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Tigertown

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Re: The 2017 melting season
« Reply #1350 on: May 19, 2017, 01:16:36 AM »
Interesting observation Jai.  Does anyone have thoughts on the significance?
I'd say Jai made some major points there. ;)
« Last Edit: May 19, 2017, 03:27:29 AM by Tigertown »

subgeometer

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Re: The 2017 melting season
« Reply #1351 on: May 19, 2017, 04:49:13 AM »
RE cracks, I was looking around 83N on Pacific side for a strip that Bremen showed as low concentration a couple of days ago and there are fairly regular parallel cracks in 2 directions. In Gimp's levels I pulled in the black point to accentuate the cracks. I've include the same area and date for last year, with the same processing. It shows a lot of cracking around the opening in the Beaufort, but less further into the basin

Looks interesting alongside  Jai's image of cracks aligned to directions of motion and stresses in Lincoln Sea. I've no idea if the 'periodicity' is significant(perhaps the pack is being stretched as much as squeezed these days?) but it does suggest a pack that will be more easily dispersed

Thomas Barlow

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Re: The 2017 melting season
« Reply #1352 on: May 19, 2017, 05:15:28 AM »
Beaufort joined to Nares?

Tigertown

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Re: The 2017 melting season
« Reply #1353 on: May 19, 2017, 05:37:43 AM »
Beaufort joined to Nares?
Yeah, when that breaks through, ice will flow freely from the Beaufort all the way through Nares. As we have seen, nothing yet has been strong enough to create a clog.

Everything is showing signs of melt onset, all over the Arctic now.

seaicesailor

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Re: The 2017 melting season
« Reply #1354 on: May 19, 2017, 07:10:09 AM »
Beaufort joined to Nares?
Yeah, when that breaks through, ice will flow freely from the Beaufort all the way through Nares. As we have seen, nothing yet has been strong enough to create a clog.

Everything is showing signs of melt onset, all over the Arctic now.

2000 km and in the worst case scenario that it doesnt close, 365 days, you are talking of 6 km / day, sustained.
A bit of a stretch.... especially when the ice in Beaufort typically flows in the opposite direction.
Cannot it come from elsewhere?
In 2007 the estimate was an outflow of 80,000 km2 or so. That is equivalent to a semicircle of radius 250 225 km approx. of MYI around the strait down the drain.
Or given the geometry around, a quarter of circle of 450 320 km. Isn't that bad?
Edit. Corrected the rough numbers
« Last Edit: May 19, 2017, 08:37:43 AM by seaicesailor »

Tigertown

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Re: The 2017 melting season
« Reply #1355 on: May 19, 2017, 07:41:17 AM »
The way the ice disintegrates now, I suppose before long, it will find its way out of the Arctic through any little nooks and crannies that open up. This will be a summer of, not just melting, but extraordinary export.

RikW

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Re: The 2017 melting season
« Reply #1356 on: May 19, 2017, 10:06:40 AM »
Kara sea looks also ready for rapid decline:

16/05/17


17/05/17


18/05/17

F.Tnioli

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Re: The 2017 melting season
« Reply #1357 on: May 19, 2017, 12:09:27 PM »
The way the ice disintegrates now, I suppose before long, it will find its way out of the Arctic through any little nooks and crannies that open up. This will be a summer of, not just melting, but extraordinary export.
This is a possibility, but not certainty, IMO. Another possibility exists: despite much increased mobility, most ice which "could" be exported - will not be exported, "running" circles within the Arctic instead, being compacted much in the process, too. I mean, if weather will change to provide that in like, say, 2 weeks, and will remain in this "making ice to go circles within the Arctic" for the whole melt season. It sure would be a surprise, of course, if this happens; but on the other hand, we had lots of surprises of various sorts last few seasons, starting with 2012's GAC, you know.

iceman

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Re: The 2017 melting season
« Reply #1358 on: May 19, 2017, 01:07:18 PM »
My impression is that volume export this time of year has a disproportionate effect on the September minimum, mainly because it reduces concentration within the pack.
Via resulting average albedo decrease, you mean? I agree.
Yes, and because of more floe edge exposed to water.  The latter might be a larger cause after the solstice - subject to weather conditions as usual.

