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Author Topic: Ice melting (Antarctica, Greenland, etc.) as a short term ASI negative feedback  (Read 4206 times)

Juan C. García

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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.
« Last Edit: September 28, 2017, 03:18:24 AM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Tigertown

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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 90o 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

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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/
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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Quote
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.
Quote
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.
Quote
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.
Quote
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/
« Last Edit: September 28, 2017, 02:46:14 AM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

miki

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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.
 
« Last Edit: September 28, 2017, 05:11:05 AM by miki »

sidd

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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

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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.
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

sidd

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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

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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.  :)
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

ChrisReynolds

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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

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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:

Quote
“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.

Quote
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.

Quote
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.

Quote
“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.”
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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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).  ;)
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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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

Quote
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.

Quote
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).
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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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.
« Last Edit: October 07, 2017, 07:44:38 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

smid1584

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If no polar ice is, then how will humans?

Alexander555

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

oren

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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

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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

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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.
« Last Edit: October 08, 2017, 11:34:23 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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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.

Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

oren

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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

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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.
« Last Edit: October 12, 2017, 02:52:39 AM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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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.  8)
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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

Quote
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
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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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.
...
« Last Edit: October 16, 2017, 10:19:27 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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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/
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

echoughton

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OMG?...really?

Juan C. García

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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/
« Last Edit: November 03, 2017, 03:15:18 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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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:

Quote
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.

Quote
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:

Quote
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:

Quote
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:
« Last Edit: November 09, 2017, 01:48:14 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Hyperion

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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.
Policy: The diversion of NZ aluminum production to build giant space-mirrors to melt the icecaps and destroy the foolish greed-worshiping cities of man. Thereby returning man to the sea, which he should never have left in the first place.
https://en.wikipedia.org/wiki/McGillicuddy_Serious_Party

Susan Anderson

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

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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

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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/

Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.