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Slowing of the Gulf Stream- new data

Threegoofs

Threegoofs

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Two papers have come out in Nature, showing how the Gulf Stream (AMOC) seems to be slowing as a response to AGW.

One of the authors and a noted authority Stefan Rahmsdorf has a post reviewing the state of the data on the AMOC at Real Climate.

Stronger evidence for a weaker Atlantic overturning circulation « RealClimate

The studies show that the AMOC is the weakest it’s been in at least 1000 years, and that it has weakened by 15% in the last decades of the 20th century. More weakening can lead to colder conditions in Europe and the Eastern US in the winter, and heat waves in Europe in the summer, in addition to higher sea level in the Eastern US.

This is fairly big news on the earth science front. It probably will set deniers all a-twitter too. You know how they get when data doesn’t say what they want it to say.


Studies:
Anomalously weak Labrador Sea convection and Atlantic overturning during the past 150 years | Nature

http://www.nature.com/articles/s415...KyeWhlTvQKe6JHGdYV8iLm4nND7KgW4aTVEUH8xo0AA==
 
Thanks for posting this. However, I don't think anyone is denying that climate changes. What causes it seems to be the issue.
 
Threegoofs said:
Two papers have come out in Nature, showing how the Gulf Stream (AMOC) seems to be slowing as a response to AGW.

One of the authors and a noted authority Stefan Rahmsdorf has a post reviewing the state of the data on the AMOC at Real Climate.

Stronger evidence for a weaker Atlantic overturning circulation « RealClimate

The studies show that the AMOC is the weakest it’s been in at least 1000 years, and that it has weakened by 15% in the last decades of the 20th century. More weakening can lead to colder conditions in Europe and the Eastern US in the winter, and heat waves in Europe in the summer, in addition to higher sea level in the Eastern US.

This is fairly big news on the earth science front. It probably will set deniers all a-twitter too. You know how they get when data doesn’t say what they want it to say.


Studies:
Anomalously weak Labrador Sea convection and Atlantic overturning during the past 150 years | Nature

http://www.nature.com/articles/s415...KyeWhlTvQKe6JHGdYV8iLm4nND7KgW4aTVEUH8xo0AA==
Click to expand...

Also, there’s a ‘News and Views’ column to put these important studies in perspective.

North Atlantic circulation slows down

Conclusion:

However, in the context of future climate-change scenarios and a possible collapse in the AMOC in response to the continued melting of the Greenland Ice Sheet, it is perhaps less reassuring, because a weakened AMOC might lead to considerable changes in climate and precipitation patterns throughout the Northern Hemisphere.
Click to expand...
 
Lovebug said:
Thanks for posting this. However, I don't think anyone is denying that climate changes. What causes it seems to be the issue.
Click to expand...

Among scientists, it’s well known and known with high certainty that greenhouse gas emissions are the primary driver.

This isn’t in question among the people who study this.

It’s only doubted by American Conservatives and cranks (an overlapping set, to some extent).
 
Nature has an interesting commentary related to these new papers about the AMOC.
https://www.nature.com/articles/d41586-018-04086-4
Two papers in Nature, by Caesar et al.4 and Thornalley et al.5, report on past AMOC variability using different approaches. Both conclude that the modern AMOC is in an unusually subdued state, but they diverge in the details of how and when the AMOC’s decline commenced.
Click to expand...
However, the roughly 100-year difference in the proposed timing of the start of the AMOC decline in these two studies has big implications for the inferred trigger of the slowdown. Caesar et al. clearly put the onus on anthropogenic forcing, whereas Thornalley et al. suggest that an earlier decline in response to natural climate variability was perhaps sustained or enhanced through further ice melting associated with anthropogenic global warming.
Click to expand...
It is really a cause vs effect, The climate does change, and the Gulf Stream has been slowing down for quite a while,
predicting it will continue to do what it was already doing is not really much of a prediction.
Attributing a cause to an observation, is even more difficult, as we have no idea what would have happened
without any human input.
 
Threegoofs said:
Two papers have come out in Nature, showing how the Gulf Stream (AMOC) seems to be slowing as a response to AGW.

One of the authors and a noted authority Stefan Rahmsdorf has a post reviewing the state of the data on the AMOC at Real Climate.