F.Tnioli

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Re: The 2017 melting season
« Reply #1359 on: May 19, 2017, 01:36:10 PM »
My impression is that volume export this time of year has a disproportionate effect on the September minimum, mainly because it reduces concentration within the pack.
Via resulting average albedo decrease, you mean? I agree.
Yes, and because of more floe edge exposed to water.  The latter might be a larger cause after the solstice - subject to weather conditions as usual.
It is my understanding that higher total edge surface will not be unavoidable consequence of lower volume, though. I am sure it may end up this way, yes - but there are also some chances it won't. Here's why i think so. Please correct me if this kind of amateur thinking is wrong, thanks!

Tiny mind experiment: imagine

1. 10 km^3 of ice in the shape of 1-meter-thick 100x100km square. Solid field. Total edge surface (abstract, "vertical" sides of the field) would be roughly 400km x 1m = 0.4 km^2.

2. 20 km^3 of ice (twice higher amount of ice), presented in the form of 200 10x10km square fields separate from each other (open water between them). Also beng 1-meter-thick. Total edge surface (again, abstract vertical sides) of those is 40km x 1m x 200 = 8 km^2, i.e. 20 times higher than in the above single-field half-volume case.

Basically if weather will lead to lots of thin ice suffering melt-favorable conditions while lots of thicker ice will be lucky not to, then it all may become (some time August for example) a thing with lots and lots of open water while some ice fields would still survive "as a whole" (much crippled, but possibly compacted by winds) through the minimum, and in this case total edge surface could perhaps be not higher, but smaller than "if without early season export" case, at least for a while.
« Last Edit: May 19, 2017, 01:52:42 PM by F.Tnioli »

georged

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Re: The 2017 melting season
« Reply #1360 on: May 19, 2017, 01:44:59 PM »
Beaufort joined to Nares?
Yeah, when that breaks through, ice will flow freely from the Beaufort all the way through Nares. As we have seen, nothing yet has been strong enough to create a clog.

Everything is showing signs of melt onset, all over the Arctic now.

2000 km and in the worst case scenario that it doesnt close, 365 days, you are talking of 6 km / day, sustained.
A bit of a stretch.... especially when the ice in Beaufort typically flows in the opposite direction.
Cannot it come from elsewhere?
In 2007 the estimate was an outflow of 80,000 km2 or so. That is equivalent to a semicircle of radius 250 225 km approx. of MYI around the strait down the drain.
Or given the geometry around, a quarter of circle of 450 320 km. Isn't that bad?
Edit. Corrected the rough numbers

As a percentage of the extent in May, or even of the extent in September, it's not particularly large.

80500 sq km, by my back of envelop calculations.

But as the export of some of the oldest and thickest ice in the Arctic basin, it's considerably more important. Its real significance will be felt in the 2018 melt season, which will see an even thinner and weaker remnant to start with.

F.Tnioli

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Re: The 2017 melting season
« Reply #1361 on: May 19, 2017, 02:00:44 PM »
Depends. If 2017/2018 freezing will not be one like 2016/2017, but more like 2012/2013 - a possibility which can hardly can be excluded at this time, - then 2018 melt season might well have a thicker start (overall / average) than this season.

But, am i going too off-topic with the above remark, i wonder? We better focus on effects which export of extra MYI would have on this year's minimum, while talking in this topic.

Speaking of which, i definitely see one thing this export would make a dent on: annual minimum volume. Lots of things affect it; in general though, it seems to me 2017 have more chances to go lower minimum volume than 2012 than any of prior 4 years. And this export surely doesn't help to decrease chances of setting one new all-time-low ASI volume this year.

P.S. If it's not any much effort for you, then could you please napkin-style-quantify how significant that export would itself be (both direct and indirect effects) on summer volume minimum? Kind of "educated guess" would be more than enough for me.
« Last Edit: May 19, 2017, 03:22:08 PM by F.Tnioli »

Thomas Barlow

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Re: The 2017 melting season
« Reply #1362 on: May 19, 2017, 04:48:25 PM »
TB - Wipneus tracks grpahs or Arctic Basin area and extent, which excludes all peripheral seas but includes the seas adjacent to the CAB. I think this is what you are asking for.

