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F.Tnioli

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Re: The 2015 melting season
« Reply #3100 on: August 06, 2015, 12:33:42 PM »
May be it's over-caution, but as you gentlemen are working on this melt season progress, it might be an excellent idea to pay some extra attention to accident prevention and mitigation, on personal level. This <snip, no linking to the no-GWPF, please; N.>  i just happened to find - makes me think that accidents are common, dangerous and can often be deadly.

This is no mocking nor hinting, please read at face value. Whatever the nature and causes of there described accidents would be, i do not in fact care. Fact is, colleagues are dead because of accidents. Stay safe, everyone. And please do be careful at all times.
« Last Edit: August 06, 2015, 02:45:04 PM by Neven »
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!

Anne

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Re: The 2015 melting season
« Reply #3101 on: August 06, 2015, 12:47:54 PM »
There's a whole thread about this here, FT:
http://forum.arctic-sea-ice.net/index.php/topic,1333.0.html

And it certainly looks as if the report shouldn't be taken at face value!

seaicesailor

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Re: The 2015 melting season
« Reply #3102 on: August 06, 2015, 01:27:13 PM »

On reflection it looks like the El Nino is actually impacting the arctic ice this year instead of next by pushing warmer water from the Pacific into the Arctic now.  But that is a purely subjective WAG and may have no basis in reality at all.

BTW, (very cautiosly) might it be that GFS and Euro are forecasting (starting five days from now), warmer air entering from the Pacific, thru both Eurasian side (in this case also with a train of storms) and Alaskan side?

iceman

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Re: The 2015 melting season
« Reply #3103 on: August 06, 2015, 02:16:25 PM »
  ....
Can you find a single example of <50% concentration ice as of July 23/24 of a given year surviving the season? I think not.
  ....

  ....
For example, using 4 August extent or compactness in Beaufort vs minimum extent... The extent suggests a significant remnant of ice by the minimum, the compactness indicates virtually no ice.
  ....

If you measure ice thickness across Beaufort, isn't the distribution unusually wide (owing partly to scattered MYI)?  That would seem to make compactness less indicative for the area/extent minimum.

F.Tnioli

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Re: The 2015 melting season
« Reply #3104 on: August 06, 2015, 02:41:00 PM »
There's a whole thread about this here, FT:
http://forum.arctic-sea-ice.net/index.php/topic,1333.0.html

And it certainly looks as if the report shouldn't be taken at face value!
Clarification: i only meant that the text of my previous post here should be taken at its face value. Still mean it. Myself, i didn't "hint" nor "mock" at anything, by any part of the text of my previous post.

Yep, thanks for the link. No intention to discuss the subject in here melt season topic, i have nor had. But since Peter Wadhams in quite some regards does things very similar to what some of gentlemen and ladies here do, - i thought it's a good idea to share the find (for me, it was) here in a post. If it'll save a life, then i did a good thing. I hope.

Again, please do be safe, everyone.
« Last Edit: August 06, 2015, 02:48:02 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!

Lou

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Re: The 2015 melting season
« Reply #3105 on: August 06, 2015, 02:42:34 PM »
Of course, I'm interested in where this melting season ends up, but I'm already more interested in what this means for next year. How much MYI and volume will there be when all of this is over?

This echoes my own view of the Arctic situation, i.e.: We know the trend for area, extent, and volume, and we're very likely to see them converge at 0 for at least a week or so very soon, within 5 years, I guesstimate.  But there's a heck of a lot of noise mixed in with that signal, and I try not to get too caught up in exactly where 2015 will fall relative to any other recent year.  But it certainly seems that the last few years are setting the stage, in terms of thicker, MYI, for the mother of all tipping point demonstrations when we get 2012-like conditions in 2019 or 2020 or whenever.

It's almost like being tied to train tracks and hearing a locomotive whistle in the distance...

crandles

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Re: The 2015 melting season
« Reply #3106 on: August 06, 2015, 02:52:41 PM »
If you measure ice thickness across Beaufort, isn't the distribution unusually wide (owing partly to scattered MYI)?  That would seem to make compactness less indicative for the area/extent minimum.

Unusually wide compared to what?

Range in Beaufort this year is probably 0 to around 2.5m. Before 2000 range in Beaufort at this time of year probably ran from 0 to 5m.

(Per Chris Reynolds regional thickness files
July 2000 Beaufort average thickness 2.189
July 2014 Beaufort average thickness 0.752

May 2015 was thinner 1.64m than May 2014 1.71m and subsequent data not available there yet.)

I guess you mean high proportion at 0 thickness and high proportion close to the thickest thicknesses (even if these thickest thicknesses are less than they used to be).

