Cooler Atlantic

[MR EXTREMES]

It would just be our luck for the cold pool to moderate or die completely, only to rise like a Phoenix again next April.

I wouldn't worry to much maybe a tripol starting to build in the Atlantic last time we had this was 2009/2010 so possibly a replay of that winter also worth noting that was an el Nino!

It could also aid waa being pumped up into the Greenland and polar regions

[Yarmy]

Latest from the NOAA.

 

 

 

A weakening, perhaps? Probably best not to read too much into the week-to-week fluctuations and pay attention to the long-term trends. 

Edited October 5, 2015 by Yarmy

[Singularity]

On one of the American weather forums someone posted a screen shot of a CFS SST prediction for next July, and it had positive SST anomalies in the tropics and extratropics, with the subtropics nearer to average (corrected as I originally thought cooler than average). That's basically the reverse of this year's dominant pattern.

 

If anyone knows where such long-range charts can be obtained I'd be grateful for a link, regardless of how little stock I put behind that model beyond a month or two's range   

 

If that did take place, the idea of a negative AMO would surely have to be binned for a little while longer, with this year's behaviour a fluctuation in an overall positive AMO.

 

 

I may as well check out the importance of the AMO to our winter patterns;

 

Having used the westerly QBO to narrow down the years, the positive AMO cases then give the composite on the left while the negative AMO cases give the one on the right:

 

 

The signal seems to be for the pattern to feature more of a negative NAO when the AMO is positive and a positive NAO when the AMO is negative. However, the anomalies are very weak, too much so to read much into. An anomalous year or two could easily be distorting the picture from what is essentially a neutral outcome.

 

In light of which, it seems the AMO is of little concern, and quite probably the QBO forcing tends to overwhelm it.

Edited October 5, 2015 by Singularity

[Nouska]

Would these be the images you saw?

 

  

 

These are from Tropical Tidbits - model section, subsection climate.

 

An edit to add the Canadian long ranger, it has a different picture for next July.

 

  

 

Another interesting new paper on Atlantic dynamics - has a look at specific regions, going back to 1975.

 

http://onlinelibrary.wiley.com/doi/10.1002/2015JC010762/full

 

Abstract.

 

 

The Extended Ellett Line (EEL) hydrographic section extends from Scotland to Iceland crossing the Rockall Trough, Hatton-Rockall Basin, and Iceland Basin. With 61 full-depth stations at a horizontal resolution of 10–50 km, the EEL samples the upper limb of the Atlantic Meridional Overturning Circulation flowing across the Iceland-Scotland Ridge into the Nordic Seas. The Rockall Trough has been sampled nearly four times per year from 1975 to 1996, and the full section annually since 1996. The EEL is an exceptionally long-time series of deep ocean temperatures and salinities. This study extends prior work in the Rockall Trough, and examines for the first time 18 year records in the Iceland and Hatton-Rockall Basins. We quantify errors in the time series from two sources: observational errors and aliasing. The data quality and annual sampling are suitable for observing interannual to decadal variability because the variability exceeds our error estimates. The upper waters of all three basins are cooler/fresher from 1997 to 2001, warmer/more saline 2001–2006, and cooler/fresher from 2006 to 2014. A reference level for geostrophic shear is developed heuristically and by comparison with sea-surface altimetry. The mean northward transport in the upper waters is 6.7 ± 3.7 Sv and there is a 6.1 ± 2.5 Sv southward flow below the thermocline. Although the magnitude of the Iceland Basin overturning circulation (4.3 ± 1.9 Sv) is greater than in the Rockall Trough (3.0 ± 3.7 Sv), the variability is greater in the Rockall Trough. We discuss the results in the context of our understanding of drivers of variability.

Edited October 5, 2015 by Nouska

[Singularity]

Latest from the NOAA.

 

 

 

A weakening, perhaps? Probably best not to read too much into the week-to-week fluctuations and pay attention to the long-term trends. 

 

The pattern over the last week or so has had high pressure ideally positioned to feed a lot of relatively warm air across the cold pool region, diminishing the seasonal release of heat from the ocean a bit. I doubt it explains the whole of the change we've seen though.

 

The coming four days flip that around with some cold air over the region so that may have some effect as the ocean-atmosphere exchange steps up a notch. Beyond that, signals are a bit mixed really.

 

As air has a hard time heating the ocean but the ocean can easily release heat to the air (as the ocean has a much higher specific heat capacity), I reckon the presence of anomalously cold air tends to have a bigger impact than the presence of anomalously warm air at this time of year. Shortwave radiation is the only thing that can really put heat into the oceans, which is why I suspect recent patterns haven't had much of an impact other than slowing the seasonal cooling. Please don't hesitate to correct me if I'm wrong 

[Jakehainton]

hello all...