Thanks to everyone for pointing me to the CAB charts. I'm bookmarking all of these.
This one seems to be showing 2nd lowest in recent years right now (with that weird, but unsustained dip in 2016 beating it out).

Tor Bejnar

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Re: The 2017 melting season
« Reply #1363 on: May 19, 2017, 05:09:48 PM »
The way the ice disintegrates now, I suppose before long, it will find its way out of the Arctic through any little nooks and crannies that open up. This will be a summer of, not just melting, but extraordinary export.

This may be true, but according to 'old' (2015) research presented in the Fram thread, Fram export is lowest during the summer.  This may, in part, be due to melting before it gets to The Fram, like we saw during the first half or so of last winter.  Of course, there are other summer exit doors (Nares, Canadian archipelago).
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Peter Ellis

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Re: The 2017 melting season
« Reply #1364 on: May 19, 2017, 06:11:53 PM »
Tiny mind experiment: imagine

1. 10 km^3 of ice in the shape of 1-meter-thick 100x100km square. Solid field. Total edge surface (abstract, "vertical" sides of the field) would be roughly 400km x 1m = 0.4 km^2.

2. 20 km^3 of ice (twice higher amount of ice), presented in the form of 200 10x10km square fields separate from each other (open water between them). Also beng 1-meter-thick. Total edge surface (again, abstract vertical sides) of those is 40km x 1m x 200 = 8 km^2, i.e. 20 times higher than in the above single-field half-volume case.

That's a useful thought experiment, but do please also bear in mind that in the first case you have 10,000 km^2 of surface area exposed to the Sun, and another 10,000 km^2 exposed to the water under the floe.  The exposed edge is 0.4 / 20,000 = 0.002% of the total exposed surface area.  Even multiplying that by 20 doesn't do a lot.

Comradez

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Re: The 2017 melting season
« Reply #1365 on: May 19, 2017, 07:02:43 PM »
This season will be interesting for calibrating how important early melt season albedo is compared to inherited sea ice thickness.  Snowcover is much more than 2016, but sea ice thickness is much less. 

In particular, here's how I would compare 2016 and 2017 for each region using worldview imagery as of 5/18, starting with the land areas where 2016 has a signficant lead:

1.  Alaska / Yukon / Mackenzie River Delta:  2016 has a slight ~5 day lead in snowmelt, particularly noticeable on Alaska's north slope, where 2016 had an extraordinarily early melt. 

2.  Nunavut / Hudson Bay shores / Quebec:  2016 has about a week lead in snowmelt. 

3.  Karelia / White Sea coast / Barentsz Sea coast:  2016 has a whopping 3-week lead in snowmelt. 

4.  Arctic coast from Gulf of Ob to East Siberian Sea:  2016 might have a lead of a couple of days.  Snow extent is roughly comparable with 2017, although the snow appears a bit grayer in 2016 at this point. 

5.  Chukotka:  2016 has about a 4-day lead. 

But what about sea ice?  Here, the tables are turned, with a few exceptions:

1.  Chukchi:  2017 has about a 1-week lead in terms of extent, although in terms of quality the difference looks even more stark.  2017 is full of rubble already, whereas 2016 was more compacted.  And we know that thickness in 2017 is less too. 

2.  Beaufort:  2016 has about a 3-week lead in terms of extent, although we know that 2017 is missing any core of really thick ice in this region that 2016 had, that allowed areas like the "Big Block" in 2016 to persist almost all summer despite being surrounded by blue ocean for months. 

3.  CAA:  About the same, both in terms of sea ice color and extent of breakup at each end of the Northwest Passage. 

4.  CAB:  2017 looks like it is about 2 weeks ahead.  2016 didn't show any substantial crack from the Beaufort all the way to north of Ellesmere Island until the first week of June. 

5.  Nares Strait:  2017 is about 2 months ahead.  You have to skip ahead all the way to about July 18th in 2016 to see the sort of network of cracks and pulverized floes that 2017 already has.  2017 looks shockingly bad in this sector. 

6.  Hudson / Baffin Bay:  (Not important for final extent, but still important for intervening albedo until then)...2016 and 2017 are about the same. 

