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When will be the first year that daily ice volume per PIOMAS goes below 1000 km^3?

2018
10 (8.5%)
2019-2021
20 (16.9%)
2022-2024
32 (27.1%)
2025-2028
30 (25.4%)
2029-2033
15 (12.7%)
2034-2039
3 (2.5%)
2040-2049
2 (1.7%)
2050-2059
1 (0.8%)
2060 or later
5 (4.2%)

Total Members Voted: 115

Voting closed: May 27, 2018, 05:31:41 PM

Author Topic: First year PIOMAS volume below 1000km^3 poll 2018  (Read 22104 times)

Alexander555

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #50 on: April 03, 2018, 05:07:45 PM »
What would be the impact on the Greenland ice, the moment the Arctic becomes ice-free in summer ?

jdallen

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #51 on: April 03, 2018, 07:52:37 PM »
What would be the impact on the Greenland ice, the moment the Arctic becomes ice-free in summer ?
Mass loss would accelerate. It might be buffered by more snowfall, but the flow of ice itself will accelerate as well.

What *I* think ahead to when considering a summer ice free Arctic, is the storms, like as have not been seen in millions of years.
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gerontocrat

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #52 on: April 05, 2018, 03:54:42 PM »
Gompertz curves, 4 parameter curves, and sound and fury. A couple of years of large decreases and it's "The ice is gone - we are doomed!" and then a couple of large increases and it's " The ice is coming back - the New Ice Age is upon us !"

Me, I am sticking with the Polar Science Center stuff, and I quote :- "March 2018 ice volume sits right on the long term trend line". The trend line is linear, for March -3.1 km3 '000 per decade.

For September, the linear trend is -3.2 km3 '000 per decade, with 4,000 km3 to go to get to 1,000 km3. As was pointed out, the poll is for the daily minimum. Taking that into account, and possible high variation when such a small volume is left, I think I voted for 2028 (biased by wishing to be still extant when it happens).



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Daniel B.

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #53 on: April 05, 2018, 04:30:54 PM »
Yes, high potential variations at low volume will make for difficult predictive capabilities.  A strict linear trend will take the minimum ice below 1000 km3 in 2040.  One or two years of large decrease will accelerate that prediction.  A more Gompertz-like curve could extent its life by decades.  I opted for the 2050s time frame, due to an expected difficulty in melting the ice protected by land.  I seriously doubt that I will be extant at that time.

crandles

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #54 on: April 05, 2018, 08:43:03 PM »
due to an expected difficulty in melting the ice protected by land.

I expect the ice will be pretty thin by the time it gets down to 1000 cubic km, much thinner than 1m average so much more area than million km^2. How much area do you expect to be 'protected by land'? Quite a bit of land warms much faster than ocean so helps melt. Ice covered land probably doesn't warm faster until the ice is gone so perhaps its a bit complicated. Shade from sunlight might help protect, but even with low sun angles, the area isn't very much unless there are huge cliffs. There isn't a million km of coastline.

I could easily be wrong about some aspects but quoted reasoning seems to me to attach too much area and importance to 'ice protected by land'.


Alexander555

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #55 on: April 05, 2018, 09:09:59 PM »
2028 Gerontocrat ? Don't put to much money on that one. Your own grap shows that it's accelerating. In 1996 there was more volume than in 1982. It's only after 1996 that it started to drop fast. And the thinner it gets, the more vulnerable it will become.

crandles

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #56 on: April 05, 2018, 10:24:37 PM »
2028 Gerontocrat ? Don't put to much money on that one. Your own grap shows that it's accelerating. In 1996 there was more volume than in 1982. It's only after 1996 that it started to drop fast. And the thinner it gets, the more vulnerable it will become.

Time to go back to beginning of thread?

Daniel B.

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #57 on: April 05, 2018, 10:37:50 PM »
due to an expected difficulty in melting the ice protected by land.

I expect the ice will be pretty thin by the time it gets down to 1000 cubic km, much thinner than 1m average so much more area than million km^2. How much area do you expect to be 'protected by land'? Quite a bit of land warms much faster than ocean so helps melt. Ice covered land probably doesn't warm faster until the ice is gone so perhaps its a bit complicated. Shade from sunlight might help protect, but even with low sun angles, the area isn't very much unless there are huge cliffs. There isn't a million km of coastline.

I could easily be wrong about some aspects but quoted reasoning seems to me to attach too much area and importance to 'ice protected by land'.

Yes, the land is ice-covered.  The glaciers in Greenland and the Canadian archipelago will not just cool their surroundings, but provide additional glacial ice.

gerontocrat

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #58 on: April 05, 2018, 10:49:03 PM »
Yes, high potential variations at low volume will make for difficult predictive capabilities.  A strict linear trend will take the minimum ice below 1000 km3 in 2040.  One or two years of large decrease will accelerate that prediction.  A more Gompertz-like curve could extent its life by decades.  I opted for the 2050s time frame, due to an expected difficulty in melting the ice protected by land.  I seriously doubt that I will be extant at that time.
Earlier this year A-team did a post to say there is no land fast ice in the Arctic. It is just ice that has been shoved against the land as in north of greenland and the caa.
Lo and behold in February that so-called  land fast ice is shoved north and there is open ocean north of greenland. If that can happen in the dead of winter then in late summer all arctic ice is at the mercy of the vagaries of the weather?
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Daniel B.

