Cooler Atlantic

[Hocus Pocus]

Why? Even natural effects have causes?

This is a natural effect though, there are no other causes other than natural in this case as this is the way the AMO behaves prior to its overall switch. I would expect this cold pool to moderate over the next 6 months or so with warmer waters returning.

[Yarmy]

I just think it's the naturally occurring gradual switch over of the AMO cycle to cold which should be expected to occur over the next 5 years or so.

 

Yeah, that's what my Great Uncle x 100 Ugg said right before a glacier buried his mud hut.

 

[Hocus Pocus]

Yeah, that's what my Great Uncle x 100 Ugg said right before a glacier buried his mud hut.

 

   

[BornFromTheVoid]

The AMO is an oscillation that encompasses the entire North Atlantic, not just the sub polar gyre region. Despite the small area of record cold, the AMO has grown increasingly positive this year, with August being the most positive month so far at +0.197 (August values range from -0.454 to +0.546).

I see no compelling reason to dismiss the accelerating Greenland melt as a possible cause of the cold blob.

[Methuselah]

This is a natural effect though, there are no other causes other than natural in this case as this is the way the AMO behaves prior to its overall switch. I would expect this cold pool to moderate over the next 6 months or so with warmer waters returning.

Just because it's a 'natural effect', doesn't preclude the fact that part of that effect may be a response to things which are not so natural? Unnatural light from sun-beds elicits the same perfectly natural response, in the skin, as does natural sunlight...Give or take a few shades of orange!

[Hocus Pocus]

The AMO is an oscillation that encompasses the entire North Atlantic, not just the sub polar gyre region. Despite the small area of record cold, the AMO has grown increasingly positive this year, with August being the most positive month so far at +0.197 (August values range from -0.454 to +0.546).

I see no compelling reason to dismiss the accelerating Greenland melt as a possible cause of the cold blob.

Indeed it does and hence why we aren't seeing a switch yet as it's not due for at least another 5 years, but these cold pools are precursors to a switch as they've always been. Not everything can be attributed down to AGW BFTV.

 

Edit; Just reread your posts and I noted the word possible to describe the above cold pooling, I'll go along with that as we can't dismiss anything BFTV.

Edited September 25, 2015 by Hocus Pocus

[BornFromTheVoid]

Indeed it does and hence why we aren't seeing a switch yet as it's not due for at least another 5 years, but these cold pools are precursors to a switch as they've always been. Not everything can be attributed down to AGW BFTV.

 

Have you any evidence that the cold blob is a precursor so a shift in the AMO?

Also, is not reasonable to suggest that a large influx of fresh cold water could influence a circulation system driven by temperature and salinity differences?

[knocker]

Steven DiMartino â€@nynjpaweather 7m7 minutes ago

nothing unusual about Atlantic cold blobs...see 2009, 2004, 2002..

Edited September 25, 2015 by knocker

[Yarmy]

Steven DiMartino â€@nynjpaweather 7m7 minutes ago

nothing unusual about Atlantic cold blobs...see 2009, 2004, 2002..

 

Maybe longevity is the difference this time? The 6th Aug 2009 and 8th 14th Aug 2004 images coincide with that weakening of the AMOC shown here:

 

 

Of course, there's no data for 2002 , and the data for 2015 will be collected shortly. 

 

I tend to agree with BftV: I think there might be something more than just natural variation going on. 

 

(Incidentally, I note that the charts shown are all El Nino years. Is the author of the tweet hinting at an alternative reason?)

Edited September 25, 2015 by Yarmy

[BornFromTheVoid]

Steven DiMartino â€@nynjpaweather 7m7 minutes ago

nothing unusual about Atlantic cold blobs...see 2009, 2004, 2002..

 

Yeah, I think that's quite a disingenuous chart (no reflection on yourself , of course!).

 

If we look at the months used in that chart, and the 9 months leading up to them, we get the following:

 

2015

 

2009

 

2004

 

2002

 

 

No comparison really. The cold blob (whatever the cause!) this year is unusual, if not exceptional, especially in the face of record breaking global warmth.

