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Poll

Volume gap to previous lowest to shrink late in melt season?

No, gap will increase mainly due to albedo effects
9 (19.6%)
Yes, gap will shrink as remaining ice gets harder to melt
15 (32.6%)
No idea or opinion
7 (15.2%)
Gap to stay similar
6 (13%)
No gap will increase mainly for reasons other than albedo
6 (13%)
Other (please explain)
3 (6.5%)

Total Members Voted: 46

Voting closes: June 11, 2017, 02:25:26 PM

Author Topic: Volume gap to previous lowest to shrink late in melt season?  (Read 1353 times)

crandles

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Over on Stoat, I wrote and William Connolley replies shown in [ xxx -W] form:
http://scienceblogs.com/stoat/2017/05/03/economist-farewell-to-the-arctic/

You seemed to believe that tends in area/extent were better than using volume.

[Perhaps that they are more familiar. And certainly they are more strongly observationally based; I know little of PIOMAS or how much I should trust it. Also, its alone: unlike the area / extent, which many centres provide -W]

Is there a test of that with this years low volume at maximum? If it is the volume trend that matters we should expect the 1.8 k km^3 volume below previous lowest to grow over the melt season due to albedo effects. (I.e. thinner ice melts out quicker allowing albedo to fall faster, more heat absorbed by ocean that can melt more ice.) If it is area or extent that shows a more consistent trend as you have seemed to indicate you believe then as we get down to low volumes shouldn’t that volume get harder to melt and so the gap to previous lowest should shrink towards the end of the melt season?

[Yes, that’s kinda what I think. I also think that the volume “matters” less. For the climate, what really matters is the albedo, to first order; which is a function of area, to first order -W]

I am not sure why you believe this and you haven’t seemed able to explain. Perhaps bathymetry effects?

Anyway do you believe the gap to previous lowest volume will shrink towards the end of the melt season. Could there be a bet about this to test the idea?

[Unfortunately I don’t have a strong opinion on that. I think it likely that the gap will shrink, yes. I’d even put money on that, just to formalise things -W]

I suspect I won’t disagree with you enough to bet but maybe others will be interested to see if you propose anything.



This seemed like an important matter to test this season, so hope it is ok to add this poll and we are not having too many.

Feel free to vote and/or add comments. Further reasoning on option 2 particularly welcome eg is it bathymetry effects or ....

Jim Williams

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #1 on: May 12, 2017, 05:32:13 PM »
I voted "No gap will increase mainly for reasons other than albedo," but I did that because I took the question as "albedo this season."  I think that albedo is the major ultimate cause after CO2 in making the Arctic warm faster that everywhere else, but I don't think it a main proximate cause.  Thus, I don't think open water early in the year is all that important in determining the volume late in the season.

jai mitchell

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #2 on: May 12, 2017, 06:42:59 PM »
The expectation of a decreasing gap to low volume toward the end of the melt season is contingent on the previous observation of large volumes of land-fast multi-year ice on the northern Greenland coast. 

Similar to the 'effective ice-free convention' in SIE of < 1M km^2

This multi-year ice no longer exists in the way it was previously understood.

The assumption that later volumes of ice will be harder to melt is no longer supported by conditions in situ nor the physics of the environment.  However, at this stage, there are many larger impacts to projections of minimum volume and extent, through the coming melt period, than albedo.

for example, the early breakup of the Nares bridge. . .
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Richard Rathbone

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #3 on: May 12, 2017, 07:14:32 PM »
Weather May-Sept in 2012 was very favorable to melt, therefore the gap will probably shrink. I might be able to outrun someone average, but that doesn't mean I can stay ahead of Bolt.


Tor Bejnar

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #4 on: May 12, 2017, 07:27:56 PM »
I understand (or imagine the possibility of) forces that will speed melting (e.g., thinner ice means more bottom melt as more light penetrates the ice and heats the top water) and others that will impede melting (snow cover); therefore I've guessed "gap will remain about the same".  Of course, weather is number 1, and we don't know what that will do.
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Juan C. García

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #5 on: May 12, 2017, 07:29:28 PM »
No idea...

I am not sure if the gap will increase or decrease. I just believe that the gap is big enough, so if it shrinks, will not be that much to have it disappear.

Emotionally, on the other hand, I hope it will not increase, because that will take us to an ice-free Arctic.   :-\  But that is just a hope, not based on science.

