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SMN444

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Re: The 2015 melting season
« Reply #1300 on: June 15, 2015, 10:07:19 PM »
@seaicesailor, the graph is GLBb0.08-92.4

A similar graph is the ARCc0.08-04.0, for the same day, June 22.

Can anyone explain the difference between these two images?

Vergent

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Re: The 2015 melting season
« Reply #1301 on: June 15, 2015, 10:08:29 PM »
Here is a second opinion on thickness:

2012:


2015:


Q: What happened to the "volume recovery"?

A: Albedo feedback.

Verg

Edit: The arctic is getting SLOTted (The Second Law of Thermodynamics).

« Last Edit: June 15, 2015, 10:20:19 PM by Vergent »

sedziobs

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Re: The 2015 melting season
« Reply #1302 on: June 15, 2015, 10:09:02 PM »
Vergent,

The HYCOM model has been updated since 2012.

Quote
Both forecast systems use similar ice and ocean components (see description below) and differ in the following manner: 1) the GOFS hindcast started from more realistic initial conditions (primarily a better ice thickness) than ACNFS, 2) GOFS assimilates ice concentration data across the full Arctic domain (not just along the ice edge as in ACNFS), 3) GOFS uses an up-to-date and improved version of the ocean model code, and 4) GOFS applies a monthly varying heat flux offset to CICE in an attempt to improve ice forecast skill.
www.arcus.org/files/sio/21233/nrl_gofs.pdf

Lord M Vader

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Re: The 2015 melting season
« Reply #1303 on: June 15, 2015, 10:14:01 PM »
Mr Cole: you said exactly what I was going to say :P Don't forget "fantasy land" (+216h and +240h which are even worse for the sea ice...)

The GFS 12z run also suggest warm conditions at +144h and beyond that..

The interesting thing is that it seems like the periphery areas of the Arctic sea ice have been the relatively coldest areas where also the thinnest ice is and helped the SIE to be put on steroids... If things falls out in a juxtapostion we may see a really BIG decline soon.

I will be interested to see if Wipneus foreseen triple century ("CCC") will materialize.. Including what comes next after the "CCC".. :)

Best, LMV

Neven

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Re: The 2015 melting season
« Reply #1304 on: June 15, 2015, 10:17:00 PM »
A few comments slipped behind this comment by a new member, because I hadn't released it yet (welcome, SMN444):

@seaicesailor, the graph is GLBb0.08-92.4

A similar graph is the ARCc0.08-04.0, for the same day, June 22.

Can anyone explain the difference between these two images?
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sedziobs

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Re: The 2015 melting season
« Reply #1305 on: June 15, 2015, 10:22:25 PM »
A few comments slipped behind this comment by a new member, because I hadn't released it yet (welcome, SMN444):

@seaicesailor, the graph is GLBb0.08-92.4

A similar graph is the ARCc0.08-04.0, for the same day, June 22.

Can anyone explain the difference between these two images?

My earlier comment spoke to the difference.  Basically, the GLB model is an updated version of the ARC, with the key difference being concentration data assimilation across the entire pack.  In the ARC model, I would guess concentration within the pack was assumed to be 100%, giving artificially high average thickness.

Rubikscube

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Re: The 2015 melting season
« Reply #1306 on: June 15, 2015, 11:13:27 PM »
The forecasts are very exciting despite moderate low pressure activity, lots of warm air is going to be dragged in on the southern flanks of these systems to hammer the pacific side. And the 168+ forecast is a wild beast, I will certainly be disappointed by the 00 run tomorrow morning :).
« Last Edit: June 16, 2015, 08:34:56 AM by Rubikscube »

seaicesailor

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Re: The 2015 melting season
« Reply #1307 on: June 15, 2015, 11:22:56 PM »
@seaicesailor, the graph is GLBb0.08-92.4

A similar graph is the ARCc0.08-04.0, for the same day, June 22.

Can anyone explain the difference between these two images?

I just wanted to show the dramatic prediction of the global model.