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #59 on: April 06, 2018, 05:41:30 PM »
Yes, high potential variations at low volume will make for difficult predictive capabilities.  A strict linear trend will take the minimum ice below 1000 km3 in 2040.  One or two years of large decrease will accelerate that prediction.  A more Gompertz-like curve could extent its life by decades.  I opted for the 2050s time frame, due to an expected difficulty in melting the ice protected by land.  I seriously doubt that I will be extant at that time.
Earlier this year A-team did a post to say there is no land fast ice in the Arctic. It is just ice that has been shoved against the land as in north of greenland and the caa.
Lo and behold in February that so-called  land fast ice is shoved north and there is open ocean north of greenland. If that can happen in the dead of winter then in late summer all arctic ice is at the mercy of the vagaries of the weather?

I cannot say that I agree with his assessment, and am attaching some recent publications on the landfast ice.

https://www.the-cryosphere.net/10/1463/2016/tc-10-1463-2016.pdf

https://www.the-cryosphere.net/10/1463/2016/tc-10-1463-2016.pdf

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014JC010353

jdallen

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #60 on: April 06, 2018, 06:34:10 PM »
If your definition of land fast ice is nonmobile ice anchored to land right now, you may be correct. However if you deine land fast ice as it was, multi year, more than 3M thick, A-Team's assessment is the more accurate one.
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Daniel B.

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #61 on: April 06, 2018, 06:39:14 PM »
If your definition of land fast ice is nonmobile ice anchored to land right now, you may be correct. However if you deine land fast ice as it was, multi year, more than 3M thick, A-Team's assessment is the more accurate one.

Since most of the ice is ~2m thickness, we may be using different metrics.

jdallen

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #62 on: April 06, 2018, 07:05:50 PM »
If your definition of land fast ice is nonmobile ice anchored to land right now, you may be correct. However if you deine land fast ice as it was, multi year, more than 3M thick, A-Team's assessment is the more accurate one.

Since most of the ice is ~2m thickness, we may be using different metrics.
... which speaks exactly to my point, as it is the older, in some cases thousands of years old land fast ice in places like the Lincoln sea and along the CAA which i think of when I say land fast ice.  It no longer exists.
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Sebastian Jones

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #63 on: April 06, 2018, 09:24:01 PM »
If your definition of land fast ice is nonmobile ice anchored to land right now, you may be correct. However if you deine land fast ice as it was, multi year, more than 3M thick, A-Team's assessment is the more accurate one.

Since most of the ice is ~2m thickness, we may be using different metrics.
... which speaks exactly to my point, as it is the older, in some cases thousands of years old land fast ice in places like the Lincoln sea and along the CAA which i think of when I say land fast ice.  It no longer exists.
Perhaps the confusion arises from terminology: The ice SHELVES of the arctic are indeed gone, land fast ice forms every year, and usually melts out each summer.

Tor Bejnar

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #64 on: April 06, 2018, 09:31:15 PM »
Not quite:
https://en.wikipedia.org/wiki/Ice_shelf#Canadian_ice_shelves
Quote
All Canadian ice shelves are attached to Ellesmere Island and lie north of 82°N. Ice shelves that are still in existence are the
  • Alfred Ernest Ice Shelf
  • Milne Ice Shelf
  • Ward Hunt Ice Shelf and
  • Smith Ice Shelf.
The M'Clintock Ice Shelf broke up from 1963 to 1966; the Ayles Ice Shelf broke up in 2005; and the Markham Ice Shelf broke up in 2008.
[formatting altered]
But yes, gone (apparently) from Russia:
Quote
The Matusevich Ice Shelf was a 222 km² ice shelf located in Severnaya Zemlya being fed by some of the largest ice caps on October Revolution Island, the Karpinsky Ice Cap to the south and the Rusanov Ice Cap to the north.[9] In 2012 it ceased to exist.[10]
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Sebastian Jones

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #65 on: April 06, 2018, 09:47:24 PM »
Not quite:
https://en.wikipedia.org/wiki/Ice_shelf#Canadian_ice_shelves
Quote
All Canadian ice shelves are attached to Ellesmere Island and lie north of 82°N. Ice shelves that are still in existence are the
  • Alfred Ernest Ice Shelf
  • Milne Ice Shelf
  • Ward Hunt Ice Shelf and
  • Smith Ice Shelf.
The M'Clintock Ice Shelf broke up from 1963 to 1966; the Ayles Ice Shelf broke up in 2005; and the Markham Ice Shelf broke up in 2008.
[formatting altered]
But yes, gone (apparently) from Russia:
Quote
The Matusevich Ice Shelf was a 222 km² ice shelf located in Severnaya Zemlya being fed by some of the largest ice caps on October Revolution Island, the Karpinsky Ice Cap to the south and the Rusanov Ice Cap to the north.[9] In 2012 it ceased to exist.[10]
Thanks for the correction. I was under the impression that they had disintegrated, e.g.:
Quote
The Ward Hunt ice sheet began breaking up approximately 100 years ago, but was believed to have stabilized by the early 1980s. However, in April 2000, satellite images revealed that a large crack in the ice had begun to form, and in 2003, it was announced that the ice sheet had split completely in two in 2002, releasing a huge pool of fresh water from the largest epishelf lake in the Northern Hemisphere, located in Disraeli Fjord.[3] In April 2008, it was discovered that the shelf was fractured into dozens of deep, multi-faceted cracks.[4] In late July 2008, it was announced that nearly 8 square miles (21 km2) broke away from the shelf.[1] In August 2010, another 50 km² (19 sq mi) calved off from the northeast quarter of the ice shelf.[5]
https://en.wikipedia.org/wiki/Ward_Hunt_Ice_Shelf
All of which, upon closer read, indicates the shelves remain, albeit much reduced. Which explains why Jill Heinurth is heading there this summer to dive in the ice shelf ice caves. :-[

gerontocrat

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #66 on: April 06, 2018, 10:17:04 PM »
Would I be right in thinking that the ice shelf remnants that remain amount to less than 1,000 km3. I ask as there is a view that ice protected by land could delay volume getting below the poll figure.
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jdallen