Doesn't your wide distribution mean there is lots of warm water surrounding lots of small blobs of ice? If so, then this is quite likely to melt out even if it is relatively thick. So I would suggest that makes compactness more important as a measure than extent particularly when we have a wide distribution.

I also tend to think area and volume are also better than extent so maybe I am a bit biased against extent as an indicator.

greatdying2

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Re: The 2015 melting season
« Reply #3107 on: August 06, 2015, 03:41:34 PM »
This floe had diameter ~50 km (area ~2000 km2). The image shows from its inception at Spring breakup to its recent demise. (Note that the dates of the images are not at all evenly spaced.)
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

seaicesailor

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Re: The 2015 melting season
« Reply #3108 on: August 06, 2015, 03:52:53 PM »
This floe had diameter ~50 km (area ~2000 km2). The image shows from its inception at Spring breakup to its recent demise. (Note that the dates of the images are not at all evenly spaced.)

That sequence is amazing, a paper could be written out of them. What is the location of this floe if I may ask?

iceman

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Re: The 2015 melting season
« Reply #3109 on: August 06, 2015, 03:57:47 PM »
If you measure ice thickness across Beaufort, isn't the distribution unusually wide (owing partly to scattered MYI)?  That would seem to make compactness less indicative for the area/extent minimum.
  ....
I guess you mean high proportion at 0 thickness and high proportion close to the thickest thicknesses (even if these thickest thicknesses are less than they used to be).
  ....

Yes, that's what I meant.  It might have been more accurate to say "unusually flat" distribution.

  ....
Doesn't your wide distribution mean there is lots of warm water surrounding lots of small blobs of ice? If so, then this is quite likely to melt out even if it is relatively thick. So I would suggest that makes compactness more important as a measure than extent particularly when we have a wide distribution.
  ....

That might be the right reading for the remainder of the melt season.  Prior to the recent/ongoing spate of mini-cyclones, though, it looked more as though the "protective arm" of thicker ice was retarding decline of area/extent.

Gonzo

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Re: The 2015 melting season
« Reply #3110 on: August 06, 2015, 04:34:26 PM »
Quote
Paul, the ACNFS model has been having problems this melting season. I don't know if things have been resolved yet, it doesn't look so to me. But even then, to assume that the model is simulating reality, is going out on a limb. Because it doesn't look realistic.
Neven

Which model is realistic in your opinion?

greatdying2

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Re: The 2015 melting season
« Reply #3111 on: August 06, 2015, 04:49:19 PM »
This floe had diameter ~50 km (area ~2000 km2). The image shows from its inception at Spring breakup to its recent demise. (Note that the dates of the images are not at all evenly spaced.)

That sequence is amazing, a paper could be written out of them. What is the location of this floe if I may ask?
Glad you like it. What, you can't find it among all the other exploding floes... jk.  It's about 400 km off the shore of Prince Patrick Island, directly "up" on Worldview (west?). It moves around a bit, but its position on July 20 for example is ~(77, -137).
« Last Edit: August 06, 2015, 06:03:54 PM by greatdying2 »
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

oren

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Re: The 2015 melting season
« Reply #3112 on: August 06, 2015, 05:21:14 PM »
This floe had diameter ~50 km (area ~2000 km2). The image shows from its inception at Spring breakup to its recent demise. (Note that the dates of the images are not at all evenly spaced.)

Impressive! Thanks for posting.

Vergent

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Re: The 2015 melting season
« Reply #3113 on: August 06, 2015, 06:05:25 PM »

Nick_Naylor

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Re: The 2015 melting season
« Reply #3114 on: August 06, 2015, 06:52:42 PM »
Looking at this, one cannot help thinking that the Bering Strait should be enlarged, to make room for unfettered access by drilling equipment and oil tankers. Right?  :o

weatherdude88

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Re: The 2015 melting season
« Reply #3115 on: August 06, 2015, 07:04:25 PM »
The significant slowdown has begun. The last two days we lost 81830 square kilometers according to IARC-JAXA. By comparison in 2014 we lost 102286 square kilometers and 2013 we lost 130287 square kilometers during the same period. The guidance shows the weather pattern remaining entrenched through the remainder of the month. We may even have higher sea ice extent than 2013 and 2014 by the time we reach minimum. 925 Hpa temperatures over the arctic continue to plummet.






Nick_Naylor

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Re: The 2015 melting season
« Reply #3116 on: August 06, 2015, 07:21:29 PM »
The significant slowdown has begun.