I can't tell you the why the differences but something that amused me is how both predict so thin ice along the Eurasian coast even when it was so cold for months, and open water is not extended very much yet. Should that be trusted?

What I most like from these models (ARC or newer GLB) and seems most reliable is how they predict ice drift and how ice edges and features are transported due to that drift. It almost always gives the right idea of what comes next due to winds. Thickness is said to be grossly overestimated in old version, newer seems to underestimate it

Vergent

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Re: The 2015 melting season
« Reply #1308 on: June 15, 2015, 11:31:06 PM »
Vergent,

The HYCOM model has been updated since 2012.

Quote
Both forecast systems use similar ice and ocean components (see description below) and differ in the following manner: 1) the GOFS hindcast started from more realistic initial conditions (primarily a better ice thickness) than ACNFS, 2) GOFS assimilates ice concentration data across the full Arctic domain (not just along the ice edge as in ACNFS), 3) GOFS uses an up-to-date and improved version of the ocean model code, and 4) GOFS applies a monthly varying heat flux offset to CICE in an attempt to improve ice forecast skill.


www.arcus.org/files/sio/21233/nrl_gofs.pdf
Quote
Thickness is said to be grossly overestimated in old version, newer seems to underestimate it

So the argument is that my post exaggerates the difference because the model has been improved. But which direction was the error in the model in 2012?

Icebridge 2012:




So, in which direction was the models error in 2012? Did they overestimate the ice like some would like to believe? Or, were they underestimating the ice?

Verg


plinius

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Re: The 2015 melting season
« Reply #1309 on: June 15, 2015, 11:52:18 PM »
@seaicesailor: My take was that we had quite some transarctic drift, which limited ice growth (and also lead to PIOMAS seeing quite some volume growth on the Canadian side).

Could you also explain to me why the arctic should have been "so cold" during the growth period?
I'd rather say the Eurasian side was quite a hothouse during this winter:
http://karstenhaustein.com/climate
scroll to the bottom and look for "all Arctic".
GISS has the Eurasian side at >2K to warm for Jan-March
http://data.giss.nasa.gov/gistemp/maps/
enter 1st quarter and enjoy the red.
April > 4K.
4th quarter was only >1K too warm. But this has been pushed onto the canadian side since then.
So all we can expect is a pretty thin mess (which you had plenty of opportunity to see with the Kara sea ice largely vanishing at the first tiny bit of sunshine and mild air.

Peter Ellis

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Re: The 2015 melting season
« Reply #1310 on: June 16, 2015, 12:15:37 AM »
My earlier comment spoke to the difference.  Basically, the GLB model is an updated version of the ARC, with the key difference being concentration data assimilation across the entire pack.  In the ARC model, I would guess concentration within the pack was assumed to be 100%, giving artificially high average thickness.

The flip side of that is that if concentration across the entire pack (or in specific areas) is being understated due to melt ponding, then unless the assimilation accounts for this, the GLB model will be biased low.

Nick_Naylor

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Re: The 2015 melting season
« Reply #1311 on: June 16, 2015, 01:11:13 AM »
The flip side of that is that if concentration across the entire pack (or in specific areas) is being understated due to melt ponding, then unless the assimilation accounts for this, the GLB model will be biased low.

OK, but GLB is showing high concentrations even in regions where it shows very low thickness.

sedziobs

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Re: The 2015 melting season
« Reply #1312 on: June 16, 2015, 01:40:39 AM »
Peter, I believe your point is correct, and indeed the low bias is acknowledged in the same reference:

Quote
A set of control runs for 2011 through 2013 were performed using the July 1 analysis for initial conditions. Comparing the mean September extent from the control runs to that of the GOFS 3.1 analyses, an estimate of the forward model bias is -0.4 Mkm2. Compared to ACNFS, the bias is smaller due to the improvements noted in the “Introduction” section; however, it has been calculated over fewer years (three in GOFS 3.1 vs. seven in ACNFS) and is less certain.