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #67 on: April 06, 2018, 10:45:30 PM »
Would I be rig3ht in thinking that the ice shelf remnants that remain amount to less than 1,000 km3. I ask as there is a view that ice protected by land could delay volume getting below the poll figure.
The volume of those shelf remnants is 10s of KM3, certainly not thousands, and their total area trivial compared to total Arctic ice extent and area.
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binntho

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #68 on: April 07, 2018, 07:47:32 AM »
Earlier this year A-team did a post to say there is no land fast ice in the Arctic. It is just ice that has been shoved against the land as in north of greenland and the caa. ...

I cannot say that I agree with his assessment, and am attaching some recent publications on the landfast ice.

https://www.the-cryosphere.net/10/1463/2016/tc-10-1463-2016.pdf

https://www.the-cryosphere.net/10/1463/2016/tc-10-1463-2016.pdf

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014JC010353
One of the least instructive and constructive postings I've seen for a long time. Links to two publications (not three) that have nothing to do with what A-Team said! No attempt to justify your position, no data, no insights. Obfuscationism in its purest form.
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Alexander555

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #69 on: April 07, 2018, 08:44:00 AM »
Maybe that's because there is much at risk. The lives of hundreds of millions of people can be fliped over in a very short periode, trillions of real-estate at risk, stockmarkets at risk, the entire global economy is at risk. And it is hard to calculate effects of everything. But what we do know for sure is that arctic winter volume is something like 20 000 km3 of ice ,and summer volume in 1980 was something like 16500 km3 of ice. The winter maximum we have today is only a little bit higher than the summer minimum from less than 40 years ago. And that is the result  from only a small change (for some) in temperature.

Daniel B.

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #70 on: April 07, 2018, 01:52:22 PM »
Earlier this year A-team did a post to say there is no land fast ice in the Arctic. It is just ice that has been shoved against the land as in north of greenland and the caa. ...

I cannot say that I agree with his assessment, and am attaching some recent publications on the landfast ice.

https://www.the-cryosphere.net/10/1463/2016/tc-10-1463-2016.pdf

https://www.the-cryosphere.net/10/1463/2016/tc-10-1463-2016.pdf

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014JC010353
One of the least instructive and constructive postings I've seen for a long time. Links to two publications (not three) that have nothing to do with what A-Team said! No attempt to justify your position, no data, no insights. Obfuscationism in its purest form.

That was because when I went to post, I was kicked off.  Going back, I must’ve inadvertently copied one link twice.  However to call it obfuscation when they are conducting research on something a previous claims does not exist, seems rather odd.

binntho

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #71 on: April 09, 2018, 08:23:39 AM »
Earlier this year A-team did a post to say there is no land fast ice in the Arctic. It is just ice that has been shoved against the land as in north of greenland and the caa. ...

I cannot say that I agree with his assessment, and am attaching some recent publications on the landfast ice.

https://www.the-cryosphere.net/10/1463/2016/tc-10-1463-2016.pdf

https://www.the-cryosphere.net/10/1463/2016/tc-10-1463-2016.pdf

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014JC010353
One of the least instructive and constructive postings I've seen for a long time. Links to two publications (not three) that have nothing to do with what A-Team said! No attempt to justify your position, no data, no insights. Obfuscationism in its purest form.

That was because when I went to post, I was kicked off.  Going back, I must’ve inadvertently copied one link twice.  However to call it obfuscation when they are conducting research on something a previous claims does not exist, seems rather odd.
I wonder if you are aware of what A-Team's "assessment" was to begin with. He never claimed that land-fast ice (as described in your links) did not exist. It obviously does, as everyone can see. But the point he made (as I understand it) was that when the CAB ice goes below e.g. 1 million square kilometers, this "land-fast" ice would not exist any more, i.e. it would simply float away.

This applies in particular to the thick land-fast ice along the coast of northern Greenland and the Arctic Archipelago - it is not grounded or made "fast" to the land in any sense, but held in place by the push of ice movement in the CAB. As we saw this winter, the land-fast ice along the northern Greenland coast wasn't - in accordance with what A-Team said - and simply floated away.

This is an important point to make when a future with much less ice is considered. Will the remaining 1 million km2 (presumably the oldest and thickest ice) stay where it is or float away into warmer waters? We may well see, when sea ice falls below a certain threshold in some future summer's melting, that the entire pack starts breaking up and floating freely, speeding the melt of the remaining bits and pieces.

So back to my critique: Your post showed that you did not know what the "assessment" was that you were objecting to, nor how your two randomly found papers that mentioned "arctic land-fast ice" could have any bearing on the discussion. With no input what so ever from yourself, I am still inclined to view this as obfuscation.
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Daniel B.

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #72 on: April 10, 2018, 05:05:44 PM »
Earlier this year A-team did a post to say there is no land fast ice in the Arctic. It is just ice that has been shoved against the land as in north of greenland and the caa. ...

