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Andreas T

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Re: The 2017 melting season
« Reply #2350 on: June 27, 2017, 08:12:08 AM »
Looks hot in the NW Passage now.
O-Bouy:
Thanks for this TB. Seems like the O-buoy local vicinity is very representative of conditions in the NW passage as a a whole. The deep blue and big cracks in your image were not there a few days ago. CLICK to animate.
If you look carefully the big cracks are old cracks which show up now because of the snow melt. You can see them to some extent as lighter shades (refreeze being different ice structure/ flatter) in earlier shots. This IR image from 11 January 2017 shows them soon after they formed.

epiphyte

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Re: The 2017 melting season
« Reply #2351 on: June 27, 2017, 08:18:47 AM »
Looks hot in the NW Passage now.

O-Bouy:

As my daughter would have it... Very punny.
 :D

Glenn Tamblyn

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Re: The 2017 melting season
« Reply #2352 on: June 27, 2017, 09:18:24 AM »
Finally, remember - the words of people on this forum don't really change the September outcome. It only seems that way  ;)

I had to laugh when I realized you may be wrong about this.  The actual raw data is pretty sparse, and I suspect that we do in fact influence at least some of the researchers.

Ahhh Jim. A new denier conspiracy theory. Paging David Rose...

'Arctic Researchers caught red-handed!!! Egged on by alarmist bloggers, researchers admit going out and melting ice!'

meddoc

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Re: The 2017 melting season
« Reply #2353 on: June 27, 2017, 09:37:07 AM »
Arctic sst's for years 2014-2017

http://polar.ncep.noaa.gov/sst/ophi/

I wouldn't seek much Comfort in this Year' s SSTs- cause according to the Laws of Physics- that missing Heat surely went somewhere:
1) Preconditioning the Ice in the Freezing Season
2) into the Atmosphere
3) underneath the Icecap
4) destabilizing Methane Hydrates in the Deep
5) all of the above

Neven

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Re: The 2017 melting season
« Reply #2354 on: June 27, 2017, 01:24:27 PM »
Today's 00Z run looks better than yesterday's 12Z run, but with high pressure remaining dominant for the coming six days.

Here's an update of that single/deterministic run vs ensemble run comparison to how it actually played out in reality. The single run had a 967 hPa cyclone for today, the ensemble said 976 hPa, but it actually turned out to be 988 hPa. All in all, it's safe to say that this cyclone hasn't lived up to the forecast.
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slow wing

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Re: The 2017 melting season
« Reply #2355 on: June 27, 2017, 02:50:31 PM »
According to the model analyses on tropicaltidbits.com, the cyclone bottomed out at 982 hPa on last Sunday and Monday, 25 and 26 June 2017.

So it was still a strong and persistent storm, only 2 hPa above the June record for the Arctic Basin in the satellite era of 980 hPa, set in 2013.

slow wing

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Re: The 2017 melting season
« Reply #2356 on: June 27, 2017, 03:00:42 PM »
A NEW storm has arrived in the Laptev Sea just as the persistent storm began to weaken.

It is already at 983 hPa, which is predicted to be its lowest pressure, so it is also a strong storm for June.

The ice in the Laptev Sea is already a mess so this storm will likely cause carnage there.


Has the 'cyclone alley' of last year - Western Siberia down into the Laptev Sea - started up earlier and stronger this year??
« Last Edit: June 27, 2017, 03:11:30 PM by slow wing »

gerontocrat

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Re: The 2017 melting season
« Reply #2357 on: June 27, 2017, 03:20:34 PM »
The Jaxa extent data and a simple arithmetic projection (based on previous 10 year average melting) says the prospects for a new record low are diminishing rapidly, and 1 million km2 is beyond reason. Also the JAXA sea ice thickness image for June 26 one year ago looks more favourable for melting than this year's image.

However, Jaxa AMSR2 volume is dropping like a stone. I think I will put my brain and pen into pause mode until PIOMAS for June comes out next week.



« Last Edit: June 27, 2017, 04:01:14 PM by gerontocrat »
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F.Tnioli

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Re: The 2017 melting season
« Reply #2358 on: June 27, 2017, 03:43:14 PM »
<snip: way off-topic; see below. JP>
« Last Edit: June 27, 2017, 05:05:36 PM by Jim Pettit »
To everyone: before posting in a melting season topic, please be sure to know contents of this moderator's post: https://forum.arctic-sea-ice.net/index.php/topic,3017.msg261893.html#msg261893 . Thanks!