[knocker]

Granted Born.

[March Blizzard]

The thing I don't get about the Greenland melt "theory" (is it just a theory??!) in relation to the cold pool is why it is so localised to the south of Greenland. If it is caused/influenced by cold freshwater ice-melt, then wouldn't (shouldn't?) there be cold SST anomalies all around Greenland?

I'm not coming at this from any angle, by the way. I'm genuinely interested.

[Yarmy]

The thing I don't get about the Greenland melt "theory" (is it just a theory??!) in relation to the cold pool is why it is so localised to the south of Greenland. If it is caused/influenced by cold freshwater ice-melt, then wouldn't (shouldn't?) there be cold SST anomalies all around Greenland?

I'm not coming at this from any angle, by the way. I'm genuinely interested.

 

 

It's the salinity of the water that's important. It's what drives the overturning circulation. As the warm waters of the tropics are transported Northwards, they become saltier through evaporation and also colder. Both these processes cause the water to become denser. The dense water sinks to the ocean depths and returns southwards. The freshwater run-off from Greenland (and indeed from melting Arctic ice: polar ice is nearly fresh) freshens (i.e. reduces the salinity) of the water and hence weakens the circulation. Fresh water has a maximum density at about 4C, but seawater continues to get denser as it gets colder. 

[BornFromTheVoid]

The thing I don't get about the Greenland melt "theory" (is it just a theory??!) in relation to the cold pool is why it is so localised to the south of Greenland. If it is caused/influenced by cold freshwater ice-melt, then wouldn't (shouldn't?) there be cold SST anomalies all around Greenland?

I'm not coming at this from any angle, by the way. I'm genuinely interested.

 

As far as the theory goes, the melt water from Greenland isn't causing the cold SSTs directly. The cold blob is being caused by reduced heat transport northward by the gulf stream. That reduced northward transport may be due to the AMOC being affected by the extra cold fresh water coming off Greenland.

 

Now, it isn't though that the last few years of large melt rates from Greenland is the cause, but rather the cumulative and accelerating influx of cooler, fresher water over the last few decades.

 

Jason Box's blog has a little more info http://meltfactor.org/a-conspicuous-area-of-cold/

[Weather-history]

I recall that there was a very cool pool of water in the North Atlantic between Newfoundland and the UK during 1972, one of the reasons that was used to explain why June 1972 was so cool. That had a particular cool May to September CET period, much cooler than we have had this year but this current period does look like the coolest since 1993. Interestingly there was an El Niño during 1972-73.

[March Blizzard]

Thanks guys!

[Gavin Hannah]

Yeah, I think that's quite a disingenuous chart (no reflection on yourself , of course!).

 

If we look at the months used in that chart, and the 9 months leading up to them, we get the following:

 

2015

 

2009

 

2004

 

2002

 

 

No comparison really. The cold blob (whatever the cause!) this year is unusual, if not exceptional, especially in the face of record breaking global warmth.

 

 

Those charts put things into perspective some what.

Maybe the warmer water has been diverted and is driving the El Nino somehows..  

[Midlands Ice Age]

Those charts put things into perspective some what.

Maybe the warmer water has been diverted and is driving the El Nino somehows..

 

Not sure that would happen...

 

But maybe the El Nino is directing  the currents in the South Atlantic slightly differently up into the Atlantic tropics and hence there is less of a push coming up thru the tropics to drive the Gulf stream. No one yet knows the power of the oceans and the array in the North Atlantic is maybe the first of many we will need to help us understand the way the oceans are moving around.

 

Also re the posts above about the start of the cold pool - The start of the cold blob occurred 1000 miles away SSE of Greenland. It is unlikely that it is a direct effect of the ice melt. But it may just be that the power of the Atlantic oceans various drifts has been impacted at both the south (as speculated above) and also by the  mechanism expanded by BFTV on the freshened Arctic water's to the north.

 

I also note that the Labrador current is now showing a tendency towards a cooling . Could this put more colder water into the North Atlantic?

