=www.washingtonpost.com

and here

https://www.nature.com/articles/s41586-018-0007-4.epdf?referrer_access_token=ufEQWt2Fl-XL6afQOgGIHNRgN0jAjWel9jnR3ZoTv0MAQC0usmARmECubT0sv_73cw8e7Uph8-WdBkYDpwNtr_YcnZI3A5E-WO2r6VQKcjCyXVvhm6vOTmIf8kNGnJHlud1rZFvRlFlVyiP-I9XabM_thcVMzFcjh4WF0HmwA9vWMsxm0fXjdj6F0_ytsjxWt_XSVFyvKQxBWUEwWkGBtAWrAsTM8HmaX9DB9GljiZ_YqjM49kz9QOhlQ2zQnPr7m2lNk8M4lyKr8P77l8FmUKXIX9nHnrFrvUgc0FBX2aUolrYfhTEX1inOLt-KDF2ewnbGt6xIh6hpCSWvzjiojxrsG04elQLKfTk0WfnpFBmM8cXRl_CL64pdZP6k6SFm&tracking_referrer=www.washingtonpost.com

Sorry for crazy links but it beats having to pay
Title: Re: AMOC slowdown
Post by: Pmt111500 on April 12, 2018, 10:56:30 AM
Thanks for the links. It lúx laik ðei kompeöd ðe situeißön naucdeis tu rcp2.6 senário in ðe modcl. Probably pretty important papers to get if the reader is planning to do science on North Atlantic currents. Nice to see they included the image with the general GW in the article. The AGW-equalised image posted to realclimate.org and FB alone might give people wrong impressions though the image caption clearly states it's made to see which areas are ahead of the general warming and which are behind.

The same sort of image might be possible about salinity too, but of course exact measurements of that are much sparser than of temperature.

Considering changing the signature to state something about English spelling.
Title: Re: AMOC slowdown
Post by: johnm33 on April 12, 2018, 11:53:35 AM
I've been looking at these recently
(https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/glfstrssh_nowcast_anim30d.gif)
(https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/natspgssh_nowcast_anim30d.gif)
it seems that there's an increase in the volume of water flowing out of the arctic.  Whatever comes out of the north has to be accelerated and i see the vortices[clockwise for hot a/c for cold] as an exchange of energy equalising energetic potentials between the two streams. So whilst the northbound flow may be slower the implication is that whatever is flowing out of the north has to be replaced. Further before it flows north it spends more time under the sub-tropical sun and may gain more energy as a result. If the flow is slowed sufficiently one has to think that any deficit is going to be made up from the pacific side. Looking at windy (https://www.windy.com/?sstanom,33.376,-76.597,5,i:pressure) it seems the northern waters are attatched to the coast as far as Florida. If the CAA garlic press really opens up I'm guessing we can expect an accelerated flow of the least saline waters from the arctic.
Links at https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/ATLANTIC.html
Title: Re: AMOC slowdown
Post by: gerontocrat on April 12, 2018, 06:13:04 PM
From Today's Guardian:

https://www.theguardian.com/environment/2018/apr/11/critical-gulf-stream-current-weakest-for-1600-years-research-finds

with links to:-
https://www.nature.com/articles/s41586-018-0007-4
Anomalously weak Labrador Sea convection and Atlantic overturning during the past 150 years


and:-
https://www.nature.com/articles/s41586-018-0006-5
Observed fingerprint of a weakening Atlantic Ocean overturning circulation

EXTRACTS FROM GUARDIAN ARTICLE

Quote
Gulf Stream current at its weakest in 1,600 years, studies show
Warm current that has historically caused dramatic changes in climate is experiencing an unprecedented slowdown and may be less stable than thought - with potentially severe consequences


The warm Atlantic current linked to severe and abrupt changes in the climate in the past is now at its weakest in at least 1,600 years, new research shows. The findings, based on multiple lines of scientific evidence, throw into question previous predictions that a catastrophic collapse of the Gulf Stream would take centuries to occur......

....Scientists know that Amoc has slowed since 2004, when instruments were deployed at sea to measure it. But now two new studies have provided comprehensive ocean-based evidence that the weakening is unprecedented in at least 1,600 years, which is as far back as the new research stretches.....

......The study by Thornalley and colleagues, published in Nature, used cores of sediments from a key site off Cape Hatteras in North Carolina to examine Amoc over the last 1600 years. Larger grains of sediment reflect faster Amoc currents and vice versa.....

.....The second study, also published in Nature, also used the characteristic pattern of temperatures, but assessed this using thermometer data collected over the last 120 years or so.

Both studies found that Amoc today is about 15% weaker than 1,600 years ago, but there were also differences in their conclusions. The first study found significant Amoc weakening after the end of the little ice age in about 1850, the result of natural climate variability, with further weakening caused later by global warming.

The second study suggests most of the weakening came later, and can be squarely blamed on the burning of fossil fuels. Further research is now being undertaken to understand the reasons for the differences.

I am beginning to understand where bbr2314 is coming from on his posts on Northern Hemisphere Snow Cover
Title: Re: AMOC slowdown
Post by: magnamentis on April 12, 2018, 09:24:37 PM
From Today's Guardian:

I am beginning to understand where bbr2314 is coming from on his posts on Northern Hemisphere Snow Cover

it's basically certain that huge amounts of freshwater due to significantly increase ice-melt will have an impact of various kinds, including some changes to the ocean currents.

there is only one thing that IMO often is missing in discussions:

- some are of the opinion that something will happen

- others are of the opinion that that does not happen

but not many consider the possibility that while something will happen, something else will compensate for the resulting effects.

so coming back to the topic of the so called gulf-stream:

if the planet will be 4-5C warmer over all and if we shall loose in some parts of the northern hemisphere a fair portion of heat due to slow down or standstill or shorter reach of the gulf stream, we shall overall still have higher temps than before, in parts similar temps and in very few specific spots perhaps a tick colder.

in short, it does not really matter when it comes to the main topic of this forum, that is arctic sea ice etc. it will melt either way.
Title: Re: AMOC slowdown
Post by: Coffee Drinker on April 14, 2018, 01:04:25 AM
Wouldn't the Amoc slowdown effects kick in way before the Earth warms at 4-5C?

4-5C is allot and I think we will have much more serious problems than AMOC slowdown by then.
Title: Re: AMOC slowdown
Post by: bbr2314 on April 14, 2018, 01:13:59 AM
It is interesting to note that impacts re: AMOC slowdown on Hawaii have been bantered about before. But I wonder if this is another chicken and egg scenario. With increasing atmospheric water vapor/heat content, does increasing snowfall atop Mauna Loa and Mauna Kea act to enhance the standing wave pattern over North America, encouraging more snow across the Canadian Shield/etc as it helps pump the RRR?

I think it is important not to get too caught up in minor details, but it is equally important not to ignore seemingly minor things that could have major impacts. The albedo impact of more snow and ice atop Mauna Kea and Mauna Loa is actually the most significant variance possible on planet earth latitudinally, as they represent an island of major forcing in the middle of what is otherwise a "geographic desert" of ocean. Wintertime snowcover over the volcanoes deflects something like 500X the insolation of Barrow.