This seems a little premature. Looking at the CT area data. A season-appropriate slowdown appears to be in progress, but nothing more. Extent data is very noisy when so much of the ice is near the 15% threshold.

http://arctic.atmos.uiuc.edu/cryosphere/arctic.sea.ice.interactive.html
http://ocean.dmi.dk/arctic/icethickness/images/FullSize_CICE_combine_thick_SM_EN_20150805.png

Hycom is laughing at us: http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn_nowcast_anim30d.gif  ???

jdallen

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Re: The 2015 melting season
« Reply #3117 on: August 06, 2015, 07:56:26 PM »
The significant slowdown has begun.

This seems a little premature. Looking at the CT area data. A season-appropriate slowdown appears to be in progress, but nothing more. Extent data is very noisy when so much of the ice is near the 15% threshold.

http://arctic.atmos.uiuc.edu/cryosphere/arctic.sea.ice.interactive.html
http://ocean.dmi.dk/arctic/icethickness/images/FullSize_CICE_combine_thick_SM_EN_20150805.png

Hycom is laughing at us: http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn_nowcast_anim30d.gif  ???
Agree, nothing unusual with these numbers and quite likely we may see a few more century breaks. The ice extent conditions are that volatile.

That bit with Hycom is vey funny. Looking at it, it appears to me they sequenced a few days twice or thrice.
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NeilT

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Re: The 2015 melting season
« Reply #3118 on: August 06, 2015, 08:24:00 PM »
 I must admit that at this time in the year I don't even bother looking at the extent.  It's almost meaningless until the melt area settles down.

This year even less meaningful.  To me extent comes into play at the end of the season in September and the end of the growth around March/April/May.

Area, to me, is the main factor when we are looking at insolation.

So until  I wake up and find all those melt ponds between 80N and 85N have frozen over again, I won't be saying the situation has slowed down all that much and, again, I also won't be betting on anything this year until the ice over by the coast has either melted out or started to grow solidly again.

I'm not the slightest bit surprised the models are having a hard time of this.  Who would have calculated this kind of melt and break up in their models?  They'd have been called either mad or eccentric right?
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12Patrick

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Re: The 2015 melting season
« Reply #3119 on: August 06, 2015, 09:11:02 PM »
The significant slowdown has begun.

This seems a little premature. Looking at the CT area data. A season-appropriate slowdown appears to be in progress, but nothing more. Extent data is very noisy when so much of the ice is near the 15% threshold.

http://arctic.atmos.uiuc.edu/cryosphere/arctic.sea.ice.interactive.html
http://ocean.dmi.dk/arctic/icethickness/images/FullSize_CICE_combine_thick_SM_EN_20150805.png

Hycom is laughing at us: http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn_nowcast_anim30d.gif  ???
Agree, nothing unusual with these numbers and quite likely we may see a few more century breaks. The ice extent conditions are that volatile.

That bit with Hycom is vey funny. Looking at it, it appears to me they sequenced a few days twice or thrice.
HYCOM has Hiccups.

ChrisReynolds

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Re: The 2015 melting season
« Reply #3120 on: August 06, 2015, 10:03:42 PM »
The Peripheral Seas of the Arctic Ocean Basin are: Beaufort, Chukchi, East Siberian Sea, Laptev Sea.



Using anomalies, which are the difference from the long term mean (here I use 1981 to 2010 to line up with NCEP/NCAR baseline period, as usual), here is the current state of extent, area and compactness in the Peripheral Seas. Data to 5 August.

Extent Anomaly.


Since 23 July the strong falls at greater than average rate (falling anomalies) have ceased giving way to a more average loss (level anomalies).

Area Anomaly.


Since 13 July the area losses have been about average (roughly level anomalies), a sharp contrast to the preceding strongly above average losses. This pattern is similar to 2007, 2011 and 2012, the relaxation of area anomaly loss after mid July is caused by the long term mean loss being high in late July, keeping up even with record years.

Compactness Anomaly.


Having followed 2012 from 19 June to 22 July, compactness now shows signs of levelling and allowing the 2012 compactness to fall away.

The levelling in extent, area, and compactness, leads up to early August (now) where in 2012 extent crashed following the Great Arctic Cyclone of 2012.

Nick_Naylor

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Re: The 2015 melting season
« Reply #3121 on: August 06, 2015, 10:13:26 PM »
Since 13 July the area losses have been about average (roughly level anomalies) . . .

True, but it's interesting that you could have made that statement about any of the years on this graph.

plg

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Re: The 2015 melting season
« Reply #3122 on: August 06, 2015, 10:44:20 PM »
Almost all the ice in the Northwest passage shows 50% or less on the Uni Bremen concentration map. Seems to be heading for an open passage.
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ChrisReynolds

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Re: The 2015 melting season
« Reply #3123 on: August 06, 2015, 10:56:24 PM »
Since 13 July the area losses have been about average (roughly level anomalies) . . .