Stronger evidence for a weaker Atlantic overturning circulation « RealClimate

The studies show that the AMOC is the weakest it’s been in at least 1000 years, and that it has weakened by 15% in the last decades of the 20th century. More weakening can lead to colder conditions in Europe and the Eastern US in the winter, and heat waves in Europe in the summer, in addition to higher sea level in the Eastern US.

This is fairly big news on the earth science front. It probably will set deniers all a-twitter too. You know how they get when data doesn’t say what they want it to say.


Studies:
Anomalously weak Labrador Sea convection and Atlantic overturning during the past 150 years | Nature

http://www.nature.com/articles/s415...KyeWhlTvQKe6JHGdYV8iLm4nND7KgW4aTVEUH8xo0AA==
Click to expand...

Rahmsdorf is a political hack prone to thug tactics.

LINK

August 14, 2017


 
Last edited:
Threegoofs said:
Two papers have come out in Nature, showing how the Gulf Stream (AMOC) seems to be slowing as a response to AGW.

One of the authors and a noted authority Stefan Rahmsdorf has a post reviewing the state of the data on the AMOC at Real Climate.

Stronger evidence for a weaker Atlantic overturning circulation « RealClimate

The studies show that the AMOC is the weakest it’s been in at least 1000 years, and that it has weakened by 15% in the last decades of the 20th century. More weakening can lead to colder conditions in Europe and the Eastern US in the winter, and heat waves in Europe in the summer, in addition to higher sea level in the Eastern US.

This is fairly big news on the earth science front. It probably will set deniers all a-twitter too. You know how they get when data doesn’t say what they want it to say.


Studies:
Anomalously weak Labrador Sea convection and Atlantic overturning during the past 150 years | Nature

http://www.nature.com/articles/s415...KyeWhlTvQKe6JHGdYV8iLm4nND7KgW4aTVEUH8xo0AA==
Click to expand...

This is just model-driven BS.
A NASA study based on observation, not models, sees acceleration, not deceleration.

A NASA study in 2010 using direct satellite measurement rather than models suggested there is no evidence the North Atlantic Current is slowing.
NASA Study Finds Atlantic ‘Conveyor Belt’ Not Slowing
03.25.10
PASADENA, Calif. – New NASA measurements of the Atlantic Meridional Overturning Circulation, part of the global ocean conveyor belt that helps regulate climate around the North Atlantic, show no significant slowingover the past 15 years. The data suggest the circulation may have even sped up slightly in the recent past.
…
Until recently, the only direct measurements of the circulation’s strength have been from ship-based surveys and a set of moorings anchored to the ocean floor in the mid-latitudes. Willis’ new technique is based on data from NASA satellite altimeters, which measure changes in the height of the sea surface, as well as data from Argo profiling floats. The international Argo array, supported in part by the National Oceanic and Atmospheric Administration, includes approximately 3,000 robotic floats that measure temperature, salinity and velocity across the world’s ocean.
With this new technique, Willis was able to calculate changes in the northward-flowing part of the circulation at about 41 degrees latitude, roughly between New York and northern Portugal. Combining satellite and float measurements, he found no change in the strength of the circulation overturning from 2002 to 2009. Looking further back with satellite altimeter data alone before the float data were available, [Josh] Willis found evidence that the circulation had sped up about 20 percent from 1993 to 2009. This is the longest direct record of variability in the Atlantic overturning to date and the only one at high latitudes.
The latest climate models predict the overturning circulation will slow down as greenhouse gases warm the planet and melting ice adds freshwater to the ocean. “Warm, freshwater is lighter and sinks less readily than cold, salty water,” Willis explained.
For now, however, there are no signs of a slowdown in the circulation. “The changes we’re seeing in overturning strength are probably part of a natural cycle,” said Willis. “The slight increase in overturning since 1993 coincides with a decades-long natural pattern of Atlantic heating and cooling.”
…
​
Read more: https://www.nasa.gov/topics/earth/features/atlantic20100325.html
One model based study suggests a 15% slowdown, a direct measurement suggests a 20% acceleration. Settled science anyone?


 
Jack Hays said:
This is just model-driven BS.
A NASA study based on observation, not models, sees acceleration, not deceleration.

