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Sterks

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Re: The 2019 melting season
« Reply #4450 on: July 23, 2019, 11:34:23 PM »
"This said, May 2019 was not so good for building up melting momentum, a point already underlined, and accumulated heat is still trailing a bit behind good years like 2012 from this point of view, as shown in the graph."

Aslan, apart from calling 2012 a "good year", how would you explain the +4 degrees anomaly on 925 Mb over almost all of the central Arctic. That anomaly accumulated all through may, june and july...
This May was the record warmest. Anything stated otherwise is a falsehood, and Aslan's statement is objectively wrong.
Objectively?
I say Aslan is objectively right if by melting momentum it means appearing great extents of melt ponds and starting to drop the albedo of the pack. That came exactly one week late wrt 2012, well into June if you check SMOS beige pixels and area anomaly plots by Steven.
But I remember in May there were theories as always suggesting that the ice was different, and couldn’t hold melt ponds on it, that melting was on nevertheless
 Look at it on July. SERIOUSLY? THIS ICE CANT HOLD MELT PONDS??? What a joke.
« Last Edit: July 23, 2019, 11:56:52 PM by Sterks »

slow wing

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Re: The 2019 melting season
« Reply #4451 on: July 23, 2019, 11:34:34 PM »
Yay! The Slater prediction has updated.  :)


The latest prediction is 4.11 million square kilometers for 11 September 2019 - which should be around the date for the extent minimum.


Bearing in mind that the map is indicative only, and is posted as a courtesy, it is seen that neither the Alaskan side nor the Russian side are predicted by the model to advance much inside 80N.

Coffee Drinker

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Re: The 2019 melting season
« Reply #4452 on: July 24, 2019, 12:01:54 AM »
This looks like the Great Arctic Anticyclone with strong winds and waves and clear skies. The sun still be high in the sky. I expect singnificant ice drop in any metrics.

High in the sky ? Under the anticyclone centre area (at 85N) the sun elevation angle will vary between 15 and 25 degrees.

Ok I know the sun does not set but from elevation angle POV, this is something similar to a January 10th afternoon in Boston, Mass.

the insolation is about the same as 30°N  right now. Are you saying that sea ice wouldn't melt under the Floridian Sun?

The only thing saving the ice from soaking up all those Watts is that it's still pretty white over a lot of the CAB, perhaps reflecting 60%. With that amount of sunshine it will darken quickly and as the ice thins the water under the ice absorbs more and more energy. The open ocean is going to soak up 90%.

I really don't think this is comparable. It makes a difference if the insulation is spread out through the day at low angles or highly concentrated during the noon period at an extreme angle (>80 degree). The Florida noon sun would burn the ice within a few hours while the current arctic sun would already allow cooling during low angle night. At this low angles, every little bump and ice pinnacle would create very long shadows.

Rod

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Re: The 2019 melting season
« Reply #4453 on: July 24, 2019, 12:07:41 AM »
In areas where sea ice abuts fast ice, the shallow water depth can allow pressure ridges to actually anchor to the sea floor. These structures are called stamukha;

Thank you for your post Ossifrage.   

A few days ago we were discussing images of ice scouring on the sea floor in the area of the ESAS that Natalia Shakhova provided in her 2017 paper, and I was struggling to think of a mechanism that could have caused it.

I completely forgot about stamukha. 

Quote
Stamukha – fixed ice which remained on a shallow of the coast or on a stamik. S. can form on nameless banks, not designated on maps, at the depths over 20 m. The cases are known when S. was formed at a much bigger depth. Around S. ice belt is formed up to 10 miles and more. In summer S. melts and disintegrates, forming mass of crushed and chafed ice, dangerous for vessels, especially in poor visibility conditions. Such hummock ice in shoals of the Arctic Region is a hazard for navigation. The East Siberian Sea has the maximum quantity of S. in the Russian Arctic Region – 71 %, due to harsh weather conditions and shallowness of the sea. In the eastern part of the sea, the largest S. is registered with the maximum draft 35 m. S. often form in the southwest along the borderline of the land ice from the New Siberia Island to the Ayon Island, along the Chukchi coastline, and on banks to the west of the Wrangel Island.

https://link.springer.com/referenceworkentry/10.1007/978-3-319-24237-8_496

DrTskoul

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Re: The 2019 melting season
« Reply #4454 on: July 24, 2019, 12:42:35 AM »
Cool info

Tor Bejnar

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Re: The 2019 melting season
« Reply #4455 on: July 24, 2019, 01:22:22 AM »
...
 Pressure ridges are an extremely important aspect of Arctic sea ice, but don't get much discussion here because the large-scale models gloss over them. Basically, where floes are forced together by currents or winds, the ice shatters into blocks. Some of these blocks are pushed upward, in a small-scale equivalent of orogeny, to form visible ridges that can peak several meters above the floes' "ground level". But more importantly in many regards, this process also forces ice blocks below sea level, somewhat akin to the keel of an iceberg writ large. Leppäranta (2005) argued that these pressure ridges, in total, amounted for about half of ASI volume. We can quibble about that number, but the ridging process unquestionably provides for hidden stores of ice.
...
A month or so ago, somewhere on the ASIF, I speculated that Nares Strait being open all winter (except for 1 month with a mostly resilient arch in the Lincoln Sea) would cause less rafting of floes in that sector of the Arctic (than is typical), as ice pushed towards this part of North America 'moved along' instead of 'piled up', so that mechanically derived multi-meter-thick ice would be relatively scarce.  Elsewhere, such as north of the central or western parts of the CAA, floes would have piled up more or less as usual.
Arctic ice is healthy for children and other living things.