True, but it's interesting that you could have made that statement about any of the years on this graph.

The period of levellish behaviour is very short, and it's only levellish, not properly flat. But yes, you could say that about any year during this period.

Area is important, but it is less instructive than extent (IMO), I often use extent and compactness as my main indicators in the summer. Summer losses of area are quite aggressive even in the past so to get exceptional drops over late July and early August, you need something really aggressive. It's worth pointing out that even in 2012 while area could lull you into a sense of 'phew, it's all over..." Extent would have you bouncing up and down with excitement.

I haven't posted these to say anything much about the coming minimum, although this data has played a bit part in making me go up one bin in the NSIDC Extent poll. I still think August will see losses much greater than average. But I could be wrong on that, and as I'm now just enjoying the rest of the season, I am allowing myself to be biassed by expectations of what seems to be an oscillation in August losses, we're on the upswing of that if it is a real feature and not just random noise in the data.

NeilT

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Re: The 2015 melting season
« Reply #3124 on: August 06, 2015, 11:21:33 PM »
Isn't it true though that in this season, if we are to see any record fall, the last thing we would be seeing is compactness.  Because compact ice is protected from the impact of both solar heat and wave action to a large degree.

I see that 2012 compactness went up during the GAC of 2012 then dropped rapidly after it to allow the ice to vanish.

If, in fact, 2015 were to continue on the same compactness level, without the 2012 storm pattern and without the melt driven by the 2012 storm itself, then simple momentum of a very dispersed pack with relatively high insolation and relatively high SST for the time of year could, in fact, cause exactly the same impact that the GAC of 2012. did.

I'm not saying it will exceed 2012 in area loss.  I don't believe it will.  However we may wind up in the odd situation where 2015 has the second lowest area and the 5th or 6th lowest extent.

What that would do to the models is not something I'd like to guess on because I don't know how much they factor in the compactness value.

Going to be interesting though.
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Neven

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Re: The 2015 melting season
« Reply #3125 on: August 07, 2015, 12:29:45 AM »
ECMWF shows a tentative Dipole formation, but it's 7-10 days out, so doesn't mean anything.
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TerryM

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Re: The 2015 melting season
« Reply #3126 on: August 07, 2015, 02:29:02 AM »
Chris
I like your "Peripheral Seas" graphs, a decent way to separate the wheat from the chaff.


Seaicesailor
Thick winter snow acts as an insulating blanket for sea ice, then as a source for low albedo fresh water melt ponds. I'd expect a negative corelation between winter snow depth and ice thickness.
 
Even a "cold low" enhances Ekman pumping, drawing deep warm waters up to where they can interact with floating ice. As you mentioned, bottom melting is the "silent killer"


I like your term "centennial-year ice", but fear there is very little left. I've followed the millennial-year ice along the northern shores of Ellesmere until we're now left with but a small remnant of the now bifurcated Ward-Hunt. (We beat the University of Guelph by 2 days in announcing the breakup!). The now less well supported eastern side might make a break for freedom this year, or the much larger western portion may lose contact with the shore a la Ayres, or simply have a small portion chipped away.
These very old, formerly huge shelves are to me the absolute, irrefutable proof that not only is the Arctic warming, but that it's warming far in excess of any natural warm periods that occurred within the last >3k yrs.
Should a large portion of this shelf break lose this year it would certainly make this year worthy of mention in someone's record book.
Terry

greatdying2

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Re: The 2015 melting season
« Reply #3127 on: August 07, 2015, 04:48:33 AM »
Seems like the fast ice west of Ellesmere has broken up (early). Here's July 26, July 31, and Aug. 6, as well as 2013 Aug 7, for comparison.
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

greatdying2

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Re: The 2015 melting season
« Reply #3128 on: August 07, 2015, 05:19:45 AM »
In the Beaufort, extent remains high, yet it's becoming rather difficult to find any large floes...
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

slow wing

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Re: The 2015 melting season
« Reply #3129 on: August 07, 2015, 05:28:55 AM »
The massive hole in the Beaufort Sea ice pack got bigger in the U. Bremen update.

As has often been the case, all the action on the Pacific side.
More yellow - ~75% concentration - North of 80 degrees N on the Pacific side.

 I hope I am paraphrasing Neven correctly in saying the yellow may indicate weakness but it comes and goes. It is only where the concentration shows green - ~below 50% - that the ice is probably in serious trouble.

