Ice melting (Antarctica, Greenland, etc.) as a short term ASI negative feedback

[Juan C. García]

Maybe this topic will not last long, but I need to ask.

On 2016, we had a lot of heat on the Atlantic Ocean, that melted the ASI. An example of the heat we had, we can see the topic Arctic Sea Ice Collapse Has Destabilized the Stratospheric Circulation. So, on 2017 I was thinking that we were going to have the same heat on the Atlantic side, but it didn't happen.

Also, on July 2017, I was surprise to see the general weakening of the Antarctic Ice, expressed on the National Geographic article The Larsen C Ice Shelf Collapse Is Just the Beginning—Antarctica Is Melting. I have been following the Arctic for more than a decade, but I must recognize that I do not have the same knowledge on the Antarctic. Five years ago, the Antarctica was for me the strong Pole, the one that could be increasing in ice, not losing the ice at the bottom. So, on July I was surprise to see that there are kind of important currents that go under the Antarctica, that they are melting the ice, generating possible collapses in several regions.

So, giving the ocean currents that go all around the world, I start to think if it is possible to have some heat go all the way from the Arctic to Antarctica (or cold currents that go from Antarctica to the Northern Hemisphere) and if this heat transfer could explain that the North Atlantic Ocean was cooler on 2017.

Given the fact that Greenland has also some places that are below sea level, I wonder if there is also bottom melting on Greenland ice. I also saw the paper of A. K. Hamilton et al: “Dynamic response of an Arctic epishelf lake” mention by sidd. And it is more of the same subject: the contact of ice on land (or close to land but below sea level) with ocean currents, that could be taking heat out of the Arctic Ocean.

What do you think? Could the melting of ice on Antarctica, Greenland, Ellesmere Island, etc. be a short term negative feedback, that could explain some facts, like that at 2017 we were expecting a stronger melt on September, but at the end, it didn’t happen?

Also, could the medicine be worse than the illness? Does a possible delay on an ice-free Arctic could mean, on the other hand, a faster melt on Greenland, Antarctica, etc.?

I will appreciate your comments and if you know about papers on this subject.

[Tigertown]

I think that the heat energy is definitely accumulating and going somewhere. For some reason it did not get routed to the Arctic as much this year. Good for the sea ice, but not so good for other places. It is almost October and 90^o F where I live, so the heat is hanging around here for now. We will have to watch and see how the distribution works out and what this will affect. Some heat may be going to Antarctica, especially at depths, and elsewhere. It also, would not be a huge surprise if some more makes it to the Arctic out of season later on.

[Juan C. García]

This is another article of Douglas Fox (same author on National Geographic), published on July 2015.

https://www.scientificamerican.com/article/high-heat-measured-under-antarctica-could-support-substantial-life/

[Juan C. García]

Near the surface, a current was streaming out from under the ice shelf that was slightly less salty than the sea around it, because it was freshened by melted ice. (The ice is fresh because it originated as snow falling on West Antarctica.) And at depths of 2,000 to 3,000 feet, along a seafloor canyon that ran straight under the ice, warmer seawater was streaming in.

Somewhere tens of miles inland, the warm water was finding the “grounding line”: the place where the glacier lifts off the seafloor and becomes a floating ice shelf. Hitting that wall of ice, the warm water was eroding it, producing a steady stream of melt-laden seawater. Because it was cooler and fresher, it was less dense, and so it was rising above the warmer, incoming water and flowing back out to sea just under the shelf.

By measuring the amount of this freshwater, the researchers could estimate how much ice was being lost. The melt rates “were just crazy,” says Adrian Jenkins, a glaciologist from the British Antarctic Survey in Cambridge. According to his calculations, the ice shelf was losing 13 cubic miles of ice per year from its underside; back near the grounding line, the ice was probably thinning up to 300 feet per year.

“It was just beyond our concept that a glacier would melt that fast,” Jenkins says.

It’s unclear when the entire ice shelf might disintegrate. The “warm” water flowing underneath it from offshore is only 4 to 6 degrees Fahrenheit above freezing. But roughly 3,000 cubic miles of it arrives every year, which means the ice shelf is receiving an amount of heat that exceeds the output of a hundred nuclear power plants, operating 24/7.

The ice shelves, Fricker says, “are the canary in the coal mine.” Because they’re already floating, they don’t raise sea level themselves when they melt—but they signal that a rise is imminent, as the glaciers behind them accelerate. Fricker and her team have found that from 1994 to 2012, the amount of ice disappearing from all Antarctic ice shelves, not just the ones in the Amundsen Sea, increased 12-fold, from six cubic miles to 74 cubic miles per year. “I think it’s time for us scientists to stop being so cautious” about communicating the risks, she says.

http://www.nationalgeographic.com/magazine/2017/07/antarctica-sea-level-rise-climate-change/

[miki]

I really thank you, JCG, for opening this thread. Since this summer I was thinking about the causes/consequences of the slowing of the melting in the Arctic.
More troubling to me, the causes/consequences of the cooler Atlantic side. Water was quite cooler on the east side of Greenland this summer for a while. My constant question being, where the heat is going?