Tor Bejnar

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Re: The 2017 melting season
« Reply #2359 on: June 27, 2017, 04:16:11 PM »
I understand the CAB sea ice stops thickening (gaining volume) in June.  (Am I wrong?)  Might this be the "hidden in plain sight" solution to part of your inquiry?
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F.Tnioli

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Re: The 2017 melting season
« Reply #2360 on: June 27, 2017, 04:18:57 PM »
<snip: way off-topic. JP>

(Again: This forum is strictly for discussing the current Arctic sea ice melting season. It is NOT the place for discussing your pet conspiracy theories about "intentional sabotage", chemtrails, data manipulation, and secretive actions by the UN Security Council.)
« Last Edit: June 27, 2017, 05:04:43 PM by Jim Pettit »
To everyone: before posting in a melting season topic, please be sure to know contents of this moderator's post: https://forum.arctic-sea-ice.net/index.php/topic,3017.msg261893.html#msg261893 . Thanks!

Thawing Thunder

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Re: The 2017 melting season
« Reply #2361 on: June 27, 2017, 04:38:32 PM »
... going for (slightly more than) half a June with average zero ASI volume loss is definitely very not "normal".

I stated before that I remember a post where someone claimed the satellite sensors were tricked by a climate phenomena to "believe" that the ice is thicker. I just couln't find that post. I now searched with the keyword "slush" and though I did not find the mentioned post, I stumbled over one from A-team that describes an earlier situation but which IMO could explain what was happening in the arctic at the beginning of June:

"The snow had undergone thaw and refreezing by mid-April, presumably from a rain-on-snow event giving an ice layer at the surface, later buried by more recent snowfall. This created a uniform ice layer within the snowpack but above the main ice which then fools the radar return; this ice crust was confirmed within the snowpack in snow-pit studies. If the non-coastal piomas thickness blob is artifactual, this is a conceivable explanation."
« Last Edit: June 27, 2017, 05:11:02 PM by Thawing Thunder »
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marcel_g

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Re: The 2017 melting season
« Reply #2362 on: June 27, 2017, 04:53:41 PM »
The Jaxa extent data and a simple arithmetic projection (based on previous 10 year average melting) says the prospects for a new record low are diminishing rapidly, and 1 million km2 is beyond reason. Also the JAXA sea ice thickness image for June 26 one year ago looks more favourable for melting than this year's image.


IMHO, the volume metric still has a good chance of accelerating its decreases again and possibly staying ahead of even 2012's dramatic drop. I'm basing this on the following reasons: a) most of 2017's anomalous thickness, and therefore, its extra volume, is located in that blob near Svalbard, which means it is going to melt out almost completely, (assuming PIOMAS is relatively correct) b) 2017 has a higher proportion of FYI, which is thinner and more saline, with a lower melting temperature, so it has a higher chance of doing that 'poof' thing that we have witnessed so many times on the periphery in previous years, c) lack of Freezing Degree Days over the winter means that most of the ice was anomalously warm going into the melt season, so it needs measurably less energy to melt, and
d) as noted in other posts, the current weather forecast doesn't look great for the ice's chances of survival, especially considering that the meltponding seems to have spread rapidly across huge areas of the CAB. There is still a lot of potential sunlight left on the calendar.

I could be wrong, and I'm not great with weather maps, so if I'm off please corrrect me, but going by Climate Reanalyzer, it looks like the (already weak looking) Pacific side is going to get hit with rain, warm temperatures, and then a lot of sunshine. (Image is the forecast for 60 hours, I believe). The Atlantic side doesn't seems to fare only slightly better.