 

Does anyone think maybe a Tripole is forming in the atlantic?

[Singularity]

Would these be the images you saw?

 

Ah! Yes, thank you very much Nouska 

 

Cheers for the paper too, even if the technicality makes my eyes water a bit 

[summer blizzard]

Would these be the images you saw?

 

  

 

These are from Tropical Tidbits - model section, subsection climate.

 

Another interesting new paper on Atlantic dynamics - has a look at specific regions, going back to 1975.

 

http://onlinelibrary.wiley.com/doi/10.1002/2015JC010762/full

 

Abstract.

 

Also forecasts a developing La Nina which is highly statistically.

[Blessed Weather]

 

Another interesting new paper on Atlantic dynamics - has a look at specific regions, going back to 1975.

 

http://onlinelibrary.wiley.com/doi/10.1002/2015JC010762/full

 

Abstract.

 

Indeed another interesting paper. A snippet in their summary section caught my eye. The finding seems in line with earlier papers in this thread about the Greenland icesheet melt and freshwater runoff impacting the N. Atlantic circulation:

 

"The decrease in potential temperature and salinity after 2010 in all basins provides the first new evidence that the eastern subpolar North Atlantic is once again being influenced by cold, fresh western subpolar water."

[Nouska]

Indeed another interesting paper. A snippet in their summary section caught my eye. The finding seems in line with earlier papers in this thread about the Greenland icesheet melt and freshwater runoff impacting the N. Atlantic circulation:

 

"The decrease in potential temperature and salinity after 2010 in all basins provides the first new evidence that the eastern subpolar North Atlantic is once again being influenced by cold, fresh western subpolar water."

 

I've now had a chance to look at it in more depth and the take away message is that the Atlantic goes through many cycles that are not necessarily reflected in the AMO index - too broad a brush to capture the micro region anomalies and changes through various depths.

 

I'm wondering about the 'Great Salinity Anomaly' of the seventies - a description of lots of cold fresh water from the Arctic but I'm not aware of a big decline in ice during the period.

 

In the Rockall Trough, temperature does not always follow the same pattern as salinity; only slight warming is in evidence as salinity increased from 1980 to 1985, and after 1986 as salinity declined, the temperature remained stable. Since 1995, the overall increase in salinity in the Rockall is accompanied by increasing temperature. Different mechanisms led to the freshening during the 1970s and the increased salinity of the 1990s and 2000s. The very low salinity in the 1970s (the Great Salinity Anomaly) [Dickson et al., 1988] was caused by a major influx of Arctic freshwater in the form of sea-ice exported through the Fram Strait. The event was first observed northwest of Iceland and propagated through the subpolar gyre and the Nordic Seas over the course of about 10 years, reaching the Rockall Trough after about 7 years. In most regions of the subpolar North Atlantic and the Nordic Seas, the GSA was accompanied by low upper ocean temperatures but this is less clear in the Rockall Trough. In contrast, the dramatic rise in salinity after the mid-1990s is actually first seen in the Rockall Trough and Iceland Basin and propagates into the Nordic Seas and central subpolar gyre over the following 5 years. The feature is understood to be the manifestation of increased transport of southern origin water masses (see below) and is accompanied by a corresponding rise in temperature in all open ocean subpolar and Nordic regions. Likewise, the indication of a freshening since 2010–2011 in the EEL basins is also accompanied by cooling. This intriguing distinction between the thermal response in the Rockall Trough upper ocean to pulses of low or high salinity with either a northern or southern source is yet to be properly understood; we speculate that air-sea heat flux dampened the cooling in the 1970s and may have enhanced the warming since 1995. This is a topic for further investigation

 

Any of the ice specialists around to comment?

[feb1991blizzard]

Everyone seems obsessed with this cold pool but the more important factors are surely a cooling in the NE Pacific and a warming around Southern Greenland, surely a better correlation with blocking than a cold pool just to the West of us, although we might have less marginality with W-NWerlies but surely wrt blocking, the aforementioned factors are more important?

[Yarmy]

Everyone seems obsessed with this cold pool but the more important factors are surely a cooling in the NE Pacific and a warming around Southern Greenland, surely a better correlation with blocking than a cold pool just to the West of us, although we might have less marginality with W-NWerlies but surely wrt blocking, the aforementioned factors are more important?

But the thread is not about UK winter prospects, it's specifically about the cold SST anomaly in the North Atlantic.

[feb1991blizzard]

But the thread is not about UK winter prospects, it's specifically about the cold SST anomaly in the North Atlantic.

 

Yes but it doesn't take a genius to work out what 90% of the people viewing these type of threads are doing it with a view to does it?, the Siberian snow cover thread is specifically about how far west the snow cover gets in October but I think we can all guess why so many people are interested in it.