In fact, I believe that it will depend on weather and it depends on some events that could or could not happen, like if we have a cyclone on early August. At this moment, nobody knows...
« Last Edit: May 12, 2017, 07:52:27 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.

magnamentis

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #6 on: May 12, 2017, 07:34:41 PM »
generally speaking, the less volume we have, the smaller the gap will be, of course with seasonal and year to year variations.

we certainly agree that with a volume of 500 we never can get a gap of 700, just to make sure that there is no misunderstanding as to what i mean.
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oren

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #7 on: May 12, 2017, 11:25:36 PM »
As 2012 was an exceptional melt year, I think there is a higher probability of the gap shrinking than the gap growing, although I still expect a new record low in volume.
If the gap does grow I doubt albedo will be the main reason, as extent and area are high and could remain relatively high for a while due to dispersion and export among other things. But when thin ice is left over large areas, strong storms and GACs could wipe it out.

johnm33

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #8 on: May 13, 2017, 02:36:25 AM »
It could go either way, but I think it will increase. There's so little thick ice against the CAA, and I suspect it could rapidly disappear, when it does, so long as the ice is driven from the coast, wave action will then act all round the pack, if so area and extent will crash, volume too. We may be lucky but the more melt that takes place for other reasons the less ice can build up to block the straits and the less extreme the conditions needed to bring this about.

Paddy

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #9 on: May 17, 2017, 12:06:27 AM »
I was tempted by the "don't know" option, but went for "no change". But there are factors that could drive it either way.

Factors that could drive a shrinking of the gap:
- Good snow cover this year -> Greater albedo on land -> cooler arctic temps
- Big drops came later in the season for the record low year of 2012 that may well narrow or close the gap

Factors that could drive a widening of the gap:
- Albedo feedback
- Thin ice fragility

Overall, I'm favouring either no change or a slight widening gap, but only time will tell.


Hyperion

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #10 on: May 17, 2017, 09:33:26 AM »
All predictions are stabs in the dark. The extremely complex system of geobioatmophysic feedback dynamics we enjoy, is well beyond our current level of scientific understanding. Due to no precedents, for tens of millions of years at least, of such explosively growing greenhouse burden added to cataclysmic biosphere degradation as we have tested this system with, we can expect no less than emphatic and unpleasant rebound behaviour. Though in saying that, I should point out that the chronological period for the response is, from what we do know, anything from days to megayears.
At present however. Large effects are in the house. FE. the meeting of warm salty tropical waters and fresher arctic is no longer a extra arctic basin phenomena. This is now a prime driver of AMOC. as the interface is well established beyond the edge of the continental shelf now, and certainly of far larger and growing length, frictional forces of cooled deep return currents on the shelfs are gone. but  the cooling of high salinity atlantic incoming waters enhanced along the extended front. Creating a subduction sheetcurrent thousands of km long that is only enhanced by extreme weather and other perturbations. And thus we are stuck now with seemingly unavoidable NAD acceleration and consequences for what future is pertinent to the lifespan of the flesh bags we inhabit.
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Archimid

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #11 on: May 24, 2017, 03:26:18 AM »
I voted "No gap will increase mainly for reasons other than albedo", but albedo is important. Specially over land. I think the gap will increase because the remaining ice will be easy to melt, warm air will keep flowing in and I think there is huge potential for export through the garlic press.
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Jim Williams

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #12 on: May 24, 2017, 02:13:30 PM »
I voted "No gap will increase mainly for reasons other than albedo", but albedo is important. Specially over land. I think the gap will increase because the remaining ice will be easy to melt, warm air will keep flowing in and I think there is huge potential for export through the garlic press.

About the only thing I might add to that is that the broken ice is subject to wave action.  (And at some point will become subject to upper ocean mixing -- though I don't know when.)

Paddy

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #13 on: May 24, 2017, 03:03:24 PM »
I voted "No gap will increase mainly for reasons other than albedo", but albedo is important. Specially over land.


On that note, Northern hemisphere snow cover is currently higher than the 10 year average:


FishOutofWater

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Re: Volume gap to previous lowest to shrink late in melt season?
« Reply #14 on: May 24, 2017, 03:36:44 PM »
I think that the CFS v2 model is right and that this summer we will see high pressure over the Pacific side of the Arctic and low pressure on the Atlantic side. This will cause compaction under the high and will enhance ice export towards the Fram. The net effect will be a precipitous decline in extent in June and July if the model verifies. Thus the "volume gap" will decline.

I think the model is getting the large scale subsidence and uplift patterns right because:

1: Persistence. The snow pack is thickest on the Kara sea side of Siberia because the polar vortex has been displaced in that direction for months. After the stratospheric polar vortex collapsed, the 500mb vortex continued to be displaced in that direction.

2: Ocean heat patterns, strong land heating in Alaska and north western Canada, and the enhanced Brewer Dobson circulation favor subsidence over the Beaufort sea where ice converges under the high.

In conclusion I think that we will see a record low September extent based on what's happening in the atmosphere. Of course, this forecast is not high confidence. Long range forecasting is hard if not impossible.