Thomas Barlow

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Re: The 2017 melting season
« Reply #2363 on: June 27, 2017, 05:15:47 PM »
The Jaxa extent data and a simple arithmetic projection (based on previous 10 year average melting) says the prospects for a new record low are diminishing rapidly, and 1 million km2 is beyond reason. Also the JAXA sea ice thickness image for June 26 one year ago looks more favourable for melting than this year's image.
However, Jaxa AMSR2 volume is dropping like a stone. I think I will put my brain and pen into pause mode until PIOMAS for June comes out next week.
Interesting.
Yes, volume.
At some point in the future, the Arctic Ocean will have a tipping point that is not seen in previous years (hopefully not this year, but it is a possibility).
I doubt it will be a slow year by year, decade by decade, slow incremental diminishment, until it is mostly blue, a long time from now.
I know everyone is aware of this, but just to re-iterate - The more open ocean (the Arctic Ocean), the more loss of albedo, the more warming waters, the more Atlantic intrusion, the more top to bottom mixing, the more cracks, the more volatility with winds (because of a more complex system is introduced). All of that impacting the lowest volume in that ocean, the most fragile we have ever seen it, then a tipping point could be reached. Whether it is this year or next year, or 3 years from now, it seems to me that's what people should think about. If there is a potential for a tipping point, then I would say there is 50-50 chance of that happening this year. If the tipping point is reached, then all bets are off. That means the glass is half empty or half full. We don't know.
So predicting what is going to happen, seems to me, needs to take into account the state of the Arctic Ocean only, and its potential for a tipping point. A critical point, at which collapse occurs quickly.
I think that is what Peter Wadhams is going on about, and I think that's what he means.
At some point, this year or in the next 2 years, that tipping point is reached, then all bets are off. Previous trajectories will no longer be valid predictors.
Are we close to that tipping point this year? If more blue ocean opens up than usual (in the Arctic Ocean) in the next month, that could be a bad sign.
I hope I am wrong.
(I also have the caveat, that even with loss of ice, there could be many, unforeseen mitigating effects from nature that could mean the loss of ice is very bad for us, but may not be as bad as people are saying - Eg. see my posts in the methane thread --> https://forum.arctic-sea-ice.net/index.php/topic,12.300.html#firstPost )

Graph courtesy of Oren (and this includes the CAA, so if that was removed, the Arctic Ocean volume could be even worse right now.)
« Last Edit: June 27, 2017, 05:26:51 PM by Thomas Barlow »

Tigertown

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Re: The 2017 melting season
« Reply #2364 on: June 27, 2017, 05:21:34 PM »
@Thomas Barlow
Re: tipping point

We saw what the open water late in the melt season last year caused to happen over the course of the freezing season, along with other factors, of course. If we get just a little more open water this year, for just a little more time, this will cause more winter troubles. If you think about it for a minute, water makes for a really good battery, simple but good. It stores heat energy very well. The end result; next melt season the ice will be  even less thick and durable, and melt even sooner. That is when battery really gets charged.  Summer 2018.
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FishOutofWater

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Re: The 2017 melting season
« Reply #2365 on: June 27, 2017, 05:49:54 PM »
Volume measurements based on satellite observations don't work once melt ponds form. The volume changes seen at the JAXA web site have not been correct since the first melt ponds formed.

Linear extrapolations of trends don't make much sense when this year's thickness vs area distribution is so different from the last 4 years. This year there is very little thick ice and very large area of ice that is so thin that it will be prone to melt out by September. It might be preserved by cool weather and favorable winds but it could almost all melt out leading to record low thickness, area and extent in September. Whatever, the linear extrapolation ignores how thin this year's ice is.

Storminess on the Siberian shelf is starting early thanks to the large temperature contrast between the Arctic ocean and Eurasia, and the persistently stronger than normal jet stream. Ice on the Siberian shelf will melt out faster than normal as it gets repeatedly blasted by warm air off the continent.

A-Team

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Re: The 2017 melting season
« Reply #2366 on: June 27, 2017, 06:10:00 PM »
Quote
satellite sensors can be tricked to "believe" that the ice is thicker.
The overall bundle of effects is called 'antarctification' in N-ICE2015 papers, in reference to (better-studied) thin annual floating sea ice subject to storms there. Ice layers of enhanced salinity too high in the snow-ice profile may even fool induction sensors hanging from low-flying helicopters, leaving us with sparse analyzed ice cores.

Quote
Linear extrapolations of trends don't make much sense when this year's thickness vs area distribution is so different from the last 4 years.
Very important point. The already-meagre tools we have for following the melt season are not being processed by product algorithms adapted to the new conditions of the ice pack, weakening comparisons to the years for which they were developed and vetted.

Sentinel-1AB, as mosaiced at DTI, offers significant improvements in pack motion, dispersion, and resolution but it is not yet integrated into extent or volume products. The bus may leave the depot before its data can be deployed.

The animation below shows Wip's AMSR2 sea ice concentration animation (at half-scale) for 16-26 June 2017 vs 2016, to which I've appended the hycom forecast from the 26th to July 4th 2017

http://forum.arctic-sea-ice.net/index.php/topic,382.msg118486.html#msg118486 full scale
« Last Edit: June 27, 2017, 06:22:52 PM by A-Team »

Lord M Vader

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Re: The 2017 melting season
« Reply #2367 on: June 27, 2017, 06:42:00 PM »
Any ideas about how the 2017 minimum will look like?

What are your guesses? Here i put my very simple idea about how the 2017 minimum might look like by the middle of September:


seaicesailor

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Re: The 2017 melting season
« Reply #2368 on: June 27, 2017, 06:42:18 PM »
Now that it has been a week since my last Worldview Sea Ice Outlook for Summer 2017, I've done a Part 2 using the latest Worldview imagery and my subjective take on it:


In summary:  things have accelerated more than I expected, such that I now think 2017 will end up somewhere between 2012 and 2016.