[Yarmy]

Yes but it doesn't take a genius to work out what 90% of the people viewing these type of threads are doing it with a view to does it?, the Siberian snow cover thread is specifically about how far west the snow cover gets in October but I think we can all guess why so many people are interested in it.

So why mention the NE Pacific? This thread is about the causes and possible consequences of the anomaly in the NATL.

[Daniel*]

hello all...

 

Does anyone think maybe a Tripole is forming in the atlantic?

it does have the characteristic 'sandwich' look but not quite there I do see similarities to 09/10.

[BornFromTheVoid]

I've now had a chance to look at it in more depth and the take away message is that the Atlantic goes through many cycles that are not necessarily reflected in the AMO index - too broad a brush to capture the micro region anomalies and changes through various depths.

 

I'm wondering about the 'Great Salinity Anomaly' of the seventies - a description of lots of cold fresh water from the Arctic but I'm not aware of a big decline in ice during the period.

 

In the Rockall Trough, temperature does not always follow the same pattern as salinity; only slight warming is in evidence as salinity increased from 1980 to 1985, and after 1986 as salinity declined, the temperature remained stable. Since 1995, the overall increase in salinity in the Rockall is accompanied by increasing temperature. Different mechanisms led to the freshening during the 1970s and the increased salinity of the 1990s and 2000s. The very low salinity in the 1970s (the Great Salinity Anomaly) [Dickson et al., 1988] was caused by a major influx of Arctic freshwater in the form of sea-ice exported through the Fram Strait. The event was first observed northwest of Iceland and propagated through the subpolar gyre and the Nordic Seas over the course of about 10 years, reaching the Rockall Trough after about 7 years. In most regions of the subpolar North Atlantic and the Nordic Seas, the GSA was accompanied by low upper ocean temperatures but this is less clear in the Rockall Trough. In contrast, the dramatic rise in salinity after the mid-1990s is actually first seen in the Rockall Trough and Iceland Basin and propagates into the Nordic Seas and central subpolar gyre over the following 5 years. The feature is understood to be the manifestation of increased transport of southern origin water masses (see below) and is accompanied by a corresponding rise in temperature in all open ocean subpolar and Nordic regions. Likewise, the indication of a freshening since 2010–2011 in the EEL basins is also accompanied by cooling. This intriguing distinction between the thermal response in the Rockall Trough upper ocean to pulses of low or high salinity with either a northern or southern source is yet to be properly understood; we speculate that air-sea heat flux dampened the cooling in the 1970s and may have enhanced the warming since 1995. This is a topic for further investigation

 

Any of the ice specialists around to comment?

 

Nobody is completely sure of what cause the Great Salinity Anomaly (GSA) in the 70s. I don't think it's related to an exceptional level of melt, but rather periodic build ups in fresh water over the surface of the Arctic ocean combined with the extra freshwater from a large volume of exported ice. The build up of fresh water is related to pressure patterns around the Beaufort Sea, where the Beaufort gyre is located. Periods of high pressure tend to cause freshwater to accumulate in a dome over the Beaufort gyre. Then then the weather patterns change, the dome of fresh water is released into more southern locations. There were reports of a large dome having formed in 2012, but I haven't heard much about it since (though the prevailing weather patterns over the Arctic did change in 2013 compared to 2007-2012), so maybe that could also be playing a factor this time around?

 

 

http://www.bbc.com/news/science-environment-16657122

 

 

 

I did my undergrad dissertation on Arctic sea ice a few years ago, looking specifically at the effect of air pressure patterns around Fram strait on sea ice extent.

Below is an index used to show the how strongly the SLP patterns drives sea ice export in each melt season (March to September).

 

 

 

1968 has the strongest value on that record, though that's only a melt season value but the extra forcing may have extended back into Autumn/Winter of 1967. The Great Salinity Anomaly was believed to have started in the late 60s and then gradually spread across the Atlantic during the 70s.

 

If I have the time, I'll extend the index to cover the rest of the year later on today.

[Hocus Pocus]

Regarding those air pressure patterns BFTV, is it not a case of the chicken and egg conundrum in which promotes what?

[knocker]

There is a 2011 paper, Causes and Consequences of the Late 1960s Great Salinity Anomaly, that may be of interest. Or it may not of course as I suspect we are getting slightly off topic.

 

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CDwQFjADahUKEwiKt4ai9K3IAhWE1RQKHTnFBT8&url=http%3A%2F%2Fepic.awi.de%2F31231%2F1%2FInTech-Causes_and_consequences_of_the_late_1960s_great_salinity_anomaly.pdf&usg=AFQjCNGULctopGxrc3kxTGpyHMeO0tMM2w&sig2=_F0PlqC_o4Q97dQC4Pg6pg&cad=rja

[Blessed Weather]

There is a 2011 paper, Causes and Consequences of the Late 1960s Great Salinity Anomaly, that may be of interest. Or it may not of course as I suspect we are getting slightly off topic.