Michael Hauber

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Re: The 2019 melting season
« Reply #4456 on: July 24, 2019, 01:37:34 AM »
With low-concentration ice extending to the pole and the ice in general thin enough that an icebreaker could run through at full speed without taking damage. 
My climate-skeptical friends are pointing out that the Norwegian "Kronprins Haakon" had to return from a planned trip to the North Pole.
https://www.arctictoday.com/for-norways-newest-icebreaker-its-almost-to-the-pole-and-back/

Report says 'decided to turn back after meeting first-year ice measuring up to 1.5 meters thick, patches of multi-year ice and little sign of thawing.' halfway from Svalbard to north pole.  Latest PIOMAS shows volume at record low, and thickness from Svalbard to pole starting near 1m and increasing to about 2m.  The article claims the sea was built to run through ice up to 2 meters. 
Climate change:  Prepare for the worst, hope for the best, expect the middle.

Pragma

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Re: The 2019 melting season
« Reply #4457 on: July 24, 2019, 01:45:06 AM »
A month or so ago, somewhere on the ASIF, I speculated that Nares Strait being open all winter (except for 1 month with a mostly resilient arch in the Lincoln Sea) would cause less rafting of floes in that sector of the Arctic (than is typical), as ice pushed towards this part of North America 'moved along' instead of 'piled up', so that mechanically derived multi-meter-thick ice would be relatively scarce.  Elsewhere, such as north of the central or western parts of the CAA, floes would have piled up more or less as usual.

I remember that, and it appears that your prediction is holding true. The question is, what happens if/when we get a good blow? Will the Nares carry the ice through, or will it pile up?

Secondly, although your theory seems valid, how does one separate Nares export from the general destruction of the ice in that area?

I ask this, because separating different influences and effects is an ongoing problem that is difficult, if not unsolvable.

philopek

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Re: The 2019 melting season
« Reply #4458 on: July 24, 2019, 02:15:12 AM »

Excellent plot, thanks edmountain.

Any melt ponds will presumably act like the 'clear sky over ocean' line ....

Yes excellent and all else I'm d'accord but that light blue melt ponds will act along the line for dark blackish ocean surface i doubt. I'd say it's somewhere in between.

subgeometer

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Re: The 2019 melting season
« Reply #4459 on: July 24, 2019, 03:13:24 AM »
"This said, May 2019 was not so good for building up melting momentum, a point already underlined, and accumulated heat is still trailing a bit behind good years like 2012 from this point of view, as shown in the graph."

Aslan, apart from calling 2012 a "good year", how would you explain the +4 degrees anomaly on 925 Mb over almost all of the central Arctic. That anomaly accumulated all through may, june and july...
This May was the record warmest. Anything stated otherwise is a falsehood, and Aslan's statement is objectively wrong.

Nevertheless the melt pond fraction remained low in May in the relative absence of clouds. Surface temps go above 0 at the start of June. The atmosphere was primed for that insane June by record temps in May, so I'm not dismissing your point, but actual surface melt began with a bang in June

subgeometer

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Re: The 2019 melting season
« Reply #4460 on: July 24, 2019, 03:50:36 AM »
The 925 hPa forecast is pretty ugly in the Atlantic sector as well as elsewhere. If ECMWF is to be believed in a few days a 1030+ high extends over Svalbard towards FJI dragging heat from Scandinavia up through Fram straight and over the CAB, so no export there in contrast to further east between FJI and Severnaya Zemlya.

Above freezing temps at 925hPa are hard to find all week from the Beaufort to the Atlantic on Windy TV/ECMWF for today, with any air traversing the massif of Ellesmere Island or Greenland warm and toasty when it descends over sea ice, plus warming from atmospheric subsidence taking place, and injections of heat from Canada and the Atlantic/Europe. Temperatures between 5-10C are widespread at this level

It gets progressively nastier, so I've included 4 maps from early tomorrow thru to a week out- hopefully thing work out more benignly in the latter stages than they do in this forecast

binntho

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Re: The 2019 melting season
« Reply #4461 on: July 24, 2019, 04:03:54 AM »
The ice north of the New Siberian Islands looks very strange today. It's gone dark except for those little strips that have stayed light. Zhokhova Island is just visible at the bottom edge of the frame.
A while back we had a section where various thoughts were presented on the dark ice bands in the ESS and elsewhere. A few competing ideas were presented with no conclusions ....
Well I certainly came to a conclusion (and it was me who started the discussion). Someone found a paper online that explains the bands in the Chukchi and ESS as originating in the Beaufort when off-shore winds create polynyas and stir up mud from a shallow sea floor. Transpolar drift then moves these bands of mudstained ice into the |Chukchi (very clear striation) and even the ESS.
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subgeometer

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Re: The 2019 melting season
« Reply #4462 on: July 24, 2019, 04:14:47 AM »
Ossifrage

Isn't a thinner weaker more mobile pack more prone to piling up and ridging when pushed into an obstacle. Its one partial negative feedback I occasionally ponder - ice thickens fastest when thin, so if new ice is continually pushed aside faster than in the past , the rate of new winter ice creation will be higher(provided the extra energy released can successfully escape to space). If the winds push that ice in the right direction, its a way the system can replenish itself somewaht after a bad season.