I cannot say that I agree with his assessment, and am attaching some recent publications on the landfast ice.

https://www.the-cryosphere.net/10/1463/2016/tc-10-1463-2016.pdf

https://www.the-cryosphere.net/10/1463/2016/tc-10-1463-2016.pdf

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014JC010353
One of the least instructive and constructive postings I've seen for a long time. Links to two publications (not three) that have nothing to do with what A-Team said! No attempt to justify your position, no data, no insights. Obfuscationism in its purest form.

That was because when I went to post, I was kicked off.  Going back, I must’ve inadvertently copied one link twice.  However to call it obfuscation when they are conducting research on something a previous claims does not exist, seems rather odd.
I wonder if you are aware of what A-Team's "assessment" was to begin with. He never claimed that land-fast ice (as described in your links) did not exist. It obviously does, as everyone can see. But the point he made (as I understand it) was that when the CAB ice goes below e.g. 1 million square kilometers, this "land-fast" ice would not exist any more, i.e. it would simply float away.

This applies in particular to the thick land-fast ice along the coast of northern Greenland and the Arctic Archipelago - it is not grounded or made "fast" to the land in any sense, but held in place by the push of ice movement in the CAB. As we saw this winter, the land-fast ice along the northern Greenland coast wasn't - in accordance with what A-Team said - and simply floated away.

This is an important point to make when a future with much less ice is considered. Will the remaining 1 million km2 (presumably the oldest and thickest ice) stay where it is or float away into warmer waters? We may well see, when sea ice falls below a certain threshold in some future summer's melting, that the entire pack starts breaking up and floating freely, speeding the melt of the remaining bits and pieces.

So back to my critique: Your post showed that you did not know what the "assessment" was that you were objecting to, nor how your two randomly found papers that mentioned "arctic land-fast ice" could have any bearing on the discussion. With no input what so ever from yourself, I am still inclined to view this as obfuscation.

The third (non-random) link, which was omitted due to the previously mentioned kick off, describes the stability of the landfast ice in the CA.

http://www.mdpi.com/2072-4292/10/1/37

The MYI landfast ice (which does not simply float away) has a median thickness of 2.7m, which is below the criteria A-team selectively chose for his definition.  This ice maintains a higher depth of snow cover during the winter, and forms fewer melt ponds during the summer.  Their study emphasizes the differences between the FYI and MYI, and that the landfast MYI is not simply "ice that has been shoved against the land."

gerontocrat

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #73 on: April 10, 2018, 05:12:09 PM »
Any data on extent and or km3 on how much of this genuinely landfast myi is still extant? If > 1000km3 then a significant parameter in guessing when the poll date happens.
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Daniel B.

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #74 on: April 10, 2018, 05:31:57 PM »
Any data on extent and or km3 on how much of this genuinely landfast myi is still extant? If > 1000km3 then a significant parameter in guessing when the poll date happens.

I have not seen any data on this.  Possibly because of the difficulty in distinguishing between landfast and floating ice.  The landfast ice is thicker, so less area is necessary to reach 1000km3.


oren

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #75 on: April 11, 2018, 04:21:49 AM »
Quote
2.1. Study Area
... collected in Victoria Strait region of the CAA during April and June 2015. Victoria Strait is part of the Northwest Passage in the CAA, which typically contains a mixture of FYI and MYI. The sea ice in the CAA is not strongly affected by wind driven movement because the ice is landfast for six to eight months of the year. Furthermore, wind driven movement of sea ice is restricted by the narrow channels that dominate the CAA [22]. During the melt season, MYI drifts into and subsequently through the CAA from the central Arctic during late summer and early fall and becomes locked in place by FYI that forms in the fall and early winter [23]. This makes for an ideal study area for understanding the evolution of sea ice from winter to summer conditions, without the need for tracking mobile ice.
DB you are confusing (again?) between actual landfast ice - ice that sticks to land during the summer, and therefore could be protected from melt-out and not be exported even in a bad year - and wintertime landfast ice, a transient phenomenon that has no bearing on the first year PIOMAS volume goes below 1000 km3.
Actual landfast ice used to exist in quantity off the coast of Ellesmere. Currently there is such ice (almost) only adjacent to Greenland, and even there it barely manages to stick around, as we see every melting season.

binntho

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #76 on: April 11, 2018, 08:29:02 AM »
Daniel, you seem to confuse resilience with "fastness" - all the ice under discussion here floats, as can be seen quite easily on satellite images. It floats back and forth, it moves away from the shore and back again.

It's a bit tricky finding clear weather in the images from last summer but the "fast" ice north of Ellesmere Island can be seen in this image from September 15th 2017. The strait between Ellesmere and Axel Heiberg is appr. 30 km wide.

Although not really visible on this image, the above mentioned strait has a static plug of 50 km, below which are floes drifting south. The area between Meighen Island and Ellef + Amund is mostly freefloating ice, but there is landfast ice between Meighen and Axel Heiberg. Other than that there is landfast ice in the inlets and fjords.

The supposedly "landfast" ice north of Ellesmere and Greenland moves quite freely every summer (and even, as recently seen, during the middle of the winter) in total accordance with A-Teams assertion that this "landfast" ice will drift wherever it will when the area to the north is ice-free at some point in the future.
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Daniel B.