I watch at Antarctica in a similar way.

I find always useful to come back, from time to time, to the good 2015 paper of James Hansen at al.

http://www.columbia.edu/~jeh1/2015/20150704_IceMelt.pdf
Ice Melt, Sea Level Rise and Superstorms: Evidence from Paleoclimate Data, Climate Modeling, and Modern Observations that 2°C Global Warming is Highly Dangerous.

For what I understand, during the melt phase, increased extent of Antarctic sea ice is assured, with "amplifying feedbacks in the Southern Ocean that slow Antarctic bottom water formation and increase ocean temperature near ice shelf grounding lines, while cooling the surface ocean and increasing sea ice cover and water column stability." What happens to Arctic ice seems less obvious, due to the slowing (stopping?) of the AMOC and therefore of ocean heat transport towards the Nordic Seas.
 

[sidd]

I think that the year to year fluctuations do not tell much about interhemispheric heat transport in the ocean since the timescales are too long there, on the order of centuries. I would look to the atmosphere instead, the timescales are much more appropriate. And especially precipitation, since the latent heat in moisture is far more effective than specific heats of air.

sidd

[Juan C. García]

I think that the year to year fluctuations do not tell much about interhemispheric heat transport in the ocean since the timescales are too long there, on the order of centuries. I would look to the atmosphere instead, the timescales are much more appropriate. And especially precipitation, since the latent heat in moisture is far more effective than specific heats of air.

sidd

Hi Sidd.

I have notice that El Niño can start on Indonesia on August and reach Peru on December, to be at Mexico coast on April.

Regarding El Niño, I have another question: Why El Niño is follow by La Niña? I always wonder why, after a hot current on the Pacific, it is normal to have a cold current on the same place.

[sidd]

Re: El Nino timescale

That timescale is set by wind variability and upper ocean. Interhemispheric transport in deep currents and up/downwelling take much longer. Again, i think perhaps atmospheric variability driving upper ocean and precipitation is a better place to look for yearly variation.

sidd

[Juan C. García]

Re: El Nino timescale

That timescale is set by wind variability and upper ocean. Interhemispheric transport in deep currents and up/downwelling take much longer. Again, i think perhaps atmospheric variability driving upper ocean and precipitation is a better place to look for yearly variation.

sidd

Thanks for your answer, Sidd. 

[ChrisReynolds]

Juan,

Interesting  question. There is a very good Wikipedia page on the North Atlantic Cold Spot.
https://en.wikipedia.org/wiki/Cold_blob_(North_Atlantic)
This very likely being a symptom of the weakening of the Atlantic Meridional Overturning Circulation.  However this has been a long turn process on the way to a cessation sometime in the future (sooner than models have previously predicted). So I don't think it plays a role in the post  2007 'levelling' of Arctic sea ice extent as it was underway before then.

As for the ice shelves of the Arctic Ocean, these were far larger in the early 20th century and their loss has been a relatively early process, long preceding the recent late 20th Century start of the decline in sea ice extent/volume. There may be a localised role due to the topography of some glaciers but most glaciers are not floating and lie in valleys with their bases above sea level.

[Juan C. García]

Hi ChrisReynolds, it is good to have you here, on this Forum.

Thank you for the link. It is great! A lot of work, if I look for all the studies mentioned on it.

Also, on the NSIDC home page, they are promoting the NASA page A submarine retreat (by Jane Beitler, October 13, 2015). I will quote the following paragraphs:

“Lots of people used to say that the Greenland Ice Sheet is not so vulnerable to climate change, because once the glaciers retreat inland about ten kilometers [six miles], they will not be connected to the ocean, and so the melting we see today will stop,” Morlighem said. There, the elevation of the valley floor would rise above sea level and stop the ocean from following a glacier up the valley. However, researchers knew that something was amiss when ice sheet models were not able to simulate current rates of melting and ice sheet thinning.

As they compiled the data, they discovered a huge canyon running from the central region of the island northward to the fjord of Petermann Glacier and the Arctic Ocean. Dubbed “Greenland’s Grand Canyon,” it is more than 750 kilometers long (466 miles), up to 800 meters deep (2,600 feet), and 10 kilometers wide (6 miles), making it the longest canyon discovered on Earth. They think the canyon is a major channel for flushing ice and meltwater off the island. Without canyons like this, meltwater might pool under the ice sheet and form subglacial lakes, as are found under the ice sheet on Antarctica. Greenland has no lakes below its ice sheet.