7.  Greenland Sea / Barentsz Sea:  Hard to do a comparison here because it is so at the mercy of short-term fluctuations based on wind drift and Fram export.  2016 clearly in the lead, though. 

8.  Kara Sea:  Similar extent in each year, although 2016 looks slightly more rubble-ey and grayer, so I give a few days' lead to 2016. 

9.  Laptev Sea:  Polynya extent is about the same.  2017's floes look more dispersed, although they also seem to have more of a blue-ish tint, whereas 2016's look slightly grayer/yellower, suggesting to me that 2017 is a few days' behind on surface snowmelt, albeit thinner overall. 

10.  East Siberian Sea:  2017 looks shockingly bad.  In terms of extent, it is about a month ahead of 2016.  The fast-ice line is hugely cut back towards the coast compared to 2016, the polynya is much larger, floes are more dispersed.  After taking into account comparable sea ice color tint (indicating comparable surface snowmelt with 2016 maybe slightly grayer/yellower and farther ahead), I'd estimate 2017 is about three weeks ahead of 2016 here overall.   

Overall, what I see is that weather has favored 2016's melting over 2017's so far, as indicated by more advanced surface snowmelt on both land and water in most places.  However, that might be more than outweighed by:
A.  Less inherited sea ice thickness for 2017.
B.  A change in the weather pattern to catch 2017's snowmelt up to 2016 and give 2017 a sunny June/July (whereas 2016 generally had a cloudy summer after the early melt).
C.  Some combination of the two above. 

What really intrigues me is the Nares breakup already in 2017.  It's not like that area is getting much absorbed sunlight.  Albedo is still high.  It has to be a combination of bottom melt and low thickness to begin with.  If the rest of the CAB is that bad, we could see it deteriorate in a flash in July/August. 
« Last Edit: May 19, 2017, 10:51:12 PM by Comradez »

Tor Bejnar

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Re: The 2017 melting season
« Reply #1366 on: May 19, 2017, 07:38:06 PM »
I believe you mean "Lincoln Sea" instead of "Nares Strait".  Nares Strait had a bridge for a couple of days (so it doesn't count) early in the winter; it has been exporting thin ice all winter and spring.  Lincoln Sea had a bridge that broke about 10 days ago, and it is now exporting 3-meter ice (per a recent in-the-field study - see Greenland - Nares thread).  But yes indeed: 2 months earlier than 2016.
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Neven

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Re: The 2017 melting season
« Reply #1367 on: May 20, 2017, 12:15:30 AM »
Nice comparison, Comradez. Thanks.
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Tigertown

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Re: The 2017 melting season
« Reply #1368 on: May 20, 2017, 01:36:11 AM »
There is certainly a valid concern wrt loosing some of the older thicker sea ice to export.

Thawing Thunder

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Re: The 2017 melting season
« Reply #1369 on: May 20, 2017, 06:30:21 AM »
Hello everybody!
I'm already lurking around here for a couple of weeks now. This season is going to get very interesting. Be assured everybody, that you have an interested and grateful reader of all your extraordinary work and contributions.

subgeometer

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Re: The 2017 melting season
« Reply #1370 on: May 20, 2017, 08:51:31 AM »
The way the ice disintegrates now, I suppose before long, it will find its way out of the Arctic through any little nooks and crannies that open up. This will be a summer of, not just melting, but extraordinary export.
This is a possibility, but not certainty, IMO. Another possibility exists: despite much increased mobility, most ice which "could" be exported - will not be exported, "running" circles within the Arctic instead, being compacted much in the process, too. I mean, if weather will change to provide that in like, say, 2 weeks, and will remain in this "making ice to go circles within the Arctic" for the whole melt season. It sure would be a surprise, of course, if this happens; but on the other hand, we had lots of surprises of various sorts last few seasons, starting with 2012's GAC, you know.