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #77 on: April 11, 2018, 02:17:23 PM »
Of course all the ice floats, that is a physical property of the ice.  The contention that it disconnects from the shore, floats out and back again, is unsupported.  Granted I could be wrong about this.  However, I have seen no evidence of this occurring with the MYI, as opposed to FYI.  Many supposed images of these occurrences, are simply melt ponds, which give the appearance of ice separation.  The landfast ice is quite thick (even that which is less than the 3m criteria for A Team's contentions), such that it will not release and reattach so easily.  Yes, from time to time, some of the ice plug break off due to compelling forces, giving the appearance of less fastness.  These are stress releases, which are completely normal, albeit more frequent as the Arctic warms.  Don't get me wrong.  I am not saying that the landfast ice is not in decline.  Rather, it will take much longer to melt this ice, than the floating FYI, in contrast to those claiming that it will disintegrate as the FYI declines.

sedziobs

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #78 on: April 11, 2018, 04:54:59 PM »
The contention that it disconnects from the shore, floats out and back again, is unsupported.  Granted I could be wrong about this.  However, I have seen no evidence of this occurring with the MYI, as opposed to FYI.  Many supposed images of these occurrences, are simply melt ponds, which give the appearance of ice separation.
Other than the small proper ice shelves occupying fjords and inlets, all of the sea ice disconnects from shore.  See uniquorn's recent gif for evidence of that.  In Dec 2017 the ice north of the CAA detached, so certainly not melt ponds then.

Edit: I should note that the below image is older (probably 20th century). Most of the shelves are now gone, with the exception of Ward Hunt and Milne.

« Last Edit: April 11, 2018, 05:46:14 PM by sedziobs »

Daniel B.

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #79 on: April 11, 2018, 08:13:32 PM »
That does merit a re-evaluation of my conclusions.

binntho

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #80 on: April 12, 2018, 08:22:17 AM »
I thought the satellite image in my last post showed this clearly, but for a newcomer this might not bee as apparent, what with clouds and everything. Individual meltponds cannot normally be seen in satellite images, but when they are present they give a light blue sheen to the whiteness of the ice.

Open water appears as very dark blue, and the cracks visible in my last posting have a width in the order of kilometers (each pixel is several hundred meters wide, so for a crack to be visible as a hairline it has to be at least that wide).

Perhaps a nice animation will help you understand this better. It has half the resolution of my last posting, but covers 15 days at the end of spring last year. Ellesmere is on the lower right.

Also take a look at Worldview, very useful if you want to follow the discussions here. (https://worldview.earthdata.nasa.gov/)

PS - gif may need a click to animate.
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binntho

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #81 on: April 12, 2018, 08:29:54 AM »
If I remember correctly, what triggered A-Teams original musings on landfast ice were the predictions of an ice-free arctic that assumed that some one million square kilometers would still be left as landfast ice hugging the shores of the Arcic Archipelago. This is where ice is normally thickest, with lots of MYI, so it would be reasonable to assume that this would be the last to go.

But A-Team's point (as I understood it) was that if there was only one million km2 of ice left, the "landfast" ice would break up into floes and drift away from the shore into open waters where it would melt quite quickly. Accordingly one could assume that if ice cover went below a certain minimum for at least a few weeks, it would simply all melt out quite quickly, including the thick, hitherto resilient, "landfast" ice along the Arctic Archipelago.
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binntho

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #82 on: April 12, 2018, 08:30:13 AM »
So am I a citizen yet?  8)
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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #83 on: April 12, 2018, 10:13:25 AM »
In the end, I still stick with my plumping for a day in 2028 when volume is less than 1000km3 , caused by ice volume loss for a few years more or less in line with the PIOMAS linear projection and a sort of collapse as volume gets close to 1,000? 1,500? 2,000? km3.

If there are any remnants of ice-shelves and genuinely land-fast ice left, I also assume the amount will not be enough to signify for this poll.

Now, all I've got to do is wait for n years, where n is, as yet, unknown.
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Daniel B.

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #84 on: April 12, 2018, 01:59:00 PM »
Based on a linear rate of volume loss, 2028 will still require accelerated ice loss.  I still believe that the deceleration over the past decade is real and not a random artifact in the data, and largely due to the previous ice being overly exposed to the warmer waters.  Therefore, I am sticking with my original prognosis of 30+ years. 

binntho

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #85 on: April 12, 2018, 06:03:30 PM »
Based on a linear rate of volume loss, 2028 will still require accelerated ice loss.  I still believe that the deceleration over the past decade is real and not a random artifact in the data, and largely due to the previous ice being overly exposed to the warmer waters.  Therefore, I am sticking with my original prognosis of 30+ years.
Using Excel's linear trend line and extending it downwards in Paint I got the following graph. Following the trend, 0 volume would be reached in 2032 and 1 million km3 in 2029. So 2028 is perhaps stretching it a bit ... but given the above discussion, perhaps we should be seeing a sudden acceleration at some point, so if the decline were to follow the linear trend more or less, one summer (perhaps 2018?) we would see a collapse of the volume, to way below 1 million km3.

The "deceleration" in the last decade looks like an artifact created by the three very low years 2010, 2011 and 2012 - and 10 data points out of 38 is far too few to tell if there has been a statistically valid change in trend. Using just the ten last years and extrapolating the trend line results in zero volume in 2047.

I've never before seen anybody state that the ice before 2007 was "overly exposed to warm waters" ... do you have any data to support this novel claim?

Personally I would guess that volume loss might accelerate at some point in the near future but I might be totally wrong.
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Daniel B.