Their results show the widespread presence of well-eroded, deep bed troughs along the edges of the ice sheet that are generally grounded below sea level, with fast-flowing ice. They extend more than 100 kilometers (62 miles) inland, not the 10 kilometers (6.2 miles) that had been thought. The full extent of some of these bed troughs had never been detected by previous radar sounders.

“In many places we thought that the bed was raised above sea level but it was below sea level,” Morlighem said. For the first time, for example, they could see that the bed of the three main branches of Upernavik Glacier in West Greenland runs below sea level for more than 80 to 140 kilometers (50 to 87 miles) inland. Up north, Humboldt Glacier’s submarine bed runs 140 kilometers (87 miles) inland. Morlighem said, “We now know that the melting of Greenland is not going to stop in a decade or so. It will keep melting. As the ice retreats, it will still be in contact with the ocean because it will follow it inland.”

[Juan C. García]

I really thank you, JCG, for opening this thread. Since this summer I was thinking about the causes/consequences of the slowing of the melting in the Arctic.
More troubling to me, the causes/consequences of the cooler Atlantic side. Water was quite cooler on the east side of Greenland this summer for a while. My constant question being, where the heat is going?

I watch at Antarctica in a similar way.

I find always useful to come back, from time to time, to the good 2015 paper of James Hansen at al.

http://www.columbia.edu/~jeh1/2015/20150704_IceMelt.pdf
Ice Melt, Sea Level Rise and Superstorms: Evidence from Paleoclimate Data, Climate Modeling, and Modern Observations that 2°C Global Warming is Highly Dangerous.

For what I understand, during the melt phase, increased extent of Antarctic sea ice is assured, with "amplifying feedbacks in the Southern Ocean that slow Antarctic bottom water formation and increase ocean temperature near ice shelf grounding lines, while cooling the surface ocean and increasing sea ice cover and water column stability." What happens to Arctic ice seems less obvious, due to the slowing (stopping?) of the AMOC and therefore of ocean heat transport towards the Nordic Seas.

Thank you for your comment, miki!
I tried to read the James Hansen paper that you recommended, but more than read it, i will need to study it (which requires more time). 

[Juan C. García]

Given the fact that Greenland has also some places that are below sea level, I wonder if there is also bottom melting on Greenland ice. ...

What do you think? Could the melting of ice on Antarctica, Greenland, Ellesmere Island, etc. be a short term negative feedback, that could explain some facts, like that at 2017 we were expecting a stronger melt on September, but at the end, it didn’t happen?

As I thought! 

Washington Post: Scientists mapping Greenland have produced some surprising – and worrying – results

Two new studies of Greenland, using sophisticated technologies and large scientific teams to pull together and process the data, have now gone further in taking the full measure of the island through that ever-so-basic scientific act: mapping.

The first, a comprehensive seabed mapping project, relying in part on new data from NASA’s OMG (“Oceans Melting Greenland”) mission, concludes that the Greenland ice sheet is far more exposed to the planet’s warming oceans than previously known — and has more ice to give up than, until now, has been recognized.

Meanwhile, on Wednesday, a separate team of scientists used another quite different large-scale mapping exercise to document a surprising — but closely related — change in Greenland’s above-water topography. Publishing in the journal Nature, they showed that the contours of the huge island are changing because with all the ice melt rushing from glaciers to the sea, river deltas are expanding outward — a rare occurrence these days when deltas around the world are generally retreating, threatened by rising seas (think of the Mississippi River delta, for instance, and its vanishing wetlands).

[Juan C. García]

I think that the year to year fluctuations do not tell much about interhemispheric heat transport in the ocean since the timescales are too long there, on the order of centuries. I would look to the atmosphere instead, the timescales are much more appropriate. And especially precipitation, since the latent heat in moisture is far more effective than specific heats of air.

sidd

Again, thank you for your answer Sidd.

After 10 days that I opened this topic, I have convinced myself that my assumption is correct. It turns out that Greenland and Antarctica have ice bottom melting, in contact with warm ocean water, that is greater than what it was believe before. This should be cooling the oceans and could be making a negative feedback on the summer ASI melting.

On the Antarctic influence, as Sidd said, the Global Conveyor Belt moves very slow: it takes centuries to circulate around the globe. But the atmospheric activity around Antarctica is usually intense. Also, it is normal to have now an anomaly on the sea surface temperature around Antarctica (that I assume that it is because of the melting ice) and as an example of the armospheric activity,  there are five very low-pressure systems (under 970 hPa) around Antarctica today, while the attention is given to Hurricane Nate (with bigger low presure).

So, the question is how to make a quantitative measure of the influence of Greenland and Antarctica ice melting (that is below sea level). These measures should be given on scientific studies (not just as an opinion), but seems to me that in 2017, the low melting that we had in summer could be influenced by this negative feedback. Also, there are some new scientific studies appearing.