It should be noted that this March/April have seen persistent snowcover across both volcanoes.

https://www.snow-forecast.com/resorts/Mauna-Kea/webcams/latest

http://today.oregonstate.edu/archives/2010/aug/ancient-hawaiian-glaciers-reveal-clues-global-climate-impacts

The study concludes that the growth of the Mauna Kea glacier caused by the AMOC current changes was a result of both colder conditions and a huge increase of precipitation on Mauna Kea - triple that of the present - that scientists believe may have been caused by more frequent cyclonic storm events hitting the Hawaiian Islands from the north.

The cold comes after the snowcover increase... IT IS THE WATER!!!!!
Title: Re: AMOC slowdown
Post by: Iceismylife on April 14, 2018, 01:43:02 AM
...

The cold comes after the snowcover increase... IT IS THE WATER!!!!!
That is the converse of what I think ended the little ice age.

Soot got into the permanent sea ice.  Caused it to melt, brake up, less reflected light, warmer.  Starting something like 1700ish.  That melting started the slowdown.
Title: Re: AMOC slowdown
Post by: oren on April 17, 2018, 04:22:58 AM
It is interesting to note that impacts re: AMOC slowdown on Hawaii have been bantered about before. But I wonder if this is another chicken and egg scenario. With increasing atmospheric water vapor/heat content, does increasing snowfall atop Mauna Loa and Mauna Kea act to enhance the standing wave pattern over North America, encouraging more snow across the Canadian Shield/etc as it helps pump the RRR?

I think it is important not to get too caught up in minor details, but it is equally important not to ignore seemingly minor things that could have major impacts. The albedo impact of more snow and ice atop Mauna Kea and Mauna Loa is actually the most significant variance possible on planet earth latitudinally, as they represent an island of major forcing in the middle of what is otherwise a "geographic desert" of ocean. Wintertime snowcover over the volcanoes deflects something like 500X the insolation of Barrow.
The islands are minuscule compared to the Pacific ocean, and their albedo impact is negligent. Also just as an example, ENSO variation in the Pacific is many orders of magnitude stronger than any Hawaii signal.
But in any case, it would be interesting to try and find any studies that support the claim that the islands play a major role in North America weather.
Title: Re: AMOC slowdown
Post by: bbr2314 on April 17, 2018, 04:41:38 AM
It is interesting to note that impacts re: AMOC slowdown on Hawaii have been bantered about before. But I wonder if this is another chicken and egg scenario. With increasing atmospheric water vapor/heat content, does increasing snowfall atop Mauna Loa and Mauna Kea act to enhance the standing wave pattern over North America, encouraging more snow across the Canadian Shield/etc as it helps pump the RRR?

I think it is important not to get too caught up in minor details, but it is equally important not to ignore seemingly minor things that could have major impacts. The albedo impact of more snow and ice atop Mauna Kea and Mauna Loa is actually the most significant variance possible on planet earth latitudinally, as they represent an island of major forcing in the middle of what is otherwise a "geographic desert" of ocean. Wintertime snowcover over the volcanoes deflects something like 500X the insolation of Barrow.
The islands are minuscule compared to the Pacific ocean, and their albedo impact is negligent. Also just as an example, ENSO variation in the Pacific is many orders of magnitude stronger than any Hawaii signal.
But in any case, it would be interesting to try and find any studies that support the claim that the islands play a major role in North America weather.

I found papers talking about atmospheric standing waves generated by the South Island of NZ and their impact. But nothing on the Big Island. I agree that the Pacific is enormous but it is flat -- while Hawaii is small, the dearth of topographic features gives it extremely outsized influence and ensures it acts as a wave break in some capacity, especially when atmospheric heights are low in the vicinity (due to the volcanoes stretching more than two miles above sea level).
Title: Re: AMOC slowdown
Post by: oren on April 17, 2018, 04:47:10 AM
I found papers talking about atmospheric standing waves generated by the South Island of NZ and their impact. But nothing on the Big Island. I agree that the Pacific is enormous but it is flat -- while Hawaii is small, the dearth of topographic features gives it extremely outsized influence and ensures it acts as a wave break in some capacity, especially when atmospheric heights are low in the vicinity (due to the volcanoes stretching more than two miles above sea level).
The south island of NZ is ten times the land area of all of the Hawaiian islands combined. I very much doubt the purported Hawaii influence.
Title: Re: AMOC slowdown
Post by: bbr2314 on April 17, 2018, 04:47:53 AM
I found papers talking about atmospheric standing waves generated by the South Island of NZ and their impact. But nothing on the Big Island. I agree that the Pacific is enormous but it is flat -- while Hawaii is small, the dearth of topographic features gives it extremely outsized influence and ensures it acts as a wave break in some capacity, especially when atmospheric heights are low in the vicinity (due to the volcanoes stretching more than two miles above sea level).
The south island of NZ is ten times the land area of all of the Hawaiian islands combined. I very much doubt the purported Hawaii influence.

It is not the size, it is the height. The Hawaiian volcanoes are taller than anything in New Zealand!
Title: Re: AMOC slowdown
Post by: oren on April 17, 2018, 05:17:01 AM
It is not the size, it is the height. The Hawaiian volcanoes are taller than anything in New Zealand!
Hawaii Island (the tall one) highest elevation 4,207 m, land area 10,430 km2
NZ South Island highest elevation 3,724 m, land area 150,437 km2
Looking at Wikipedia, I doubt a 13% difference in height compensates for a 14.4 times difference in area.
Title: Re: AMOC slowdown
Post by: bbr2314 on April 17, 2018, 05:32:01 AM
It is not the size, it is the height. The Hawaiian volcanoes are taller than anything in New Zealand!
Hawaii Island (the tall one) highest elevation 4,207 m, land area 10,430 km2
NZ South Island highest elevation 3,724 m, land area 150,437 km2
Looking at Wikipedia, I doubt a 13% difference in height compensates for a 14.4 times difference in area.
It is not the area, it is the altitude differential WRT the Pacific Ocean... area is relevant for Albedo.
Title: Re: AMOC slowdown
Post by: dnem on April 17, 2018, 02:25:33 PM
It is not the size, it is the height. The Hawaiian volcanoes are taller than anything in New Zealand!
Hawaii Island (the tall one) highest elevation 4,207 m, land area 10,430 km2
NZ South Island highest elevation 3,724 m, land area 150,437 km2
Looking at Wikipedia, I doubt a 13% difference in height compensates for a 14.4 times difference in area.
It is not the area, it is the altitude differential WRT the Pacific Ocean... area is relevant for Albedo.

What about the impact of the huge sea mount on coupled ocean/atmosphere dynamics?  The image is of the Galapagos, but might HI have a similar impact? No idea, but HI "sticks down" into the ocean way more than it sticks up into the atmosphere.
Title: Re: AMOC slowdown
Post by: bbr2314 on April 17, 2018, 07:42:02 PM
It is not the size, it is the height. The Hawaiian volcanoes are taller than anything in New Zealand!
Hawaii Island (the tall one) highest elevation 4,207 m, land area 10,430 km2
NZ South Island highest elevation 3,724 m, land area 150,437 km2
Looking at Wikipedia, I doubt a 13% difference in height compensates for a 14.4 times difference in area.
It is not the area, it is the altitude differential WRT the Pacific Ocean... area is relevant for Albedo.

