By P Gosselin
The ice sheet and the Atlantic overturning circulation (AMOC): No Alarm
AMOC. Source: Woods Hole
By Frank Bosse
We hear it over and again: the melting ice in Greenland due to warming will soon lead to a collapse of the AMOC, making it difficult for it to “restart”.
The salt content in the north is critical because the salt-rich tropical water cools down and sinks due to the higher salt content, which is the “pump” that makes circulation possible in the first place. It also transports very large amounts of heat into the North Atlantic.
Scenarios have been published that calculate a drastic cooling of the greater area (especially Europe) around it if the AMOC is “switched off”. The “Day after Tomorrow” scenario.
A more recent summary of these “tipping point” assumptions comes from Prof. Rahmstorf. It refers to reconstructed phases of such collapses, especially during “Heinrich Events” in the last ice age. At that time, large quantities of icebergs advanced far to the south, where they melted and thus probably brought the AMOC to a standstill through sweetening.
New paper finds no alarm
A completely new paper sheds light on these events in detail and reconstructs the freshwater inputs very precisely. A very detailed discussion can be found here.
It finds a decisive difference in the situation during the last ice age and the present: whereas at that time the ice entered the Atlantic primarily in the form of icebergs from the large continental ice sheets, in the present it is Greenland – the island supplies the lion’s share of the freshwater. This has consequences: as the glaciers continue to melt and retreat further inland, fewer and fewer icebergs are released and more and more liquid water is released. This has a major impact on the AMOC. Icebergs are much more “effective”. They briefly freeze the surrounding surface seawater, which leads to warming of the water below, as ice insulates against temperature loss to the (cold) atmosphere. Due to the large mass of the icebergs, they also travel much further south before they melt and finally disappear, leading to much larger-scale sweetening.
The paper concludes that the iceberg discharges from Greenland will not last long enough to drive the AMOC into collapse. Another reason for this is that it was much weaker in ice ages than at present anyway. The lead author of the study is quoted as saying:
This is good climate news that will hopefully dissuade people from climate doomism.”
So whoever reads something about the “soon to dry up North Atlantic Current” and the catastrophic effects in the future: The current piece in “Science” files this under doomsday fantasies (“doomism”).
Regardless of what happens to the miniscule amount of ice in the Greenland ice cap (next to nothing when compared to the masses of the Atlantic and Arctic Oceans), even if it were possible to suddenly melt (the only possible mechanism for a sudden melting would be a meteor hit that would disrupt the entire Earthian environment any way) the AMOC will continue because the driving forces of the AMOC will remain the same. The driving forces are the much larger heat content of the tropical seas, which heat will move to where there is less heat according to the second law of thermodynamics; the salt content may be lessened in the immediate area of Greenland, but most of the mass volume of the ocean current system is hundreds of miles from Greenland, so there will still be a large density difference between southern waters and north Atlantic waters.
Besides, Greenland is not losing much if any ice due to warming, as any atmospheric warming can only affect the upper few cm of the ice cap. The ice cools the air far more than the air warms the ice, due to simple physics.
Finally, the warmunists keep pointing to icebergs calving off as proof, somehow, that the icecap is melting and losing mass. That ridiculous assumption is easily disproven by the fact that ice is a semi solid material that flows like water, but with a much higher viscosity. Gravity is what causes ice to move, and of course, gravity causes anything to move downhill, not uphill. More active ice calving at the fringes of Greenland can only be due to a larger mass of ice uphill. Just like a liquid river can only flow faster at its discharge if there is a greater mass of water upriver. Engineers refer to this as the “hydraulic gradient”, which is a measure of elevation change. Unless the underlying rock in Greenland is somehow rapidly increasing in elevation, then the only way that there can be an increase in calving at the extreme downstream “end” of a glacier is if there is more ice up hill.
But clearly, warmunists understand neither science nor engineering – it is obvious in all their alarmist modeling and rhetoric.
GRACE measurements shows massive mass loss from Greenland ice sheet. https://svs.gsfc.nasa.gov/31156
“while lower-elevation and coastal areas experienced over 20 feet (6 meters) of ice mass loss (expressed in equivalent-water-height; dark red) over this 21-year period.”
“More active ice calving at the fringes of Greenland can only be due to a larger mass of ice uphill.”
How about increased melt water between the ice and rocks reducing the friction as the ice flows? That’s one other factor which can increase the amount of ice calving.