There isn't any green to speak of inside 80 degrees on the Pacific side. Nor is there much on the Atlantic side - which has been quiet.
Further, NASA WorldView shows fairly solid ice pack nearly everywhere there is ice inside 80 degrees North, e.g.

https://earthdata.nasa.gov/labs/worldview/?p=arctic&l=MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Graticule,Reference_Labels(hidden),Reference_Features(hidden),Coastlines&t=2015-08-07&v=-3542026.35441595,-345294.8659937555,263157.6455840501,1692465.1340062446

Still further, the weather forecast predicts little wind except on the Pacific side peripheral seas and along the Siberian coast.

So maybe we aren't going to lose too much of the remaining ice inside the 80 degrees North circle? (Unless there is a big storm.) Conversely, in the Beaufort and the ESS there is a good battle between the wind and the remaining ice and I suspect the wind will mostly win out in those regions.

Click on gif to flash back to a comparison with yesterday..


Paul Beckwith

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Re: The 2015 melting season
« Reply #3130 on: August 07, 2015, 08:35:02 AM »
Can the satellites differentiate between MYI and ridged younger ice? If not, then is it possible there is no MYI left? If yes, then how do they do this?

NeilT

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Re: The 2015 melting season
« Reply #3131 on: August 07, 2015, 08:45:22 AM »
slow wing, if you zoom in on that expanding yellow section between 80N and 85N you will see patches of green.  If you look on the Arctic Mosaic, you will see the disorganised ice with opening patches of water in the Beaufort spreading both clockwise and north.  Unlikely to be much of a game changer without a storm though.

Paul, Chris answered one of those when I queried ASCAT.  It measures the backscatter off the ice by the signal from different ice types.  MYI gives a different signature.  Others (of which cyrosat2, I'm sure is one), measure the freeboard of the ice above the water.

The freeboard measuring is one that Dr Barber was taking aim at because he stated that older ice which was disintegrating inside would return similar freeboard to solid MYI, creating a false picture of the ice volume.  As to how that same ice would return ASCAT signatures I don't know.
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TCsaba

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Re: The 2015 melting season
« Reply #3132 on: August 07, 2015, 10:45:47 AM »
According to Earth Wind Map (earth.nullschool.net), it looks like there's a low-pressure system moving from the Chukchi sea to the Beaufort sea bringing in warm (6-8 C) air into the Beaufort and Canadian Archipelago area from the Bering strait and Alaska in the next 5 days.

Could anyone check other forecasts about this?

EDIT: I just noticed that this cyclone has already been mentioned in some threads, just curious how much damage it could do the ice in that area.
« Last Edit: August 07, 2015, 02:24:47 PM by TCsaba »

Blaine

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Re: The 2015 melting season
« Reply #3133 on: August 07, 2015, 12:33:35 PM »
The disintegration of the floes north of Greenland and especially north of the Canadian Archipelago isn't consistent with the high thicknesses PIOMAS is indicating.  ASCAT doesn't contradict this, by the way, since it's mostly a measure of surface roughness, and not thickness.  Compare these two images, for example. http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/2012/msfa-NHe-a-2012211.sir.gif
http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/2012/msfa-NHe-a-2012252.sir.gif

As time passes and the floes disintegrate, ASCAT brightness goes up, not down.  The brighter ASACAT images of 2015 relative to 2012 indicate floe disinitigration running ahead of 2012, as do the visible satellite images.

Barber argues for decreased floe strength with time, and I suppose you could also argue that the first year glue holding the multi-year pieces together has melted out earlier, but with more mulit-year ice pieces this doesn't require the volume to be lower.  I still find a lower volume to be the most likely explanation.  I'd quite like to see a recent altimetry-based volume estimate, since with this little snow left they should be quite accurate.  There's clearly something strange going on here.

http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/pubs/Schweiger-2011-Uncertainty%20in%20model.pdf

PIOMAS validation (figure 6) shows the model dealing poorly with this region in particular, although with the opposite error, underestimating rather than overestimating thickness.  The model does quite well with the overall energy balance, and not quite as well with compressional ridging and fast ice.  For the small-scale wind-driven upwelling of heat on the lee side of an island, I don't see why it should do well at all.

I still think it's unlikely that these areas north of the CAA and Greenland will melt out all that much.  There's still a lot of ice there to melt out this late in the season, even if there's less than PIOMAS is indicating.
« Last Edit: August 08, 2015, 12:32:20 PM by Blaine »

Blaine

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Re: The 2015 melting season
« Reply #3134 on: August 07, 2015, 12:39:02 PM »
2015 so far has had even better melting weather on the Pacific side than 2012.  It's not that surprising that it's been catching up.  A lot of this has just been the ice being blown away from the shore, creating dark open water, with extreme amounts of sunlight.  The reverse-dipole so far in August has been poor melting weather, but not poor enough yet to make up for earlier in the year.