The fourth improvement noted in the introduction [GOFS applies a monthly varying heat flux offset to CICE in an attempt to improve ice forecast skill] is likely a melt pond correction.  It seems that melt pond parameterizations are currently being improved to account for coverage changes due to deformation among other things, and that current inputs are limited to ice thickness and time of year:

Quote
In the current release of the Los Alamos sea ice model (CICE version 4.1), there are two meltpond parameterizations available. In the original scheme, ponds are implicit, that is, their radiative effects are modeled through the albedo parameterization without explicitly accounting for meltpond physical processes such as the collection of melt water into pools. The albedo depends on the temperature and thickness of ice and snow and on the spectral distribution of the incoming solar radiation (Hunke, 2010). Parameters are chosen such that the average sea ice albedo behaves similarly to that observed when melt ponds would be present as well as throughout the rest of the year
Quote
In this paper we have presented a parameterization of melt ponds carried as tracers on the simulated level ice area fraction. Physical descriptions of pond processes have been incorporated, including infiltration of melt water in snow, drainage through permeable ice, and pond refreezing. Snow in particular affects the radiative properties of the ponds, sometimes hiding them completely in both spring and fall. Melt ponds first appear at southerly latitudes in spring, moving north as the melt season progresses. Thinner ice tends to be more permeable than thicker ice, and therefore pond drainage is more evident on thinner ice. Because of variations in topography, we find deeper ponds on thicker, more deformed ice, and these are the last to freeze over in autumn. Ice on top of refrozen ponds can collect snow, thus preventing solar radiation from being absorbed below; this effect is most pronounced near the end of the summer but is present earlier in the season.

Our simulated melt ponds exhibit the four stages of pond evolution as outlined by Polashenski et al. (2012), following Eicken et al. (2002), although the increase of pond area in Stage III in the model is due to continuing snow and ice melt rather than direct connection with seawater through macroscopic flaws in the ice. Ponds deepen throughout the season, while their areal coverage first spikes then gradually increases until fall refreezing again shrinks them to nothing.
http://www7320.nrlssc.navy.mil/pubs/2014/hebert-2014.pdf

The entire paper is a very interesting read regarding melt pond modeling processes.

sedziobs

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Re: The 2015 melting season
« Reply #1313 on: June 16, 2015, 01:51:28 AM »
OK, but GLB is showing high concentrations even in regions where it shows very low thickness.

In my view, the impacts of concentration assimilation should only be seen when comparing ARC to GLB for the same date.  High concentration would simply indicate that the GLB thickness is close to ARC thickness, even if both show low thickness.  The differences are clearly seen in the Beaufort, Chukchi and Hudson areas where low concentration yields lower thickness in GLB than in ARC.

Nick_Naylor

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Re: The 2015 melting season
« Reply #1314 on: June 16, 2015, 04:04:28 AM »
My point was just that GLB doesn't appear to be underestimating concentration, due to melt ponds or otherwise, so that doesn't seem to be the cause of a low thickness bias - at least to my eyes and compared to what really seems to be happening with the ice.

seaicesailor

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Re: The 2015 melting season
« Reply #1315 on: June 16, 2015, 09:23:09 AM »
@seaicesailor: My take was that we had quite some transarctic drift, which limited ice growth (and also lead to PIOMAS seeing quite some volume growth on the Canadian side).

Could you also explain to me why the arctic should have been "so cold" during the growth period?
I'd rather say the Eurasian side was quite a hothouse during this winter:
http://karstenhaustein.com/climate
scroll to the bottom and look for "all Arctic".
GISS has the Eurasian side at >2K to warm for Jan-March
http://data.giss.nasa.gov/gistemp/maps/
enter 1st quarter and enjoy the red.
April > 4K.
4th quarter was only >1K too warm. But this has been pushed onto the canadian side since then.
So all we can expect is a pretty thin mess (which you had plenty of opportunity to see with the Kara sea ice largely vanishing at the first tiny bit of sunshine and mild air.

 I should have said " month" instead of plural. See below the last PIOMAS Wipneus maps (thickness and monthly change), notice the solid 2m thickness all along the ESS coast (and North of it). Can this change so fast, was my question (rethoric).