Grace is a gravity based measurement. Greenland sits on active, moving magma sacs.
In the mean time, here is the graph of Greenland Total Ice Mass since 1900
Pretty graph. See all the bumps?
Effective friction could only be reduced if the underlying rock surface was at uniform and smooth elevation gradient, no hills, rills, gullies, arroyos, canyons, ridges or mountains. But of course that is not how surface topography is in the real world. In the real world no such uniform flat planar surface exists on land. Again, the only driving force is gravity acting on an increasing ice mass uphill. That is the only force that can accelerate ice flow in the real world.
And how do you measure erosion caused by glacier movement?
We know about 6,000 years ago the AMOC was still operating fine. And SL was 2 meters higher than today. That should not be ignored.
By the way, how would all that liquid water that is supposedly lubricating the bottom of the glacial ice mass going to penetrate thousands of feet of ice from the surface, ice that is all at temperatures well (far) below the freezing point of water? Explain that mechanism, please.
Glacier ice surface melting water will sink into the glacier and refreeze. It does not make it to the bottom of a thick ice pack.
This is how packed snow becomes ice.
In your world, somehow a satellite scanning extremely narrow pathways over days, then stitching the tinsel like scans together coupled with meandering aerial surveys somehow manages to gauge total ice loss/gain gravimetrically, for ice a mile deep.
The error bars for that measurement must be huge. But, that never stopped or even slows up NOAA or NASA.
Here is an image of Greenland. Compare and contrast Greenland’s size to Alaska. The video is worth watching, too.
https://science.nasa.gov/wp-content/uploads/2023/09/Greenland_Hotspot_720.mp4
All this fear mongering about ice loss, the reality is that Greenland is an immense island that dwarfs small town thinking.
Never mind that the altitude of most of Greenland’s surface ice is high enough that it rarely, if ever melts.
Greenland’s interior is a bowl. Ice does flow out river valleys between peaks and Greenland’s southern rim does melt a bit in the summers. But that Greenland rim where ice melts is like the skin of an apple compared to the great bulk of Greenland’s ice.
Part of the engineering involved is apart from gravity is the ever increasing perimeter as inland ice seeks to relieve pressure as it expand outwards. Even if the land was flat the lack of restraint would allow any increase in volume inland to seek the path of least resistance much the same of a mob of climate alarmists pushing against a police line linking arms trying to contain them.
Yes, that is correct. That is what I referred to above as the “hydraulic gradient”, a term engineers use. Hydraulic gradient is independent of the topographical gradient. Just as water can flow over a river bottom that is at an adverse gradient (like a dam, or a rock cataract), as long as the hydraulic gradient maintains its slope. The hydraulic gradient is determined the surface elevation profile of the water body, not by the underlying topography.
Slow MOC events occur during negative North Atlantic Oscillation episodes, the most obvious slow events were at both ends of 2010 and in March 2013.
The positive NAO regime since 2014 has led to the average MOC rate slightly increasing again.
The paper indicates that calving of Greenland ice burgs alone will not lead to a collapse of the AMOC, not that there is no risk of collapse at all. From the abstract:
But it’s the catastrophic predictions that are newsworthy. Circulation instability is indistinguishable from what happens anyway.
We can adapt to bad weather. But not a global catastrophe.
Calving is the only way for Greenland to lose much ice. The interior is way to cold for the ice to start melting.
And calving is totally natural, has been happening for billions of years.
No human causation.
Iceberg calving is as natural as a river running into the sea. Apart from the physical state of the water, it is largely indistinguishable from that.
Imagine if the climate alarmists started panicking about rivers flowing? Such is the absurdity of the modern age that this is effectively what is happening.
Warmunists don’t comprehend gravity, period.
Calving of glaciers means that glacial ice is moving downhill (due to gravity and the hydraulic gradient of the ice cap) towards its discharge point at the ocean edge, not that the edge of the glacier is melting. The meltwater edge effect is virtually unmeasurable compared to the mass of ice in the ice cap.
This is the fundamental science and engineering that warmunists simply do not understand, or if they do, they ignore it because it violates their narrative. All civil engineers understand this well – it’s the science of hydraulics taught to every second year engineering student in college, if not in high school physics class.
