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Interesting stuff. 8.5cm rise would be about 1.3% loss of the current total Greenland ice sheet volume, and would melt the ice sheet completely after about 76 years. Given that this freshwater input lasts from 2000 to 2100 and is added in between 50N and 70N, it's actually impossible to be from Greenland. Even the collapse f the WAIS would time to contribute fresh water to the north Atlantic. 

 

However, as the author stated, climate models generally fail to reproduce past AMOC shutdowns, so I think this was a case of getting it to shutdown through whatever means and keeping it that way, so the plausibility of the fresh water source probably wasn't much of a concern. It's really about seeing how a potential shutdown would compete with GhG emissions. In that case, for anyone alive in the NH now, the shutdown would be the dominant aspect of our climate.

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Interesting stuff. 8.5cm rise would be about 1.3% loss of the current total Greenland ice sheet volume, and would melt the ice sheet completely after about 76 years. Given that this freshwater input lasts from 2000 to 2100 and is added in between 50N and 70N, it's actually impossible to be from Greenland. Even the collapse f the WAIS would time to contribute fresh water to the north Atlantic. 

 

However, as the author stated, climate models generally fail to reproduce past AMOC shutdowns, so I think this was a case of getting it to shutdown through whatever means and keeping it that way, so the plausibility of the fresh water source probably wasn't much of a concern. It's really about seeing how a potential shutdown would compete with GhG emissions. In that case, for anyone alive in the NH now, the shutdown would be the dominant aspect of our climate.

 

Hans Renssen has done a lot of research on past climate events in the N. Atlantic/Arctic region - an extensive list below.

 

http://www.falw.vu/~renh/pub_list.html

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Hans Renssen has done a lot of research on past climate events in the N. Atlantic/Arctic region - an extensive list below.

 

http://www.falw.vu/~renh/pub_list.html

 

Thanks for the list, Nouska.

 

Its going to take a while to get through that list !!

 

I did notice the PDF document as not being behind a paywall, and is a review of the oceanic effect in all parts of the world and the way their modelling is throwing up a lot of unexpected atmospheric feedbacks.

 

It discusses the way the models see these in every area as found from their studies of the last 100000 years.

 

There are certainly an awful lot of pertinent papers in there for all reader/contributors on this thread.

 

MIA

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https://twitter.com/CONWEATHER/status/658406606443540480

Interest over NA especially towards east coast of America.

 

Yes, a cooling of SST's on the coastal fringe of the eastern seaboard. But what I spotted was the 7-day change in the location of the N'Atlantic cold pool (it's showing a red blob on the 7-day change). A look at the NOAA anomaly charts for 15th and 22nd Oct does indeed show an easing of the cold pool anomaly (although this isn't unusual in October).

 

15th Oct post-20040-0-05638700-1445846773_thumb.g 22nd Oct post-20040-0-65491600-1445846791_thumb.g

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Yes, a cooling of SST's on the coastal fringe of the eastern seaboard. But what I spotted was the 7-day change in the location of the N'Atlantic cold pool (it's showing a red blob on the 7-day change). A look at the NOAA anomaly charts for 15th and 22nd Oct does indeed show an easing of the cold pool anomaly (although this isn't unusual in October).

 

15th Oct attachicon.gifSST Anom 15Oct15.gif 22nd Oct attachicon.gifSST Anom 22Oct15.gif

 

BW...

 

All looks interesting to me after reading the  Renssen reports above!!!

 

Probably totally confused now.

 

You have already mentioned the reduction of the cold blob in the N Atlantic.and the fact that the Nino looks to be starting to cool.

 

The other 3 data items that I noticed on the charts that could be relevent according to  Renssen that he is examining as possible drivers are -

 

1) The very cold anomalies in the waters off the Antartic.

 

2) The warm anomalies in the environs of the Arctic..

 

3) The change in the flow around the tip of Africa coming up into the south central Atlantic coming around the tip of Africa from a warm Indian ocean. (Known as the Agulhas Leakage - AL for short), that has occured in the recent past.. Now it could be a red herring but on reading the appropriate section in the PDF documet  at the end of the list (page 22) it does describe this effect. 