Nice explanations, thank you
There is an awful lot of ice so vulnerable, like the ice you point out that has "crumbled down" in almost a single blow

Clenchie

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Re: The 2017 melting season
« Reply #2369 on: June 27, 2017, 06:49:47 PM »
Any ideas about how the 2017 minimum will look like?

What are your guesses? Here i put my very simple idea about how the 2017 minimum might look like by the middle of September:

Lordy, I have added my effort in purple, the darker the thicker.
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Clenchie

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Re: The 2017 melting season
« Reply #2370 on: June 27, 2017, 07:52:24 PM »
Now that it has been a week since my last Worldview Sea Ice Outlook for Summer 2017, I've done a Part 2 using the latest Worldview imagery and my subjective take on it:


In summary:  things have accelerated more than I expected, such that I now think 2017 will end up somewhere between 2012 and 2016.

Nice explanations, thank you
There is an awful lot of ice so vulnerable, like the ice you point out that has "crumbled down" in almost a single blow

Nice work Sis, I found your comments on the melt ponding particularly interesting.  I look forward to the next update.

Cheers, Clenchie.
« Last Edit: June 27, 2017, 08:01:13 PM by Clenchie »
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werther

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Re: The 2017 melting season
« Reply #2371 on: June 27, 2017, 08:14:37 PM »
Here’s a combined set of MODIS tiles featuring the CAB 26th of June:



You may remember, I’ve forecast a ‘black swan’-event for ’17 since early ’16. By that date, it was obvious to me that the weak ‘winter power’ could generate such a crisis. A second winter like that and the stage would be set.

Well, it’s dead set.

Yet this season isn’t ahead in the race. A colder March, April, May somewhat compensated the extreme lack of ‘winter power’ during the first half of the freezing season. A matter of weather.
Still, an extreme July could finish the job. Because the ice condition is worse than last year. The lessening gap in PIOMAS volume could fool us to believe there’s not much difference. But it’s not the result of a good freeze-up. It’s delayed melt.

Even average summer weather during July, like last year, will contribute to a new minimum record come September. If July weather gets anywhere near as bad as in ’07, we’ll see the event unfolding soon.

What does the pic reveal: an app. 2 Mkm2 swath around the Pole, snow cover protected by last week’s Low. The already bad state on the Pacific and Siberian side aggravated by melting weather, sucked in by the Low. Not much different when compared to 2016 06 23 in my archive. Lots of holes, cracks, fragmentation and melt ponds on both dates. However, there’s more open water now.
The remaining CAB snow cover could be bad news when July melt arrives. The ice pack isn’t very thick and badly fragmented.

The main difference is extent on the Atlantic side. But, over there, more fragmentation than ever. Under the right conditions, a lot of ice will be pushed South and melt, even though the Atlantic may not be that warm now.

There’s a dipole in the make. It could be the beginning of the event. Hold on.
« Last Edit: June 27, 2017, 08:28:34 PM by werther »

cesium62

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Re: The 2017 melting season
« Reply #2372 on: June 27, 2017, 08:30:51 PM »
The Jaxa extent data and a simple arithmetic projection (based on previous 10 year average melting) says the prospects for a new record low are diminishing rapidly

The AMSR2 data shows that most of the peripheral seas are on track to melt out by 1 Sep.  The Greenland Sea and CAA are on track to be close to where they been the past few years.  From just the extent graphs, the CAB remains the crap shoot it always is.

The SPIE is predicting mid-august extent higher than last year.

Cook

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Re: The 2017 melting season
« Reply #2373 on: June 27, 2017, 09:19:25 PM »
IMHO, the volume metric still has a good chance of accelerating its decreases again and possibly staying ahead of even 2012's dramatic drop. I'm basing this on the following reasons: a) most of 2017's anomalous thickness, and therefore, its extra volume, is located in that blob near Svalbard, which means it is going to melt out almost completely, (assuming PIOMAS is relatively correct) b) 2017 has a higher proportion of FYI, which is thinner and more saline, with a lower melting temperature, so it has a higher chance of doing that 'poof' thing that we have witnessed so many times on the periphery in previous years,

I agree. In terms of ice that will survive the summer, then the blob near Svalbard that is currently boosting PIOMAS figures is irrelevant. I suspect that during the month of July we will see huge tracts of ice that are here one week and gone the next.

jdallen

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Re: The 2017 melting season
« Reply #2374 on: June 27, 2017, 09:26:09 PM »
<snippage>

The ice pack isn’t very thick and badly fragmented.