A NASA study in 2010 using direct satellite measurement rather than models suggested there is no evidence the North Atlantic Current is slowing.
NASA Study Finds Atlantic ‘Conveyor Belt’ Not Slowing
03.25.10
PASADENA, Calif. – New NASA measurements of the Atlantic Meridional Overturning Circulation, part of the global ocean conveyor belt that helps regulate climate around the North Atlantic, show no significant slowingover the past 15 years. The data suggest the circulation may have even sped up slightly in the recent past.
…
Until recently, the only direct measurements of the circulation’s strength have been from ship-based surveys and a set of moorings anchored to the ocean floor in the mid-latitudes. Willis’ new technique is based on data from NASA satellite altimeters, which measure changes in the height of the sea surface, as well as data from Argo profiling floats. The international Argo array, supported in part by the National Oceanic and Atmospheric Administration, includes approximately 3,000 robotic floats that measure temperature, salinity and velocity across the world’s ocean.
With this new technique, Willis was able to calculate changes in the northward-flowing part of the circulation at about 41 degrees latitude, roughly between New York and northern Portugal. Combining satellite and float measurements, he found no change in the strength of the circulation overturning from 2002 to 2009. Looking further back with satellite altimeter data alone before the float data were available, [Josh] Willis found evidence that the circulation had sped up about 20 percent from 1993 to 2009. This is the longest direct record of variability in the Atlantic overturning to date and the only one at high latitudes.
The latest climate models predict the overturning circulation will slow down as greenhouse gases warm the planet and melting ice adds freshwater to the ocean. “Warm, freshwater is lighter and sinks less readily than cold, salty water,” Willis explained.
For now, however, there are no signs of a slowdown in the circulation. “The changes we’re seeing in overturning strength are probably part of a natural cycle,” said Willis. “The slight increase in overturning since 1993 coincides with a decades-long natural pattern of Atlantic heating and cooling.”
…
​
Read more: https://www.nasa.gov/topics/earth/features/atlantic20100325.html
One model based study suggests a 15% slowdown, a direct measurement suggests a 20% acceleration. Settled science anyone?


Click to expand...

Thanks for your ‘insight’... undoubtedly cribbed from some denier blog.

I’ll stick with the guys who published in Nature.
 
longview said:
Nature has an interesting commentary related to these new papers about the AMOC.
https://www.nature.com/articles/d41586-018-04086-4


It is really a cause vs effect, The climate does change, and the Gulf Stream has been slowing down for quite a while,
predicting it will continue to do what it was already doing is not really much of a prediction.
Attributing a cause to an observation, is even more difficult, as we have no idea what would have happened
without any human input.
Click to expand...
zomg... The cherry-picking just does not stop.

The two papers do not contradict one another, or numerous earlier papers investigating this topic.

Thornalley is simply looking at a longer time frame (1600 years). His position is that anthropogenic warming has perpetuated and accelerated the rate of slowdown in recent years.
 
Visbek said:
zomg... The cherry-picking just does not stop.

The two papers do not contradict one another, or numerous earlier papers investigating this topic.

Thornalley is simply looking at a longer time frame (1600 years). His position is that anthropogenic warming has perpetuated and accelerated the rate of slowdown in recent years.
Click to expand...
The connection between observed warming, the cause of the observed warming, and the attribution
of the anthropogenic portion of the observed warming, is still very subjective.
Here is what Thornalley says in his abstract,
https://www.nature.com/articles/s41586-018-0007-4
Here we provide several lines of palaeo-oceanographic evidence that Labrador Sea deep convection and the AMOC have been anomalously weak over the past 150 years or so (since the end of the Little Ice Age, LIA, approximately ad 1850) compared with the preceding 1,500 years.
Click to expand...
and
The lack of a subsequent recovery may have resulted from hysteresis or from twentieth-century melting of the Greenland Ice Sheet6.
Click to expand...
SO he says the lack of recovery could be ether from a delayed effect from the end of the little ice age, or from recent melting from Greenland.
Also the words perpetuated and accelerated are not in the abstract.
 
longview said:
The connection between observed warming, the cause of the observed warming, and the attribution
of the anthropogenic portion of the observed warming, is still very subjective.
Here is what Thornalley says in his abstract,
https://www.nature.com/articles/s41586-018-0007-4

and

SO he says the lack of recovery could be ether from a delayed effect from the end of the little ice age, or from recent melting from Greenland.
Also the words perpetuated and accelerated are not in the abstract.
Click to expand...
Yes, the best way to deal with accusations of cherry-picking is with... yet more cherry-picking!

