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When will the Arctic Extent dip below 1,000,000 Km^2

2018-2019
12 (17.9%)
2020-2025
21 (31.3%)
2026-2030
13 (19.4%)
2031-2040
15 (22.4%)
2041-2060
2 (3%)
2061-2080
0 (0%)
2081-2099
1 (1.5%)
2100-beyond
3 (4.5%)

Total Members Voted: 64

Voting closed: July 27, 2018, 07:46:32 AM

Author Topic: When will the Arctic Go Ice Free?  (Read 133142 times)

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1400 on: November 21, 2019, 10:57:19 AM »
A possible mechanism for correlation of bathy with summer ice edge from Svalbard to FJL and possibly to SZ.

Strangely enough, I had some difficulty seeing the correlation (talk about confirmation bias!), but I guess you are talking about where the ice edge is a fairly straight line at the beginning, north of Svalbard, Franz Josef Land and the "Communist Archipelago".

But looking closer, I wonder why the ice edge that is seemingly following the shelf edge is actually either op to 100 km south of, or 50 km north of, the edge. There is almost never any exact match, or anything where you could say that the two are correlated with a shift of one against the other.

I am still not convinced that this seeming correlation is a temporary artifact - the shelf is aligned east to west, the minimum summer ice edge is also aligned east to west, and for some years the two will therefore invariably seem to follow each other.

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The east spitsbergen current is probably not in doubt on this thread. It's effects can be seen on the surface clearly at times during the animation and, in my view, also beneath the ice as leads or lower concentration up until the line where the 'warm water waterfall' falls into the Nansen basin.
You mean the West Spitzbergen Current? The one that flows up the Fram strait to the west of Svalbard? That is admittedly most likely closely linked to the bathymetry, but then again, that's only a tiny area of the Arctic.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1401 on: November 21, 2019, 11:02:43 AM »
binntho, I think where I most differ with you is that you give the impression your only considering surface and near surface waters.
Not at all. But the ice is obviously only on the surface, and for bathymetry to have an effect there has to be a mechanism for different depths to affect the surface.

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For me there is no resident water in the Norwegian sea, it's constantly being renewed by 'gulf stream/nad' waters from further south, so that water occupies the whole depth. Moving north/east it splits into energetic fractions the densest flowing north along the steep contours of the Barents shelf towards and around Svalbard then east along the shelfs contours and here the turbulence it creates in the waters coming off the shelf causes weak ice to melt.

Much as gerontocrat pointed out. And it's very probably right to say that bathymetry has an effect on the West Spitzbergen Current which again has an effect on the ice edge north of Svalbar. But that's still only a very small part of the supposed ice edge / continental shelf correlation.
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The energetic potential of the lightest fraction [recently at 60degN, @500mph surface speed now 68degN, @370mph] rounding Norway loses some of it's kinetic energy to heat but never enough to allow it to return by the same route, thus there's a constant but variable flow off the shelf into Nansen.
 Enough images here
because a thing is eloquently expressed it should not be taken to be as necessarily true
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binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1402 on: November 21, 2019, 11:47:08 AM »
johnm33 kindly posted a link to images on Google,  and it is certainly worth having a look if for no other reason than to refresh our memory of how the currents are shown on the various maps.

But they did make me wonder: We all know that the warm currents flowing northwards are surface currents. What is it that makes the incoming water sink, even to such dephts that they start following the continental slope?

There are two possible mechanisms:
  • The warm water cools and sinks. This is one of the main drivers behind the AMOC.
  • The warm(ish) water, being salty, will dip below the freshwater lens found under the ice.

Neither of the two has anything obvious to do with bathymetry. The first one indicates that as the air (and ocean) warms up, the sinking areas will move northwards. No bathymetric requirements here.

The second indicates that the warm water will sink when it meets the ice - the fresh water lens is under the ice, as the warm current meets the ice it is pushed downwards. But at the same time, it will be warming up the edges of the fresh water lense, and if the waters are getting warmer then the balancing line will shift northwards. No bathymetric requirements here.

Waters that sink because of 1) will obviously follow bathymetric contours after it sinks. But not before, and since the ice is at the surface, I find it difficult to see any correlation.

Waters that sink because of 2) should just slip under the fresh water lens, however if the ocean depth is close to the thickness of the lens then obviously something has to give. So a potential correlation here - the warm waters want to sink, but the fresh-water lens is obstructing them in shallower waters. Once the barrier meets deeper water, there is suddenly room for the warm water to slip under the freshwater lense, releasing a lot of pressure.