PS. GLB map for May 15 agreed somehow with PIOMAS (the map above is for May 15 too I believe) at least for ESS:

« Last Edit: June 16, 2015, 09:34:57 AM by seaicesailor »

F.Tnioli

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Re: The 2015 melting season
« Reply #1316 on: June 16, 2015, 01:32:25 PM »
Edit Neven: I've removed the content of this comment on your request. I'm not deleting the other comment, as a) it wasn't written by you, b) I don't think it was written on purpose, and c) it is all insignificant.

Edit F.Tnioli: i did not request to remove contents of this post; i requested removal of the post itself, in its entirety. Just for the record.
« Last Edit: June 17, 2015, 12:55:17 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!

Nightvid Cole

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Re: The 2015 melting season
« Reply #1317 on: June 16, 2015, 02:38:07 PM »
OSISAF is showing dropping concentration extending into the central Arctic region:



CT should follow shortly.

johnm33

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Re: The 2015 melting season
« Reply #1318 on: June 16, 2015, 04:19:35 PM »
Ref GLB/ARC my understanding is that the navy models where sea ice hazards may be rather than overall thickness, thus the 5m area shows the extent of the area where it's likely one may run into 5m thick ice, not that the area is all 5m ice. This is why there are substantial differences between their models and for instance ADS NIPR Jaxa. Am i wrong?

sedziobs

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Re: The 2015 melting season
« Reply #1319 on: June 16, 2015, 05:20:19 PM »
johnm33, I have heard that view expressed on these forums before, but I can't find anything in the documentation to support it.  Perhaps the old PIPS model was used that way, but it certainly seems that current efforts are to improve upon a fully coupled model.  This is from a 2014 overview of the Navy's models:
Quote
The ice environment in the Arctic Ocean is also important for strategic and economic reasons. Navy interest in the region has always been high but has grown over the past decade because of the diminishing trend in year-to-year sea ice extent and thickness (National Snow and Ice Data Center, 2013). The occasional seasonal navigability of both the Northwest Passage and the Northern Sea Route brings increased military and commercial maritime operations to a region that previously had limited activity. Thus, a new sea ice prediction system that focuses on the Arctic was developed to provide forecasts of the rapidly changing ice environment.
Plus a bit more on melt ponds and concentration assimilation:
Quote
The summertime NIC-ACNFS ice edge discrepancy is due in part to a known problem with passive microwave satellite imagery underestimating ice due to surface melt ponds. To correct this, research is currently underway to assimilate the more accurate Multisensor Analyzed Sea
Ice Extent product created by the NIC and distributed by the National Snow and Ice Data Center. Posey et al. (2010) validated this interim ice prediction system, which will be replaced by the global coupled HYCOM/CICE/NCODA system in the near future.
https://hycom.org/attachments/443_Metzger_etal_2014_Oceanography.pdf

ChrisReynolds

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Re: The 2015 melting season
« Reply #1320 on: June 16, 2015, 06:45:14 PM »
John,

I got the impression from IceBridge & PIOMAS that PIPS was over thick, that is not the case with HYCOM-CICE in my opinion.

ChrisReynolds

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Re: The 2015 melting season
« Reply #1321 on: June 16, 2015, 07:03:56 PM »
I can't tell you the why the differences but something that amused me is how both predict so thin ice along the Eurasian coast even when it was so cold for months, and open water is not extended very much yet. Should that be trusted?

Ice motion.  :)

This year has seen a very strong transpolar drift. As fast as the ice can thicken new open water opens and new ice grows. Hence thinner ice off the Siberian coast, particularly Laptev.

Average vector wind Jan to April



While for Jan to March over Laptev meridional wind (northwards is positive) has been the highest since 1948.



Hence the thin ice in that region.


Peter Ellis

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Re: The 2015 melting season
« Reply #1322 on: June 16, 2015, 07:13:35 PM »
Ref GLB/ARC my understanding is that the navy models where sea ice hazards may be rather than overall thickness, thus the 5m area shows the extent of the area where it's likely one may run into 5m thick ice, not that the area is all 5m ice. This is why there are substantial differences between their models and for instance ADS NIPR Jaxa. Am i wrong?