What about the impact of the huge sea mount on coupled ocean/atmosphere dynamics?  The image is of the Galapagos, but might HI have a similar impact? No idea, but HI "sticks down" into the ocean way more than it sticks up into the atmosphere.

I would agree that this also has major impact! Perhaps the impact of Hawaii increases as SSTs also rise? More heat, more impact, perhaps exponentially so.
Title: Re: AMOC slowdown
Post by: Sleepy on May 29, 2018, 06:24:24 AM
Yesterdays article by Ramstorf.
http://www.realclimate.org/index.php/archives/2018/05/if-you-doubt-that-the-amoc-has-weakened-read-this/ (http://www.realclimate.org/index.php/archives/2018/05/if-you-doubt-that-the-amoc-has-weakened-read-this/)
Title: Re: AMOC slowdown
Post by: nowayout on May 29, 2018, 08:04:19 AM
Yesterdays article by Ramstorf.
http://www.realclimate.org/index.php/archives/2018/05/if-you-doubt-that-the-amoc-has-weakened-read-this/ (http://www.realclimate.org/index.php/archives/2018/05/if-you-doubt-that-the-amoc-has-weakened-read-this/)

Great, thank you. The next question: what are the effects / impacts. I found this:
https://link.springer.com/article/10.1007/s00382-015-2540-2 (https://link.springer.com/article/10.1007/s00382-015-2540-2)

Sorry, if this was already discussed in an other thread.
Title: Re: AMOC slowdown
Post by: bbr2314 on May 29, 2018, 06:14:58 PM
Yesterdays article by Ramstorf.
http://www.realclimate.org/index.php/archives/2018/05/if-you-doubt-that-the-amoc-has-weakened-read-this/ (http://www.realclimate.org/index.php/archives/2018/05/if-you-doubt-that-the-amoc-has-weakened-read-this/)
In the comments Ramsdorf seems to dismiss Greenland melt's impacts.... I would say that is quite incorrect...
Title: Re: AMOC slowdown
Post by: sidd on May 29, 2018, 06:29:53 PM
In the response he indicated that melt has impact on surface salinity but not on largescale temperature.

"[Response: You mean by cold meltwater from Greenland flowing in? You can work that out from a simple heat budget calculation. The amount is far too small to matter for the large-scale sea surface temperature, but enough to matter for sea surface salinity. -Stefan] "

I did a simple heat calculation, and i agree with him.

sidd
Title: Re: AMOC slowdown
Post by: bbr2314 on May 29, 2018, 06:32:49 PM
In the response he indicated that melt has impact on surface salinity but not on largescale temperature.

"[Response: You mean by cold meltwater from Greenland flowing in? You can work that out from a simple heat budget calculation. The amount is far too small to matter for the large-scale sea surface temperature, but enough to matter for sea surface salinity. -Stefan] "

I did a simple heat calculation, and i agree with him.

sidd
What about snowmelt from adjacent areas in North America as well? I think a look at recent evolving SSTAs shows this is indeed a major factor...

I would also add that contrary to his research, you can see the pulse of high heights begin to rise off the East Coast of North America in July / August / September rather than in wintertime (each and every year, most recently). Again, this supports a greater relationship with melt (IMO).
Title: Re: AMOC slowdown
Post by: bbr2314 on May 29, 2018, 10:49:59 PM
See attached -- I would be extremely surprised if the residual albedo anomalies due to extra extant land-snowcover and the melt from that extra SWE/Greenland are unrelated to the worsening NATL anomalies we have seen this month. The currents may be the driver, but the situation ^^^ has, IMO, been a major aggravator to the current appearance.



Title: Re: AMOC slowdown
Post by: sidd on May 30, 2018, 05:34:39 AM
The graf in the post above is air temperature. SST is more appropriate in AMOC/Rahmstorf context.

sidd

Title: Re: AMOC slowdown
Post by: Richard Rathbone on May 30, 2018, 02:33:46 PM
In the response he indicated that melt has impact on surface salinity but not on largescale temperature.

"[Response: You mean by cold meltwater from Greenland flowing in? You can work that out from a simple heat budget calculation. The amount is far too small to matter for the large-scale sea surface temperature, but enough to matter for sea surface salinity. -Stefan] "

I did a simple heat calculation, and i agree with him.

sidd

Stefan's being a little disingenuous here. It makes a big difference to the cooling whether the ice melts on shore and meltwater enters the sea, or whether icebergs fall off Greenland and the ice melts at sea. Hansen reckoned that cooling was important enough to hose with a berg/meltwater mix rather than the traditional meltwater only, and I'm inclined to accept his judgement on it.

Title: Re: AMOC slowdown
Post by: bbr2314 on May 30, 2018, 04:50:58 PM
In the response he indicated that melt has impact on surface salinity but not on largescale temperature.

"[Response: You mean by cold meltwater from Greenland flowing in? You can work that out from a simple heat budget calculation. The amount is far too small to matter for the large-scale sea surface temperature, but enough to matter for sea surface salinity. -Stefan] "

I did a simple heat calculation, and i agree with him.

sidd

Stefan's being a little disingenuous here. It makes a big difference to the cooling whether the ice melts on shore and meltwater enters the sea, or whether icebergs fall off Greenland and the ice melts at sea. Hansen reckoned that cooling was important enough to hose with a berg/meltwater mix rather than the traditional meltwater only, and I'm inclined to accept his judgement on it.

And I would argue it makes an even bigger difference if hosing effects in Quebec begin prior to other regions, amplifying albedo / extent beyond normal bounds, and allowing (relatively) cold continental winds to blow across the anomalous region, further compounding the cold blob...!
Title: Re: AMOC slowdown
Post by: bbr2314 on July 02, 2018, 07:39:38 PM
Welp.

The change over the past 30 days has been extremely severe. I would say this is probably the worst disruption or occurrence of melt we have witnessed in the satellite era, at least in my recollection.

It looks like the second melt pulse of SWE in early June was the causative factor.

(https://ccin.ca/home/sites/default/files/snow/snow_tracker/na_swe.png)

If this occurs with current departures vs. normal, I hate to think about what happens if we accumulate enough volume to result in a July melt pulse. It seems evident that the +++volume and April melt pulse was sufficient to stall May melt momentum substantially.