Those stamukha anchors explain the scour marks in the ESS discussed at length here earlier I think

(But lets not derail the thread, back to weather forecasts for me!)

aslan

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Re: The 2019 melting season
« Reply #4463 on: July 24, 2019, 06:39:06 AM »
Is there any prospect of extending the model back in time to before June 2017?
(I've always been very interested in the longer term trend in salinity.)
I have looked but mercator data pre june2017 is, I think, in different format, netcdf?, larger file sizes and only 0m, ie out of my download volume and probaby low results for effort. I would love to see it though if anyone has the skills and the internet connection.

Data can be download from Copernicus, available from 1992 to near real time. If you have specifics questions you can ask. But yeah, it is ncdf and it is big files, epic download and epic data manipulation. For example, surface SST for a 6 month period, northward of 60°N, is about 500 Mo XD

http://marine.copernicus.eu/services-portfolio/access-to-products/?option=com_csw&view=details&product_id=GLOBAL_ANALYSIS_FORECAST_PHY_001_024

slow wing

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Re: The 2019 melting season
« Reply #4464 on: July 24, 2019, 08:14:25 AM »
Thanks uniquorn and aslan for your replies on the salinity trends.

The amount of model data sounds huge.

The actual physical data though - the salinity data recorded from tethered buoys, drifting buoys and ships - is presumably quite manageable.

Wouldn't looking at the actual physical data give us some idea of salinity changes prior to the modelling from June 2017? (It's a genuine question - I don't know how sparse or rich the physical data is, and I don't know how easy or difficult it would be to notice salinity trends from looking at the physical data.)

I posted a suggestion for one way to present the salinity physical data, on the "Arctic Ocean salinity, temperature and waves" thread.

AmbiValent

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Re: The 2019 melting season
« Reply #4465 on: July 24, 2019, 08:29:03 AM »
With low-concentration ice extending to the pole and the ice in general thin enough that an icebreaker could run through at full speed without taking damage. 
My climate-skeptical friends are pointing out that the Norwegian "Kronprins Haakon" had to return from a planned trip to the North Pole.
https://www.arctictoday.com/for-norways-newest-icebreaker-its-almost-to-the-pole-and-back/
Report says 'decided to turn back after meeting first-year ice measuring up to 1.5 meters thick, patches of multi-year ice and little sign of thawing.' halfway from Svalbard to north pole.  Latest PIOMAS shows volume at record low, and thickness from Svalbard to pole starting near 1m and increasing to about 2m.  The article claims the sea was built to run through ice up to 2 meters.
What I had meant with the icebreaker going full speed with no problem was at the time of the minimum. According to PIOMAS, the ice volume in Mid-July was just below 9000 km^3, and at minimum it will be about half of that. (A lot of extent with lose ice thickness completely, but even the region around the North Pole will see a further reduction in thickness)
Bright ice, how can you crack and fail? How can the ice that seemed so mighty suddenly seem so frail?

bbr2314

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Re: The 2019 melting season
« Reply #4466 on: July 24, 2019, 08:49:03 AM »
The 00z EURO continues the worsening trend evident over the past few runs. Wow.



The block now merges with the other block over Scandinavia, leaving Svalbard roasting under heights surpassing 580DM.

bbr2314

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Re: The 2019 melting season
« Reply #4467 on: July 24, 2019, 08:59:24 AM »
First inkling of a major cyclonic event now appearing around D9-10 in Laptev on both EC and CMC btw.


Sterks

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Re: The 2019 melting season
« Reply #4468 on: July 24, 2019, 10:47:31 AM »
The weekly U Hamburg comparison, July 16 vs July 23.
Really amazing what the storms have done on ESS and Beaufort

sailor

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Re: The 2019 melting season
« Reply #4469 on: July 24, 2019, 11:07:25 AM »
The 00z EURO continues the worsening trend evident over the past few runs. Wow.



The block now merges with the other block over Scandinavia, leaving Svalbard roasting under heights surpassing 580DM.

Expect compacting winds of 30 to 40 km per hour with that pressure gradient. Since floes travel at 1/20th to 1/25th the speed of the wind (back-envelope approximation), and markedly toward the right of the wind, expect compacting drifts of 30 to 40 km per day. This event is sustained only for four days. Yet, expect an maximum accumulated 150 km of compaction. Probably less, except for places like the Beaufort sea and the Beaufort-CAB that are completely loose and may collapse in extent.

The perimeter affected by compaction follows the pressure gradient from Beaufort to FJL. That's 3500 km roughly, that multiplied by 150 km gives us an extent loss of 500K km2 only from compaction. Probably this number is inflated, and the impact of compaction alone will be 200-300K extent loss in the next four-five days.
« Last Edit: July 24, 2019, 11:17:55 AM by sailor »
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uniquorn

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Re: The 2019 melting season
« Reply #4470 on: July 24, 2019, 11:45:49 AM »
<>Elsewhere, such as north of the central or western parts of the CAA, floes would have piled up more or less as usual.
Except for the NAC (CAA/CAB crack) dispersing everything every couple of weeks

Rich

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Re: The 2019 melting season
« Reply #4471 on: July 24, 2019, 12:04:34 PM »
The weekly U Hamburg comparison, July 16 vs July 23.
Really amazing what the storms have done on ESS and Beaufort

Very interesting view there of developments in the Archipelago. NW Passage Route 7 is showing a lot of promise.

Nice animation Sterks.