So perhaps the mechanism has been found after all? Seems to me a bit too easy given how many people have been claiming correlation but unable to spell out the causality. And anyway this only applies to  the Atlantic side - there is very little correlation north of the Alaskan coast, and the Siberian coast seems to be more complicated (fairly good correlation, but then there's the Laptev bite ... but it wouldn't surprise me if there was a good bathymetric explanation for that too).
because a thing is eloquently expressed it should not be taken to be as necessarily true
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oren

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Re: When will the Arctic Go Ice Free?
« Reply #1403 on: November 21, 2019, 12:04:11 PM »
Waters that sink because of 2) should just slip under the fresh water lens, however if the ocean depth is close to the thickness of the lens then obviously something has to give. So a potential correlation here - the warm waters want to sink, but the fresh-water lens is obstructing them in shallower waters. Once the barrier meets deeper water, there is suddenly room for the warm water to slip under the freshwater lense, releasing a lot of pressure.

So perhaps the mechanism has been found after all? Seems to me a bit too easy given how many people have been claiming correlation but unable to spell out the causality. And anyway this only applies to  the Atlantic side - there is very little correlation north of the Alaskan coast, and the Siberian coast seems to be more complicated (fairly good correlation, but then there's the Laptev bite ... but it wouldn't surprise me if there was a good bathymetric explanation for that too).
Binntho, this is what people here have been saying all along - the correlation is mostly on the Atlantic side, and it has a good physical reason that you have just outlined. People did spell it out. A-Team even discussed this back in 2016 if I am not mistaken.
Currently the battleground is along the shelf break and is weather dependent, some years the fresh water lens is more advanced due to constant export, and some years it is driven back, which is why the correlation is not totally "on the line". But it's certainly there.
In other regions of the Arctic the story is different and there that correlation is typically missing.

johnm33

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Re: When will the Arctic Go Ice Free?
« Reply #1404 on: November 21, 2019, 12:17:03 PM »
" We all know that the warm currents flowing northwards are surface currents."
This is where we differ, in the image below the current splits where it meets the Barents shelf close to Norway, the shelf contour here is 500m implying that that acts as a barrier suggesting the current is below that level, and i suspect flowing across the contours at much greater depths, it may even be forced up by denser waters when it rounds SV. and heads towards SZ and Laptev, thus washing up and down the shelf as it moves east still driven by the inertia it aquired further south.

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1405 on: November 21, 2019, 01:01:01 PM »
Binntho, this is what people here have been saying all along - the correlation is mostly on the Atlantic side, and it has a good physical reason that you have just outlined. People did spell it out. A-Team even discussed this back in 2016 if I am not mistaken.

Well, recently they've been saying it very quietly. I myself didn't remember what A-Team actually said about any causality, but I remember him pointing out the correlation. And I've seen people making all sorts of wild claims about warm waters plummeting down into the abys and whatnot. So a refresher into the actual physics of the thing is surely a good thing?

Perhaps what's bugging me is that people make claims, and then when you ask "why" they become all defensive instead of simply explaining. Perhaps because they don't know the explanation?
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

binntho

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Re: When will the Arctic Go Ice Free?
« Reply #1406 on: November 21, 2019, 01:02:41 PM »
" We all know that the warm currents flowing northwards are surface currents."
This is where we differ, in the image below the current splits where it meets the Barents shelf close to Norway, the shelf contour here is 500m implying that that acts as a barrier suggesting the current is below that level, and i suspect flowing across the contours at much greater depths, it may even be forced up by denser waters when it rounds SV. and heads towards SZ and Laptev, thus washing up and down the shelf as it moves east still driven by the inertia it aquired further south.


Up to the point where the current starts sinking, it is most definitely flowing along the surface. And I think I did say something about the continental slope and the current having sunk enough to actually follow that slope. But not before it sinks!
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

gerontocrat

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Re: When will the Arctic Go Ice Free?
« Reply #1407 on: November 21, 2019, 02:36:09 PM »
When will the Arctic Go Ice Free? - when the Arctic gets too warm.

https://productiongap.org/2019report/
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Governments are planning to produce about 50% more fossil fuels by 2030 than would be consistent with limiting warming to 2°C and 120% more than would be consistent with limiting warming to 1.5°C.
I made a longer post on "Paris 2015 & Beyond"
"Para a Causa do Povo a Luta Continua!"
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uniquorn

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Re: When will the Arctic Go Ice Free?
« Reply #1408 on: November 21, 2019, 03:26:19 PM »
A possible mechanism for correlation of bathy with summer ice edge from Svalbard to FJL and possibly to SZ.
Strangely enough, I had some difficulty seeing the correlation (talk about confirmation bias!),
Wow. A possible mechanism to confirmation bias in one line.

El Cid

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Re: When will the Arctic Go Ice Free?
« Reply #1409 on: November 21, 2019, 03:28:09 PM »
"But I presume that you have no idea as to any mechanism behind why there should be any correlation between the edge of the continental shelf and the summer ice edge"

Well, people did not know for a long time the mechanisms behind why some herbs are useful, or eg. why winters are colder than summers. But they realized the pattern and without knowing the exact mechanisms, used these...