This begs the question of whether we need crazy departures for snow to make it through summer. If we have another 1000KM^3 of volume in 10-15 years, that could suffice for allowing enough melt pulsage that, by July/August, the remaining extant volume (now occupying a much greater area) is substantially more protected by the larger extant continental crysophere (further aided by decaying sea ice up north causing it to be "stuck" between oceanic ridging derived from continually accumulating heat). So summer quickly goes from abbreviated (2018) to non-existent (2035).

https://weather.gc.ca/saisons/animation_e.html?id=month&bc=sea

Title: Re: AMOC slowdown
Post by: Alexander555 on July 02, 2018, 09:41:09 PM
A July melt puls ? If the information is correct there is less snow in the Americas below Canada. So how would that extra volume preventing the summer to kick in ? Would it not be possible that the area with snow cover gets smaller or the periodes shorter if the temperature keeps going up ? Anyway , you keep the debat going  ;)
Title: Re: AMOC slowdown
Post by: bbr2314 on July 03, 2018, 03:04:33 AM
A July melt puls ? If the information is correct there is less snow in the Americas below Canada. So how would that extra volume preventing the summer to kick in ? Would it not be possible that the area with snow cover gets smaller or the periodes shorter if the temperature keeps going up ? Anyway , you keep the debat going  ;)
I am talking about future years. If we have another 1000KM^3 of volume vs 2018 by 2035, there will be enough mass that the spring melt pulses / ensuing protective freshwater runoff will allow the pack to last into July. You can see how the melting of the SWE follows distinctive pulses and doesn't run off all at once.

Also here is June 2018 vs. 2012. Some regions are now 20F+ colder (on monthlies!) than they were only six years ago.
Title: Re: AMOC slowdown
Post by: AbruptSLR on July 30, 2018, 04:43:07 AM
Consensus scientist's like to gamble with public safety that a slow-down of the AMOC it doesn't increase the rate of global warming, but that does not make it so:

Title: "Does a slow AMOC increase the rate of global warming?"

http://www.realclimate.org/index.php/archives/2018/07/does-a-slow-amoc-increase-the-rate-of-global-warming/
Title: Re: AMOC slowdown
Post by: FishOutofWater on July 30, 2018, 02:10:44 PM
That cool area south of Greenland was not caused by melting of Canadian snow. The fresh water from Canadian snowmelt stays close to the coastline and moves south with the Labrador current.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fstatic-bulletin.mercator-ocean.fr%2Fimg%2F-1%2Fsections%2Fpsy4qv3r1%2F20180729%2FA%2Fpsy4qv3r1_20180729_sarc1_salinity.png&hash=c1ae5ab198f27da550fd17f84b6912ad)

The Greenland vortex pattern that has been dominating the weather since spring is the cause of that pattern. Storms and persistent NW winds down the Labrador sea has increased mixing in the Labrador and Greenland seas and cooled the surface layer.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fstatic-bulletin.mercator-ocean.fr%2Fimg%2F-1%2Fsections%2Fpsy4qv3r1%2F20180729%2FA%2Fpsy4qv3r1_20180729_sarc1_temperature.png&hash=d561f06077f6fbb09953b7a2d68c8b2b)

The AMOC slowdown may be a problem for the Arctic sea ice because heat not transported northwards into the Labrador sea may be transported northeastwards wards into the Arctic ocean.
Title: Re: AMOC slowdown
Post by: AbruptSLR on August 04, 2018, 08:12:55 PM
The linked research provides more evidence that a slowing of the AMOC will lead to increased warming at high latitudes due to abrupt warming during the summer months (which increases Arctic Amplification):

G. Bromley et al. (06 April 2018), "Interstadial Rise and Younger Dryas Demise of Scotland's Last Ice Fields", Paleoceanography and Paleoclimatology, Vol. 33, Issue 4, https://doi.org/10.1002/2018PA003341

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2018PA003341

Abstract
Establishing the atmospheric expression of abrupt climate change during the last glacial termination is key to understanding driving mechanisms. In this paper, we present a new 14C chronology of glacier behavior during late‐glacial time from the Scottish Highlands, located close to the overturning region of the North Atlantic Ocean. Our results indicate that the last pulse of glaciation culminated between ~12.8 and ~12.6 ka, during the earliest part of the Younger Dryas stadial and as much as a millennium earlier than several recent estimates. Comparison of our results with existing minimum‐limiting 14C data also suggests that the subsequent deglaciation of Scotland was rapid and occurred during full stadial conditions in the North Atlantic. We attribute this pattern of ice recession to enhanced summertime melting, despite severely cool winters, and propose that relatively warm summers are a fundamental characteristic of North Atlantic stadials.

Plain Language Summary
Geologic data reveal that Earth is capable of abrupt, high‐magnitude changes in both temperature and precipitation that can occur well within a human lifespan. Exactly what causes these potentially catastrophic climate‐change events, however, and their likelihood in the near future, remains frustratingly unclear due to uncertainty about how they are manifested on land and in the oceans. Our study sheds new light on the terrestrial impact of so‐called “stadial” events in the North Atlantic region, a key area in abrupt climate change. We reconstructed the behavior of Scotland's last glaciers, which served as natural thermometers, to explore past changes in summertime temperature. Stadials have long been associated with extreme cooling of the North Atlantic and adjacent Europe and the most recent, the Younger Dryas stadial, is commonly invoked as an example of what might happen due to anthropogenic global warming. In contrast, our new glacial chronology suggests that the Younger Dryas was instead characterized by glacier retreat, which is indicative of climate warming. This finding is important because, rather than being defined by severe year‐round cooling, it indicates that abrupt climate change is instead characterized by extreme seasonality in the North Atlantic region, with cold winters yet anomalously warm summers.
Title: Re: AMOC slowdown
Post by: sidd on August 05, 2018, 07:59:56 AM
How does that paper indicate that " a slowing of the AMOC will lead to increased warming at high latitudes due to abrupt warming during the summer months "

All i see is increased summer temperatures shortly after 12.8 to 12.6 Kyr BP.

sidd
Title: Re: AMOC slowdown
Post by: bbr2314 on August 05, 2018, 11:55:22 AM
How does that paper indicate that " a slowing of the AMOC will lead to increased warming at high latitudes due to abrupt warming during the summer months "

All i see is increased summer temperatures shortly after 12.8 to 12.6 Kyr BP.

sidd
I would think it is because the "bubble" of super-warm ATL SSTs reaches the high Arctic, turns it ice-free, and forces progressively colder continents. This may be a self-reinforcing mechanism until the cold continents sufficiently overwhelm the SSTs to cause the Arctic to refreeze entirely. Thus, you end up with an "interlude" of extremely warm temps / summers in certain regions as the domino effect kicks in, which first occurs adjacent to extant ice sheets (i.e., Greenland), before spreading across the rest of the NHEM and resolving the warm oceanic anomalies.
Title: Re: AMOC slowdown
Post by: AbruptSLR on August 06, 2018, 05:52:00 PM
How does that paper indicate that " a slowing of the AMOC will lead to increased warming at high latitudes due to abrupt warming during the summer months "

All i see is increased summer temperatures shortly after 12.8 to 12.6 Kyr BP.