BenB

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Re: The 2019 melting season
« Reply #4472 on: July 24, 2019, 12:18:54 PM »
Warm air is already entering the Beaufort/Chukchi margin, and by 72 hours the Euro has it covering most of the CAB and CAA (first image). The heat then intensifies and merges with heat coming from the Atlantic side (second image), with the "high" temperatures lasting for a good 4 days. Then there appear to be twin cyclones on the horizon, but a lot could change by then.

be cause

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Re: The 2019 melting season
« Reply #4473 on: July 24, 2019, 01:18:37 PM »
Bordeaux yesterday , Brussels tomorrow , Bergen on Friday then Spitzbergen ? The heat marches north ..  b.c.

p.s.  the latest gfs run has the Arctic pretty much frost-free for the next 2 weeks . Looks like this July has bucked the recent trend of being the 'cold' month in the Arctic ..

   
« Last Edit: July 24, 2019, 01:27:28 PM by be cause »
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

Killian

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Re: The 2019 melting season
« Reply #4474 on: July 24, 2019, 01:29:33 PM »
7/23/2011 stood at 6.75M km sq. on this date.
7/23/2019 stands at 6.665M km sq., a record low for this date.

I called a 125k+/- 10k drop.  :-[ Got 85k. Only 30k off.  :o

7/24/2011 stood at 6.68M km sq. on this date.
7/23/2019 stands at 6.67M km sq., needing < +15k (non-rounded) increase for a record low on the 24th.

Let's keep this simple: Another record low on 7/24/2019.

NOTE: This will be the last day vs. 2011. 2012 overtakes 2011 on the 25th.

-----------------

Updated:
7/25/2012 stood at 6.62M km sq. on this date.
2019 needs an average daily drop of > 25k km sq. for a record low on this date. (2 days)

8/10/2012 stood at 4.94M km sq. on this date.
2019 needs an average daily drop of > 96.11k km sq. for a record low for this post-GAC date. (18 days)

9/15/2012 stood at 3.18M km sq. on this date.
2019 needs an average daily drop of > 64.6k km sq. for a record low for this date. (54 days)

peterlvmeng

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Re: The 2019 melting season
« Reply #4475 on: July 24, 2019, 01:34:21 PM »
Bordeaux yesterday , Brussels tomorrow , Bergen on Friday then Spitzbergen ? The heat marches north ..  b.c.
 

I think the real problem is not such extreme heatwave will cause essentially the real damage to the ice from Atlantic side BUT almost 10 days heating from Southern part to the Northern part of Atlantic SEA WATER!

Up to now, except Barent sea and Kara sea, all the visible ice melting is coming from the pacific side. I think the Atlantic will show its strength in August.

Up to now, we have not seen strong cyclone in arctic. The less ice covered arctic sea, more moisture and heat will transport to the atmosphere, more likely cause a strong cyclone.

I have a few academic questions. Traditionally, the atmosphere boundary layer of arctic region is within 500m. The height of troposphere is 8km. As more heat and vapor convection exist in the summer, will the height of troposphere expand higher? The circulation pattern could completely change.

Also, will the stratosphere of arctic also get warmer in summer?



Rich

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Re: The 2019 melting season
« Reply #4476 on: July 24, 2019, 01:51:55 PM »
First inkling of a major cyclonic event now appearing around D9-10 in Laptev on both EC and CMC btw.



We could see the CAB drawn and quartered under that setup.

FishOutofWater

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Re: The 2019 melting season
« Reply #4477 on: July 24, 2019, 03:57:24 PM »
The observations from the icebreaker are consistent with PIOMAS and ice drift maps. The strong transpolar drift this year has pushed ice towards the north coast of Svalbard and the Fram strait. The presence of multiyear ice in that region is not good news because that's ice about to be melted by warm Atlantic water.

Ice ridges would make crossing the ice that piled up north of Svalbard difficult to cross by icebreaker. The captain rightly turned back to protect his ship and his passengers, but that does not mean that Arctic ice is in good shape this summer. It means that some of the thickest ice is being exported out of the Arctic.

F.Tnioli

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Re: The 2019 melting season
« Reply #4478 on: July 24, 2019, 04:08:23 PM »
They just don't, in my book. Assuming that the "high" you mentioned will happen not only "oh-so-high Arctic", of course. So, you can not state both in the same time. But you just did. Care to explain? Thank you very much in advance!

Not sure what you are referring to with oh so high arctic. ...
I was referring to regions not oh-so-close to North Pole. Sorry about that, i assumed this to be very clear reference to the figure of speech you youself used in your post i was replying to: namely, you mentioned, quote, "not-so high Arctic". I apology for any confusion caused by my wrong assumption. And in any case, of course there are no hard feelings whatsoever, we do good thing here even on such occasions: namely, building consensus. Salute!

Ktb

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Re: The 2019 melting season
« Reply #4479 on: July 24, 2019, 04:20:00 PM »
Another gain on Slater today, appears to be that their model predicts the first August minimum rather than a September minimum.
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Ossifrage

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Re: The 2019 melting season
« Reply #4480 on: July 24, 2019, 04:22:24 PM »
Ossifrage

Isn't a thinner weaker more mobile pack more prone to piling up and ridging when pushed into an obstacle. Its one partial negative feedback I occasionally ponder - ice thickens fastest when thin, so if new ice is continually pushed aside faster than in the past , the rate of new winter ice creation will be higher(provided the extra energy released can successfully escape to space). If the winds push that ice in the right direction, its a way the system can replenish itself somewaht after a bad season.

Those stamukha anchors explain the scour marks in the ESS discussed at length here earlier I think

(But lets not derail the thread, back to weather forecasts for me!)

I'll give a caveat that the mechanics of this process haven't been studied in a great deal of depth. I'm not sure that anyone has ever meaningfully revised Parmeter and Coon's model of pressure ridge formation, and that dates back to 1972!