If one considers a typical glacier mass in a mountain environment, where the sharp slope of the topography and the fact that more snow falls at higher elevations means that the glacier is being driven by gravity to flow downhill, it is easy to visualize. The glacial mass is visually striated and looks like a frozen fast water current as it moves downhill in the canyon or valley towards its downstream edge.
Thanks for all the excellent comments on glaciers, Duane.
Greenland ice sheet had a lot less area during the peak of the Holocene Optimum.
The planet is still here.
In fact, it is currently at near record levels, just a big down from the extreme high of the LIA
typo last line.. big -> bit
The current Greenland Ice Sheet has a surface area of 1.7 million sq km, so less than any point on that graph.
Ignorance of what Briner calculated is par for your MO
He included all the Canadian Archipelago islands.
You FAIL, yet again.
Notice how it is basically the inverse of Holocene temperatures from places like GISP and GRIP… as to be expected.
Briner did no such calculation he attributes that graph to Larsen et al who in turn attribute it to the HUY3 model of Lecavalier et al, it does not include the Canadian Archipelago!
Fig. 7. The chronology of lateral ice extent for the Huy3 model (16 ka BP – pink; 14 ka BP – dark blue; 12 ka BP – light blue; 10 ka BP – yellow; 9 ka BP – orange; 6 ka BP – red; 4 ka BP – green; present-day – black).
Yep, and plus 2 meters of SL compared to today, did not cancel the AMOC.
Story Tip
New Study: Western Greenland Was ‘1.5-2°C Warmer Than Today’ During Medieval Warm Period (notrickszone.com)
Circulation stability is not the same as collapse.
Note the north to south cold water flow on the coast of Greenland. The melt runoff is moved away from the warm waters flowing south to north.
We’re still in an ice age. In the article, “the last ice age” should be “the last glacial period”. It matters. The fraudsters keep chipping away at everything, they try to claim the Quaternary has ended, they even try to claim that the Holocene has ended. The double standards are tough, but everyone else really has to get things right.
This detail is “lost in translation”. In German (the language the article was first written) the meaning of “Eiszeit” (which was used) is glacial period.
Chinese whispers.
Indeed!
“that the Holocene has ended”
When the Holocene ends, the planet drops down into another major Ice Age.
Canada, New York, a mile deep in ice. etc !
Glacial Period. The Earth is still in an Ice Age, the Quateryare or Fourth Ice Age, until all natural ice melts.
Ok, I worded it badly.
When the Holocene Interglacial ends, the planet drops down into the much colder temperature of the current longer-term Ice Age.
Is that better . 🙂
It is certainly NOT something we want to happen. !
All those climate refugees moving to the States especially Trudeau.
It is certainly NOT something we want to happen. !
He’ll be shot at the border.
Correct – there is no evidence whatsoever that the dozens of glacial/interglacial cycles of the Pleistocene have ended. We are merely within a much repeated interglacial period that is just more of the same. Unfortunately for the biosphere, the average length of glacial periods is much longer than the interglacials.
Maybe if the last glacial period ended a couple hundred thousand years ago, then we could say the Pleistocene is truly over.
salt..
Tips to reduce your salt intake
https://www.nhs.uk/live-well/eat-well/food-types/salt-in-your-diet/
Salt and alcohol are preservatives, and at my age I need all the preservatives I can get. ( 25yo with 59 years experience of being 25yo. )
Salt is crucial to your body’s health.
https://www.theepochtimes.com/health/misunderstood-salt-and-its-lesser-known-benefits-5463597
The Greenland Ice Sheet is also known as the ‘Inland Ice Sheet’ and sits in a saucer like basin between coastal mountains on the west and east with an average depth of 5000 feet. It is 1380 miles (2220km) long north to south and has a maximum width of 680 miles (1094km)
As Rud Istvan has often said it is not going to melt
So according to my favorite data source Wiki Greenland has 2.9M GT of ice. 5000GT over 20 years is 250GT. 2.9M / 250 is 11,600 years. Now of course, what is the error bar on 2.9M? probably more that 5K. The two biggest factors in Greenland ice are how much will it snow in the winter and what is the atmospheric pressure setup over Greenland in the summer during the melt season? It varies a lot over a time period.
When I saw that a main opponent of this paper’s assertions is Stefan Rahmstorf 🙄, I knew the paper was highly likely to be accurate and truthful.
Given Stefan Rahmstorf’s credentials, his persistently grossly inept analysis of the data over the years shows that he is: A. Psychotic or B. Lying.
