NASA Study Finds Atlantic 'Conveyor Belt' Not Slowing

Mar 26, 2010
Illustration depicting the overturning circulation of the global ocean. Throughout the Atlantic Ocean, the circulation carries warm waters (red arrows) northward near the surface and cold deep waters (blue arrows) southward. Image credit: NASA/JPL

(PhysOrg.com) -- 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 slowing over the past 15 years. The data suggest the circulation may have even sped up slightly in the recent past.

The findings are the result of a new monitoring technique, developed by oceanographer Josh Willis of NASA's Jet Propulsion Laboratory in Pasadena, Calif., using measurements from ocean-observing satellites and profiling floats. The findings are reported in the March 25 issue of .

The Atlantic overturning circulation is a system of currents, including the , that bring warm surface waters from the tropics northward into the North Atlantic. There, in the seas surrounding Greenland, the water cools, sinks to great depths and changes direction. What was once warm surface water heading north turns into cold deep water going south. This overturning is one part of the vast conveyor belt of that move heat around the globe.

Without the heat carried by this circulation system, the climate around the North Atlantic -- in Europe, North America and North Africa -- would likely be much colder. Scientists hypothesize that rapid cooling 12,000 years ago at the end of the last was triggered when freshwater from altered the ocean's salinity and slowed the overturning rate. That reduced the amount of heat carried northward as a result.

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 altimeters, which measure changes in the height of the , 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, 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."

If or when the overturning circulation slows, the results are unlikely to be dramatic. "No one is predicting another ice age as a result of changes in the Atlantic overturning," said Willis. "Even if the overturning was the Godzilla of climate 12,000 years ago, the climate was much colder then. Models of today's warmer conditions suggest that a slowdown would have a much smaller impact now.

"But the Atlantic overturning circulation is still an important player in today's climate," Willis added. "Some have suggested cyclic changes in the overturning may be warming and cooling the whole North Atlantic over the course of several decades and affecting rainfall patterns across the United States and Africa, and even the number of hurricanes in the Atlantic."

With their ability to observe the Atlantic overturning at high latitudes, Willis said, satellite altimeters and the Argo array are an important complement to the mooring and ship-based measurements currently being used to monitor the overturning at lower latitudes. "Nobody imagined that this large-scale circulation could be captured by these global observing systems," said Willis. "Their amazing precision allows us to detect subtle changes in the ocean that could have big impacts on climate."

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User comments : 27

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Skeptic_Heretic
2 / 5 (4) Mar 26, 2010
I'd think you'd expect the conveyor to speed up with the surface warming we've observed in the ocean. Warmer water flows faster and as such, regardless of salinity (to a degree) the warmer water would reach colder environments faster and release that energy into the environment and other saltier currents more rapidly causing an overall speed increase.
jonnyboy
1.8 / 5 (5) Mar 26, 2010
and from there it is a fairly small step to the air is being warmed more rapidly and further north and showing up as global warming
Caliban
3 / 5 (5) Mar 26, 2010
The article was a little garbled- it does say that the current speed had increased by about 20% over the last 15 years or so- and then characterized that as a slight increase?
At the very least, you would expect this to affect fisheries, due to increased nutrient transfer and the moderating effect it would likely have upon acidity. It seems likely that there would be climatic influence, as well- as was mentioned.
Too bad they weren't able to combine this information with the temperature data over the same time period to look for correlation.
Glyndwr
4.7 / 5 (3) Mar 26, 2010
fisheries in the north atlantic are on their knees already from over-fishing....this factor will dominant populations of fish over any recent slight temp increases I am afraid to say but would be interesting to see any underlying trends in fisheries still :)
Shootist
1 / 5 (8) Mar 27, 2010
The planet has been warming and cooling for 4.8 billion years. It will continue to warm and cool.

Man is too ephemeral to notice anything but his nose.

There were dairy farms in Greenland 1000 years ago. It was warmer then.

The Hudson River froze solid enough for cannon to be dragged across at Haarlem Heights in 1776. It was cooler then.
Husky
5 / 5 (1) Mar 27, 2010
Mpemba effect?
stealthc
1 / 5 (5) Mar 27, 2010
nice to see yet another IPCC claim go down the tubes, I swear I can remember those greenies saying that this conveyor belt would slow and eventually stop, or reform into something radically different. See look nothing is happening and your government's are buying what these nutjobs say hook line and sinker.
Caliban
3.7 / 5 (7) Mar 27, 2010
@stealthhc,
It might be a little early to be making that call.