But the short answer is no, thinner ice doesn't make better pressure ridges. Thicker, stronger ice subjected to loading forces sheared into relatively large blocks that allow (well ... increasingly, allowed) for greater value as structural elements. Thinner ice does not have the tensile strength to respond in this manner and instead crumbles or crumples at floe boundaries; indeed, we've all watched image progressions that show large floes making contact and breaking apart rather than conglomerating. Even to the extent that thinner, weaker ice can form traditional pressure ridges, they are limited to smaller "masts" and (presumably) correspondingly shallower "keels".

Ice does thicken fastest when thin, and there are ridging processes that play a part in that, but their physical mechanics are very different than those of traditional MYI pressure ridges. It's not a negative feedback mechanism.

Back to the condition of current ice, there's enough clearing of the cloud deck to get the first good update for the Sverdrup Islands area in several days, and the CAA/CAB crack is really taking its toll. Fast ice on the east shore of Borden Island has retreated some 20 km since the 19th, and there is clear -- if less pronounced -- ice loss across the northern boundary of the Prince Gustav Adolf Sea.

At the primary southern outlet of the PGAS, the Maclean Strait, the situation is more dire. This area has been under cloud for quite awhile, although as recently as the 18th-19th, what little was visible under the clouds seemed to be largely holding intact. That's no longer the case. Ice in the Maclean visibly cracked on (or before) the 22nd, and clear skies on the 23rd show the entire triangle between Loughead, King Christian, and Bathurst has shattered completely. In 2012, this area saw considerable melting. Even if this region doesn't melt enough to show on the top-line metrics, the speed at which its quality has degraded is concerning; that's especially true because increased motility in the Maclean allows it to act as an export channel for ice from the PGAS.

Further east, a large (~10km) floe has separated from fast ice immediately to the west of Meighan Island. This isn't likely to melt immediately; there's a 20+ km floe northeast of Meighan that's just been hanging out for awhile now. But that floe originated with the breakup of CAB sea ice north of Axel Heiberg in late May and has drifted over 150 km since. The rate and direction of floe movement is in part weather dependent (but also will tend to increase, to some limit, as the ice becomes more free to move). But if we use the last two months as a rough benchmark, both of these floes could make it nearly to Ellef Ringnes before the end of the season. In turn, that suggests why the Beaufort has seemed so resistant to clearing this year; it is being supplied with ice from the CAA/CAB boundary at a prodigious rate, some of which represents the remaining MYI stores in that region. In effect, the "crack" is dumping large volumes of typically-protected ice into the Beaufort. Even if quite a bit survives this season, it isn't where it needs to be long term.

The melt pressure on the CAA from the north is perhaps unprecedented. Damage is being done, even if extent and area don't take hits.

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Re: The 2019 melting season
« Reply #4481 on: July 24, 2019, 04:23:00 PM »
Another gain on Slater today, appears to be that their model predicts the first August minimum rather than a September minimum.
End of season wobbles. Could do a switcheroo.
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F.Tnioli

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Re: The 2019 melting season
« Reply #4482 on: July 24, 2019, 04:30:30 PM »
Insolation at 90 degrees is greater than at the Equator until the first week in August.

Ought to settle this question.
Except that the albedo of the underlying surface is in large part a function of the angle of incidence of the solar radiation. This is true not just for water but also for sea ice.


Source: Hudson, 2011 https://doi.org/10.1029/2011JD015804

At 90°N latitude at this time of year the solar zenith angle is about 70° so that all the time is spent in the high-albedo part of the curve. South of 30°N, once the sun rises, almost all daylight hours have a solar zenith angle less than 70° and for much of the day less it's than 40°; at tropical latitudes it can obviously reach 0° at high noon. The end result is a great deal of time is spent in the low-albedo part of the curve.

I have no idea how to quantify this difference. My point is that it's not as simple as calculating the theoretical 24-hour solar insolation based on latitude alone and calling it a day.
Actually there is even more to it. On top of actual effective albedo, there is also the fact that the greater solar zenith angle is, the longer distance sunlight travels within athmosphere, which means not only losses to optical depth of air itself, but also higher chance for any particular photon to encounter particulates and/or clouds on its way to the ice.

On the other hand, the data you present is most likely made using massively simplified idea of "sea ice", both dark and white. I suspect solid 100% concentration sea ice is meant. Well, nearly whole Arctic ocean is now very different from that old normal. Even few % of open water / melt ponds dramatically lower albedo, "slush" and wave action through broken ice does it too.

But since we do basic discussion here - and not a dedicated paper, - i'd say we can safely settle on very approximate range of ~180...300 W/m2 absorbed at the surface under clear skies (high pressure systems) for late July / early August, depending on ice concentration, condition, wave action, etc etc. And that amount is still higher than Florida when averaged over 24 hours, since it's polar day - i.e. sunshine 24/7, while Florida has darkness of the night for significant part of each 24 hours period - during which, for practical purposes, we should count night time as a sort of "negative insolation" value, since surface rapidly loses heat to near-Earth space (clear skies means clouds don't prevent that loss).

So yep, for forum purposes, i'd say we can be quite sure sunshine is still a monster thing for this melt season, and will remain so for couple more weeks; and even after couple more weeks, it won't become non-issue instantly, but will remain serious melting force for few more weeks forward, too.

I hope now this post closes the matter in an acceptable for all of us way... :)
« Last Edit: July 24, 2019, 04:43:51 PM by F.Tnioli »

Phil.

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Re: The 2019 melting season
« Reply #4483 on: July 24, 2019, 04:42:02 PM »
This paper shows that the solar heating of the surface waters has increased dramatically in recent years and seems likely to continue to do so.


