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Niall Dollard

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North Atlantic Cold Blob
« on: January 21, 2022, 07:55:46 PM »
Opening up a thread specifically for discussions on the North Atlantic Cold Blob.

The North Atlantic Cold Blob (I'll call it the NACB) is really a temperature anomaly affecting the surface of the ocean. Not to be confused with the AMOC which goes to great depths in the oceans.

The cold blob may (or may not) be closely related to the AMOC. It is after all a surface feature - so is exposed to atmospheric conditions (jet streams and synoptic weather patterns) in addition to what changes are going on beneath the surface.

The NACB gained particular notoriety back in 2015, when it became particularly noticeable on global temperature anomaly charts. It is located just south of Greenland.

Contrast to last year 2021 when the blob is not nearly as noticeable.

So the blob is waning. Is this as a result of little ice export east of Greenland during the year 2021 ?

Attachments :

2015 LOTI annual global anomalies (wrt 1961-1990)

2021 LOTI annual global anomalies (wrt 1961-1990)

GIF (needs as click) running 2015 LOTI to 2021 LOTI

ECMWF 2021 Annual SST anomaly for North Atlantic (wrt 1991-2020)
« Last Edit: January 21, 2022, 08:02:05 PM by Niall Dollard »

oren

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Re: North Atlantic Cold Blob
« Reply #1 on: January 21, 2022, 08:30:47 PM »
Thanks, Niall.
It does seem like the cold blob is not really a significant anomaly, after looking at the animation. 2015 was huge but recent years not so much.

Niall Dollard

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Re: North Atlantic Cold Blob
« Reply #2 on: October 04, 2022, 08:16:46 AM »
Since 2021 the cold blob was non existent and this year, especially since July, it has morphed into the North Atlantic hot blob !

Niall Dollard

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Re: North Atlantic Cold Blob
« Reply #3 on: June 13, 2023, 08:18:42 AM »
Cold blob has really become the Atlantic warm blob. SSTs over 2.5° C above

Rodius

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Re: North Atlantic Cold Blob
« Reply #4 on: June 13, 2023, 08:44:01 AM »
Having anomaly images shows what the situation is compared to previous times.

This means there needs to be an agreed upon time reference, which can shift.
Much like the global temp increases are compared to certain time periods so we get a range of different global temp increases based on when the frame of reference is.

I am probably wrong here, but if we want to know what is happening with the cold blob, it might be more useful to get the actually temps today and compare them to actual temps before to see what is going on.

This will tell us if the cold blob is just looking less cold due to a change of the reference point which is changing as well.

I hope this makes sense... it doesnt feel like I explained this very well

johnm33

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Re: North Atlantic Cold Blob
« Reply #5 on: June 13, 2023, 09:49:41 AM »
My guess is this is temporary, there have been few lows passing over the Faroes gap this inhibits sub surface waters flowing into the Nordic seas, so longer dwell and insolation in the south, plus having to shift direction some kinetic energy is expressed as heat. Second the water flowing out of the Arctic is coming out at depths where the salinity is higher so as it passes south through Denmark strait it's cold/dense enough to sink. The melt has begun along Greenlands east coast so I expect fresher water will arrive soon, that will mix more readily with circulating Atl. waters yet still be fresher/lighter when it reaches an equilibrium point south of Greenland.

Linus

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Re: North Atlantic Cold Blob
« Reply #6 on: June 13, 2023, 04:22:12 PM »
Here is a recent deep dive into the North Atlantic SST anomalies if anyone is interested in further reading.
https://www.severe-weather.eu/global-weather/unusual-ocean-anomaly-el-nino-north-atlantic-pressure-system-impact-united-states-europe-fa/

kassy

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Re: North Atlantic Cold Blob
« Reply #7 on: June 13, 2023, 05:21:56 PM »
Thanks that was interesting.
Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.

Niall Dollard

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Re: North Atlantic Cold Blob
« Reply #8 on: June 13, 2023, 05:40:46 PM »

This will tell us if the cold blob is just looking less cold due to a change of the reference point which is changing as well.