But here is nothing t hold the ice in especially on the Atlantic side but also through the garlic press and Bering, the Bulwarks have failed. Surely the leads to less compaction and more export as well as more mobility generally, especially with consistent winds into the Barents and out through Fram - where ice is chugging along at a good pace as can be clearly seen on worldview

rboyd

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Re: The 2017 melting season
« Reply #1371 on: May 20, 2017, 09:07:25 AM »
The extra dispersion could keep the extent numbers higher for a while.

subgeometer

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Re: The 2017 melting season
« Reply #1372 on: May 20, 2017, 09:28:32 AM »
Previous GFS  forecasts of rain turned to snow as they got closer - anyway GFS is now predicting a pair of deep lows - both bottoming in 970s- to enter through the Laptev Sea from about 5 days out with above freezing temps, strong wind and and copious rain. The first slings the second right out across the basin. It's a way off so hopefully it won't eventuate

Neven

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Re: The 2017 melting season
« Reply #1373 on: May 20, 2017, 10:24:42 AM »
High pressure and anomalously warm temperatures taking over, is very bad news with regards to preconditioning. If a lot of melting momentum is built up in coming weeks, more than we have seen last year for instance, it will bite the Arctic in the ice* in August. We can count our blessings that extent-wise 2017 is 'only' in fourth position and way behind 2016, but I don't really find comfort in that when I look at other parameters.

* I wanted to write 'ass', but got a reverse Freudian slip instead.

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be cause

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Re: The 2017 melting season
« Reply #1374 on: May 20, 2017, 11:13:18 AM »
.. meanwhile in the real world it remains anomalously cold north of 80' . This bit of the world has ignored all the 'hot' forecasts of the last couple of weeks . I know things will change .. except week 2 of the gfs forecast .. if it was real we would have been ice-free for the last 3 summers .
« Last Edit: May 20, 2017, 02:09:45 PM by be cause »
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Random_Weather

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Re: The 2017 melting season
« Reply #1375 on: May 20, 2017, 11:17:22 AM »
be cause,

correct at all, GFS is performing very bad in Forecast, there is a huge warm bias

Look here: http://www.karstenhaustein.com/reanalysis/gfs0p5/ANOM2m_arctic/verification/ANOM2m_bias_past07_arctic.html


seaicesailor

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Re: The 2017 melting season
« Reply #1376 on: May 20, 2017, 12:20:40 PM »
.. meanwhile in the real world it remains anomalously cold north of 80' . This bit of the world has ignored all the 'hot' forecasts of the last couple of weeks . I know things will change .. except week 2 of the gfs forecast .. if it was real we would have been ice-free for the last 3 summers .
Not completely. The CFSv2 did forecast a cold CAB until third week of May included. The melt has reached Beaufort Chukchi and ESS coasts meanwhile (check Terra 7-2-1 carefully).
The GFS passed from a cold bias to a very warm one but the ECMWF has clearly diverged from it.
That the DMI 80N is in negative anomaly reflects more than anything the general circulation that, incidentally, keeps ice pack tilted toward the Atlantic. It can be read in many different ways.
I ignore the operational run of the GFS since ages (or try to, in favor of the EC), but the weekly predictions of the CFSv2 that ive been following this year have not been bad at all. This coming week however we'll see how warm things end up or not.
(BTW most of CAA, North Canada, Alaska, and Eastern Siberia snow cover melting as forecasted)
« Last Edit: May 20, 2017, 01:24:24 PM by seaicesailor »

seaicesailor

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Re: The 2017 melting season
« Reply #1377 on: May 20, 2017, 02:19:02 PM »
The next six days of ACNFS ice drift forecast. Painful sustained for the ESS ice
EDIT. It won't work... trying to fix it.
No way. Today the system is in a mood and won't play the gifs correctly. Will try later
« Last Edit: May 20, 2017, 02:36:52 PM by seaicesailor »

iceman

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Re: The 2017 melting season
« Reply #1378 on: May 20, 2017, 02:27:50 PM »
   ... comparing this year with last year and 2012/others --

... the heating of Okhotsk/Barents much earlier than normal (due to their possibly record-early dearth of sea ice) means that storms approaching from this direction will have much more insolation to take advantage of, and that heat will ultimately be deposited/resolved over the Arctic Ocean -- first Chuchki, Beaufort, ESS, and then the CAB.
   ....