Warming of the interior Arctic Ocean linked to sea ice losses at the basin margins
Mary-Louise Timmermans1,*, John Toole2 and Richard Krishfield2
Science Advances  29 Aug 2018:
Vol. 4, no. 8, eaat6773
DOI: 10.1126/sciadv.aat6773

Abstract
Arctic Ocean measurements reveal a near doubling of ocean heat content relative to the freezing temperature in the Beaufort Gyre halocline over the past three decades (1987–2017). This warming is linked to anomalous solar heating of surface waters in the northern Chukchi Sea, a main entryway for halocline waters to join the interior Beaufort Gyre. Summer solar heat absorption by the surface waters has increased fivefold over the same time period, chiefly because of reduced sea ice coverage. It is shown that the solar heating, considered together with subduction rates of surface water in this region, is sufficient to account for the observed halocline warming. Heat absorption at the basin margins and its subsequent accumulation in the ocean interior, therefore, have consequences for Beaufort Gyre sea ice beyond the summer season.

Shared Humanity

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Re: The 2019 melting season
« Reply #4484 on: July 24, 2019, 04:43:00 PM »
The observations from the icebreaker are consistent with PIOMAS and ice drift maps. The strong transpolar drift this year has pushed ice towards the north coast of Svalbard and the Fram strait. The presence of multiyear ice in that region is not good news because that's ice about to be melted by warm Atlantic water.

Ice ridges would make crossing the ice that piled up north of Svalbard difficult to cross by icebreaker. The captain rightly turned back to protect his ship and his passengers, but that does not mean that Arctic ice is in good shape this summer. It means that some of the thickest ice is being exported out of the Arctic.

And if the approaching dipole anomaly manages to push a lot of that ice into the Barents, we could very well see a late end to the melt season as the warm waters in the Barents melts much of this ice.

F.Tnioli

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Re: The 2019 melting season
« Reply #4485 on: July 24, 2019, 05:09:00 PM »
...
The melt pressure on the CAA from the north is perhaps unprecedented. Damage is being done, even if extent and area don't take hits.
I saw couple signs that say that you're absolutely correct about the CAA part, lately. And very true about extent and area, too. Apart from (often difficult, uncertain, or not available) measurements of current ice volume / thickness, i'd say small dips in concentration % could sometimes be one useful hint about such processes. I wonder if you use that as one of quick things to check, yourself.

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Re: The 2019 melting season
« Reply #4486 on: July 24, 2019, 06:05:53 PM »
Re: the icebreaker.
According to this article the ship had to return due to a leakage in the propellerhouse. The thicknes of the ice was not a problem. The icebreaker was built in Italy and was one year late due to construction problems, according the article. https://www.nrk.no/troms/forskningsskipet-_kronprins-haakon_-skadet-etter-mote-med-is-1.14636312

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Re: The 2019 melting season
« Reply #4487 on: July 24, 2019, 06:13:36 PM »
I saw couple signs that say that you're absolutely correct about the CAA part, lately. And very true about extent and area, too. Apart from (often difficult, uncertain, or not available) measurements of current ice volume / thickness, i'd say small dips in concentration % could sometimes be one useful hint about such processes. I wonder if you use that as one of quick things to check, yourself.

Well, hints like that help, certainly. One of the challenges, of course, is determining how to section off areas for analysis. That's why I tend to focus on just the Sverdrup Islands, rather than wider areas like the Queen Elizabeth Islands or the whole of the CAA.

Even a small change in one of the satellite-discernible metrics (area, concentration, extent) for the Sverdrups alone is likely to be significant. But changes of similar magnitude for the whole of the CAA are potentially just noise. For example, the CAA's conventional boundaries include the North Water Polynya, at least in part. The CAA also includes smaller areas of continuously (or nearly so) open water, including at the west end of James Sound (at North Kent Island) and in the general vicinity of Bailie-Hamilton Island. Even absent significant regional melt or fragmentation, the exact boundaries of these open water phenomena can easily swamp the signal of more concerning events when considering the region broadly.

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Re: The 2019 melting season
« Reply #4488 on: July 24, 2019, 06:15:25 PM »
Compactness dive taken a recess lately even rebounding, depending on the data used (from Wipneus AMSR2 thread).


FishOutofWater

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Re: The 2019 melting season
« Reply #4489 on: July 24, 2019, 07:08:07 PM »
Thanks Hopen Times for the correction concerning the icebreaker.

Open water is showing up on the north and east sides of the Parry channel now and ice movement can be seen on RAMMB slider. Ice in the southern channels is melting and ice from further north is getting compacted into the southern channels. I wasn't able to tell if the whole Parry channel had moving ice, but the ice is in very bad shape now.

And yes, this has been a very bad year for multiyear ice. The Nares strait was open all year. The brief arch in the Lincoln sea was maintained for a month by winds that sent ice towards the Fram strait, not the Nares. That did not help maintain thick ice. When high pressure returned in May the Beaufort became a thick ice killing zone. I expect a record minimum volume in September with little thick ice remaining.

Ossifrage

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Re: The 2019 melting season
« Reply #4490 on: July 24, 2019, 09:13:05 PM »
Thanks Hopen Times for the correction concerning the icebreaker.

Open water is showing up on the north and east sides of the Parry channel now and ice movement can be seen on RAMMB slider. Ice in the southern channels is melting and ice from further north is getting compacted into the southern channels. I wasn't able to tell if the whole Parry channel had moving ice, but the ice is in very bad shape now.