[smid1584]

If no polar ice is, then how will humans?

[Alexander555]

The 2 pics above  , from Greenland. What are they telling us ? The central part, blue/white, is that below sea level ?

[oren]

The 2 pics above  , from Greenland. What are they telling us ? The central part, blue/white, is that below sea level ?

Yes. The legend on each of the pics shows this, enlarge to see clearly.

It turns out that Greenland and Antarctica have ice bottom melting, in contact with warm ocean water, that is greater than what it was believe before. This should be cooling the oceans and could be making a negative feedback on the summer ASI melting.

Juan, check the currents around Greenland, they are all flowing southward, so Greenland melt is surely affecting the Atlantic ocean but I doubt it has much to do with low ASI melt in the Arctic.

[Alexander555]

So how did they calculated the thickness of the Ice on Greenland ? The ice below sea level will not add to a higher sea level if it would melt. And if you look at the east coast, which has a high elevation, that makes it hard to imagen it hold 1500 meter of ice. So how much ice do we have on Greenland left that could rise the sea level in the worst situation of a complete melt ?

[Juan C. García]

Juan, check the currents around Greenland, they are all flowing southward, so Greenland melt is surely affecting the Atlantic ocean but I doubt it has much to do with low ASI melt in the Arctic.

Hi Oren.

In this topic, I am trying to see the Earth and the oceans as a whole, not as pieces. I am also looking to see the oceans like a drink that we have on a warm beach: as long as you have ice on it, it is going to stay cool. So, we have just one huge ocean and two huge ice blocks: Antarctica and Greenland. We know that around 90% of the heat ends up in the oceans. If the oceans are absorbing the heat and they have increased the temperature on average by 1° C, the question is if the increase should not be 1.2° C, if we did not have bottom melting on Antarctica and Greenland.

On a local view, there is an important volume of ice on North East Greenland, that it is external and that it has an important part below sea level. I remember that at 2016, Neven made notorious that the Greenland Sea was almost with no ice. So, this is a new development and the bottom melting in 2016 and 2017 on the North East should be important and should be locally cooling the Arctic at the Greenland Sea and possible at the Lincoln Sea.

[Juan C. García]

Juan, check the currents around Greenland, they are all flowing southward, so Greenland melt is surely affecting the Atlantic ocean but I doubt it has much to do with low ASI melt in the Arctic.

In fact, all the Greenland currents are flowing southward, but then they clash with the Atlantic meridional overturning circulation (AMOC), maybe slowing the AMOC and turning northward.

[oren]

Thanks for the explanations Juan. I like the drink analogy. Surely ice melting in Greenland and Antarctica significantly affects the heat balance in the whole ocean system.

[Juan C. García]

Thank you for your answer Oren.  Hi everybody.

In a way, I think that I have convinced others and myself that ice bottom melting on Antarctica and Greenland are ASI negative feedbacks. I used the qualifier “short term” because with bottom melting, it increases the possibility of an abrupt sea level rise, when the top falls. Then, the sea level rise can increase the permafrost melting, liberating GHG and becoming a positive feedback.

I started with Antarctica, because it was the July National Geographic article the one that convince me that ice bottom melting was important. After Sidd comment, I have realized that it is going to be impossible to trace the heat transfer between the Arctic and Antarctica. The heat just dissipates on the oceans and atmosphere. But I want to emphasize the importance that I see on Antarctica. There are some pictures on the printed edition (I annex the Spanish version) that are not on the digital edition. These images shock me. From these images, I think that ¹/₄ of West Antarctica is losing thickness. Seems terrible that at the same time, on NSIDC ASI values, 2016 and 2017 are the sixth and seventh lowest on the satellite record. Seems that we are fine, because the Arctic is the weakest pole, while an abrupt sea level rise could be a possibility in the medium term (not after 2100, as the IPCC is suggesting).

Continuing with this topic, the best that we can do is to follow the currents between Greenland and the Arctic. This could be a way to better understand the negative feedback on the ASI and to know why we have a bounce on 2008-09 and on 2013-14. From my point of view, the bounce that we could see on 2015-17 is just fake. We must see the weakness on the ASI and the entire year, not just September, that can be influenced by a negative feedback.

Anyway, I will be looking to include studies that analyze bottom melting, on Greenland and Antarctica.

[Juan C. García]

On the comment above, I wrongly said that 1/4 of Antarctica was losing thickness. From the image, what the scale measures is the speed in which the ice is moving (m/year). My mistake. 