The main difference is extent on the Atlantic side. But, over there, more fragmentation than ever. Under the right conditions, a lot of ice will be pushed South and melt, even though the Atlantic may not be that warm now.

There’s a dipole in the make. It could be the beginning of the event. Hold on.

To your point, Werther, while we have considerably more extent and area in the Barentsz, Greenland and Kara seas, that extent is mostly slash and extremely vulnerable.  I think the three images (first two using bands 7-2-1, last visible) I selected over the last three days illustrate that.  I tried to select periods with lower cloud cover.

The visible light shot of Svalbard/Fram very much highlight your point.  As the pack breaks out of the CAB into the strait, the infill around what appear to be MYI blocks rapidly disappears, and ice which is backed up against the islands themselves shows signs of attack from both above and below.

(Edit/post script)
I think it quite possible we could see 2017 reach lowest SIA but not quite reach lowest SIE.

As posted elsewhere, all hinges on July's weather now.  Unfortunately with the forecast Beaufort high and dipole, it's not starting out well for the ice.
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solartim27

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Re: The 2017 melting season
« Reply #2375 on: June 27, 2017, 10:30:19 PM »
What are your guesses? Here i put my very simple idea about how the 2017 minimum might look like by the middle of September:
Trouble is this years melt will probably continue well past mid September.
FNORD

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Re: The 2017 melting season
« Reply #2376 on: June 27, 2017, 10:38:47 PM »
What are your guesses? Here i put my very simple idea about how the 2017 minimum might look like by the middle of September:
Trouble is this years melt will probably continue well past mid September.
Why should this year's melt be prolonged? What am I missing ?
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Neven

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Re: The 2017 melting season
« Reply #2377 on: June 27, 2017, 10:45:23 PM »
As posted elsewhere, all hinges on July's weather now.  Unfortunately with the forecast Beaufort high and dipole, it's not starting out well for the ice.
Actually, the latest ECMWF forecast doesn't have the high pushing far over the Beaufort Sea, but rather has its centre hovering over the CAA, which is actually very bad news for that zone where most of the thickest ice is. And it's still a Dipole, of course, with winds continuing to push the ice towards the Atlantic.

Of course, the high pressure system might still decide to move further towards the Beaufort/Chukchi.

I don't have a good feeling about this melting season, but then again, I rarely do.  ;)
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VeliAlbertKallio

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Re: The 2017 melting season
« Reply #2378 on: June 27, 2017, 10:50:36 PM »
[Image heavily processed to bring out the details.]

I must add to your 'attacks from both above and below' perhaps the most important effect: that is the sideway pounding for reduction of ice. I wonder if this can become the final tipping point that reduces thinned CAB ice prior to its final demise and curious to see if the storms can soon pulverize entire CAB ice by tossing violently like this to rounded 'pancake ice'.

Pounding lowers spatial viscosity further as ice durability is now too weak to survive sea ice tossing each other (rounded objects pass each other easier than rectangular or irregular shapes that lock to each other). CAB location North of Greenland is here: https://worldview.earthdata.nasa.gov/?p=arctic&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Graticule,Reference_Labels(hidden),Reference_Features(hidden),Coastlines&t=2017-06-27&z=3&v=271543.2246794036,-643994.4474063759,533687.2246794036,-478874.4474063759

<snippage>
As the pack breaks out of the CAB into the strait, the infill around what appear to be MYI blocks rapidly disappears, and ice which is backed up against the islands themselves shows signs of attack from both above and below.
« Last Edit: June 27, 2017, 11:06:15 PM by VeliAlbertKallio »
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Tigertown

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Re: The 2017 melting season
« Reply #2379 on: June 27, 2017, 11:14:23 PM »
What are your guesses? Here i put my very simple idea about how the 2017 minimum might look like by the middle of September:
Trouble is this years melt will probably continue well past mid September.
Why should this year's melt be prolonged? What am I missing ?
The batteries will be fully charged already, as the sun begins to go down.
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cesium62

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Re: The 2017 melting season
« Reply #2380 on: June 28, 2017, 04:54:00 AM »
The Slater Probablistic Sea Ice Extent is essentially predicting that what I consider the main northwest passage will be open come mid-August.  Although I suppose it matters whether the 20% of predicted ice is the northern most ice in the channel, or the east-west-central-most ice...