 

Reading Renssen's section  they have seen evidence (from paleo records from the last inter-glacial) that  they produced for similar conditions to today, that this ocean warm/cold ocean  current seems to move in phase with the AMO but with a negative amplitude.Thus a warm strong AL seems to correspond with a cold AMO and a cold weak AL with a warm AMO in the north atlantic. They sighal this mechanism as being the likely transfer of heat between the southern and northern hemispheres oceans..

 

All very interesting.           Hopefully the link to the relevent PDF is attached below.

 

http://www.pages-igbp.org/download/docs/magazine/2015-1/PAGESmagazine_2015(1)_Magazine_LoRes.pdf

 

I dont appear to be able to get the link to work!

 

Anyway the title is in volume 23 of Past Global Changes Magazine of January 2015 . The title is 'Glacail Terminations and Interglacials'. Relevant bit is page 22 - 5, but all is interesting..

 

MIA

Edited by Midlands Ice Age

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^ Yes, an interesting report MIA. Although I note the authors are not sure if the Agulhas Leakage (AL) "responded passively..... or played an active role" in previous glacial/interglacial events. But I've only had time for a quick read so would like to digest it properly when a get a moment. (But there does appear to be a warm SST anomaly where the Agulhas leaks!).

 

For the benefit of others who may be interested and wish to form an opinion, here are a few snippets and the diagram that summarises the AL theory:

 

Millennial-scale Agulhas Leakage variability

The paleo-evidence discussed above testifies to the link between variations in AL strength and interhemispheric or even global climate changes. In particular the Pleistocene glacial terminations feature prominent AL events.

 

The “terminal leakage events†during glacial-interglacial transitions were millennial-scale maxima of inter-ocean transport that, like their smaller scale counterparts, developed in response to AMOC weakening and ensuing North Atlantic cooling.

 

…………it remains to be determined whether the AL responded passively to these changes or played an active role in them.

 

post-20040-0-59026800-1445889777_thumb.j

 

Here's another link to the Magazine and the report on page 22 (which hopefully works) http://www.pages-igbp.org/download/docs/magazine/2015-1/PAGESmagazine_2015%281%29_Magazine_HiRes.pdf

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BW... Thanks for the link above>>>

 

I tried to do it in Firefox and couldn't get it to work!

 

I am  currently printing the whole report as it is a summary of the interglacial ocean activities in all the different oceans of the world and viewed from all the angles such as saline sensitivity to the ocean depths.

 

It is looking at whether the oceans act independently or possibbly as to whether there are linkages between them which could have impacted climate. .

 

It is very interesting, and should be read by all interested in this subject.

 

MIA

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BW... Thanks for the link above>>>

I tried to do it in Firefox and couldn't get it to work!

I am currently printing the whole report as it is a summary of the interglacial ocean activities in all the different oceans of the world and viewed from all the angles such as saline sensitivity to the ocean depths.

It is looking at whether the oceans act independently or possibbly as to whether there are linkages between them which could have impacted climate. .

It is very interesting, and should be read by all interested in this subject.

MIA

I would've thought there would be some sort of linkage between the oceans keeping a sort of equilibrium. For me the oceans can be viewed like a simple radiator where movement of heat slowly pushes from one area to another. Do,we have any oceanographers in our midst who post here? Edited by Hocus Pocus

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Interesting stuff. 8.5cm rise would be about 1.3% loss of the current total Greenland ice sheet volume, and would melt the ice sheet completely after about 76 years. Given that this freshwater input lasts from 2000 to 2100 and is added in between 50N and 70N, it's actually impossible to be from Greenland. Even the collapse f the WAIS would time to contribute fresh water to the north Atlantic. 

 

However, as the author stated, climate models generally fail to reproduce past AMOC shutdowns, so I think this was a case of getting it to shutdown through whatever means and keeping it that way, so the plausibility of the fresh water source probably wasn't much of a concern. It's really about seeing how a potential shutdown would compete with GhG emissions. In that case, for anyone alive in the NH now, the shutdown would be the dominant aspect of our climate.