As indicated by the low concentrations, the ice in the Beaufort and Chukchi is presently in mid-collapse.  This always causes a pause in extent and area measures, as the ice expands to take up more area before melting out completely.  I expect rapid drops in extent and area soon, followed by a slowdown.

The Atlantic side started with little open water to get the albedo domino chain going, and has mostly maintained high albedo.  Heat flow from the Atlantic is down somewhat from the peak as well.  The weather hasn't been good, either.  Most of the ice from around 30W to 150E is in quite good shape compared to other recent years.

I expect area and extent from 150E to 30W (Pacific Side) to be near a record low, but with a lot of ice on the Atlantic side, I expect totals to be around 4th lowest, with a small chance of 2nd.

AmbiValent

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Re: The 2015 melting season
« Reply #3135 on: August 07, 2015, 12:44:25 PM »
Blaine, please check and correct the link. Thanks!
Bright ice, how can you crack and fail? How can the ice that seemed so mighty suddenly seem so frail?

12Patrick

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Re: The 2015 melting season
« Reply #3136 on: August 07, 2015, 02:14:38 PM »
Can the satellites differentiate between MYI and ridged younger ice? If not, then is it possible there is no MYI left? If yes, then how do they do this?
I think GRACE can measure the mass Paul...

shendric

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Re: The 2015 melting season
« Reply #3137 on: August 07, 2015, 02:22:11 PM »

 I'd quite like to see a recent altimetry-based volume estimate, since with this little snow left they should be quite accurate.  There's clearly something strange going on here.


Blaine, radar altimetry in the melt season in general is hopeless. You will only see the melt ponds and very little else.

Gonzo

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Re: The 2015 melting season
« Reply #3138 on: August 07, 2015, 02:29:55 PM »
Quote
Blaine
The disintegration of the floes north of Greenland..
Looking back through previous years satellite, it looks to me that north of Greenland is breaking up along that brown line and it stretches a long way. And there are many open areas along the Greenland and Canadian coast, compared to other years at this time.

Jim Hunt

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Re: The 2015 melting season
« Reply #3139 on: August 07, 2015, 04:24:18 PM »
I'm back at my usual desk, so here's an update on one of the few ice mass balance buoys that isn't already floating in it's drill hole:

http://GreatWhiteCon.info/resources/ice-mass-balance-buoys/summer-2015-imbs/#2014I-Temp

The current location of 2014I is 75.25 N, 138.26 W, and the thermistors seem to agree with the current thickness reading of 85 cm of ice plus 3 cm of snow. Also attached is the current view from the until recently colocated O-Buoy 11:
« Last Edit: August 07, 2015, 04:42:17 PM by Jim Hunt »
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Nick_Naylor

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Re: The 2015 melting season
« Reply #3140 on: August 07, 2015, 06:08:25 PM »
Seeing the state of the ice connecting the pack to Greenland, Ellesmere and the CAA, it seems the day may not be too far in the future when it would make sense to say that the ice pack had completely detached from land - if only for a few hours or days when it first happens.

How would we define such an event? The lack of a 100 mile contiguous length of 90+% concentration ice? Just wondering, since a good blast of wind in the right direction in the next couple of weeks could create a controversy over what had just happened.

Gonzo

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Re: The 2015 melting season
« Reply #3141 on: August 07, 2015, 06:19:59 PM »
I notice that fissure I mentioned above, that follows the brown line in the satellite photos, that starts off NE Greenland and heads across the ice sheet, also shows up on that concentration chart that 'Slow Wing' posted, only appears as a fissure line going even further west.
That detachment that Nick just mentioned could happen this year..at least in terms of concentration. Sure, there will be a lot of debris left over in the fissure, so will show up as part of area, but it will be essentially be broken loose. I think you will see most of the ice on the Atlantic side melt and/or float away, with a few islands of ice off nearer those islands near Russia and Finland, and most of the ice sheet essentially dislocated from Greenland and Canada. There is also a line developing in that concentration map, and in satellite, from Lincoln Sea up to that brown line. I think you could see a large triangle of loose ice hugging NW Greenland, and the bulk of the ice 'west' of the north pole, essentially floating free.

jlessard80

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Re: The 2015 melting season
« Reply #3142 on: August 07, 2015, 06:28:18 PM »
NOAA has artic sea ice gaining 1.7 million km yesterday (which seems unlikely :) ). I have not seen this sort of anomaly in their data before. Is this likely just a typo, or is there some reason when this happens?

ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/north/daily/data/NH_seaice_extent_nrt.csv

Bob Wallace

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Re: The 2015 melting season
« Reply #3143 on: August 07, 2015, 06:37:34 PM »
NOAA has artic sea ice gaining 1.7 million km yesterday (which seems unlikely :) ). I have not seen this sort of anomaly in their data before. Is this likely just a typo, or is there some reason when this happens?

ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/north/daily/data/NH_seaice_extent_nrt.csv

Sometimes "stuff" happens.  Glitch in the recording process.  Glitch in the analysis process.  Take a look out toward December on this graph...

https://sites.google.com/site/arctischepinguin/home/amsr2/grf/basin-area-multiprod.png

Rick Aster

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Re: The 2015 melting season
« Reply #3144 on: August 07, 2015, 07:32:16 PM »
Statement from NSIDC:

Quote
On August 5, 2015, a problem arose with the F17 DMSP satellite that provides data to generate the daily maps and time series in the NSIDC Sea Ice Index and Arctic Sea Ice News and Analysis, as well as the Greenland Today daily melt extent. This has led to spurious values of sea ice for both the Arctic and Antarctic, and unreliable melt data for Greenland for this date. NSIDC is in the process of removing the spurious data, and will be closely monitoring the incoming F17 data stream.

http://nsidc.org/arcticseaicenews/

ChrisReynolds

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Re: The 2015 melting season
« Reply #3145 on: August 07, 2015, 07:32:52 PM »
The disintegration of the floes north of Greenland and especially north of the Canadian Archipelago isn't consistent with the high thicknesses PIOMAS is indicating.  ASCAT doesn't contradict this, by the way, since it's mostly a measure of surface roughness, and not thickness.  Compare these two images, for example. http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/2012/msfa-NHe-a-2012211.sir.gif
http://manati.star.nesdis.noaa.gov/ascat_images/ice_image/2012/msfa-NHe-a-2012252.sir.gif

As time passes and the floes disintegrate, ASCAT brightness goes up, not down.  The brighter ASACAT images of 2015 relative to 2012 indicate floe disinitigration running ahead of 2012, as do the visible satellite images.


This is not correct.

What ASCAT is showing is greater radar return signal due to the difference in dielectric properties of FYI and MYI.
http://www.cartel.recherche.usherbrooke.ca/Documents/Langlois_Alex/Isleifson_etal_2009.pdf

Quote
Scattering mechanisms can generally be grouped into surface and volume scatterings. As a first-order approximation, surface scattering is caused by the dielectric differences at the interfaces of two media (for example, the air–ice interface) where surface roughness on both small and large scales has an impact on the backscattered energy. Volume scattering is caused by inhomogeneities within the dielectric layer. Practically speaking, the scattered electromagnetic energy is actually a mixture of both of these mechanisms, which are inherently coupled.

And...

Quote
The gradual decrease in backscatter values as the incidence angle was increased indicated
that the dominant scattering mechanism was volumetric scattering, with the presence of surface scattering causing a reduction of the return at higher incidence angles.

Thus the predominant mechanism determining backscatter in C band scatterometers (of which ASCAT and QuikScat are two instances), is due to dielectric properties of the ice, not surface roughness.

With regards PIOMAS. I have some 'sneak peak' code I can use to look at  grid box within the PIOMAS data for a given time slot.

Here is a sample output from a grid box off the CAA, near the border of the Beaufort Sea and  Central Arctic. June data is used as I do not have July data.

Quote
Grid Data loaded OK         17:33:25
Source Data loaded OK       17:33:25

Latitude:      76.57
Longitude:     238.44
Area:          872.2024
Region:        10
EffThick:      3.011963
 0             0.3570565
 0.26          8.170998E-02
 0.71          7.626907E-02
 1.46          1.993893E-02
 2.61          0.1117831
 4.23          0.1755214
 6.39          7.599543E-02
 9.1           3.565836E-02
 12.39         2.743983E-02
 16.24         2.264041E-02
 20.62         1.096192E-02
 25.49         5.02444E-03

GICE Thick:    3.010586
Error (%):     4.575796E-02 %
GICESum:       0.9999994
Error (%):    -5.960464E-05 %

The emboldened figures are the Gice thickness distribution which is normalised to 1. Instead of applying this to calculate volume contributions I can use it to determine what area of the grid cell is occupied by ice and how much open water there is. I do this by multiplying the grid box area 872.2024km^2 by the fraction.

There is an area of 311.426km^2 within the grid cell that is open water, that is 36% open water, 64% ice, this reflects the presence of a coastal flaw lead through that cell in June.

Now consider a region of really thick ice...