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #86 on: April 12, 2018, 07:35:58 PM »
I have been using the minimum volume, but I suspect that is not much difference from the September average.  In either case, it comes down to whether you feel that the higher volume loss in the first decade of this century or the slower volume loss since will predominate. 


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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #87 on: April 12, 2018, 08:02:55 PM »
I have been using the minimum volume, but I suspect that is not much difference from the September average.  In either case, it comes down to whether you feel that the higher volume loss in the first decade of this century or the slower volume loss since will predominate. 


We are at low enough volume that the volatility matters.  Even with an anemic melt this season volume will likely dip under 5000KM3 again.  A more serious melt could take us under 3000, which will border on catastrophic, as it would suggest all but a very limited extent along the CAA  and isolated bergs will be gone. This would have very dramatic consequences for northern hemisphere weather.
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crandles

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #88 on: April 12, 2018, 08:46:46 PM »

The "deceleration" in the last decade looks like an artifact created by the three very low years 2010, 2011 and 2012 - and 10 data points out of 38 is far too few to tell if there has been a statistically valid change in trend. Using just the ten last years and extrapolating the trend line results in zero volume in 2047.

The gompertz fit puts the point of inflection between 2005 and 2006 whether using April or September volume data. There are 11 years data after 2006.

Statistically valid change in trend? Well I would trust Tamino on this. For extent
see for example https://tamino.wordpress.com/2017/11/01/arctic-sea-ice-4/

I think the pattern shows up more clearly in the volume data than in extent.

binntho

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #89 on: April 12, 2018, 09:13:22 PM »

The "deceleration" in the last decade looks like an artifact created by the three very low years 2010, 2011 and 2012 - and 10 data points out of 38 is far too few to tell if there has been a statistically valid change in trend. Using just the ten last years and extrapolating the trend line results in zero volume in 2047.

The gompertz fit puts the point of inflection between 2005 and 2006 whether using April or September volume data. There are 11 years data after 2006.

Statistically valid change in trend? Well I would trust Tamino on this. For extent
see for example https://tamino.wordpress.com/2017/11/01/arctic-sea-ice-4/

I think the pattern shows up more clearly in the volume data than in extent.
Well Tamino is the guy, and I made a donation at his site earlier today hoping he would somehow divine my wish that he would work this out. So Tamino, if you are reading this, pretty please ...

But as for your link, there is a very large problem with it: It is about extent, not volume. Another minor problem: Tamino does not directly address whether the change in the smoothed trendline is statistically significant or not. I myself am not qualified to tell whether a "Gompertz inflection point" is statistically significant or not, but given the paucity of data in my earlier graph, and the magnitude of noise, I'd be extremely surprised if there were any statistically significant changes in the trend.
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Urbanus Simpliticus

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #90 on: April 12, 2018, 09:50:19 PM »
Well, I've been lurking on the periphery way too long so I'm a gonna wade in on this with bare feet.
My interpretation of the single ice cube 10 Km high limit is that given the dynamic equilibrium between land fast ice and open ocean ice, the endpoint of absolute zero floating Ice is unachievable.
(As long as there are still conditions that have most of glacier ice intact )
And I'm not going to fact check myself or revisit definitions at this point.
Therefore an amount of ice that is 1 meter thick and has an area of a million kilometers has to be the arbitrary endpoint of floating ice, since it's physical origin is irrelevant, within the narrow focus of what matters. What matters is that is the crashing of the Arctic is definable when there is an insignificant amount of floating ice versus open water.
And "insignificant" has to be some arbitrary value that is not zero, because that is the physical reality of approaching the limit from the direction of "ice is still present". And freshwater melt and calving and other contribution from land and natural processes of the cycle.
If it were that sea ice was an isolated system, than "zero" could be zero. 
As it is, a tenth of normal coverage or a Fourteenth of total available area are a fair threshold for a "no ice" definition. 

binntho

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #91 on: April 13, 2018, 08:27:36 AM »
I'm not sure what you mean by "dynamic equilibrium" between landfast ice and open ocean ice. The landfast ice under discussion here is floating in the open ocean - it is sea ice that abuts land.

There are other areas of landfast ice in the arctic that are not in the open ocean - all the inlets and fjords, the straits and sounds in the Canadian Arctic Archipelago contain a fair bit of landfast ice, but a very large proportion of this melts out each summer, leaving some 0,1 million km2 (a significant part of which are free-floating floes in the various straits).

The only source of arctic sea ice is frozen ocean water. There may be tiny bits of calved glacier floes to the north of Greenland, but nothing that makes any difference. So all the ice has the same origin, i.e. the ocean surface freezes in winter.

Last summer, the Arctic Ocean was still more than 50% covered in ice at minimum, even 2012 barely reached 60% open ocean in a short dip, recovering quickly. Open ocean  soaks solar energy while the sun shines, and wind driven waves stir up the warmer underlying waters. The more open ocean there is (and for longer periods) the more heat will be absorbed from the sun, more and bigger waves will batter the ice and bring up warmer waters, and the tendrils of warm surface waters from the Atlantic may well seek to go further north (as they have apparently been doing as the ice retreats).

But the remaining 4 million km2 or so make their own barrier of size - the warm seas can't reach them, waves batter the periphery and any warm air intrusions quickly cool down. And being also the thickest part of the ice, solar melt does not suffice to melt it out.

So if there is a "dynamic balance" it is one between extent on the one hand and waves and weather on the other. And as extent diminishes, the weather seems to be getting worse, with more warm air intrusions, bigger waves and, of course, more heat absorbed from the sun. A smaller extent will have proportionally more ice facing the open ocean, and weather systems will have an easier time of bringing warm air across.