sidd

In addition to bbr2314's points, the fact that the Scottish glacier melted with a slowing AMOC is physical evidence of at least local Artic Amplification .
Title: Re: AMOC slowdown
Post by: johnm33 on August 07, 2018, 11:45:03 PM
It looks like the AMOC is changing in a more complex way than just slowing. Open the ssh/t/s gifs on these two pages to look at the vortices and the various streams. https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/glfstr.html
https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/natspg.html
The way i see this is you have water coming out of the arctic moving more or less orthogonally away from the axis of rotation that has to gain 15mph/24kph every deg. it moves south to be at equilibrium. It's energetic state is indicated by the low ssh and the fact that it holds fast to the east coast as it moves south, both on Greenland and America. From the south there's water that has shifted about 110 and 1/8 closer [not much] in relation to the axis since it rose from the depths off equatorial Africa where it was already moving slower than the planets rotational speed which remains the case untill it gets to 35N . Then these two bodies meet and begin to exchange qualities, heat, inertia, salinity and spin one slows the other accelerates.
 There's a gif here (http://www.mt-oceanography.info/IntExerc/basic5/quest23.html) that helps to visualise the tidal rotation around the amphidromic point in the N.ATL. also shown. Looking at the ssh gif in the second link above it appears that there are vortices of polar water moving south and east feeding a growing area of cooler water going south from Spain as far as the Cape Verde islands. The amphidromic point seems to coincide with a relatively quiet [vortice wise] area of the N.ATL. on Nullschool (https://earth.nullschool.net/#current/ocean/surface/currents/overlay=sea_surface_temp_anomaly/orthographic=-34.61,49.08,1821/loc=-36.287,53.604) . It appears that this fraction of water is being drawn south away from there as the tides rotate, whether this is permanent or just one of the random fluctuations we can expect ?
hope that makes sense.
 
Title: Re: AMOC slowdown
Post by: AbruptSLR on August 14, 2018, 11:06:54 PM
The linked reference evaluates various factors influencing the AMO including the AMOC.  It does note that a slowdown of the AMOC results in a warming of the Tropical Atlantic waters:

ROBERT C. J. WILLS et a;. (2018), "Ocean-atmosphere dynamical coupling fundamental to the Atlantic Multidecadal Oscillation", Journal of Climate,

https://atmos.washington.edu/~rcwills/papers/2018_Wills_etal_AMO_JClim.pdf

Abstract: "The North Atlantic has shown large multidecadal temperature shifts during the 20th century. There is ongoing debate about whether this variability arises primarily through the influence of atmospheric internal variability, through changes in ocean circulation, or as a response to anthropogenic forcing. This study isolates the mechanisms driving Atlantic temperature variability on multidecadal timescales by using low-frequency component analysis (LFCA) to separate the influences of high-frequency variability, multidecadal variability, and long-term global warming. This analysis objectively identifies the North Atlantic subpolar gyre as the dominant region of Atlantic multidecadal variability. In unforced control runs of coupled climate models, warm subpolar temperatures are associated with a strengthened Atlantic Meridional Overturning Circulation (AMOC) and anomalous local heat fluxes from the ocean into the atmosphere. Atmospheric variability plays a role in the intensification and subsequent weakening of ocean overturning and helps to communicate warming into the tropical Atlantic. These findings suggest that dynamical coupling between atmospheric and oceanic circulations is fundamental to the Atlantic Multidecadal Oscillation (AMO) and motivate approaching decadal prediction with a focus on ocean circulations."
Title: Re: AMOC slowdown
Post by: Niall Dollard on August 22, 2018, 10:52:46 AM
2018 International AMOC Science Meeting Agenda

There is a wealth of information available here on the current state of the AMOC, with many of the presentations freely available to download :

https://usclivar.org/meetings/2018-amoc-rapid-meeting-agenda
Title: Re: AMOC slowdown
Post by: bluesky on September 18, 2018, 05:37:27 PM
A new paper makes the dot between drop in oxygen content in St Laurent estuary, weakening of the Labrador current and a correlation with weakening AMOC

"Rapid coastal deoxygenation due to ocean circulation shift in the northwest Atlantic"
Mariona Claret et al. Sept 2018

Abstract
"Global observations show that the ocean lost approximately 2% of its oxygen inventory over the past five decades1,2,3, with important implications for marine ecosystems4,5. The rate of change varies regionally, with northwest Atlantic coastal waters showing a long-term drop6,7 that vastly outpaces the global and North Atlantic basin mean deoxygenation rates5,8. However, past work has been unable to differentiate the role of large-scale climate forcing from that of local processes. Here, we use hydrographic evidence to show that a Labrador Current retreat is playing a key role in the deoxygenation on the northwest Atlantic shelf. A high-resolution global coupled climate–biogeochemistry model9 reproduces the observed decline of saturation oxygen concentrations in the region, driven by a retreat of the equatorward-flowing Labrador Current and an associated shift towards more oxygen-poor subtropical waters on the shelf. The dynamical changes underlying the shift in shelf water properties are correlated with a slowdown in the simulated Atlantic Meridional Overturning Circulation (AMOC)10. Our results provide strong evidence that a major, centennial-scale change of the Labrador Current is underway, and highlight the potential for ocean dynamics to impact coastal deoxygenation over the coming century."

under paywall, but I think it can be requested on research gate so should be accessible:
https://www.researchgate.net/publication/327702404_Rapid_coastal_deoxygenation_due_to_ocean_circulation_shift_in_the_northwest_Atlantic
Title: Re: AMOC slowdown
Post by: sidd on September 25, 2018, 10:18:01 PM
Here is an interesting paper in GRL on a global climate model that has a bistablity between glaciated and nonglaciated states. It is a crude model, but rather nice in that it explicitly shows the origin of the bistability.

"Two stable equilibria of climate are supported, one "Cold" and one "Warm" for the same external forcing and parameters, thus demonstrating that multiple equilibria are possible in a coupled GCM comprising a myriad of degrees of freedom. The difference in the climate of the two states is of planetary scale. Global average sea surface temperature and surface air temperature differ by 8.2 and 13.5 ∘ C, respectively (patterns are shown in Figure S1). In the southern hemisphere (SH), the sea ice edge (as measured by the 15% annual mean concentration) expands by about 15 ∘ of latitude in the Cold state (Figure 1). The northern hemisphere, which is nearly ice free in the Warm state, exhibits a large ice cap extending over the subpolar gyre (45 N) in the Cold state, with a similar expansion of snow cover over land (Figure 1, top left)."

Why do i post the paper in this thread: Because the bistability is not driven by AMOC collapse:

"The multiple states described here differ fundamentally from AMOC bistability and are supported by coupled ocean-atmosphere-sea ice dynamics. Although the MOC does change between states in our simulations (Figure 3), this change does not correspond to a collapse and is in fact a symptom rather than a driver of the bistability (Ferreira et al., 2011)."


I attach fig 1

sidd
Title: Re: AMOC slowdown
Post by: bbr2314 on November 14, 2018, 08:18:53 AM
I don't know where to ask this question so perhaps this is the right place. While shelf temps along the NE seaboard are dropping, the EURO is showing what I believe to be an unprecedented surge of heat developing and arriving very close offshore (GIF is 11/23/2017 vs 2018). This starts around D4 and the end result appears to follow the continental shelf fairly closely. So what is causing this / could it be the freshwater input from whatever happened with Beaufort Gyre this summer (maybe it intensified the GS response?) or also albedo / SST interaction due to Quebec's snowy autumn?

This may portend significant disturbances down the line as well.