But with continued heating, it is expected that the conveyor would increase in extent, and that at some point, the existing pattern would break, if for no other reason than ocean floor topography and coriolis force. It has before.

Then there is the possibility of inundation by freshwater glacial melt from Greenland- and who's to say that even as we speak, there might not be some massive entrapped pool of meltwater under the ice?

The question is more like: not when, but how soon?
dachpyarvile
1 / 5 (5) Mar 27, 2010
...Then there is the possibility of inundation by freshwater glacial melt from Greenland- and who's to say that even as we speak, there might not be some massive entrapped pool of meltwater under the ice?

The question is more like: not when, but how soon?


No, Caliban, stealhc is making the right call. This is yet another small bit of IPCC-shaking data.

There isn't any trapped meltwater of the amount necessary to cause the effect to which you allude--anywhere in Greenland--and the topography necessary for such does not exist in Greenland even with all the ice stripped off the island.

How soon? Try sometime after the next ice age, when conditions in North America might be set up again to cause this phenomenon.
Caliban
3.7 / 5 (7) Mar 27, 2010
Dachy,
You are certainly welcome to your opinion, but that doesn't change the fact that there is plenty of reason for concern. You don't have to do anything that you aren't already doing. I expect we'll be presented with the truth soon enough.
dachpyarvile
1.7 / 5 (6) Mar 27, 2010
There is little to no reason for concern, in my opinion (and I have over 50,000 scientists backing the same opinion). There is nothing on the North American continent that will set up the conditions necessary for stoppage of the so-called Atlantic Conveyor. That requires heavy glaciation across the continent followed by rapid melt on a topography like that of North America.

Check out information on Lake Agassiz and other such glacial lake formations that are believed to have burst beyond their bounds suddenly. There is nothing present on earth in the correct region to cause such a happenstance again.

As to learning the truth soon enough, we already have...the IPCC has published a bunch of false, alarmist crapology that is being exposed for what it is--a bit at a time. :)
Caliban
3.7 / 5 (6) Mar 28, 2010
I'm happy to hear that you have so many friends and supporters.

While the likelihood of a massive subglacial lake is admittedly small, it isn't completely out of the question, either- your claims regarding suitable topography notwithstanding. However, a relatively rapid melt of the GIC will amount to the same thing, and appears to be happening already.

Also, as I said earlier, an overextension of the conveyor belt will also create the conditions for a disconnect.

And lastly, don't try to claim this new study as some sort of refutation of any of the IPCC science claims. This is an enhancement and extension of that science- not a refutation- regardless of how much you might like to coopt it. I beleieve that we have had very similar exchanges before.
stealthc
1 / 5 (5) Mar 28, 2010
Anybody else notice lots of people supporting AGW on here. Seems like the scientists love the idea because it gives them power. It isn't called a corporate/scientific dictatorship for no reason, scientists have a huge vested interest in AGW.
goldengod
1.4 / 5 (5) Mar 29, 2010
@stealthc: There are lucid arguments from both sides but some are more aggressive in their wording than others. The data in this article was sponsored by NASA which many of the AGW peeps consistently rubbish.

I find it hypocritical of them to accept this data at face value when it appears to support their agenda.

In two days we will have a new article from different sources refuting the data that they will rubbish becuase it doesn't support their agenda.

And on and on...
lengould100
5 / 5 (4) Mar 29, 2010
"and I have over 50,000 scientists backing the same opinion" -- That's the Oregon group, isn't it? Veterinarians and MD's mostly... anybody who could claim a doctorate before their name, including, hilariously, some doctors of divinity.

goldengod "I find it hypocritical of them to accept this data at face value when it appears to support their agenda." exactly. I accept the science for what it is, facts. I'm pleased to hear that NASA has determined that loss of the meridonal overturning may be less of a possibility than thought (yet unproven), but still see sufficient reason for concern in the net science in hand.

dachpyarvile
1 / 5 (5) Mar 29, 2010
"and I have over 50,000 scientists backing the same opinion" -- That's the Oregon group, isn't it? Veterinarians and MD's mostly... anybody who could claim a doctorate before their name, including, hilariously, some doctors of divinity....


Ummm, no. This has nothing to do with the Oregon Group. And, you folks should talk, what with all the AGW supporters on a list that was not screened.

And, yes, that list was not screened. The climategate emails provide evidence to that effect. "Don't screen, don't check credentials, no oneo cares about how many of them have Ph.D.s after their names, don't ask for publishing history--just get the names." :)

Even a canvass of 51,000 scientists in Canada alone showed that 68% of them agree that the science is not settled.

http://www.climat...-Removed
Caliban
3.7 / 5 (6) Mar 29, 2010


Even a canvass of 51,000 scientists in Canada alone showed that 68% of them agree that the science is not settled.