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Re: The 2017 melting season
« Reply #2381 on: June 28, 2017, 06:17:53 AM »
Latest thawing degree days: [from http://sites.uci.edu/zlabe/arctic-temperatures/]

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epiphyte

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Re: The 2017 melting season
« Reply #2382 on: June 28, 2017, 07:51:00 AM »
Latest thawing degree days: [from http://sites.uci.edu/zlabe/arctic-temperatures/]

I find myself asking what it is that this graph is measuring. In the presence of ice the surface itself can never get above freezing can it? So if it is possible for this number to be higher than that must  it not reflect the air temperature at some hight above the surface?

If the above is the case, and the temperature is at or above the melting-point of seawater ice, then I don't see how that of itself sheds any light on whether freezing or thawing conditions are extant.


I'm far from an expert on this and absolutely open to correction but it seems sensible to me that at the extremes -

 - a temp of 2C, under cloudy conditions, in still air, might indicate that no atmospheric heat is being lost to the surface - i.e. no melting.

- OTOH, under equally cloudy conditions, with a 40 knot surface wind, a 3 degree 950MB air temp, 100% humidity and 2MM/hr of rain, a "surface" temp of -1.6C might indicate that heat is being sucked out of the air almost instantly - i.e. rapid melting.

...is this wrong?



Tigertown

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Re: The 2017 melting season
« Reply #2383 on: June 28, 2017, 07:57:01 AM »
Moving(warmer than surface) air and moisture speed up heat transfer, yes.
"....and the appointed time came for God to bring to ruin those ruining the earth." Revelation 11:18.

epiphyte

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Re: The 2017 melting season
« Reply #2384 on: June 28, 2017, 08:13:26 AM »
Moving(warmer than surface) air and moisture speed up heat transfer, yes.

...So carrying that forward one more step, when theres a persistent, soggy (albeit low-grade) LP area over much of the arctic, as there has been for a while now, what useful information does the "thawing degree day" metric impart?

Andreas T

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Re: The 2017 melting season
« Reply #2385 on: June 28, 2017, 08:40:22 AM »
If you look closely at the graph that Zach posted, the y-axis is labelled 2m temperature, so it shows air temperature 2m above the surface, calculated by a model which assimilates the available measurements.
You are right that melting can take place while that temperature is below 0, although the -1.6 you picked for your example is too low. That 2m height is chosen as indicative of the boundary layer where the atmosphere is cooled or heated by the surface. When convective heat transfer takes place there must be a temperature gradient in that boundary layer as warm air (for example) moves towards the surface and air which has already cooled at the surface moves up to make way for that downward movement. This is mostly a turbulent process so any temperature reading will be an average of a fluctuating measurement.

But even if the temperature value of a particular day is not a strong indicator of the ice volume melted on that day, the comparison of a whole season between different years can be informative, if its limitations especially as conditions in the arctic change.
Since the ice surface is less saline than the ocean ice surface temperatures are often slightly higher than water temperatures, so more open water means initially lower surface temperature until that water has warmed further


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Re: The 2017 melting season
« Reply #2386 on: June 28, 2017, 09:45:55 AM »
Latest thawing degree days: [from http://sites.uci.edu/zlabe/arctic-temperatures/]


With all due respect, I am not sure what kind of information one can extract from the thawing dd. It is influenced by things other than an indication of thawing, like:
- Proportion of first year ice vs. multi-year ice
- In summer, change in circulation pattern affect temps often in ways that, although it may seem the main pack is around freezing temps, the periphery area and extent are plummeting.

And it misses a few:
- Heat absorption from direct insolation (insolation, as AndreasT pointed us several times, is not that well correlated with temperature and onset of surface melting; conversely, as Andreas pointed out too, can be causing direct melting beneath the ice by heating algae, bottom water, the ice itself)
- Heat transfer by rain, or humidity effects,
- Heat transfer by whatever other means, ocean currents
- Mechanical effects of storms that may even induce a dip in the atmospheric temperatures but that in August are devastating in the marginal ice, churning down ice to smaller and smaller pieces until the last bits melt out at temperatures that may be even lower in average than in the 80's

And there is a certain, although very small, downwards trend in the DMI 80N 2m temp. especially in August for the recent years, possibly because of much less MYI in the Arctic, the equillibrium temperature of the melting ice is overall slightly lower. We would end up with lower valyes of thawing degree days or with diminished in the last stretch of the melting season in the 2010's ?
« Last Edit: June 28, 2017, 10:18:59 AM by seaicesailor »

BenB

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Re: The 2017 melting season
« Reply #2387 on: June 28, 2017, 11:47:39 AM »
Fast ice breaking up in the southern Laptev: 26 June:



28 June:



It's been showing signs of melt ponding for a while, so it's not terribly surprising to see this happen.