(https://media.giphy.com/media/ftdVXIHphN5idpigoO/giphy.gif)
Title: Re: AMOC slowdown
Post by: oren on November 14, 2018, 09:53:44 AM
Interesting but I think the best time to ask that question is after this event will have happened, in 10 days from now. Then the comparison will be fully valid.
Title: Re: AMOC slowdown
Post by: bbr2314 on November 15, 2018, 06:20:43 AM
Interesting but I think the best time to ask that question is after this event will have happened, in 10 days from now. Then the comparison will be fully valid.
So after your rebuke I went back and compared EURO forecasts for the same region in recent weeks with reality upon verification. And you are correct to be wary, because it appears the EURO has a systemic bias of GREATLY overwarming the NATL adjacent to the NE seaboard. This is actually very good to know and it partially explains why it is always too progressive with ejecting airmasses from Northeast North America (fake oceanic warmth -> more ridging, verification of less warmth -> more troughing vs forecast).
Title: Re: AMOC slowdown
Post by: aperson on November 15, 2018, 06:30:15 AM
The ECMWF wasn't even atmosphere-ocean coupled until this year. It's definitely got a long way to go before it can be used as any sort of useful indicator for D10 SSTs. A lot of the other global models aren't even coupled altogether.
Title: Re: AMOC slowdown
Post by: Sleepy on November 15, 2018, 06:48:53 AM
https://www.ecmwf.int/en/newsletter/156/meteorology/ifs-upgrade-brings-more-seamless-coupled-forecasts (https://www.ecmwf.int/en/newsletter/156/meteorology/ifs-upgrade-brings-more-seamless-coupled-forecasts)
Quote
On 5 June 2018, ECMWF implemented a substantial upgrade of its Integrated Forecasting System (IFS). IFS Cycle 45r1 brings coupling to all ECMWF forecasts, from forecast day 1 to one year, by including the three-dimensional ocean and sea-ice model in the single high-resolution forecast (HRES). This is a further step towards the implementation of the 2016–2025 Strategy, whose goals include a more complete and seamless description of the Earth system across all ECMWF configurations.
Title: Re: AMOC slowdown
Post by: Pmt111500 on November 15, 2018, 08:29:15 AM
https://www.ecmwf.int/en/newsletter/156/meteorology/ifs-upgrade-brings-more-seamless-coupled-forecasts (https://www.ecmwf.int/en/newsletter/156/meteorology/ifs-upgrade-brings-more-seamless-coupled-forecasts)
Quote
On 5 June 2018, ECMWF implemented a substantial upgrade of its Integrated Forecasting System (IFS). IFS Cycle 45r1 brings coupling to all ECMWF forecasts, from forecast day 1 to one year, by including the three-dimensional ocean and sea-ice model in the single high-resolution forecast (HRES). This is a further step towards the implementation of the 2016–2025 Strategy, whose goals include a more complete and seamless description of the Earth system across all ECMWF configurations.
Browser crashed, not going to write the longer response again. Looks like the tropical forecasts get an improvement in ecmwf. Does someone know if they incorporate weekends, holidays and similar cultural effects on their model? Simple yes or no will do. I mean, have they checked if forecasts made on Monday data are more accurate than those done on Fridays' data? This might be one way to improve on longer forecasts, but would require some predictability of human behavior... Not something many endorse, it's entirely possible humans stop emissions on their freetime instead of rushing to the shores of plastic seas.
Title: Re: AMOC slowdown
Post by: Sleepy on November 15, 2018, 09:38:32 PM
Pmt, I haven't thought about that but it seems like they will hit the roof soon (with todays tech) even without incorporating human behaviour.
https://www.ecmwf.int/en/about/what-we-do/scalability (https://www.ecmwf.int/en/about/what-we-do/scalability)
(https://www.ecmwf.int/sites/default/files/scalability-efficiency-gains.png)
Title: Re: AMOC slowdown
Post by: gerontocrat on November 15, 2018, 10:06:10 PM
Pmt, I haven't thought about that but it seems like they will hit the roof soon (with todays tech) even without incorporating human behaviour.
/quote]
I wonder if a similar sort of scary graph is where mankind is going on power use by computer /communications gear in general as world-wide systems and data storage expand exponentially . Chuck in AI, which apparently requires a quantum jump in data and processing power, and ......

ps: My doubts on AI have always been that the brain must work fundamentally differently from computers. The brain has ridiculously low processing speeds and pathetically low amounts of data storage but.....

pps: But should I be reminding sleepy of his less than wonderful experiences of the IT industry.
Title: Re: AMOC slowdown
Post by: Sleepy on November 15, 2018, 10:28:17 PM
Oh, they were wonderful gerontocrat, I had everything except a life. Now it's the other way around. And you?
Title: Re: AMOC slowdown
Post by: gerontocrat on November 15, 2018, 11:45:39 PM
Oh, they were wonderful gerontocrat, I had everything except a life. Now it's the other way around. And you?
It was good for a long time in some of the poorest parts of the world. I even did stuff for the Swedish International Development Association - they sent me to Vasteras to learn Portuguese..

But socialism died, the demand was to support privatisation and the Anglo-Saxon Capitalist model. Once I was sent a project proposal to tax famine ( I kid you not). So in the end I chucked it. I have a CV that says to prospective employers - you did too much, you know too much. Over-qualified people are unemployable.

So nowt to do now but be a witness to the coming shit-storm and try to persuade my daughter to prepare her defences. People tell me to write the book - it seems we all have one book inside us. Too much like hard work?

AMOC slowdown ? whoops.
Title: Re: AMOC slowdown
Post by: Pmt111500 on November 16, 2018, 05:26:11 AM
Oh, they were wonderful gerontocrat, I had everything except a life. Now it's the other way around. And you?
I have a CV that says to prospective employers - you did too much, you know too much. Over-qualified people are unemployable.
AMOC slowdown ? whoops.
AMOC slowdown.
It could be the increased heat absorption by the AGW in the North Atlantic is responsible for the continued decrease of ice in the Arctic Atlantic sector. Rather than trying to directly measure the heat transport from Tropics we might do better relying on satellite/ship measurements over the whole North Atlantic. It's been clear that East Greenland and Baffin current systems have brought an almost steady feed of cold water southwards.
Nowadays, probably for 3 years now the Nares transport has been diminishing (well way longer, just throwing a number here) and the eastern parts of north Atlantic currents have on occasion backtracked (not sure this is how it happens) along the edge of the ice all the way over the northern tip of Greenland. Thus the heat transport via the North Atlantic eastern coasts might be seen to be a factor in the melt of NE Greenland, a place at least I once thought to be among the last to start melting.
This heat absorbed by the Eastern North Atlantic might neatly connect to the bbr hypothesis of Quebec and Labrador harshness. Cutting out a conduit (the East Greenland Current and Nares Transport) for cold waters might increase transport elsewhere (CAA channels), unless the ice melts in place.
Anyway, the 'cold patch' South of Greenland, occasionally can manifest itself on a much wider area in CAA, Labrador and Quebec giving the residents (and bbr) much to talk about. Personally I do not think part of Greenland ice should melt and be transported by warped airflows to the mainland Canada. What the cold patch (along with its other counterpart (the other one in the Southern hemisphere might be a figment of  my imagination) warmch in North Pacific) does do is to help create the Ridiculously Resilient Ridge and the associated high amplitude waves over the whole hemisphere. Thus we might see bbrs' hypothesis as an extreme case of standing waves directing only cold rains (yea, it's snow) towards Canadian eastern seaboard.