[Juan C. García]

Washington Post -
Worrying new research finds that the ocean is cutting through a key Antarctic ice shelf

The new study calculates that as a result of this highly uneven melting, the Dotson ice shelf could be melted all the way through in 40 years, rather than 170 years, which would be the time it would take if the melt were occurring evenly. And it speculates that as the thinning continues, the shelf may not go quietly or steadily any longer — something dramatic could occur, such as a breakup.

https://www.washingtonpost.com/news/energy-environment/wp/2017/10/11/alarming-new-research-finds-that-the-ocean-is-cutting-through-a-key-antarctic-ice-shelf/?utm_term=.da94284bfb0f&wpisrc=nl_green&wpmm=1

[Juan C. García]

I believe that I don't have the knowledge, nor the resources nor the time to develop this topic, even that I am convinced that it is happening and that it is worthwhile to try to develop it.

Anyway, there is some discusion in "What's new in Greenland?" that is interesting, so I recomend to follow this subject on that topic:

The first article mentioned in the post above, Morlighem 2017, represents a very substantial refinement in mapping of Greenland fjords whose bathymetry is key to warm ocean water access to the grounding lines of the glaciers.

The article is open access and even better, so is the data. That's a first. It's all packaged as a single giant 2.5 GB netCDF file and stored at NSIDC at the link below (nuisance registration req'd). The download opens readily as seven Panoply map options despite the immense grid of 18346 x 10218 = 187,459,428 cells.
...

[Juan C. García]

Global sea level rise will be one of the major environmental challenges of the 21st Century. Oceans Melting Greenland (OMG) will pave the way for improved estimates of sea level rise by addressing the question: To what extent are the oceans melting Greenland’s ice from below?

https://omg.jpl.nasa.gov/portal/

[echoughton]

OMG?...really?

[Juan C. García]

OMG?...really?

OMG: "Oceans Melting Greenland"

Why? Do they have bad reputation? Or the meaning of the title, on a NASA page, seems surprising?

Edit:
They make the question: "To what extent are the oceans melting Greenland’s ice from below?"

But I have a second question: To what extent does the Greenland’s ice melting, has been cooling the Arctic Ocean, especially on September? From my point of view, 2017 was the second worse year, after 2012, but the negative feedback of Greenland's ice melting contributed to make it the seventh worse on record.

So, are NSIDC/NASA showing the whole picture?

https://climate.nasa.gov/vital-signs/arctic-sea-ice/

[Juan C. García]

https://www.nasa.gov/feature/jpl/new-greenland-maps-show-more-glaciers-at-risk

'New maps of Greenland’s coastal seafloor and bedrock beneath its massive ice sheet show that two to four times as many coastal glaciers are at risk of accelerated melting as previously thought.'

Sigh.

On the link provided by Adam Ash:

The new maps reveal that two to four times more oceanfront glaciers extend deeper than 600 feet (200 meters) below sea level than earlier maps showed. That's bad news, because the top 600 feet of water around Greenland comes from the Arctic and is relatively cold. The water below it comes from farther south and is 6 to 8 degrees Fahrenheit (3 to 4 degrees Celsius) warmer than the water above. Deeper-seated glaciers are exposed to this warmer water, which melts them more rapidly.

OMG Principal Investigator Josh Willis of JPL, who was not involved in producing the maps, said, "These results suggest that Greenland's ice is more threatened by changing climate than we had anticipated."

My opinion is:

The new maps reveal that two to four times more oceanfront glaciers extend deeper than 600 feet (200 meters) below sea level than earlier maps showed. That's bad news, because the top 600 feet of water around Greenland comes from the Arctic and from Greenland's ice melting and is relatively cold. The water below it comes from farther south and is 6 to 8 degrees Fahrenheit (3 to 4 degrees Celsius) warmer than the water above. Deeper-seated glaciers are exposed to this warmer water, which melts them more rapidly.

And it is based on what I think it is happening in Greenland, that could be similar to what it has been happening in Antarctica:

They made a disturbing discovery. Near the surface, a current was streaming out from under the ice shelf that was slightly less salty than the sea around it, because it was freshened by melted ice. (The ice is fresh because it originated as snow falling on West Antarctica.) And at depths of 2,000 to 3,000 feet, along a seafloor canyon that ran straight under the ice, warmer seawater was streaming in.

Stan Jacobs, an oceanographer from the Lamont-Doherty Earth Observatory in New York, quickly understood what was going on. The warm water was coming from the South Pacific, more than 200 miles north. It was so heavy with salt that it was following the floor of a submarine canyon, which sloped down toward the glacier. The glacier itself had carved that canyon, thousands of years ago during the Ice Age, when it and the other glaciers in West Antarctica advanced hundreds of miles out from their present-day positions.