3 WUWT Articles Exposing Rahmstorf’s Errors
I. Frank Lansner on Foster and Rahmstorf 2011
“[Having] evaluated what F&R has done, now let’s consider issues:
1) F&R assume that temperature change from, for example, El Nino … will disappear fully immediately after such an event ends. F&R assumes that heat does not accumulate from one temperature event to the next.
***
3) Missing corrections for human aerosols – (supposed to be important)
4) Missing corrections for AMO
… .”
(Source: https://wattsupwiththat.com/2011/12/17/frank-lansner-on-foster-and-rahmstorf-2011/ )
3 COMMENTS (below above article)
jens raunsø jensen:
“…The paper and result of Foster and Rahmstorf (FR) is in my view questionable on the following main grounds: [1] the T-records are non-linear, and [2] the time period considered is too short compared with the number of variables/parameters estimated.
1. *** The step change model gives a significantly higher R2 than a simple linear model (at least in the cases I have studied, incl. the global T-curves). These step changes in T-regime are obviously linked somehow with extreme ENSO events. The T-records during the period is, thus, most appropriately considered to be non-linear.
2. *** The time trend parameter represents a warming signal mainly caused by non-linear natural processes in the period.
— FR fits 4 parameters (plus 3 lags, 7 parameters ?) to only 32 data points, whereas it is a general statistical recommendation in multiple regression analysis that the number of observations should at least be about 10 to 20 times the number of independent variables/parameters, to avoid unstable solutions.
The degrees of freedom in the FR analysis are marginal, and the statistical robustness of the result is therefore in any case questionable.
Regards …. Jens”
(https://wattsupwiththat.com/2011/12/17/frank-lansner-on-foster-and-rahmstorf-2011/#comment-835341 )
Bob Tisdale:
“ ***
1) *** Foster and Rahmstorf (2011) misrepresent the process of ENSO by attempting to remove its wiggles from global temperature with the MEI. The authors either misunderstand ENSO or they are attempting to mislead their readers.
***
3) Missing corrections for AMO — Yup, Foster and Rahmstorf (2011) missed that. *** .”
(https://wattsupwiththat.com/2011/12/17/frank-lansner-on-foster-and-rahmstorf-2011/#comment-835390 )
Terry Oldberg:
“In their paper, Foster and Rahmstorf reveal either a lack of understanding of or a disdain for the scientific method of inquiry by presenting models that are neither statistically validated nor susceptible to statistical validation. Models of this kind lie outside science.”
(https://wattsupwiththat.com/2011/12/17/frank-lansner-on-foster-and-rahmstorf-2011/#comment-836134 )
***********
II. Mythbusting Rahmstorf and Foster [2012] by Bob Tisdale
(Source: https://wattsupwiththat.com/2012/11/28/mythbusting-rahmstorf-and-foster/ )
*************
III. NASA Refutes Mann and Rahmstorf – Finds Atlantic Conveyor Belt Not Slowing
COMMENT:
[Moreover,]
SkepticGoneWild: “Climate Audit trashes Mann’s paper: http://climateaudit.org/2015/03/25/reductio-ad-mannium/ .”
(https://wattsupwiththat.com/2015/03/25/nasa-refutes-mann-and-rahmstorf-finds-atlantic-conveyor-belt-not-slowing/#comment-1891351 )
(Source: https://wattsupwiththat.com/2015/03/25/nasa-refutes-mann-and-rahmstorf-finds-atlantic-conveyor-belt-not-slowing/ )
Slowing AMOC and Rahmstorf are symbiotic, it’s Rahmstorfs obsession. 😀
No idea, how may papers he wrote about, but all were refuted 😀
Therefore he was cited…
If the draining of Lake Agassiz is what it takes to stop interrupt the AMOC, I sincerely doubt anything shy of a well placed meteor strike will cause a problem to be concerned with.
Let’s see…. in the paleological timeline, Greenland has been ice free.at different times. If the melting of the ice caused the collapse of the AMOC, then (1) how did it restart (if it indeed stopped), and if it stopped, the Day After Tomorrow fiction (aka tipping point nonsense) should have dumped enough snow to immediately reform the glaciers.
From this we can conclude that the total melt of the Greenland ice cap could not be what the climate cabalists are claiming and more so, a partial melt will have minimal, if any, affect.