Very good point. Agreeing- en masse- that the science is in no way proof to the contrary.

I know that you, dachy, aren't in the habit of outright denial, and apparently remain open to new information, but you will have to agree that there are numbers of posters here that reject the notion of AGW out-of-hand, and will go to any lengths of subterfuge and chicanery to support their POV.

It is difficult for me to view them as rational or worthy the effort of debate.
po6ert
1.3 / 5 (4) Mar 29, 2010
In 1875 ce the entire population of scientists believed in many things and many of the thing they believed in false. the atom could not be split.
ether was responsible for light waves. leshgt could not be a particle, to mention just a few.
what any group of scientist may or may not believe
is a very poor justification for any arguement.

believe me we will look just as foolish to coming generations
XQZME
1 / 5 (3) Apr 02, 2010
The ARGO floats show the oceans have been cooling or holding steady for the last several years. The Arctic ice cap is returning to its normal extent. The Antarctic ice cap is now starting to shrink after reaching a 200 year record extent.
dachpyarvile
1 / 5 (3) Apr 03, 2010
That is true. Unfortunately, they may have found a way to justify modifying the initial data and using 'fudge factors' to show a net warming of the oceans.

It is coming. Read it from something the lead scientist involved in the program wrote. :)
Skeptic_Heretic
3 / 5 (3) Apr 03, 2010
It is difficult for me to view them as rational or worthy the effort of debate.
I think I can speak for dach when I say, we're jsut as disenfranchised by the opposite. The rampant supposition is unreal.

When you take the average of answers from a diverse group of people you'll typically find that the average is the correct answer.
dachpyarvile
2.3 / 5 (4) Apr 03, 2010
Skeptic_Heretic,

You speak correctly. I have often found the middle ground to be the correct ground to take. And, I have been attacked by those on both sides of the debate because of my tentative stance. Yet, neither side has given me what I seek. :)
Skeptic_Heretic
3 / 5 (2) Apr 05, 2010
Yet, neither side has given me what I seek. :)

Same here. It does keep my reading schedule full though.
dachpyarvile
2 / 5 (4) Apr 05, 2010
Same here. It does keep my reading schedule full though.


Isn't that the truth!?! But, that is the important thing. Science by nature needs to be debated to death. Otherwise, it ceases to be science and becomes religion.

Now, this article has given additional room for debate. The predicted slowdown has not occurred. Therefore, the models that predicted the slowdown of the so-called conveyor are wrong and it becomes obvious that something is missing. We need to find what that 'something' is and modify the models accordingly.

At this point, as I am sure you will agree, there is no room for catastrophism or fearmongering in the science. This is particularly so in that there are no conditions in place as there were in ancient times that would lead up to a catastrophic event. There is no land bridge in the Bering Strait and no pent up melt-water from melting glaciation anywhere built up that could rapidly flow out and interfere with the so-called conveyor as is theorized.
Skeptic_Heretic
2.3 / 5 (3) Apr 05, 2010
At this point, as I am sure you will agree, there is no room for catastrophism or fearmongering in the science.
Completely agreed. The rampant alarmism detracts from the actual science and process of understanding involved. I've remained open minded, but I decry the alarmism as from the basis of fear, fact will never be found.
stealthc
2 / 5 (2) Apr 06, 2010
I have no problems accepting it, it's up to the skeptics to find holes in it and convince me. I don't think nasa screws with all of their data, only some of it, and only the stuff directly relating to the limited vision of the IPCC, they certainly do miss more nowadays since they are busy trying to look like they aren't a bunch of shills.

@stealthc: There are lucid arguments from both sides but some are more aggressive in their wording than others. The data in this article was sponsored by NASA which many of the AGW peeps consistently rubbish.

I find it hypocritical of them to accept this data at face value when it appears to support their agenda.

In two days we will have a new article from different sources refuting the data that they will rubbish becuase it doesn't support their agenda.

And on and on...

dgilsdorf
not rated yet Apr 21, 2010
@The article (no agenda, here):

Willis called the Atlantic overturning "the Godzilla of climate 12,000 years ago". Just an observation: This coincides pretty closely with the opposite end of Earth's precession, which runs in a 26,000 year cycle. This cycle has strong effects on global climate, as it alters the direction Earth faces at perihelion. The Atlantic overturning's influence at the time may well be an effect of this, as well as a cause of other changes.