Bill Fothergill

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Re: The 2017 melting season
« Reply #2388 on: June 28, 2017, 11:58:21 AM »
... I am not sure what kind of information one can extract from the thawing dd...

TDDs represent just one factor amongst many that combine chaotically to determine in the incredibly complex annual melt process. The Polar Science Centre at Washington University has this to say on the matter...
http://psc.apl.washington.edu/nonwp_projects/landfast_ice/freezing.php

It could just be my interpretation, but I suspect that the TDD concept has a much more direct bearing on permafrost than on sea ice, as evinced by this NSIDC article...
http://nsidc.org/data/nsidc-0063


... In the presence of ice the surface itself can never get above freezing can it? So if it is possible for this number to be higher than that must  it not reflect the air temperature at some hight above the surface?...

As Andreas T has already stated, it is important to think in terms of a thermal gradient - not just within the ice, but in a sort of "boundary layer" extending both above and below the ice surfaces.

In winter, the coldest part of the ice will be virtually at its surface, with the warmest part being that in contact with the underlying ocean. During the melt season, the situation changes markedly, resulting in a temperature inversion happening such that the coldest part of the ice is near its core.

Whilst you are correct in saying that the temperature at the ice surface (either the air-ice or ocean-ice boundary) is effectively clamped to the freezing point during the melt season, the thermal gradient (which enables the energy transfer conduit) continues into these extended boundary layers.

seaicesailor

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Re: The 2017 melting season
« Reply #2389 on: June 28, 2017, 12:26:13 PM »
I promise my last OT comment on this. I can imagine a thought scenario, unrealistic but not by much, where the Arctic melts out with negative TDD (say, a massive and unprecedented inflow of Bering water, for instance, combined with a high anticyclone with relatively cold temperatures but sun radiation helping the ocean current in bottom melting the ice).
However I cannot imagine a weak winter without low FDD

Add storm effects to enhance ice melting. All that is elusive to the Thawing DD. Just saying.

FredBear

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Re: The 2017 melting season
« Reply #2390 on: June 28, 2017, 12:28:50 PM »
Latest thawing degree days: [from http://sites.uci.edu/zlabe/arctic-temperatures/]
Thawing degree days are measured from freezing point of sea water (-1.8°C) in this graph so will be positive over ice melting at 0°C.
It is only a modelled average for 80oN+ so will be damped by the general sea ice in the area - but if that starts to disappear in that region and a warm southerly wind sets up the graph should warn us. The numbers of melt-days are low so it should be sensitive to changes (but also subject to spikes).
This type of graph will give a warning trend over the years if we need it or if it suddenly kicks up - a short term crisis shot across our bows.

F.Tnioli

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Re: The 2017 melting season
« Reply #2391 on: June 28, 2017, 01:19:02 PM »
As posted elsewhere, all hinges on July's weather now.  Unfortunately with the forecast Beaufort high and dipole, it's not starting out well for the ice.
Actually, the latest ECMWF forecast doesn't have the high pushing far over the Beaufort Sea, but rather has its centre hovering over the CAA, which is actually very bad news for that zone where most of the thickest ice is. And it's still a Dipole, of course, with winds continuing to push the ice towards the Atlantic.

Of course, the high pressure system might still decide to move further towards the Beaufort/Chukchi.

I don't have a good feeling about this melting season, but then again, I rarely do.  ;)
Any signs of that high pressure system weakening or dissolving on those latest forecasts, though? If CAA could go without much clear skies for just few more weeks - it'd be very helpful in terms of annual minimums not ending up being record lows, obviously.

About your feeling: then again, 'em seasons these days rarely do "good", either. Record low this, record low that. Like this season, it's jaw-dropping record low number of freezing days. Ever since 2012, i feel all those seasons after it, - 2013...2016, - were "dodging bullets" ones for ASI. All four of them. Whether or not this one would be similarly lucky, i say the trend is obvious and that feeling we talk about - is apropriate.
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Re: The 2017 melting season
« Reply #2392 on: June 28, 2017, 03:24:14 PM »
Back on May 2nd, Wayne Davidson on his EH2R blog wrote a few predictions for the melting season.  Of particular interest to me was this:
Quote
"I would expect record number of melt Ponds -late- from all that thick snow cover. This will accelerate the melt rapidly, numerous melt ponds will signal the start of very rapid melting, after seemingly sluggish melt daily rates interspersed with at times great variations caused by the lack of sea ice consolidation."

I would say that this is exactly what has come to pass in the past week.  Rather than just extrapolating from past years or trends Wayne was actually applying some logic, basic physics, and meteorological insight Of course it helps that he's been making measurements of the snow and ice near his home in Resolute these past 20 years or so.