They discuss the LIA because they're trying to explain why convection weakened in the past 150 years. I.e. they aren't citing it as a causal factor in recent changes, more as a temporal demarcation.

Their thesis is that convection is slowing, at an accelerating rate, due to melting of the GIS, which is... wait for it... accelerating due to anthropogenic causes of warming. And of course, this fits in with the evidence that the GIS is melting much faster than in the past.

There is no "subjectivity" here. Almost every climatologist in the field accepts that most of the warming and its effects over the past ~150 years is caused by human activity. Snipping a statement here and there does not change any scientists' actual views on these matters.
 
Jack Hays said:
This is just model-driven BS.
A NASA study based on observation, not models, sees acceleration, not deceleration.

A NASA study in 2010 using direct satellite measurement rather than models suggested there is no evidence the North Atlantic Current is slowing.
NASA Study Finds Atlantic ‘Conveyor Belt’ Not Slowing
03.25.10
PASADENA, Calif. – New NASA measurements of the Atlantic Meridional Overturning Circulation, part of the global ocean conveyor belt that helps regulate climate around the North Atlantic, show no significant slowingover the past 15 years. The data suggest the circulation may have even sped up slightly in the recent past.
…
Until recently, the only direct measurements of the circulation’s strength have been from ship-based surveys and a set of moorings anchored to the ocean floor in the mid-latitudes. Willis’ new technique is based on data from NASA satellite altimeters, which measure changes in the height of the sea surface, as well as data from Argo profiling floats. The international Argo array, supported in part by the National Oceanic and Atmospheric Administration, includes approximately 3,000 robotic floats that measure temperature, salinity and velocity across the world’s ocean.
With this new technique, Willis was able to calculate changes in the northward-flowing part of the circulation at about 41 degrees latitude, roughly between New York and northern Portugal. Combining satellite and float measurements, he found no change in the strength of the circulation overturning from 2002 to 2009. Looking further back with satellite altimeter data alone before the float data were available, [Josh] Willis found evidence that the circulation had sped up about 20 percent from 1993 to 2009. This is the longest direct record of variability in the Atlantic overturning to date and the only one at high latitudes.
The latest climate models predict the overturning circulation will slow down as greenhouse gases warm the planet and melting ice adds freshwater to the ocean. “Warm, freshwater is lighter and sinks less readily than cold, salty water,” Willis explained.
For now, however, there are no signs of a slowdown in the circulation. “The changes we’re seeing in overturning strength are probably part of a natural cycle,” said Willis. “The slight increase in overturning since 1993 coincides with a decades-long natural pattern of Atlantic heating and cooling.”
…
​
Read more: https://www.nasa.gov/topics/earth/features/atlantic20100325.html
One model based study suggests a 15% slowdown, a direct measurement suggests a 20% acceleration. Settled science anyone?


Click to expand...

I have more confidence that this is more credible research because it is based on actual observation than that of a Modeling exercise.
 
Visbek said:
Yes, the best way to deal with accusations of cherry-picking is with... yet more cherry-picking!

They discuss the LIA because they're trying to explain why convection weakened in the past 150 years. I.e. they aren't citing it as a causal factor in recent changes, more as a temporal demarcation.

Their thesis is that convection is slowing, at an accelerating rate, due to melting of the GIS, which is... wait for it... accelerating due to anthropogenic causes of warming. And of course, this fits in with the evidence that the GIS is melting much faster than in the past.

There is no "subjectivity" here. Almost every climatologist in the field accepts that most of the warming and its effects over the past ~150 years is caused by human activity. Snipping a statement here and there does not change any scientists' actual views on these matters.
Click to expand...
If that is what you believe, then you would need to answer what signal the described hysteresis was in reference of.
No, you are just reading it wrong!
The statement,
The lack of a subsequent recovery may have resulted from hysteresis or from twentieth-century melting of the Greenland Ice Sheet
Click to expand...
has an or between the two probable causes.
 
longview said:
If that is what you believe, then you would need to answer what signal the described hysteresis was in reference of.
No, you are just reading it wrong!
Click to expand...
No, I'm really not.