That's actually a trope that originated on denialist sites ("The Navy is sailing ships through these areas, therefore they make sure their models are accurate"), and then got repurposed by alarmist sites ("The Navy needs to be cautious, therefore they deliberately overstate thickness").

Neither version is true.  If you read the documentation, you'll see that the models were originally developed (PIPS) to forecast the ice edge, with no particular regard to the thickness accuracy of the central pack.  The later models (various iterations of Hycom) are developing the central thickness modelling using a range of different starting assumptions. 

seaicesailor

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Re: The 2015 melting season
« Reply #1323 on: June 16, 2015, 09:56:22 PM »
Thanks plinius and Chris about pointing out the transpolar drift strength of this year, that surely caused Laptev sea thin ice, but East of? As I said above, both HYCOM+CICE and PIOMAS show 2m ice along ESS in mid May.

Anyway, we'll see at the end of the month how this "thin ice" plays out (and what PIOMAS tells us too).

Lord M Vader

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Re: The 2015 melting season
« Reply #1324 on: June 16, 2015, 09:59:25 PM »
Something for you Neven worth a blog post or so?  8)

https://translate.google.se/translate?sl=da&tl=en&js=y&prev=_t&hl=sv&ie=UTF-8&u=http%3A%2F%2Fwww.dmi.dk%2Fnyheder%2Farkiv%2Fnyheder-2015%2F06%2Fusaedvanlig-sen-smelte-debut-for-groenlands-indlandsis%2F&edit-text=

https://translate.google.se/translate?sl=da&tl=en&js=y&prev=_t&hl=sv&ie=UTF-8&u=http%3A%2F%2Fwww.dmi.dk%2Fnyheder%2Farkiv%2Fnyheder-2015%2F06%2Fusaedvanlig-sen-smelte-debut-for-groenlands-indlandsis%2F&edit-text=

While the melt onset in the Arctic basin was 3 days earlier than normal according to the Danish Meteorological Institute, the melt onset at Greenland was extremely late. In fact, the melt onset there is the latest date the Danish Meteorological Institute have recorded since they started to calculate the start of the melt season at Greenland in 1991.

As a rather weird occasion, the earliest melt onset date was April 29 in 1996 which was a year with extremely high SIE in the Arctic. this years melt onset occurred at June 12.

Best, LMV

jdallen

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Re: The 2015 melting season
« Reply #1325 on: June 16, 2015, 10:06:59 PM »
Something for you Neven worth a blog post or so?  8)

https://translate.google.se/translate?sl=da&tl=en&js=y&prev=_t&hl=sv&ie=UTF-8&u=http%3A%2F%2Fwww.dmi.dk%2Fnyheder%2Farkiv%2Fnyheder-2015%2F06%2Fusaedvanlig-sen-smelte-debut-for-groenlands-indlandsis%2F&edit-text=

https://translate.google.se/translate?sl=da&tl=en&js=y&prev=_t&hl=sv&ie=UTF-8&u=http%3A%2F%2Fwww.dmi.dk%2Fnyheder%2Farkiv%2Fnyheder-2015%2F06%2Fusaedvanlig-sen-smelte-debut-for-groenlands-indlandsis%2F&edit-text=

While the melt onset in the Arctic basin was 3 days earlier than normal according to the Danish Meteorological Institute, the melt onset at Greenland was extremely late. In fact, the melt onset there is the latest date the Danish Meteorological Institute have recorded since they started to calculate the start of the melt season at Greenland in 1991.

As a rather weird occasion, the earliest melt onset date was April 29 in 1996 which was a year with extremely high SIE in the Arctic. this years melt onset occurred at June 12.