I hope this makes sense... it doesnt feel like I explained this very well

My bad for cropping out the base line. Here it is together with the key.

Also the weblink has useful animations. Such as this one which goes back 1 year.

The cold blob makes a brief appearance in Dec 2022 and the area slowly warms in 2023. The recent very high sst anomalies west of Morocco have extended westwards well out into the centre of the North Atlantic

https://psl.noaa.gov/map/clim/sst.anom.anim.year.html
« Last Edit: June 13, 2023, 05:47:19 PM by Niall Dollard »

vox_mundi

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Re: North Atlantic Cold Blob
« Reply #9 on: August 02, 2023, 04:56:11 PM »
North Atlantic Oscillation Contributes to 'Cold Blob' In Atlantic Ocean
https://phys.org/news/2023-08-north-atlantic-oscillation-contributes-cold.html



A patch of ocean in the North Atlantic is stubbornly cooling while much of the planet warms. This anomaly—dubbed the "cold blob"—has been linked to changes in ocean circulation, but a new study found changes in large-scale atmospheric patterns may play an equally important role, according to an international research team led by Penn State.

Sea surface temperatures in the subpolar North Atlantic have decreased by about 0.7°F over the last century, and a trend toward a more frequent positive phase of the North Atlantic Oscillation (NAO) may have contributed significantly, the scientists reported in the journal Climate Dynamics.

The NAO represents atmospheric circulation patterns involving a low-pressure system near Iceland and a high-pressure system near the Azores Islands, and it influences how westerly winds blow across the ocean. In the positive phase, both pressure systems are stronger than average, resulting in a stronger jet stream and a northward shift of the westerly winds, the scientists said.

"As the NAO becomes more positive, it intensifies the surface wind over the subpolar North Atlantic," said Li, who is also an associate of the Earth and Environmental Systems Institute and a co-hire of the Institute for Computational and Data Sciences at Penn State. "When we would like to cool a cup of hot coffee, we stir the surface, and it promotes heat loss. That's exactly what wind intensification is going to do to the ocean surface—it provides a direct cooling effect."

The team analyzed weather data and found the positive NAO has become more dominant during the past century, consistent with previous research. This shift could be due to warming of the tropical Indo-Pacific and sea ice loss in the Labrador Sea, according to the researchers, but its exact causes remain an open question.

"We know the atmosphere can not only force surface temperature change but also can passively respond to the surface temperature change itself—we call this forcing and damping," said Yifei Fan, a doctoral candidate at Penn State and lead author on the study. "Our model separates these two processes and can quantify the impact of wind on the surface turbulent heat flux and thus the resultant sea surface temperature changes."

The NAO alone could explain 67% of the sea surface temperature cooling trend, the scientists said. But other atmospheric patterns that have a warming effect may partially offset this, decreasing the overall impact of atmospheric circulation changes to 44%. Those findings are consistent with previous estimations from the group.

The findings suggest, the researchers said, that the NAO may have an equally important role in the cold blob as the Atlantic Meridional Overturning Circulation—or AMOC—ocean currents that carry warm water from the tropics north to the North Atlantic like a conveyor belt. Other studies have suggested the sea surface cooling is a sign the conveyor belt is weakening.

The results, however, should not be interpreted as a line of evidence against the role of oceanic processes, which also likely play a large role in the cooling, according to the scientists. But atmospheric circulation change should also be considered moving forward.

... "Once you have temperature cooling set up over the subpolar North Atlantic, it increases the instability in the atmosphere and favors the passage of storms that can come across the ocean basin and bring extreme weather events to North America and Europe," Li said. "This might add another layer of complexity to projections of future high-impact weather events and uncertainties to climate projections for heavily populated areas."

Yifei Fan et al, North Atlantic Oscillation contributes to the subpolar North Atlantic cooling in the past century, Climate Dynamics (2023)
https://link.springer.com/article/10.1007/s00382-023-06847-y
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Niall Dollard

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Re: North Atlantic Cold Blob
« Reply #10 on: August 02, 2023, 06:42:00 PM »
Thanks VM for posting.