And yes, this has been a very bad year for multiyear ice. The Nares strait was open all year. The brief arch in the Lincoln sea was maintained for a month by winds that sent ice towards the Fram strait, not the Nares. That did not help maintain thick ice. When high pressure returned in May the Beaufort became a thick ice killing zone. I expect a record minimum volume in September with little thick ice remaining.

I mean, I do expect the Peary to clear (or largely clear) as far in as Cornwallis or Bathurst even absent a record-setting year. The eastern reaches of the channel have been passable at late summer in many years even before the recent cryosphere collapse. That's how the Polaris mine was able to operate, after all. The 23rd showed essentially open water to Somerset, and rubble at least to Cornwallis. But it's tough to evaluate further west on Worldview, at least, because of cloud cover over the Viscount Melville Sound.

The northwest end of the Peary -- M'Clure Strait -- looks terrible, though, with ice essentially fully clear of Prince Patrick Island. There's a region of almost 1000 sq. km that might as well be ice free (and a larger area that certainly isn't area anymore); mere compaction seems unlikely to explain the loss. I actually suspect that quite a bit of the ice that belongs at the mouth of the M'Clure has been swept west and out by the crack, although I'll need to do some more detailed comparisons to confirm that.

Tor Bejnar

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Re: The 2019 melting season
« Reply #4491 on: July 24, 2019, 09:32:39 PM »

that suggests why the Beaufort has seemed so resistant to clearing this year; it is being supplied with ice from the CAA/CAB boundary at a prodigious rate, some of which represents the remaining MYI stores in that region. In effect, the "crack" is dumping large volumes of typically-protected ice into the Beaufort. Even if quite a bit survives this season, it isn't where it needs to be long term.
...
I was pretty sure this was the case, having watched (on posted GIFs) a few 'identifiable' floes move 'toward Alaska' and disappear [OK, break up and melt] so the 'little stuff' near them had to be melting too, yet the amount of Beaufort ice seemed to remain relatively stable.

I see the NAC (North American Crack) as being a frictionless boundary allowing the free movement of ice to where it won't survive long.  I appreciate your indicating that if this ice movement continues for the next 3 months, there will be Beaufort ice, newly arrived from the CAB, that won't melt out this year, but undoubtedly will next year, and leaving behind thinner ice in the areas we used to presume the last bastion would be.
Arctic ice is healthy for children and other living things.

uniquorn

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Re: The 2019 melting season
« Reply #4492 on: July 24, 2019, 09:50:36 PM »
Ice at the mouth of the mclure strait didn't seem to 'bind' this year, feb1-jul23
Having seen the rammb animations, these days I wonder if that's due to thinner ice and tidal effects.

slow wing

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Re: The 2019 melting season
« Reply #4493 on: July 24, 2019, 10:34:43 PM »
Another gain on Slater today, appears to be that their model predicts the first August minimum rather than a September minimum.
No, that's not how the plot works. Each day, an independent estimate of extent is produced and added to the plot. The older estimates are still displayed in the plot but their current estimates for those August dates are not shown. Presumably, their current estimates for those August dates will be higher than the old extent estimates that are displayed and also higher than the current predictions for 11 or 12 September.

slow wing

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Re: The 2019 melting season
« Reply #4494 on: July 24, 2019, 11:05:59 PM »
i'd say we can safely settle on very approximate range of ~180...300 W/m2 absorbed at the surface under clear skies (high pressure systems) for late July / early August

So about 5-9 cm of ice per day might be melting under the clear skies of the big high pressure system soon to arrive in the CAB.


Reason: it takes about 35 W/m^2 to melt each centimeter of ice per day:

Energy flux to melt 1 cm thickness of ice per day [in units of W/m^2] = 1 cm x (10^4 cm^2/m^2) x (334 J/g latent heat of melt) x (0.9 g/cm^3 density) / ( 3600x24 seconds/day)
= 35 W/m^2


(Uses the definition W = J/s)




DISCUSSION POINT

Doesn't that seem a bit high?

Let's say, roughly speaking, that the Arctic sea ice is observed to lose on average about 2 cm per day (that's 200 cm over a 100 day melt season). Then, from the above calculation, that's 70 W/m^2 delivered to the ice on average from all sources combined: sun, air and water.

Is that compatible with the insolation plot shown - where 'clear skies' are presumed to add 180-300 W/m^2 - and that is for more than a month past the Summer solstice?


If we believe '180-300 W/m^2' then it seems like only a small fraction of 'clear skies' over the ice would use up the energy budget to produce the amount of melt we observe.


So I'm skeptical that all the insolation shown in the plot actually does get to heat up the ice, even under 'clear skies'.


Asking the experts then: is that insolation plot for the top of the atmosphere and, further, is a considerable fraction of that energy lost even under what we consider to be 'clear skies'?

That's my suspicion.
« Last Edit: July 24, 2019, 11:40:05 PM by slow wing »

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Re: The 2019 melting season
« Reply #4495 on: July 24, 2019, 11:34:51 PM »
i'd say we can safely settle on very approximate range of ~180...300 W/m2 absorbed at the surface under clear skies (high pressure systems) for late July / early August

So about 5-9 cm of ice per day might be melting under the clear skies of the big high pressure system soon to arrive in the CAB.


Reason: it takes about 35 W/m^2 to melt each centimeter of ice per day:

Energy flux to melt 1 cm thickness of ice per day [in units of W/m^2] = 1 cm x (10^4 cm^2/m^2) x (334 J/g latent heat of melt) x (0.9 g/cm^3 density) / ( 3600x24 seconds/day)
= 35 W/m^2


(Uses the definition W = J/s)




DISCUSSION POINT

Doesn't that seem a bit high? Let's say, roughly speaking, that the Arctic sea ice is observed to lose on average about 2 cm per day (that's 200 cm over a 100 day melt season).