That is about my current understanding of what's happening in Overturning, I know salinity plays a role in the Ocean, but I left it out since I don't get it well enouhj.
Title: Re: AMOC slowdown
Post by: Sleepy on November 16, 2018, 05:52:34 AM
Another by Wei Liu, paywalled and not (yet) available to cheap non paying customers.

The mechanisms of the Atlantic Meridional Overturning Circulation slowdown induced by Arctic sea ice decline
https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-18-0231.1 (https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-18-0231.1)
Quote
We explore the mechanisms by which Arctic sea ice decline affects the Atlantic Meridional Overturning Circulation (AMOC) in a suite of numerical experiments perturbing Arctic sea ice radiative budget within a fully coupled climate model. The imposed perturbations act to increase the amount of heat available to melt ice, leading to a rapid Arctic sea ice retreat within 5 years after the perturbations are activated. In response, the AMOC gradually weakens over the next ∼100 years. The AMOC changes can be explained by the accumulation in the Arctic and subsequent downstream propagation to the North Atlantic of buoyancy anomalies controlled by temperature and salinity. Initially, during the first decade or so, the Arctic sea ice loss results in anomalous positive heat and salinity fluxes in the subpolar North Atlantic, inducing positive temperature and salinity anomalies over the regions of oceanic deep convection. At first, these anomalies largely compensate one another, leading to a minimal change in upper ocean density and deep convection in the North Atlantic. Over the following years, however, more anomalous warm water accumulates in the Arctic and spreads to the North Atlantic. At the same time, freshwater that accumulates from seasonal sea ice melting over most of the upper Arctic Ocean also spreads southward, reaching as far as south of Iceland. These warm and fresh anomalies reduce upper ocean density and suppress oceanic deep convection. The thermal and haline contributions to these bouyancy anomalies, and therefore to the AMOC slowdown during this period, are found to have similar magnitudes. We also find that the related changes in horizontal wind-driven circulation could potentially push freshwater away from the deep convection areas and hence strengthen the AMOC, but this effect is overwhelmed by mean advection.

Edit; that didn't take long...
Title: Re: AMOC slowdown
Post by: vox_mundi on May 15, 2019, 10:29:38 PM
Century-Scale Deep-Water Circulation Dynamics in the North Atlantic Ocean
https://phys.org/news/2019-05-century-scale-deep-water-circulation-dynamics-north.html

... AMOC is a process whereby cold and salty surface water sinks into deep ocean in the high-latitude North Atlantic, the lower level deep water (known as North Atlantic Deep Water: NADW) flows southward (Image 1), and eventually rises to the surface in the North Pacific Ocean. The force of this circulation is known to affect global heat flow and regional climates. To study these circulation dynamics, the North Atlantic Ocean is especially important, because it is the place that deep water is formed through cooling surface water in the high latitudes.

The lower (deeper) part of NADW below 2,500 meters is well studied, but upper NADW (intermediate water) behavior is poorly understood since the last deglaciation—that is, the transitional period from the last ice age to the warmer contemporary interglacial climate state. Furthermore, NADW dynamics for the past ~11,700 years (known as the Holocene) remain equivocal. Dr. Yasuhara and his collaborators showed that subtropical North Atlantic intermediate-water temperature varied significantly during both of these time periods, based on trace element geochemistry of calcified shells of deep-sea microcrustacean Ostracoda in a sediment core. Their reconstructions reveal a series of multi-century-scale abrupt deep-water warming events likely caused by the reduction deep-water circulation. The authors also discovered that many of these weakening events of deep-water circulation can be widely recognized in the western North Atlantic.

Lead author of the study Dr. Yasuhara said "Holocene deep-water circulation was more dynamic than previously thought. There is increasing evidence that this circulation change in the North Atlantic affects climates of remote places including East Asia and also marine and terrestrial ecosystems. As recently discovered by scientists including my HKU colleagues Drs Benoit Thibodeau and Christelle Not, this global deep-water circulation has substantially weakened during the last century. If further weakening happens in the future, there may be unexpectedly broad implications not only on our atomospheric and ocean systems, but also on Earth's ecological systems and our society.

https://youtu.be/9kXsBux13qo
Deepwater circulation around Svalbard & Greenland

Moriaki Yasuhara et al. North Atlantic intermediate water variability over the past 20,000 years (https://pubs.geoscienceworld.org/gsa/geology/article-abstract/570484/north-atlantic-intermediate-water-variability-over), Geology (2019)

Benoit Thibodeau et al. Last Century Warming Over the Canadian Atlantic Shelves Linked to Weak Atlantic Meridional Overturning Circulation (https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL080083), Geophysical Research Letters (2018)
Title: Re: AMOC slowdown
Post by: johnm33 on June 15, 2019, 05:46:14 PM
Looking at this https://phys.org/news/2019-06-link-north-atlantic-currents-sea.html it seems a no brainer to me that if you have increased Arctic waters flowing down the coast lets say with the inherent inertia of 750N then it'll have two main effects. The first is that it will force itself into the coast, and continue to do that further south. The second is that once it is forced by Gulf stream waters away from the coast those waters will mix until equilibrium is reached slowing down the gulf stream/north atlantic drift.
What does this model show if not that?
(https://media.giphy.com/media/JtBsfrkwzwXG3a0yJu/giphy.gif)
If you open nullschool (https://earth.nullschool.net/#current/ocean/surface/currents/overlay=sea_surface_temp_anomaly/orthographic=-39.83,37.03,272/loc=-67.264,39.956) and select O from projections you'll see from 90-600N is about half of the distance of the equator from the axis of rotation and 300N about an eighth of the distance. Thus the inertia of tropical waters is too low to separate from the coast until the distance to the axis [surface speed] begins to decrease, so I would expect the highest effects of slr to be where both streams detatch and all points north, until the water reaches equilibrium with rotational speed, which may vary but just now appears to be about 52N, so peaking around 41N. Why am I wrong?
Title: Re: AMOC slowdown
Post by: bbr2314 on June 15, 2019, 07:05:31 PM
Looking at this https://phys.org/news/2019-06-link-north-atlantic-currents-sea.html it seems a no brainer to me that if you have increased Arctic waters flowing down the coast lets say with the inherent inertia of 750N then it'll have two main effects. The first is that it will force itself into the coast, and continue to do that further south. The second is that once it is forced by Gulf stream waters away from the coast those waters will mix until equilibrium is reached slowing down the gulf stream/north atlantic drift.
What does this model show if not that?
(https://media.giphy.com/media/JtBsfrkwzwXG3a0yJu/giphy.gif)
If you open nullschool (https://earth.nullschool.net/#current/ocean/surface/currents/overlay=sea_surface_temp_anomaly/orthographic=-39.83,37.03,272/loc=-67.264,39.956) and select O from projections you'll see from 90-600N is about half of the distance of the equator from the axis of rotation and 300N about an eighth of the distance. Thus the inertia of tropical waters is too low to separate from the coast until the distance to the axis [surface speed] begins to decrease, so I would expect the highest effects of slr to be where both streams detatch and all points north, until the water reaches equilibrium with rotational speed, which may vary but just now appears to be about 52N, so peaking around 41N. Why am I wrong?