A paper echoing much of my own thoughts and highlighting the folly of recent papers by the Ditlevsen twins and Zhu et al using the very volatile North Atlantic SSTs as "proof" that the AMOC is weakening.

Why is there not more criticism in the scientific world ?

The "weakening AMOC" has become the darling bud of climate scientists.

This part of the snippet almost reads like well we have our own thoughts but we better not upset the "AMOC is weakening" scientists !

"The findings suggest, the researchers said, that the NAO may have an equally important role in the cold blob as the Atlantic Meridional Overturning Circulation—or AMOC—ocean currents that carry warm water from the tropics north to the North Atlantic like a conveyor belt. Other studies have suggested the sea surface cooling is a sign the conveyor belt is weakening.

The results, however, should not be interpreted as a line of evidence against the role of oceanic processes, which also likely play a large role in the cooling, according to the scientists. But atmospheric circulation change should also be considered moving forward."

Although in this part I think they are sending out a clear message to the other scientists using SSTs as an indicator of AMOC weakening.

They should be very careful indeed !

"Here we do provide evidence that there is no one-to-one relationship between sea surface temperature change and overturning circulation change," Li said. "So we should be very careful when extrapolating this overturning circulation change or great conveyor belt change from sea surface temperature alone."


« Last Edit: August 02, 2023, 07:19:30 PM by Niall Dollard »

Steven

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Re: North Atlantic Cold Blob
« Reply #11 on: August 02, 2023, 07:40:36 PM »
A paper echoing much of my own thoughts and highlighting the folly of recent papers by the Ditlevsen twins and Zhu et al using the very volatile North Atlantic SSTs as "proof" that the AMOC is weakening.

Why is there not more criticism in the scientific world ?

The "weakening AMOC" has become the darling bud of climate scientists.

There has been a lot of skepticism from climate scientists about last week's Ditlevsen paper that uses the cold blob to predict a forthcoming AMOC collapse.  But some journalists only report the scary predictions of AMOC collapse and ignore any criticism.

This is a good overview of opinions from a dozen experts about last week's AMOC collapse paper:
https://www.sciencemediacentre.org/expert-reaction-to-paper-warning-of-a-collapse-of-the-atlantic-meridional-overturning-circulation/

vox_mundi

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Re: North Atlantic Cold Blob
« Reply #12 on: February 28, 2024, 08:19:41 AM »
Meltwater In the North Atlantic Can Lead to European Summer Heat Waves, Study Finds
https://phys.org/news/2024-02-meltwater-north-atlantic-european-summer.html



Scientists from the National Oceanography Centre (NOC) have discovered that increased meltwater in the North Atlantic can trigger a chain of events leading to hotter and drier European summers.

The paper, which is published in the open access journal Weather and Climate Dynamics, suggests that European summer weather is predictable months to years in advance, due to higher levels of freshwater in the North Atlantic during the preceding winter.

Discussing the implications, lead author Marilena Oltmanns, Research Scientist at the National Oceanography Centre, said, "While the UK and northern Europe experienced unusually cool and wet weather in Summer 2023, Greenland experienced an unusually warm summer, leading to increased freshwater input into the North Atlantic."

"Based on the identified chain of events, we expect that the ocean-atmosphere conditions will be favorable for an unusually warm and dry summer over southern Europe this year."

"Depending on the pathway of the freshwater in the North Atlantic, we are also expecting a warm and dry summer in northern[/I[ Europe within the next five years. We will be able to estimate the exact year of the warm and dry summer in northern Europe more closely in the winter before it occurs."

Marilena Oltmanns et al, European summer weather linked to North Atlantic freshwater anomalies in preceding years, Weather and Climate Dynamics (2024)
https://wcd.copernicus.org/articles/5/109/2024/
« Last Edit: February 28, 2024, 03:40:55 PM by vox_mundi »
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El Cid

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Re: North Atlantic Cold Blob
« Reply #13 on: February 28, 2024, 01:50:25 PM »
Very interesting article vox!

***

BTW, the Blob we talked so much about a few years ago (and which according to some indicated the serious slowdown of AMOC) is gone :