 

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CDwQFjADahUKEwiKt4ai9K3IAhWE1RQKHTnFBT8&url=http%3A%2F%2Fepic.awi.de%2F31231%2F1%2FInTech-Causes_and_consequences_of_the_late_1960s_great_salinity_anomaly.pdf&usg=AFQjCNGULctopGxrc3kxTGpyHMeO0tMM2w&sig2=_F0PlqC_o4Q97dQC4Pg6pg&cad=rja

 

Actually knocker I found the paper to be relevant and interesting.

 

If I’ve interpreted it correctly, it appears the Great Salinity Anomaly (GSA) of the 1960’s was generated when three modes of climate variability (decadel, bidecadel and multidecadel) became synchronised, causing surface level pressure and wind patterns to cause “strong sea-ice export from the Artic†which then impacted N. Atlantic salinity and thus caused the AMOC to weaken with consequences for precipitation and SSTs patterns. Two climate modes mentioned were the AO and AMO. Some extracts:

 

Anomalous strong sea-ice export from the Arctic through Fram Strait, as that associated with the GSAs, would increase the fresh water fluxes in the North Atlantic and can modulate the AMOC. Numerical experiments show that a fresh water pulse applied in the North Atlantic can generate an AMOC shift to a weak state, which is manifested at the surface as a centre of pronounced negative anomalies south of Greenland.

 

A multi model ensemble of numerical experiments related to the ocean response to fresh water forcing reproduces well the general features of the SST pattern of the shift and accurately the dipole anomaly pattern in North Atlantic, which includes cooling south of Greenland and warming over the Barents and Nordic Seas.

 

It is conceivable that the freshwater pulse associated with the GSA in the 1960s altered the convection pattern and the AMOC. The changed convection pattern is possibly responsible for the jump to a weaker state. According to model simulations, the associated ~1.5°C change in SST can be translated to a moderate AMOC reduction of 10%-20%. This results in a freshening of the North Atlantic surface layers in the last decades.

 

The identification of abrupt AMOC changes over the modern period and its association with climate regime shifts suggest that future rapid climate changes are also likely in a globally warming world. The fact that an abrupt but moderate MOC reduction caused a climate regime shift in surface variables points to a larger climatic impact generated by possibly more significant AMOC changes.

 

The paper even included a chart showing the resultant SST anomaly resulting from the abrupt change to the AMOC (which looks similar to the current N. Atlantic cold pool anomaly, the subject of this thread).

 

 

Although the impact of the GSA event discussed above ended in the 1990's, with the AMOC recovering, we once again have an AMOC weakening and an increased freshening and cooling of the N. Atlantic - so to me, a relevant paper.

[knocker]

Interesting tweet by Recretos

 

Andrew - Andrej â€@Recretos 6h6 hours ago

Interesting ocean subsurface anomalies. Espec. the Atlantic sector, looking very neg AMOish.

 

It initiated the odd comment such as:

 

 

AMO may reset anyway w/an El Nino of this magnitude.

Edited October 7, 2015 by knocker

[Recretos]

Well gee, I was planning to post that one here myself, but oh well.

 

Since there was some talk about salinity, here is some recent data from my side. The most obvious feature, is of course that fresh water blob that still exists around the Beaufort Gyre, tho perhaps not at the same location as in the BFTV graphics. Could have moved in the past years. i will have to check it out with some reanalysis data. If this were the same batch of fresh water as the original "bulge", then this indicates that it has moved SW since then. Of course of note is also more fresher water in the North Atlantic.

 

  

 

And at depth, where the anomalies are less intense, but that is normal down with depth. We tho do have some lower salinity in the north cell of AMOC, which is interesting, and could perhaps indicate some mixing of the salty flow with the fresh waters from the north.. 

 

  

Edited October 7, 2015 by Recretos

[knocker]

My humblest apologies Recretos. Great post and best remember we read your tweets before you even send them.

[Nouska]

Well gee, I was planning to post that one here myself, but oh well.

 

 

Regard as another feather in your cap!   

 

Good to see the anomalies at depth in that format

 

Those deeper layer anomalies suggest the cold pool will re-emerge again this winter (as discussed in the paper I posted in the climate section).

[BLAST FROM THE PAST]

Regard as another feather in your cap! 

 

Good to see the anomalies at depth in that format

 

Those deeper layer anomalies suggest the cold pool will re-emerge again this winter (as discussed in the paper I posted in the climate section).

Will storms like Joaquim assist in this process

 

BFTP

[Nouska]

Will storms like Joaquim assist in this process

 

BFTP

 

You can certainly see his footprint further south... but I suspect it will not be noticeable in the cold pool area.

 

  

Edited October 7, 2015 by Nouska