So I see no reason what there should be any sort of natural barrier to the trend - at some point almost all the ice will disappear, and the end will probably be quick.
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Daniel B.

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #92 on: April 13, 2018, 04:54:11 PM »
Many posters have discussed whether volume or extent is the best measure of the sea ice.  In reality, there both are, as long as one recognizing their connection.  As stated previously, a liner fit for both would have volume reaching zero much before extent, which is an impossibility.  Others have pushed for a gompertz fit to the volumetric data.  This would nearly correspond to a linear decrease in extent, particularly going forward.

Individual data points appear to support this, as in 2007, extent fell below 70%, while volume plunged below 50%, and extent fell below 50% briefly in 2012, as volume fell below 25%.  A gompertz fit for volume and linear fit for extent would be the best current match for the observed data.  Indeed mathematics and physics suggests that extent would be the better measure, as the ice melts 2-dimensionally (mostly).  The third dimension (thickness) is six orders of magnitude less than either of the other two, reducing its effect on the total.  The ice melts mostly from above (solar) and below (water), with minimal side effects.  The third dimension has influenced the melt in the past through wave action (namely the infamous 2012 summer storm), but this effect has been the anomaly, not the norm.

Archimid

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #93 on: April 13, 2018, 11:28:43 PM »
  As stated previously, a liner fit for both would have volume reaching zero much before extent, which is an impossibility. 

Why do you say it is an impossibility? If volume goes to zero while extent is still relatively large it will look like a poof from a satellite perspective.



This gif from the 2016 Melting Season thread illustrate how that last poof might look like. During September of the melting season most volume loss is in the from of bottom melt. If a state like the one in the image is reached in early to mid August then the ice will keep melting from below until it all the summer energy is spent or the ice is gone. That will probably look like a series of poofs.

Quote
  Indeed mathematics and physics suggests that extent would be the better measure, as the ice melts 2-dimensionally (mostly).
 

Sea ice does not melt in 2 dimensions at all. Ice melting or freezing is a function of mass, volume and temperature.

Quote
The third dimension (thickness) is six orders of magnitude less than either of the other two, reducing its effect on the total.

Volume is not just the third dimension. Volume contains all the information of area plus the information for a third dimension.

Quote
The ice melts mostly from above (solar) and below (water), with minimal side effects.

And both the melt and freezing, both from above and below have to interact with the entire thickness of the ice to produce melt or freeze from above or below.

Quote
The third dimension has influenced the melt in the past through wave action (namely the infamous 2012 summer storm), but this effect has been the anomaly, not the norm.

Ice grows mostly from below, that means that heat must flow through the entire thickness of the ice to form ice. The thicker the ice is, the slower it melt or freezes. The thinner it is the faster it melts or freezes.

Volume contains all the information area has plus all the information for thickness.

Ice is literally some volume of water at freezing temperature.

Thickness plays a vital role in ice formation.

Area and extent have very important uses, and without them volume wouldn't have meaning but to determine the future of ice in the Arctic volume is a much better metric.
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CameraMan

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #94 on: April 14, 2018, 12:37:21 AM »
Ah, the hazy crystal ball.   Following trends, I'd guess late 20s to mid 30s, but temps have been rising, and broken up ice is easier to melt, so I'm going with 22-24.  Of course a couple seasons of unusual weather could toss that in either direction.

binntho

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #95 on: April 14, 2018, 07:17:53 AM »
There is no mathematical impossibility in volume decreasing faster than extent. But of course it would be impossible for there to be extent without volume. Whatever metric reaches zero first pulls the other down with it.

Extent or volume - which is more important? Well, extent is what we see directly, it's extent that affects the weather and the flow of heat from the ocean. But a decrease in volume is the hidden danger lurking underneath the surface. Volume has been decreasing faster than extent which means that the ice is getting thinner. And as Archimid points out, once the ice is thin enough, normal summer melt will easily destroy it.

So volume is the key to an eventual ice-free summer. Winter freezing will continue to cover the entire Arctic Ocean with ice, and peripheral areas that always melt out may well see more ice as cold air is repeatedly pushed out of the Arctic as has been happening this winter.

But the thickness of the ice will be less, mainly due to warmer winter air over the Arctic and warmer underlying waters. And once summer melt gets going, the thin ice may well disappear with a "poof" over a few weeks given the right weather.

And such a precipitous meltout may alter the Arctic permanently - a sudden vast increase in open ocean, with wind, waves and other turbulence, may well delay refreeze significantly, leading to almost inevitable meltout the following summer.

But that's just my guess - let's wait and see, I don't think we will have to wait for that many years to find out - but then again I may be totally wrong!
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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #96 on: April 14, 2018, 02:44:18 PM »
No, it is not an impossibility for volume to decrease faster than extent.  Rather it is a mathematical certainty, unless thickness somehow remains unchanged.  They both cannot decrease linearly.  Hence, a linear loss in extent (or area) will result in much faster volumetric losses, which taper to zero to coincide with the two dimensional losses.  Volume will not hit zero first, and “pull” extent down with it.  This is not physically possible.  Since melt is mainly two dimensional, extent seems to be the logical metric.  With the exception of MYI, the thickness has much less relevance that you claim.  The second cm is no easier to melt than the first, and so on.  The only exception is when the ice becomes so thin, that the smallest forces break the connection.  But that is just a change of a day or so. 