Now that same canyon was channeling warm ocean water under the Pine Island Ice Shelf. Somewhere tens of miles inland, the warm water was finding the “grounding line”: the place where the glacier lifts off the seafloor and becomes a floating ice shelf. Hitting that wall of ice, the warm water was eroding it, producing a steady stream of melt-laden seawater. Because it was cooler and fresher, it was less dense, and so it was rising above the warmer, incoming water and flowing back out to sea just under the shelf.

https://www.nationalgeographic.com/magazine/2017/07/antarctica-sea-level-rise-climate-change/

That matches with the OMG picture:

[Hyperion]

But I have a second question: To what extent does the Greenland’s ice melting, has been cooling the Arctic Ocean, especially on September? From my point of view, 2017 was the second worse year, after 2012, but the negative feedback of Greenland's ice melting contributed to make it the seventh worse on record.

James Hansen and colleagues paper rather strongly made the case that Greenland's melting was in fact destined to only become a negative feedback after its rate had doubled every 5-10years for a couple of centuries.
Short term it's modelled to be a strong positive feedback of up to ten times the magnitude of total worldwide anthropogenic greenhouse gases. The puddle of meltwater flowing south from it protects the underlying north flowing warm waters from energy loss and evaporation. The magnet use of the increase in heat reaching the Arctic and reduction in thermal radiation into space from this effect is thought to be so large that an exponential accerating warming and melt will proceed until the latent energy of annual melt exceeds ghg and surface cold pool blocked outgoing radiation losses in the energy sector budget a century ago or two from now. At this point the melting icecube can start to cool back down our drink.

[Susan Anderson]

Was looking for where to put this, not news to most, about the Beaufort Gyre @ Yale360 [highlighted bits & conclusion here]

How a Wayward Arctic Current Could Cool the Climate in Europe

The Beaufort Gyre, a key Arctic Ocean current, is acting strangely. Scientists say it may be on the verge of discharging a huge amount of ice and cold freshwater that could kick off a period of lower temperatures in northern Europe.

The gyre’s strange behavior is likely linked, at least in part, to the profound warming of the Arctic.

It remains to be seen when the next big flush will occur and whether it will set off a “ticking climate bomb.”

Carmack, Woods Hole’s Krishfield, and others are not ruling out the possibility that the gyre will weaken or reverse direction sooner rather than later. In fact, research conducted by the expedition this summer suggests that a change may be coming. The volume of freshwater in the gyre had not increased since the previous summer’s expedition, and changes in atmospheric circulation suggested a possible shift to the cyclonic activity that might weaken the clockwise rotation of the gyre.

Abrupt sea level rise looms as an increasingly realistic threat. Read more.
But it remains to be seen when and whether the next big flush will occur and whether it will set off the “ticking climate bomb” that Proshutinsky has forecast.

Speaking about the possibility of a gyre-driven surge of cold water temporarily altering the climate of the North Atlantic, NASA’s Petty says, .... we just don’t know. There just isn’t enough Arctic data out there to make firm predictions in a world where climate change, ocean currents, and atmospheric forces interact in complex ways.”

Ed Struzik • December 11, 2017

http://e360.yale.edu/features/how-a-wayward-arctic-current-could-cool-the-climate-in-europe

[Juan C. García]

Thanks, Susan and Hyperion, for your comments! 

For the ones that are interested in feedbacks, there will be the following AGU sessions:

https://fallmeeting.agu.org/2017/virtual-options/

[Juan C. García]

I was thinking that I was wrong in this theory that I post one year ago. But after seeing a video that Neven post on his blog (great video! ), I think that I am right in my theory, so I am reactivating the topic.

The idea is that the melting of the ice (specially but not only in Greenland) with other factors as well (like Jennifer Francis says), is so important that is cooling a part of the Atlantic and Arctic Oceans. In this video, it is important to notice the cool or cold blob, located south of Greenland.

The second factor is the slowing down of the AMOC. I thought that with climate change, the AMOC was going northward, to the north of Russia. But Jennifer Francis tell us that is getting deep into the Ocean on southern regions. So, this can be a negative feedback as well.

I need to make a summary of my thoughts on this subject, but for the moment, I want to share these ideas with you.

[Pmt111500]

Some larger anomaly of ocean currents south of Africa might have happened after last El Nino, producing the early spring over Antarctic Ocean.

Possibly I could find a record of that. The anomalous current would have diverted the heat due South Atlantic southwards stopping the possibility of a high melt year of ASI.

[Juan C. García]

Even that now I know that the melting on Antarctica doesn't have a relation with the ASI melt slowdown after 2012, I still believe that the influence of Greenland ice melting can contribute to slowdown the ASI melt, so that it is very difficult to break the 2012 record (I don't discard a new volume record on 2019, but it is going to be so close to 2012, that it will be a tie record).

So well, I also like this vid on this topic.

Good vid on the blob .

[binntho]

I've been wondering about this supposed connection between Greenland meltwater and low SSTs. This year has seen record melt in Greenland, particularly in July. Annual melt has been increasing rapidly, was around 280 Gt/year 10 years ago and increasing by 30 Gt/y2, see e.g. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2009GL040222

Most of the meltwater flows off the Southern end of the island, and along the Western coast, see e.g. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010GL042460

According to some newspaper stories, the melt in July alone raised sea levels by 0.5mm which equates to  roughly 180Gt .