Best, LMV
Questions begged.... What have been the onset dates for the last ten years, and is there a correlation to annual fluctuations in sea ice minima and maxima?
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Neven

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Re: The 2015 melting season
« Reply #1326 on: June 16, 2015, 10:16:59 PM »
Something for you Neven worth a blog post or so?  8)

Thanks, LMV, but I just did a re-post of a blog post on Jason Box' blog, basically saying the same thing. But I'll probably do another Greenland post next month or in August, so I've got this one bookmarked.
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ChrisReynolds

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Re: The 2015 melting season
« Reply #1327 on: June 16, 2015, 10:28:47 PM »
Ahh, yes, now it's pointed out the credit goes to Plinius for pointing out the transpolar drift.

Sea Ice Sailor,

Isn't it about average for the ESS? Here's PIOMAS May thickness for the ESS in meters (sorry, I can't be bothered uploading a graph, it's bedtime).

2000   2.62
2001   3.03
2002   2.09
2003   1.85
2004   2.60
2005   2.20
2006   2.63
2007   2.10
2008   2.15
2009   2.02
2010   2.77
2011   1.83
2012   2.28
2013   2.31
2014   1.76
2015   2.11

Lord M Vader

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Re: The 2015 melting season
« Reply #1328 on: June 16, 2015, 10:45:18 PM »
ChrisReynolds: interesting that 2003 was a year which such low ice thickness in ESS... Sleep well! :) Let's hope Mr. Sandman comes early tonight :)

Neven: had forgotten your blogged re-post from Jason Box..

//LMV

Vergent

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Re: The 2015 melting season
« Reply #1329 on: June 16, 2015, 11:09:31 PM »


All of the models have errors. Why argue models when we have recent observation based data?

http://www.cpom.ucl.ac.uk/csopr/seaice.html?lat=86.56&lon=2.12&thk_period=28&month=Jan&year=2015&basin_selected=2&seltype=point

Verg

cesium62

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Re: The 2015 melting season
« Reply #1330 on: June 17, 2015, 12:25:30 AM »
Am I naive?  IMHO, there is no "geo-engineering" in the Arctic.  Even if there was, IMHO it would change nothing compared to the variability in weather and energy carried by air masses and ocean...

There are these drilling rigs sucking out hyrdrocarbons so they can be converted to CO2.  That's part of a much vaster ongoing geo-engineering project.

seaicesailor

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Re: The 2015 melting season
« Reply #1331 on: June 17, 2015, 12:53:18 AM »
Ahh, yes, now it's pointed out the credit goes to Plinius for pointing out the transpolar drift.

Sea Ice Sailor,

Isn't it about average for the ESS? Here's PIOMAS May thickness for the ESS in meters (sorry, I can't be bothered uploading a graph, it's bedtime).

2000   2.62
2001   3.03
2002   2.09
2003   1.85
2004   2.60
2005   2.20
2006   2.63
2007   2.10
2008   2.15
2009   2.02
2010   2.77
2011   1.83
2012   2.28
2013   2.31
2014   1.76
2015   2.11

Yes it is.
Thank you very much for the data.

seaicesailor

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Re: The 2015 melting season
« Reply #1332 on: June 17, 2015, 01:05:09 AM »
Unsettling image of part of chukchi, cab and ess form worldview.

http://1.usa.gov/1GXETqv

Frivolousz21

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Re: The 2015 melting season
« Reply #1333 on: June 17, 2015, 01:57:08 AM »
Its all about that red











Inspite of lots of cloudy days so far WAA has been tremendous.
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it go e-e-e-e-ow e-e-e-e-e-e-blaow

Frivolousz21

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Re: The 2015 melting season
« Reply #1334 on: June 17, 2015, 02:04:13 AM »
by no means am I saying it's been like the worst years but melting has been much different than 2013-14.

May 20th - June 14th 2013-15.









Even within the cloudy areas the averages are above 0C. 
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Nightvid Cole

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Re: The 2015 melting season
« Reply #1335 on: June 17, 2015, 04:24:08 AM »
Snow cover is projected by MyOcean (based on TOPAZ4) to be almost entirely absent by June 25th, which appears to be without precedent. (Note that the depth thresholds are now down to just 1 cm, since the maps are nearing the end of June.)