Though I have some reservations about using HYCOM for such comparisons, this is a good analysis and highlights the importance of how weather interacts with preconditioning.  The excess heat buildup in the northern Pacific will be more damaging if it intensifies an August cyclone crossing into the Arctic than if it feeds a series of moderate lows earlier in the season.  The latter, bringing cloudy conditions, could mitigate the effect of melt ponding that appears to be well under way on the Pacific side.

gerontocrat

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Re: The 2017 melting season
« Reply #1379 on: May 20, 2017, 03:26:40 PM »
It is May 20th, the beginning of those magic 2 months, one each side of the solstice, when even at 52 degrees N daylight hours are wonderfully long, and insolation (though not temperature) is at the maximum.

So I thought I would add some boring (Jaxa) numbers to the thread. Since All Fools' Day (April 1) melting per day this year to May 19 has been on average 36 thousand km2, compared with 50 thousand last year. i.e. quite slow. BUT I also looked forward and looked at average melt from May 19 to each previous year's minimum, and averaged the last 10 years.

To achieve the 2007 minimum extent, the melt in 2017 for the rest of the season has to be just 2 percent greater than the average during that period in 2007-2016, and to equal the 2016 minimum, 3 percent above that average. But to achieve the 2012 result a 14 percent above average melt from today is necessary.

Of interest, at least to me, was also seeing how the yearly melt from now to minimum is increasing over time.
1980's Average    5,834,805
1990's Average    6,096,434
2000's Average    6,732,728
Average 2007-2016    7,547,773

With all the images showing the pre-conditioning (per Neven) of the remaining ice cap for melting I must assume (which is pre-conditioning for being totally wrong) that the balance of risk is towards a very low extent. Only two weeks for the May PIOMAS results.




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Re: The 2017 melting season
« Reply #1380 on: May 20, 2017, 03:52:49 PM »
Surely , as we approach ice free, the melt of remaining ice accelerates? We , thankfully , have never witnessed the ice get low enough across the basin for this to happen but we have seen stricken areas 'blink out' once cover become real low?

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gerontocrat

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Re: The 2017 melting season
« Reply #1381 on: May 20, 2017, 04:28:39 PM »
Surely , as we approach ice free, the melt of remaining ice accelerates? We , thankfully , have never witnessed the ice get low enough across the basin for this to happen but we have seen stricken areas 'blink out' once cover become real low?

More (approximate) numbers, I'm afraid.

Volume at maximum (per PIOMAS) has gone down by 10 percent per decade while extent (per NSIDC) at only 2.5 percent per decade. Therefore average thickness at maximum is in decline.

Volume at minimum(per PIOMAS) has gone down by 20 percent per decade while extent (per NSIDC) only 12.5 percent per decade. Therefore average thickness at minimum is in decline.

Therefore extent has reduced at a lower rate than volume at all times in the year.

If minimum volume continues to decline at 2 percent per annum then goodbye September sea ice by 2029. At some point extent would then have to catch up to also be zero. Arithmetic is wonderful.

But nature abhors a straight line. I don't know how gray a gray-wolf you are, sir, but this old fella is fairly sure he will see a blue arctic ocean somewhat before 2029.

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Re: The 2017 melting season
« Reply #1382 on: May 20, 2017, 05:27:05 PM »
.. meanwhile in the real world it remains anomalously cold north of 80' . This bit of the world has ignored all the 'hot' forecasts of the last couple of weeks . I know things will change .. except week 2 of the gfs forecast .. if it was real we would have been ice-free for the last 3 summers .
trying to get an idea why the warming does not show up north of 80N (more strongly, temperatures are rising, just not above average) I made this gif blending from visible / 3,6,7 into band31 IR (temp scale squashed to 244K - 280K) https://go.nasa.gov/2rD3JpF
Since IR sees cloud tops where they obscure the surface I was  hoping to distinguish clouds from surface that way.
The result is a lot more complex than I expected.
First I'll state the obvious: the warmest surface on view is snow free land, the coldest are high cloud tops (white in the IR because below my colour scale)
Clouds are quite warm where they originate from advection of air which has been warmed further south, cold where they are at altitudes where adiabatic expansion means air is cold wherever it started.
What makes this worth posting I think is that in shows a fairly thin, even (not showing much sign of movement) layer of cold cloud over much of the >80N area. This cloud lowers insolation as all clouds do but would radiate less IR to the ground than the stuff which at the moment keeps Obuoy14 at a cosy -5C at local midnight further south. What makes the trade off between incoming sunlight and downwelling IR so hard to gauge is that the cold snow surfaces still present on most of the arctic ocean don't absorb much sunlight and therefore are warmed only little by it. The open water in the Chukchi sea for example soaks this up but over a depth of water which also means a slow temperature rise.
Hope this makes sense to someone, would like to hear a meteorologists input.