I wonder if we are seeing amplified seasonal flux moreso than other factors. I.E. during the winter and springtime snow melts, the stream is pushed south more than it used to be (especially so by spring). And then, as snowmelt ceases, the Stream is more prone to drifting farther north than normal due to the tropical thermal inertia and slackening of freshwater supply.

Long-term, as Greenland contributes more and more to summer melt, I guess the end result would be a more permanent pattern matching late springtime that persists through most of the year.
Title: Re: AMOC slowdown
Post by: bbr2314 on June 15, 2019, 08:29:52 PM
Spring is already failing in many recent years (2013, 2014, 2015, 2018, 2019).

(https://hprcc.unl.edu/products/maps/acis/120dTDeptUS.png)

What happens next? If 2019 is any reasonable guide, it is going to start snowing in much of the populated Midwest into June by the 2020s, and into June in the unpopulated innermost regions of the continent (with proximity to the Great Lakes and Hudson Bay). We are seeing record-worst corn harvests this year due to the conditions that have prevailed. And it is almost certainly only a preview of what's to come within another decade.
Title: Re: AMOC slowdown
Post by: johnm33 on June 16, 2019, 12:26:13 AM
bbr.
I intend to have another look for numbers on the export of arctic waters through Davis strait, they may indicate when the amoc slows, or not? I think we agree that Hudson will grow colder as a result of increased flow and Quebec will cool as a consequence, and i've said elsewhere that cooling and increased precipitation falling on Alberta/Montana is to be expected but thats another topic.
 Looking at the increased flow through Nares and potentially the whole NWP if my present opinion has any merit then we should see +anomalous slowing of amoc later this year. 
Nice suite btw
john
Title: Re: AMOC slowdown
Post by: Tom_Mazanec on August 17, 2019, 08:39:36 PM
https://www.yaleclimateconnections.org/2019/08/video-the-north-atlantic-ocean-current-may-be-slowing/
A region of the North Atlantic south of Greenland has experienced some of its coldest temperatures on record in recent years, a cooling unprecedented in the past thousand years. What explains that anomaly?
Climatologist Michael Mann of Penn State University, in this month’s “This is Not Cool” video, explains that this phenomenon may be an indication that the North Atlantic current, part of a larger global ocean circulation, is slowing down.

Title: Re: AMOC slowdown
Post by: kassy on September 18, 2019, 11:53:07 AM
Atlantic Ocean may get a jump-start from the other side of the world

Summary:
A key question for climate scientists in recent years has been whether the Atlantic Ocean's main circulation system is slowing down, a development that could have dramatic consequences for Europe and other parts of the Atlantic rim. But a new study suggests help may be on the way from an unexpected source -- the Indian Ocean.

...

For the new study, they looked at warming in the Indian Ocean.

"The Indian Ocean is one of the fingerprints of global warming," said Hu, who is first author of the new work. "Warming of the Indian Ocean is considered one of the most robust aspects of global warming."

The researchers said their modeling indicates a series of cascading effects that stretch from the Indian Ocean all way over to the Atlantic: As the Indian Ocean warms faster and faster, it generates additional precipitation. This, in turn, draws more air from other parts of the world, including the Atlantic, to the Indian Ocean.

With so much precipitation in the Indian Ocean, there will be less precipitation in the Atlantic Ocean, the researchers said. Less precipitation will lead to higher salinity in the waters of the tropical portion of the Atlantic -- because there won't be as much rainwater to dilute it. This saltier water in the Atlantic, as it comes north via AMOC, will get cold much quicker than usual and sink faster.

"This would act as a jump-start for AMOC, intensifying the circulation," Fedorov said. "On the other hand, we don't know how long this enhanced Indian Ocean warming will continue. If other tropical oceans' warming, especially the Pacific, catches up with the Indian Ocean, the advantage for AMOC will stop."

https://www.sciencedaily.com/releases/2019/09/190916114032.htm
Title: Re: AMOC slowdown
Post by: be cause on September 18, 2019, 12:18:07 PM
So it's not so much 'world climate runs amok' , more , 'AMOK runs the world's climate' ?   b.c.
Title: Re: AMOC slowdown
Post by: Hefaistos on November 28, 2019, 02:49:06 PM
Atlantic Ocean may get a jump-start from the other side of the world


Maybe this 'jump start' already started.

Seems that the AMOC slowdown has reversed, but has incredibly large variability.
Measured and reported in research paper "Atlantic Meridional Overturning Circulation: Observed Transport and Variability"
Eleanor Frajka-Williams, et al. 2019

"...the AMOC ranged from 4 to 35 Sv over a single year, had a seasonal cycle
with amplitude over 5 Sv, and that the dip in 2009/10 of 30%
exceeded the range of interannual variability found in climate
models.  ... 
striking differences between the AMOC mean state and variability amongst models."

Figure caption: FIGURE 6 | A time series of AMOC transport (MOCρ ) at the OVIDE section (eastern subpolar gyre: Portugal to Cape Farewell) for 1993–2017, constructed from
altimetry and hydrography. The gray line is from altimetry combined with a time-mean of Argo velocities; the green curve is low-pass filtered using a 2-year running
mean. The black curve is from altimetry and Argo. Red circles are estimates from OVIDE hydrography with associated errors given by the red lines. The mean of the
gray curve is given by the black dashed line (Updated from Mercier et al., 2015).
Title: Re: AMOC slowdown
Post by: Hefaistos on November 28, 2019, 03:14:50 PM
"Stronger evidence for a weaker Atlantic overturning"

AMOC "...is weaker today than any time before in more than 1000 years. Sea surface temperature data analysis provides new evidence that this major ocean circulation has slowed down by roughly 15 percent since the middle of the 20th century"

https://phys.org/news/2018-04-stronger-evidence-weaker-atlantic-overturning.html

Conflicting evidence.

Seems to me that these researchers, using Sea surface temperature data,  have a weaker case than Frajka-Williams, et al. 2019 in my previous post, who found the exact opposite result, and the AMOC slowdown has been reversed as measured by buyous down in the AMOC itself.

It seems implausible that you would be able to dispute the fact that a certain amount of Sverdrups of water are passing by the dedicated measuring arrays they used for their analysis.

Need to change a lot of conclusions on climate change if this research holds up:
"As the currents slow down increase, they bring less more heat toward the north"
etc.etc.
Title: Re: AMOC slowdown
Post by: blumenkraft on December 30, 2019, 03:33:54 PM
North Atlantic Current may cease temporarily in the next century
Total collaps in the next 1,000 years unlikely


Link >> https://www.eurekalert.org/pub_releases/2019-12/uog-nac122719.php
Title: Re: AMOC slowdown
Post by: pleun on December 31, 2019, 01:20:24 PM
different article about the same research :

https://www.nature.com/articles/s41598-019-56435-6