 

I ignored the plausibility of the total melting potential as the negative temperature feedback meant that it would be unlikely to progress that far. It depends what is meant by AMOC shutdown as generally it is just reduced in depth and extent - this paper linked previously tried it with double the freshwater - 1 SV average for two centuries with a peak of 2 SV - http://www.climate.unibe.ch/~stocker/papers/renold09qsr.pdf

An alternative conclusion could be not that shutdown would be dominant, but rather any global warming hiatus would be short lived before recommencing and Greenland's buffer is gone. European agriculture would continue to suffer from cold for a longer period, whilst elsewhere would be renewed pressure from warming, drought etc.

 

Anyway this study from August is more realistic - Representing Greenland ice sheet freshwater fluxes in climate modelshttp://onlinelibrary.wiley.com/doi/10.1002/2015GL064738/abstract

 

 

Abstract

 
Here we present a long-term (1850–2200) best estimate of Greenland ice sheet (GrIS) freshwater runoff that improves spatial detail of runoff locations and temporal resolution. Ice discharge is taken from observations since 2000 and assumed constant in time. Surface meltwater runoff is retrieved from regional climate model output for the recent past and parameterized for the future based on significant correlations between runoff and midtropospheric (500 hPa) summer temperature changes over the GrIS. The simplicity of this approach enables assimilation of meltwater runoff into coupled climate models, which is demonstrated here in a case study with the medium-resolution (1°) Community Earth System Model. The model results suggest that the decrease in Atlantic Meridional Overturning Circulation (AMOC) is dominated by warming of the surface ocean and enhanced GrIS freshwater forcing leads to a slightly enhanced (−1.2 sverdrup in the 21st century) weakening of the AMOC.

 

Full paper - http://repository.tudelft.nl/assets/uuid:b5f67368-0300-4470-9625-a7d0d7b61b28/319493.pdf

 

Their results in a nutshell - reductions in AMOC is primarily due to warmer SSTs reducing overturning and "Our model output suggests that even for a strong warming scenario, enhanced GrIS FWF (Greenland ice sheet freshwater forcing) advances the timing of AMOC weakening but that the overall impact on AMOC stability is small"

 

These are in line with the findings of this paper from 2014 - On the reduced sensitivity of the Atlantic overturning to Greenland ice sheet melting in projections: a multi-model assessmenthttp://link.springer.com/article/10.1007%2Fs00382-014-2270-x

 

 

Abstract

Large uncertainties exist concerning the impact of Greenland ice sheet melting on the Atlantic meridional overturning circulation (AMOC) in the future, partly due to different sensitivity of the AMOC to freshwater input in the North Atlantic among climate models. Here we analyse five projections from different coupled ocean–atmosphere models with an additional 0.1 Sv (1 Sv = 106 m3/s) of freshwater released around Greenland between 2050 and 2089. We find on average a further weakening of the AMOC at 26°N of 1.1 ± 0.6 Sv representing a 27 ± 14 % supplementary weakening in 2080–2089, as compared to the weakening relative to 2006–2015 due to the effect of the external forcing only. This weakening is lower than what has been found with the same ensemble of models in an identical experimental set-up but under recent historical climate conditions. This lower sensitivity in a warmer world is explained by two main factors. First, a tendency of decoupling is detected between the surface and the deep ocean caused by an increased thermal stratification in the North Atlantic under the effect of global warming. This induces a shoaling of ocean deep ventilation through convection hence ventilating only intermediate levels. The second important effect concerns the so-called Canary Current freshwater leakage; a process by which additionally released freshwater in the North Atlantic leaks along the Canary Current and escapes the convection zones towards the subtropical area. This leakage is increasing in a warming climate, which is a consequence of decreasing gyres asymmetry due to changes in Ekman pumping. We suggest that these modifications are related with the northward shift of the jet stream in a warmer world. For these two reasons the AMOC is less susceptible to freshwater perturbations (near the deep water formation sides) in the North Atlantic as compared to the recent historical climate conditions. Finally, we propose a bilinear model that accounts for the two former processes to give a conceptual explanation about the decreasing AMOC sensitivity due to freshwater input. Within the limit of this bilinear model, we find that 62 ± 8 % of the reduction in sensitivity is related with the changes in gyre asymmetry and freshwater leakage and 38 ± 8 % is due to the reduction in deep ocean ventilation associated with the increased stratification in the North Atlantic.