edit: the 3,6,7 band image generally shows snow/ ice in red / cloud in white, but very cold, ice clouds also have a red tint. This has confused me for a while, so thought it worth pointing out.
« Last Edit: May 20, 2017, 05:42:40 PM by Andreas T »

StopTheApocalypse

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Re: The 2017 melting season
« Reply #1383 on: May 21, 2017, 01:10:38 AM »
This might belong in the stupid questions thread, but how long should I trust GFS? Forecast for four days from now indicates some high temperatures heading towards 80N+.

Csnavywx

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Re: The 2017 melting season
« Reply #1384 on: May 21, 2017, 03:15:27 AM »
This might belong in the stupid questions thread, but how long should I trust GFS? Forecast for four days from now indicates some high temperatures heading towards 80N+.

In times of high volatility (like right now) 96 hours is as far as I would go. 120 is usable, but you'll probably get better results from the ensemble mean run. Ensembles can be used up to 168. In times of lower volatility, those numbers change to 120/144 and 186. Only the EPS maintains useful skill to 240. If the EPS and GEFS agree at those longer ranges, it can lend some confidence to the result.

Tigertown

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Re: The 2017 melting season
« Reply #1385 on: May 21, 2017, 07:55:14 AM »
All the ice between the Beaufort and Chukchi is starting to break up.
A close up look.

Shared Humanity

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Re: The 2017 melting season
« Reply #1386 on: May 21, 2017, 03:47:05 PM »
All the ice between the Beaufort and Chukchi is starting to break up.
A close up look.


Doesn't ice generally start fracturing extensively at this time in the Beaufort and Chukchi? I am more interested in how it breaks up which reveals the overall strength (thickness, temperature etc.) of the ice. Does it quickly turn into a melange or rubble, very small floes, or do we see it fracturing in large rafts, rhomboids and such? From that image, it looks like a mix (perhaps a little heavy on rubble) but I do not know the scale of the image. How large are the largest floes?

romett1

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Re: The 2017 melting season
« Reply #1387 on: May 21, 2017, 03:52:03 PM »
Interesting to watch Sachs Harbour (Banks Island). Long-term average for end of May is about -4 °C.
Now we have almost July temps there (long-term average for July is 6.2 °C). Also area surrounding Hudson Bay is extremely warm next week.
Image: https://www.yr.no/place/Canada/Other/Sachs_Harbour,_N._W._T_/long.html

Shared Humanity

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Re: The 2017 melting season
« Reply #1388 on: May 21, 2017, 03:55:53 PM »
Given the anomalously warm winter (record anomalies) and the historically thin ice cover, the overall strength of the ice and its resultant mobility will be a key feature of this melt season. High resolution images of the entire basin, particularly at the start of the melt season, will be very revealing, certainly of the state of the ice but perhaps also revealing how this melt season will play out. We should be posting these images of the entire CAB continuously on this thread and analyze the progression.

Shared Humanity

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Re: The 2017 melting season
« Reply #1389 on: May 21, 2017, 04:02:55 PM »
Several of the past winters had a feature called "The Great Crackopalypse", I believe, where the ice north of the CAA had large curved fractures which appeared during the winter and propagated all the way to the Nares. We worried this was evidence of extraordinary weakness of this ice. This feature was missing this year and I think these cracking events where the fractures extended continuously towards the pole was actually evidence of the relative strength of the ice as compared to this year. The integrity of the ice between these large fractures was impressive (massive floes IIRC).

Shared Humanity

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Re: The 2017 melting season
« Reply #1390 on: May 21, 2017, 04:06:43 PM »
I've never posted these kinds of detailed images of the ice and, quite frankly, don't know how to do this but I think this community should try to do this across the entire basin this year. Perhaps each of us could take a sea or area of our choice and post these with analysis for the community.