Quote
Grid Data loaded OK         18:07:54
Source Data loaded OK       18:07:54


Latitude:      78.88
Longitude:     249.56
Area:          697.1407
Region:        10
EffThick:      4.944252
 0             0.1943358
 0.26          0.0316701
 0.71          7.811907E-03
 1.46          1.856194E-02
 2.61          0.1543876
 4.23          0.2800487
 6.39          0.1338063
 9.1           6.377196E-02
 12.39         4.739371E-02
 16.24         3.845075E-02
 20.62         1.873093E-02
 25.49         1.102991E-02
GICE Thick:    4.942818
Error (%):     2.900874E-02 %
GICESum:       0.9999996
Error (%):    -4.172325E-05 %


Even here amongst a grid box effective thickness of 4.9m, there is about 20% open water within the grid box. This compares with 0.3% open water for the same grid box in February. With the right ice motion it is quite easy for ice to open up regions of open water within the pack, or for substantial features like that off Greenland to open up.


Barber argues for decreased floe strength with time, and I suppose you could also argue that the first year glue holding the multi-year pieces together has melted out earlier, but with more mulit-year ice pieces this doesn't require the volume to be lower.  I still find a lower volume to be the most likely explanation.  I'd quite like to see a recent altimetry-based volume estimate, since with this little snow left they should be quite accurate.  There's clearly something strange going on here.

PIOMAS shows decreasing strength of ice too. See Zhang et al "Recent changes in the dynamic properties of declining Arctic sea ice: A model study."
http://psc.apl.washington.edu/lindsay/pdf_files/Zhang%202012%20GRL%20-%20dynamic%20properties%20of%20decliing%20sea%20ice.pdf
Quote
The decline of ice thickness is at the center of the simulated changes in sea ice dynamic properties. It is linked to a decrease in ice strength and hence internal stress and interaction force, which boosts ice speed and hence deformation.

And...

Quote
As the ice cover becomes thinner and weaker, ice motion may approach a state of free drift not only in summer but also in parts of spring and fall. Thus the ice cover will be more sensitive to changes in wind forcing.

And...

Quote
While model studies can shed light on the changes in the dynamic properties of Arctic sea ice, it is important to monitor the changes through satellite and in situ observations. Our knowledge about Arctic sea ice is largely based on a system dominated by thick, multi-year ice. It is necessary to learn more about the dynamic processes of a thinner and younger sea ice cover.


href="http://psc.apl.uw.edu/wordpress/wp-content/uploads/schweiger/pubs/Schweiger-2011-Uncertainty%20in%20model.pdf

PIOMAS validation (figure 6) shows the model dealing poorly with this region in particular, although with the opposite error, underestimating rather than overestimating thickness.  The model does quite well with the overall energy balance, and not quite as well with compressional ridging and fast ice.  For the small-scale wind-driven upwelling of heat on the lee side of an island, I don't see why it should do well at all.

I still think it's unlikely that these areas north of the CAA and Greenland will melt out all that much.  There's still a lot of ice there to melt out this late in the season, even if there's less than PIOMAS is indicating.

I have no disagreement with this.

ChrisReynolds

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Re: The 2015 melting season
« Reply #3146 on: August 07, 2015, 07:34:57 PM »
Statement from NSIDC:

Quote
On August 5, 2015, a problem arose with the F17 DMSP satellite that provides data to generate the daily maps and time series in the NSIDC Sea Ice Index and Arctic Sea Ice News and Analysis, as well as the Greenland Today daily melt extent. This has led to spurious values of sea ice for both the Arctic and Antarctic, and unreliable melt data for Greenland for this date. NSIDC is in the process of removing the spurious data, and will be closely monitoring the incoming F17 data stream.

http://nsidc.org/arcticseaicenews/

Thanks Rick.

cesium62

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Re: The 2015 melting season
« Reply #3147 on: August 07, 2015, 07:44:48 PM »
'west' of the north pole
A good title for a puzzle book:  "West of the North Pole (and other conundrums)"

Gonzo

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Re: The 2015 melting season
« Reply #3148 on: August 07, 2015, 08:10:50 PM »
Quote
cesium62: A good title for a puzzle book:  "West of the North Pole (and other conundrums)"
Heh heh. Yes, I am not sure what to call it?  On the equinox, I think anyone not standing within 100-200 k of the north pole would have a sunrise in the traditional east, coming more from the Russian side, and a sunset in the west, towards the Alaskan side, so I guess that's what I mean. Is there another way to say it?
« Last Edit: August 07, 2015, 08:23:00 PM by Gonzo »

AmbiValent

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Re: The 2015 melting season
« Reply #3149 on: August 07, 2015, 08:48:14 PM »
Maybe Atlantic, Pacific, Russian and Canadian sides of the Arctic? Not sure where the borders would be, though.
Bright ice, how can you crack and fail? How can the ice that seemed so mighty suddenly seem so frail?