 

Full paper - http://www.researchgate.net/profile/Didier_Swingedouw/publication/265211755_Impact_of_Greenland_ice_sheet_melting_on_the_Atlantic_overturning_A_multi-model_assessment/links/54057d420cf2bba34c1d42af.pdf

 

Again SST warming is more significant than melt in reducing AMOC - "Stratification increases because the surface temperature warms faster than in the layers below. This mitigates the potential effect of any additional freshwater input" - and there are large changes in gyre circulation.

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The Monthly Mean SST’s for October were published on the NOAA website today. Running the data for the Cold Pool (CP) co-ordinates shows the Monthly Mean was 12.4C. This continues the run of monthly CP SST’s being below the long-term 1948-2015 average, but with the average October over the last 67 years coming in at 12.7C, clearly only just. For comparison, the coldest October SST for the CP was 11.7C in 1982.

 

Graph showing Cold Pool Monthly Mean SST 2012-2015  post-20040-0-25952000-1446580648_thumb.j

 

My graph shows that this October’s fall was less than the long-term average decrease for the month (and also less than the last few years). Does the 500 hPa geopotential height anomaly for October hold a clue? Did predominantly southerly winds impact the cold pool area?

 

post-20040-0-17799100-1446580699_thumb.g

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The cooler Atlantic doesn't appear to be having any influence on the weather at the moment, unlike June.

Has it gone now ?

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Well now

 

above normal heights have been an 'epidemic' in the NH this year

 

 

post-12275-0-76300100-1446795247_thumb.p

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Well now

 

above normal heights have been an 'epidemic' in the NH this year

 

That chart is largely a reflection of a warmer atmosphere as seen in a graph of average April-October NH 500mb geopotential over time -

 

post-2779-0-49399600-1446802858_thumb.pn

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Very true but does emphasise the low geopotential heights over the Atlantic this year.

Edited by knocker

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Please ignore if this has already been posted only I don't feel like ploughing through all the back posts.

 

New article here that suggests solar cycle is driving cool N Atl SSTs

 

http://www.nature.com/ncomms/2015/150915/ncomms9268/full/ncomms9268.html â€¦

 

Hi knocker. Can't say I blame you for not wanting to plough through 22 pages of posts! For info, I posted some comments & extracts on the paper you mention back on Page 7 of this topic. My post: https://forum.netweather.tv/topic/83908-cooler-atlantic/?p=3260125

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A new technique for measuring the overturning circulation at the bottom of the ocean using the GRACE satellites:

 

http://www.jpl.nasa.gov/news/news.php?feature=4761

 

There's a pre-publication preview (first page only) of the source paper here:

 

http://www.readcube.com/articles/10.1002%2F2015GL065730?r3_referer=wol&tracking_action=preview_click&show_checkout=1&purchase_referrer=onlinelibrary.wiley.com&purchase_site_license=LICENSE_DENIED

 

Key point is that it appears to agree with the RAPID array but can measure a much larger area.

Edited by Yarmy

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A blog post by Isaac Held

 

Disequilibrium and the AMOC

 

http://www.gfdl.noaa.gov/blog/isaac-held/2015/11/21/64-disequilibrium-and-the-amoc/

 

Thanks Knocker for finding this.

 

A good overall summary of where we are today (A new word  'disequilibrium' for me is introduced).

 

A lot work is being put in on the overturning current simulations.

 

It will be even more interesting to see what happens when the new series of arrays at more northern latitudes release their results.

 

Also, there seems to be an implicit agreement(?) now that the AMO© is the worlds primary agent for the redistribution of heat between the southern and northern hemispheres..

 

Which seems amazing that the AMO is still not incorporate in the climate models (as stated in this report)..  

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