Can somebody here tell me how to do this? Please keep in mind that I am old and technically challenged. Imagine having to teach your grandmother over the phone and we will be fine.

There will be some fascinating threads to follow this melt season but this is one of the most important. Lets use this thread, as a group, to increase our level of understanding, both for the community and visitors. If we do this every melt season from now on, we will be conducting research, I believe, that is not currently being done, a detailed, live analysis of the behavior of weak ice under various forces, sun, storms, waves and wind etc.

(Neven) Could you post detailed instructions here to let various regulars pick this up and run with it? Assume we are all grandmothers even though some of us are computer wiz's.
« Last Edit: May 21, 2017, 04:14:45 PM by Shared Humanity »

Shared Humanity

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Re: The 2017 melting season
« Reply #1391 on: May 21, 2017, 04:20:59 PM »
By the way Neven, I just want to thank you for your efforts as a citizen scientist in helping us become informed but also in creating other citizen scientists who contribute here regularly. Can any real scientists in this community (I know you are out there. Don't be shy.) weigh in on my proposal?

I know we regularly scoop the real scientific community here, have actually seen this blog be referenced by actual science sites (kudos again Neven). I think it is because we can put so many eyes on events. Lets use this unique asset (we've got numbers on our side) and run with it. We could help climate science in general if we do this.

Shared Humanity

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Re: The 2017 melting season
« Reply #1392 on: May 21, 2017, 04:26:06 PM »
Oh...and don't go getting a big head. I laid it on pretty thick there.

Andreas T

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Re: The 2017 melting season
« Reply #1393 on: May 21, 2017, 04:49:43 PM »
I have attempted on some occasions in a small way to use the images on worldview to track floes and learn from their behaviour over a season.( for example big block last year )  I think such work would be more productive if it can be coordinated with more people.
I think this should have a dedicated thread, this one is rightly for a general discussion where people like to chat because there is a larger audience. Detailed work with a narrow focus is quickly lost up the thread here.



Tigertown

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Re: The 2017 melting season
« Reply #1394 on: May 21, 2017, 04:50:16 PM »
WRT the image in reply #1385,
I do not know the scale of the image.

My best guess would be about 8 km = 1 cm.

Give it a little time and I will bet this ice will shatter into smaller pieces. It hasn't really been exposed to persistent heat yet.

Thomas Barlow

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Re: The 2017 melting season
« Reply #1395 on: May 21, 2017, 06:18:10 PM »
All the ice between the Beaufort and Chukchi is starting to break up.
A close up look.

A lot of peripheral regions seem to be disintegrating now. Including the Lincoln Sea, which is unusual (maybe unique). Because of its position in the jigsaw puzzle, it could be the straw that breaks the donkey's back. (I hope not.)

Shared Humanity

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Re: The 2017 melting season
« Reply #1396 on: May 21, 2017, 06:52:42 PM »
I have attempted on some occasions in a small way to use the images on worldview to track floes and learn from their behaviour over a season.( for example big block last year )  I think such work would be more productive if it can be coordinated with more people.
I think this should have a dedicated thread, this one is rightly for a general discussion where people like to chat because there is a larger audience. Detailed work with a narrow focus is quickly lost up the thread here.

Thank you. That suggestion makes sense. It should be a separate thread. Now all I need to know is how to make these images.

Can you point me to the site? (worldview)

Thomas Barlow

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Re: The 2017 melting season
« Reply #1397 on: May 21, 2017, 08:20:47 PM »

Andreas T

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Re: The 2017 melting season
« Reply #1398 on: May 21, 2017, 09:09:12 PM »
Can you point me to the site? (worldview)

---> http://tinyurl.com/nykf7bz

what Thomas said ;)
I have opened a thread
As suggested by shared Humanity:
.....

in Arctic Background where it will stay more easily near the top of the board
if you like to change the title that can be done but it doesn't matter too much if people get to know it.

seaicesailor

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Re: The 2017 melting season
« Reply #1399 on: May 21, 2017, 10:04:08 PM »
I think a visible light sat image of a blueish Hudson is no off topic here.