 

It certainly seems as though if this colder  pool maintains for a little while we could have a very interesting and observable climate event with which to enhance our climate dynamics knowledge.

 

MIA

Edited September 25, 2015 by Midlands Ice Age

[Methuselah]

Not sure that would happen...

 

 

Also re the posts above about the start of the cold pool - The start of the cold blob occurred 1000 miles away SSE of Greenland. It is unlikely that it is a direct effect of the ice melt. But it may just be that the power of the Atlantic oceans various drifts has been impacted at both the south (as speculated above) and also by the  mechanism expanded by BFTV on the freshened Arctic water's to the north.

 

 

MIA

Maybe the water didn't sink as far as it should?

[Nouska]

Maybe this stunning animation of the thermohaline circulation, over the Atlantic bathymetry, will help identify the overturning zones and how a weakening might show itself as a colder pool of water to the SE of Greenland.

 

http://pmm.nasa.gov/education/sites/default/files/videos/thermohaline_conveyor_30fps.mp4

[BornFromTheVoid]

I recall that there was a very cool pool of water in the North Atlantic between Newfoundland and the UK during 1972, one of the reasons that was used to explain why June 1972 was so cool. That had a particular cool May to September CET period, much cooler than we have had this year but this current period does look like the coolest since 1993. Interestingly there was an El Niño during 1972-73.

 

1972 was the 3rd coldest year for the AMO, and the 2nd coldest for the May to September period and the coldest on record for June.

 

[Midlands Ice Age]

Maybe this stunning animation of the thermohaline circulation, over the Atlantic bathymetry, will help identify the overturning zones and how a weakening might show itself as a colder pool of water to the SE of Greenland.

 

http://pmm.nasa.gov/education/sites/default/files/videos/thermohaline_conveyor_30fps.mp4

 

A great piece of evidence. So it could be that a weakening of the AMO from the south would enable the returning colder waters to surface and take control at that point.

 

I would also be useful to see if the El Nino had disturbed the patterns in the South Atlantic. I notice that the start of the Atlantic drift northwards start from the Indian Ocean not the Pacific. Have the oceans around the Cape been performing themselves recently?

 

MIA 

[knocker]

Just musing about the unusual going's on in Antarctica this winter.

 

Impacts of the north and tropical Atlantic Ocean on the Antarctic Peninsula and sea ice

 

 

In recent decades, Antarctica has experienced pronounced climate changes. The Antarctic Peninsula exhibited the strongest warming^{1, 2} of any region on the planet, causing rapid changes in land ice^{3, 4}. Additionally, in contrast to the sea-ice decline over the Arctic, Antarctic sea ice has not declined, but has instead undergone a perplexing redistribution^{5, 6}. Antarctic climate is influenced by, among other factors, changes in radiative forcing⁷ and remote Pacific climate variability^{8, 9}, but none explains the observed Antarctic Peninsula warming or the sea-ice redistribution in austral winter. However, in the north and tropical Atlantic Ocean, the Atlantic Multidecadal Oscillation^{10, 11} (a leading mode of sea surface temperature variability) has been overlooked in this context. Here we show that sea surface warming related to the Atlantic Multidecadal Oscillation reduces the surface pressure in the Amundsen Sea and contributes to the observed dipole-like sea-ice redistribution between the Ross and Amundsen–Bellingshausen–Weddell seas and to the Antarctic Peninsula warming. Support for these findings comes from analysis of observational and reanalysis data, and independently from both comprehensive and idealized atmospheric model simulations. We suggest that the north and tropical Atlantic is important for projections of future climate change in Antarctica, and has the potential to affect the global thermohaline circulation⁶ and sea-level change^{3, 12}.

 

http://www.nature.com/nature/journal/v505/n7484/full/nature12945.html

Edited September 25, 2015 by knocker

[lorenzo]

Great thread this - some brilliant input from a variety of detectives.. good discussion - keep up the good work folks !

[Methuselah]

I agree Lorenzo; that animation Nouska posted illustrated something similar to what I was suggesting. Only a thousand times better!