The part that you're quoting discusses part of the scope of their inquiry -- is the current weakening of the AMOC due to delayed natural causes, or the melting of the GIS? Ultimately, they think that historical models may place too much emphasis on hysteresis for recent decades, and that they see climate forcings as the cause of a weaker AMOC in recent years. Thus:

In conclusion, our study reveals an anomalously weak AMOC over the past 150 years or so. Because of its role in heat transport, it is often assumed that AMOC weakening cools the Northern Hemisphere. However, our study demonstrates that changes in the AMOC are not always synchronous with temperature changes. That AMOC weakening occurred during the late LIA and onset of the industrial era, rather than earlier in the LIA, may point to additional forcing factors at this time, such as an increase in the export of thickened Arctic and Nordic sea ice, or the melting of circum-Arctic ice shelves. The persistence of a weak AMOC during the twentieth century, when there was pronounced Northern Hemisphere and global warming, suggests that other climate forcings—such as greenhouse gas warming—were dominant during this period. We therefore infer that the AMOC has responded to recent centennial-scale climate change, rather than driven it.
(Emphasis added)
 
Visbek said:
No, I'm really not.

The part that you're quoting discusses part of the scope of their inquiry -- is the current weakening of the AMOC due to delayed natural causes, or the melting of the GIS? Ultimately, they think that historical models may place too much emphasis on hysteresis for recent decades, and that they see climate forcings as the cause of a weaker AMOC in recent years. Thus:

In conclusion, our study reveals an anomalously weak AMOC over the past 150 years or so. Because of its role in heat transport, it is often assumed that AMOC weakening cools the Northern Hemisphere. However, our study demonstrates that changes in the AMOC are not always synchronous with temperature changes. That AMOC weakening occurred during the late LIA and onset of the industrial era, rather than earlier in the LIA, may point to additional forcing factors at this time, such as an increase in the export of thickened Arctic and Nordic sea ice, or the melting of circum-Arctic ice shelves. The persistence of a weak AMOC during the twentieth century, when there was pronounced Northern Hemisphere and global warming, suggests that other climate forcings—such as greenhouse gas warming—were dominant during this period. We therefore infer that the AMOC has responded to recent centennial-scale climate change, rather than driven it.
(Emphasis added)
Click to expand...
Yep, that saws the AMOC was already slow, and did not recover, the lack of recovery could have been the cause of the
lack of recovery, or as the abstract stated the lack of recovery could also be attributed to hysteresis from the end of the little ice age.
 
longview said:
If that is what you believe, then you would need to answer what signal the described hysteresis was in reference of.
No, you are just reading it wrong!
The statement,

has an or between the two probable causes.
Click to expand...

The authors are pretty clear. The editorial is pretty clear. The Real Climate post by one of the authors is pretty clear.

But somehow, you find a different explanation than all those others.

They all attribute this as most likely due to man made climate change. They also acknowledge, like all scientists, that there may b e another explanation too. But they seem pretty clear that the other explanation is pretty remote.

But you keep doing you!
 
Threegoofs said:
The authors are pretty clear. The editorial is pretty clear. The Real Climate post by one of the authors is pretty clear.

But somehow, you find a different explanation than all those others.

They all attribute this as most likely due to man made climate change. They also acknowledge, like all scientists, that there may b e another explanation too. But they seem pretty clear that the other explanation is pretty remote.

But you keep doing you!
Click to expand...
That is not what the abstract Thornalley says!
It says that the AMOC slowed down at the end of the little ice age, and
The lack of a subsequent recovery may have resulted from hysteresis or from twentieth-century melting of the Greenland Ice Sheet
Click to expand...
I went ahead and bolded the or for you, in case you missed it.
 
longview said:
That is not what the abstract Thornalley says!
It says that the AMOC slowed down at the end of the little ice age, and

I went ahead and bolded the or for you, in case you missed it.
Click to expand...

CO2 didn't start going up until around 1885, which is long after the LIA ended in 1850.

Thus no CO2 effect can be a cause of the changes in the AMOC.
 
Sunsettommy said:
CO2 didn't start going up until around 1885, which is long after the LIA ended in 1850.

Thus no CO2 effect can be a cause of the changes in the AMOC.
Click to expand...
Well the Scientist says the recovery of the AMOC to it's earlier flow "may" be a result of
ether a delayed response of the end of the little ice age, or recent melting.
I wounder if he had to leave open the possibility of Human involvement to get published?
 
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