If you don't read his blog regularly, you should.  Always some thought provoking ideas.


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Re: The 2017 melting season
« Reply #2393 on: June 28, 2017, 03:49:13 PM »
   ....
Quote
Linear extrapolations of trends don't make much sense when this year's thickness vs area distribution is so different from the last 4 years.
Very important point. The already-meagre tools we have for following the melt season are not being processed by product algorithms adapted to the new conditions of the ice pack, weakening comparisons to the years for which they were developed and vetted.
   ....

Does that mean our intuitions are more valuable than usual?  Mine feel decidedly hazy.  Earlier in the season I guessed wrong on melt ponding, having failied to account for the powerful negative feedback of snow cover.  But thickness distribution has been poor all along, and still indicates a high likelihood of a record minimum.  A near-term lull in Fram export won't help distribution much as the Pacific side continues to weaken.

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Re: The 2017 melting season
« Reply #2394 on: June 28, 2017, 04:13:41 PM »
This means one has to trust intuition of people who work in the field, personally, - more than usual.

"Our" intuitions per se may vary from person to person, depending on what kind of data one considers as reliable input; i'd say the more processed such data is, - analyzed, re-analyzed, summarized, modelled, ensembled, etc, - the less value any intuition based on such data will have. Why? Because as known from basic calculus, whenever there is more than one mathematical operation involving any uncertainty range, final uncertainty is exponential, and sadly we can never know for sure what kind of errors (or even worse - bias) data processing made by other people may have.

In particular, satellite and on-site phtography, and (whenever possible) videos, - are now more valuable than ever before.
« Last Edit: June 28, 2017, 04:20:34 PM by F.Tnioli »
To everyone: before posting in a melting season topic, please be sure to know contents of this moderator's post: https://forum.arctic-sea-ice.net/index.php/topic,3017.msg261893.html#msg261893 . Thanks!

Lord M Vader

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Re: The 2017 melting season
« Reply #2395 on: June 28, 2017, 09:26:14 PM »
Intersting ECMWF 12z op run depicting a return to more cyclonic weather again after D6-D7. Let's see what the ensemble says!

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Re: The 2017 melting season
« Reply #2396 on: June 28, 2017, 10:09:35 PM »
Intersting ECMWF 12z op run depicting a return to more cyclonic weather again after D6-D7. Let's see what the ensemble says!

Yes, very interesting, especially as GFS/Reanalyzer is showing that Beaufort, ESS, and CAA are going to get warm temps and mostly clear skies for the next 5 days. That ice is already blue in Worldview, and is mostly < 2m, so I'm guessing that sun and warmth will have a significant affect on those areas. Maybe the more cyclonic weather you mention brings enough cloud cover to give the ice a chance of surviving?

Laptev and CAB seem to be getting mostly cloud and rain for the next 5 days, so maybe those areas won't melt as much?

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Re: The 2017 melting season
« Reply #2397 on: June 28, 2017, 10:39:35 PM »
Ha marcel you posted before i could - but i'll chime in anyway since i made a gif. Yup looks like clear skies and warm temps for next 4+ days. So more torching of Beaufort and CCA likely, with possible preconditioning and snow-ice melt extending well into CAB. Below is 4 days Euro 12Z operational 850hpa temp anomalies along with GFS 2M temps.

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Re: The 2017 melting season
« Reply #2398 on: June 29, 2017, 12:59:56 AM »
The ice in the Kara Sea, next to Novaya Zemlya certainly seems to be holding on well past its due date. The sea temperatures around it look relatively cool. Six to seven days out, climate reanalyzer has temperatures there jumping above zero so maybe then it will start to disappear.

Still relatively cold for the rest of the Atlantic side though, as large parts of the Pacific side and CAA stay above zero.



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Re: The 2017 melting season
« Reply #2399 on: June 29, 2017, 01:06:10 AM »
Laptev and CAB seem to be getting mostly cloud and rain for the next 5 days, so maybe those areas won't melt as much?

Most people understand that moisture in the air transfers heat better than dry air. Whether its vapour or liquid or solid a lot of this is not just conductive. Particularly when the energy is being exchanged with bodies of water. Like the ice or our fleshbags. Liquid water is a constant flux of breaking and forming hydrogen bonds. Everytime one forms a radiant photon is emitted of just the perfect quanta to break another one. Around melting or triple point temps the flux is large. Most likely rain and fog is negative to the extreme for the ice. Most of the insolation will still get down but in a most non reflective wavelength for water. Albedo unimportant.
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