But there's something that doesn't add up here. Where is the meltwater - if the meltwater has such a cooling effect on SSTs, shouldn't we be seeing that happening? And yet the areas receiving these record amounts of meltwater are showing warm and even very warm SST anomalies.

The whole edifice of "cold blob caused by Greenland run-off" seems to me to be built on sand.

[Juan C. García]

But there's something that doesn't add up here. Where is the meltwater - if the meltwater has such a cooling effect on SSTs, shouldn't we be seeing that happening? And yet the areas receiving these record amounts of meltwater are showing warm and even very warm SST anomalies.

The whole edifice of "cold blob caused by Greenland run-off" seems to me to be built on sand.

I think it should be this greener area. It is still warm, but -2°C versus the surroundings.
Thanks for your comment. 

[binntho]

But there's something that doesn't add up here. Where is the meltwater - if the meltwater has such a cooling effect on SSTs, shouldn't we be seeing that happening? And yet the areas receiving these record amounts of meltwater are showing warm and even very warm SST anomalies.

The whole edifice of "cold blob caused by Greenland run-off" seems to me to be built on sand.

I think it should be this greener area. It is still warm, but -2°C versus the surroundings.
Thanks for your comment. 

Well, thank you Juan!

But I don't think that meltwater from this summer (and nota bene still in full spate) is to be found 1000-2000 km further south. No way.

[KiwiGriff]

Satellite derived anomaly values for SST Represents only the surface temperature not that of the  water column.
Could the lack of ice and high absorption of solar energy by surface waters  this year be responsible for the lack of a blob in its usual position?
The Atlantic is still showing a cold patch just more southerly than  it has been.

5. DIFFERENT DEPTHS OF SST: AN IMPORTANT CONSIDERATION

Because of temperature gradients below the ocean's surface, the depth at which measurements are made will significantly impact the SST. Measurements made at only a depth of one or two molecules below the ocean's surface are considered the "interface SST" and cannot be realistically measured. Just below this, however, at a depth of roughly 10 µm is what is known as the "skin SST". The attenuation length of thermal infrared radiation corresponds to this depth. The "sub-skin SST" is at a depth of ~1 mm and corresponds to the attenuation length of microwave radiation. Beyond this depth is what is commonly referred to as the "bulk SST", "near-surface SST", or "SSTdepth". Below is an illustration of these different depths of SST, showing two different temperature gradients:

As can be discerned from the illustration above, the bulk SST (or SSTdepth) may vary greatly from the skin and sub-skin SSTs depending on the temperature gradient. The skin temperature may also vary from the sub-skin temperature for the same reason. Diurnal heating will cause these differences to be greatest during the afternoon and least right before dawn. Since SST measurements made from buoys and ships are usually bulk temperature measurements, temperature gradients must be taken into consideration when comparing them to SST measurements made by either thermal infrared or passive microwave remote sensing observations.

Since thermal infrared instruments measure the skin temperature and passive microwave instruments measure the sub-skin temperature, furthermore, one must also consider differences due to evaporative cooling at the sea surface when comparing measurements derived from these methods. The difference can be as great as 1 Kelvin in combination with diurnal heating effects, and so both properties must be properly accounted for when comparing or blending thermal infrared and microwave products.

http://www2.hawaii.edu/~jmaurer/sst/

[binntho]

Baffin current, speed roughly 17km per day. Would cover 2000 km in six months.

[binntho]

Satellite derived anomaly values for SST Represents only the surface temperature not that of the  water column.

Yes, and freshwater runoff would lie on the surface.

Could the lack of ice and high absorption of solar energy by surface waters  this year be responsible for the lack of a blob in its usual position?

Lack of ice where?

The Atlantic is still showing a cold patch just more southerly than  it has been.

There are many cold areas in the oceans, in the Northern Hemisphere I count at least 5 fairly large blue spots. Perhaps just random fluctuations in weather and ocean currents?

[KiwiGriff]

Shows an anomaly value for ice off greenlands eastern coast.
Currents

Light blue surface current from there and north.
From a paper that has more information .
https://www.sciencealert.com/we-might-have-been-wrong-about-ocean-circulation-and-it-will-have-big-impacts

Just ideas neither of us know the answers .
Trashing world respected scientists work is easy on a blog not so easy to refute their ideas in published literature  .
The blob, AMOC and the effects of Greenlands increasing melt is a topic of research that is as yet unanswered.

[binntho]

Just ideas neither of us know the answers .
Trashing world respected scientists work is easy on a blog not so easy to refute their ideas in published literature  .
The blob, AMOC and the effects of Greenlands increasing melt is a topic of research that is as yet unanswered.