Then that's 70 W/m^2 delivered to the ice on average from all sources combined: sun, air and water.

Is that compatible with the insolation plot shown - where 'clear skies' are presumed to add 180-300 W/m^2 - and that is for more than a month past the Summer solstice?


If we believe '180-300 W/m^2' then it seems like only a small fraction of 'clear skies' over the ice would use up the energy budget to produce the amount of melt we observe.


So I'm skeptical that all the insolation shown in the plot actually does get to heat up the ice, even under 'clear skies'.


Asking the experts then: is that insolation plot for the top of the atmosphere and, further, is a considerable fraction of that energy lost even under what we consider to be 'clear skies'?
If I'm not mistaken, your calculation assumes the ice is already at a temperature of 0°C.

slow wing

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Re: The 2019 melting season
« Reply #4496 on: July 24, 2019, 11:47:12 PM »
If I'm not mistaken, your calculation assumes the ice is already at a temperature of 0°C.

Yes it does. It's a back-of-the-envelope calculation with implicit approximations and assumptions.


The assumption is a reasonable approximation because:

1) The specific heat of ice is only 2.1 J/g-(degree Celsius), whereas the melting heat is 334 J/g. So even if the ice starts at, say, -10 degrees C, then that is only a 6% effect.

2) By the start of August, I presume that the ice will anyway be close to zero degrees C.
« Last Edit: July 24, 2019, 11:53:12 PM by slow wing »

UCMiami

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Re: The 2019 melting season
« Reply #4497 on: July 24, 2019, 11:50:25 PM »
Isolation is only one of many heat gain/loss processes that are occurring in the arctic - as a few examples, huge amounts of energy are lost from evaporation of water/ice (evaporation cools the surface) and radiation back into the atmosphere/space from the ice/water.

And as stated by edmountain the starting temperature in the arctic and in the ice is significantly below zero.

The arctic is a very complex system and simple equations cannot provide the answer - complex and powerful models struggle to provide meaningful projections of what will happen in a week in only one part of the total arctic system, let alone for a season or over longer periods. That does not mean the simple equations are incorrect, just that no where in nature do the exist in an isolated state.

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Re: The 2019 melting season
« Reply #4498 on: July 24, 2019, 11:58:01 PM »
i'd say we can safely settle on very approximate range of ~180...300 W/m2 absorbed at the surface under clear skies (high pressure systems) for late July / early August

So about 5-9 cm of ice per day might be melting under the clear skies of the big high pressure system soon to arrive in the CAB.
Reason: it takes about 35 W/m^2 to melt each centimeter of ice per day:
Energy flux to melt 1 cm thickness of ice per day [in units of W/m^2] = 1 cm x (10^4 cm^2/m^2) x (334 J/g latent heat of melt) x (0.9 g/cm^3 density) / ( 3600x24 seconds/day)
= 35 W/m^2
(Uses the definition W = J/s)
DISCUSSION POINT
Doesn't that seem a bit high?
Let's say, roughly speaking, that the Arctic sea ice is observed to lose on average about 2 cm per day (that's 200 cm over a 100 day melt season). Then, from the above calculation, that's 70 W/m^2 delivered to the ice on average from all sources combined: sun, air and water.
Is that compatible with the insolation plot shown - where 'clear skies' are presumed to add 180-300 W/m^2 - and that is for more than a month past the Summer solstice?
If we believe '180-300 W/m^2' then it seems like only a small fraction of 'clear skies' over the ice would use up the energy budget to produce the amount of melt we observe.
So I'm skeptical that all the insolation shown in the plot actually does get to heat up the ice, even under 'clear skies'.
Asking the experts then: is that insolation plot for the top of the atmosphere and, further, is a considerable fraction of that energy lost even under what we consider to be 'clear skies'?
That's my suspicion.
Not an expert.
The thing is that this is a short event.
I’m more concerned with compaction of certain areas. The ice drift response will be immediate.
And concerned with the continuation or not. Both GFS and EC ensembles hint of a high over CAA and Greenland providing, beyond day 5, of a weaker distorted dipole-like circulation, which is going to keep transport of ice in the Pacific-> Atlantic direction albeit slower. And compaction will go on in the American side unless a storm decides to hang out around Beaufort, seems improbable.
GLB ice drift from July 24 to 30
« Last Edit: July 25, 2019, 12:09:36 AM by Sterks »

deconstruct

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Re: The 2019 melting season
« Reply #4499 on: July 24, 2019, 11:58:49 PM »
The Florida noon sun would burn the ice within a few hours
I think that this conclusion is flawed. The insolation in Florida is comparable from its latitude to that in Peru, where you have Glaciers in the Cordillera Blanca. The ice of those glaciers is not melting in a speed like a meter of ice will be melted with in a few days, but is in reality much slower.

The fact that if you would put a 1x1x1m cube of ice at the beach of Miami and that ice would melt may be within a day or so, is not due to the insolation there, but because air temperature will be 30°C or more, whereas air temperature in the Arctic or on high mountains in the Andes is around 0°C, so the ice will not be melted by the air temperature at all, but only by insolation.

And that the temperature in the Arctic is only around 0°C is not due to the low insolation there, but because there is ice nearly everywhere and all heat that goes there (by insolation or convection) will go completely into melting of ice, and therefore temperature cannot rise higher, as long there is a lot of ice.