The sea ice is not an ice cube in water, where melting occurs from all sides, as someone falsely referenced earlier.  It is a long sheet, more or less, which melts from above and below.  Mathematically, either extent losses accelerate to catch up with volume, or volumetric losses must decelerate to match extent.  Physics points to volumetric deceleration.

binntho

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #97 on: April 14, 2018, 04:04:14 PM »
Daniel, you seem to be confusing some things. At the moment, both volume and extent may well be decreasing linearly and at different rates - nothing wrong with that. The thickness of the ice is changing which is saying the same thing in a different way.

Of course, both metrics will have to reach zero at the same time (since you can't have one without the other), so if e.g. volume decreases linearly and at a faster rate than extent, and continues to do so until it reaches zero, then at some point extent will have to decrease faster and thus deviate from any earlier linear trend. Because both have to reach zero at the same time.

Other scenarios are of course possible - volume decrease may flatten out to match extent, or both may change their trends. But one thing is absolutely certain: If one metric reaches zero, the other will by necessity reach zero at the same time.

As you have pointed our repeatedly, melting is primarily from above and below. Once melt starts, 1 meter thick ice will lose volume at the same rate as 2 m thick ice.

Each winter, ice in the Arctic reaches very similar extent, constrained by geography - the Arctic Ocean simply freezes over, with small exceptions. So each melting season starts with similar extent, but since volume is going down, the average thickness is less each year.

Average thickness at maximum has been going down from some 2.6 meters in the 80's to around 1.7 meters the last few years (from eyeballing the graphs - not a scientific number!), a drop of some 35%.  Extent at max has gone down from some 15.5 million km2 in the 80's to just under 14 now, a drop of 10%. So thickness at max is going down some three times faster than extent at max.

Each year the thickness drops some 0.9 meters between max and min, and this has not really changed during the last 40 years. If we take this to mean that a given thickness of ice loses 0.9 meters during melt season, any ice thicker than that should survive the summer, the rest melts out (again the 0.9 figure is from eyeballing the graph - some years, e.g. 2017 lost only 0.7 meters, admittedly from a very low start, while 2012 lost 0.9 meters in a record-breaking year).

So thickness at max (and hence volume at max) seems to be the important variable here - extent is more or less the same each winter, and the rate of loss of thickness is the same as well. So extent at minimum is perhaps driven mostly by thickness at maximum?

It's interesting to note that the decline in extent at minimum is 45% (from 7.2 in the 80's to some 4 million km2 now) which seems to coincide surprisingly well between a 10% fall en extent at max + 35% fall in thickness at max.

But this is only playing around with numbers. My gut feeling is the same as has been expressed by others here - as thickness keeps going down, a rapid melt year could simply make it all more or less vanish. So both metrics at minimum, volume and extent, will deviate sharply downwards form any linear trend, getting damn close to zero (and well below 1million km2 or 1000 km3 in one big leap). But given a linear trend in thickness decline, it may well take another 20 years before thickness is below 1 meter on average at max.
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Archimid

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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #98 on: April 14, 2018, 06:31:50 PM »
Volume will not hit zero first, and “pull” extent down with it.  This is not physically possible.

Why not? That makes no sense. If top and bottom melt makes up most of the melt, then the ice will poof out of existence when it is thin enough, regardless of how large the area is. In fact the physics clearly indicate that if the ice get's too thin, too early, area will be reduced almost instantly.

Quote
Since melt is mainly two dimensional, extent seems to be the logical metric.
 

Melt is not mainly 2 dimensional. Melt is not at all 2 dimensional. Melt is literally 3 dimensional. Area reduction of sea ice is called melt because it is a good indicator of melt from the periphery, but it doesn't represent the physical process of melt at all.

Quote
With the exception of MYI, the thickness has much less relevance that you claim.  The second cm is no easier to melt than the first, and so on.


The thinner the ice the faster it melts.

Quote
Mathematically, either extent losses accelerate to catch up with volume, or volumetric losses must decelerate to match extent.  Physics points to volumetric deceleration.

Mathematically, that is nonsense. In terms of physics, as the ice approaches the north pole it  receives less insolation, making it harder to melt. That leads to slowdown in melt apparent volume lost because most of the easy ice has already melted. This may be confusing you into thinking that volume loses will stop increasing. However there is no physical reason for volume losses to stop increasing. You are using the same fallacy as "no warming since 1998".
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Re: First year PIOMAS volume below 1000km^3 poll 2018
« Reply #99 on: April 14, 2018, 06:35:32 PM »
Quote
As you have pointed our repeatedly, melting is primarily from above and below. Once melt starts, 1 meter thick ice will lose volume at the same rate as 2 m thick ice.
I don't think this is exactly true.  I'm no expert, but I recall reading on these threads that sunlight penetrating the ice helps with bottom melt.  I expect this bottom-melt assist increases with decreased ice thickness.  In addition, ice temperature is a significant factor in ice melt, and thinner ice will probably, during the melt season, be warmer on average than thicker ice.  (If melt is occurring at top and bottom, then the coldest ice will be in the middle, and if there is less 'middle' ...)

I appreciate folks posting statistics about Arctic ice thickness/volume/extent/area and drawing projections from them.  I'd much rather see statistics about the CAB.  I do not believe the ice-loss experience (rate of loss) of marginal seas will replicate in the CAB: shorter summer (CAB ice thickens into late May or early June, I understand) and more protected from boundary issues (marginal seas melt edge [waves, warmed water] long predate most CAB melt edges).
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