How true. But perhaps I'm not being entirely honest here - because none of the published research I've read (nor scholarly articles) state that the cold blob is directly caused by cold meltwater runoff.

It has therefore come as something of a surprise to me to see that idea repeatedly put forward here in the Forum, or at least, not objected to.

What I've read uptil now is as stated in the article you linked to, "And the suggestion has been that this [i.e. the "cold blob"] represents a decline in the volume of heat being transported northward by the circulation."

So the cold blob happens (supposedly, but quite likely according to various lines of reasoning) because less heat is being transported northwards. Not because meltwater from Greenland is cooling the ocean surface. That's a fundamental difference, extremely important - but unknown to the participants in this forum?

But increased meltwater runoff could be one of the causes of a slowdown of the AMOC since cold salt water doesn't sink as readily if mixed with fresh meltwater from Greenland.

And yet this is all on very much on a "we don't know half of it" level still. There is simply so much that the scientists do not understand about the AMOC circulation yet, what change do we mere mortals have?

And given that the cold blob has simply vanished now, perhaps things will get back to normal in spite of the massive melt runoff this year? Let's see what happens over the next few months.

[KiwiGriff]

Thank you. I reconsidered that snark but you took it well 
We don't know. I have read that the blob is due to a slowing AMOC  .
But it is fascinating to learn  as we both are . Our shared ideas make us both more informed.

And a third point: in summer, the effect of heat flow through the sea surface should dominate, in winter the effect of ocean currents. That is because the well-mixed surface layer of the ocean is thin, so only the uppermost part of the ocean heat transport gets to affect the surface temperature. But the thin surface layer still feels the full brunt of atmospheric changes, and even stronger than in winter, because the thermal inertia of the thin summer surface layer is small. In our paper we analysed the seasonal cycle of the temperature changes in the subpolar Atlantic. The cooling in the “cold blob” is most pronounced in winter – both in the climate model (where we know it’s due to an AMOC slowdown) and in the observations. That yet again suggests the ‘cold blob’ is driven from the ocean and not the atmosphere.

http://www.realclimate.org/index.php/archives/2018/05/if-you-doubt-that-the-amoc-has-weakened-read-this/
Seems to suggest I may be part right as to why the blob is not apparent this summer.

[binntho]

That is a very good link. I was interested to read this:

While the upper northward branch of the AMOC does flow via the Gulf Stream, it thus only contributes about one fifth to the Gulf Stream flow. Any change in Gulf Stream strength could thus be due to a change in the other 80% of Gulf Stream flow, which are wind-driven. The AMOC does however provide the major northward heat transport which affects the northern Atlantic climate, because its return flow is cold and deep. Most of the Gulf Stream flow, in contrast, returns toward the south near the sea surface at a similar temperature as it flowed north, thus leaving little heat behind in the north.

[binntho]

Also the following paragraph, about an increase in the North Atlantic Current (NAC), measured more or less on the eastern side of the "cold blob"

Likewise for 1994-2013, Roessler et al. (2015) found an increase of 1.6 Sv in the transport of the North Atlantic Current between 47° and 53° North. This is a current with a mean transport of ~27 Sverdrup, 60% of which is subtropical waters (i.e., stemming from the south via the Gulf Stream). For this period, our reconstruction yields an AMOC increase by 1.3 Sv.

Which would fit in with the actual state of the climate in Northern Europe. As an example, Icelandic climate is very closely tied in with ocean temperatures, and a slowdown in the NAC would severely affect us. But temperature measurements seem to show a steady warming on par with the rest of the world, with no letup in the last 20 - 30 years.

Which leads me to another conclusion: The cold blob, and associated slowdown of the AMOC, doesn't really affect anything other than the East Coast of the US, with higher temperatures, more storm activity and higher sea levels.

Northern Europe, and the Northern Atlantic, seem not to be affected at all.

[Juan C. García]

Well, thank you Juan!

But I don't think that meltwater from this summer (and nota bene still in full spate) is to be found 1000-2000 km further south. No way.

I will not pretend that I am an expert on this subject. This topic started as an hypothesis (assumption or guess) and continue to be that way. It is just that I still believe that the hypothesis could be right.
I will have to study your comments, binntho, KiwiGriff and all the others.

Thank you for your answers. 
And I hope that you and others will continue to contribute on this topic.

[blumenkraft]

Thanks, Juan for opening this thread. And thanks for the informative posts, everyone.

The topic is fascinating and was one of the reasons i started to develop an interest in Arctic sea ice.

[binntho]

I will not pretend that I am an expert on this subject. This topic started as an hypothesis (assumption or guess) and continue to be that way. It is just that I still believe that the hypothesis could be right.

I think so too. But getting a grip on the magnitude of this effect is a lot harder than it seems.