Click for larger version.


« Last Edit: June 17, 2015, 04:29:43 AM by Nightvid Cole »

jdallen

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Re: The 2015 melting season
« Reply #1336 on: June 17, 2015, 05:05:29 AM »
Unsettling image of part of chukchi, cab and ess form worldview.

http://1.usa.gov/1GXETqv
I've been browsing EOSDIS.

Pretty much anything outside of the CAB is rotten as hell.  Western Kara.  Eastern Kara.  Laptev.  ESS.  Chukchi.  Beaufort.  CAA.  Foxe Basin.  Hudson's Bay.  Baffin Bay.

*All* of them, covered in melt ponds and/or showing the grey/brown rotting ice that's the signature of extent ready to disappear within 10 days.

Don't take seaicesailor's or my word for it.  Have a look yourselves.  It's really very ugly; more so than I remember even than 2013 before it cooled down.

https://earthdata.nasa.gov/labs/worldview/?p=arctic&l=MODIS_Aqua_CorrectedReflectance_TrueColor,Reference_Labels(hidden),Reference_Features(hidden),Coastlines&t=2015-06-16&v=-3521823.105638532,-866762.057577042,1729248.894361468,2090549.942422958
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Michael Hauber

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Re: The 2015 melting season
« Reply #1337 on: June 17, 2015, 05:12:38 AM »
I would put the transition to mostly red on MODIS to be about a week behind 2012.  I would also say that 2013 and 2014 were only a little far behind on this date, however 2013 gets colder and cloudier with lots of clouds, and bits of orange visible between the cloud for the rest of June.  2014 does much better, and I estimate reaches about the same level as today about the 21st, and continues to show significant areas of deep red for the rest of June, alongside moderate areas of cloud, with no orange ice easily visible.

Earlier surface melt in 2012, but earlier loss of snow in 2015?  Is the snow data wrong?  Or perhaps there was a lot more snow to begin with in 2012?  Once the surface is melting does it make any difference whether the surface is snow or ice for albedo?  Will the fact that salty ice melts at a lower temperature than fresh snow make enough difference to be noticeable?

If there was more snow in 2012, I'd suspect that may result in more insulation of the ice over winter, making it harder for the ice to thicken, and resulting in a thinner ice sheet during 2012.  The thickness of 1st year ice at the end of winter is strongly influenced by a thermodynamic balance between heat escaping from the ocean below, and the cooling effect of the very cold air above.  Once the insulation from the thickening ice sheet grows high enough that the two are balanced no more thickening occurs.  Snow provides more insulation per litre of frozen water due to the air trapped in it.  The other factor is that higher amounts of snow will fall when temperature are close to freezing, which is poor conditions for ice thickening.  When temperatures are very cold the atmosphere cannot hold much moisture and less snow will fall.
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jdallen

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Re: The 2015 melting season
« Reply #1338 on: June 17, 2015, 05:18:14 AM »
If there was more snow in 2012, I'd suspect that may result in more insulation of the ice over winter, making it harder for the ice to thicken, and resulting in a thinner ice sheet during 2012. 

I don't think 2012 had more or thicker snow.  If anything, I think 2015 had more snowfall, considering the tremendous surges of moisture that came in both across the Bering and via the Barents with storms. I'm not finding sources.  Links anyone?

(Edit: Looking at EOSDIS/Worldview 2012 for the same date, I'd say conditions are pretty comparable; I don't see 2012 being particularly more worse off at this date than we are currently in 2015)

https://earthdata.nasa.gov/labs/worldview/?p=arctic&l=MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Reference_Labels(hidden),Reference_Features(hidden)&t=2012-06-16&v=-5977896.525204973,-2383829.8434166024,4524247.474795027,3530794.1565833976
« Last Edit: June 17, 2015, 05:24:46 AM by jdallen »
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jdallen

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Re: The 2015 melting season
« Reply #1339 on: June 17, 2015, 05:30:39 AM »
Consider also temperatures:
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Michael Hauber

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Re: The 2015 melting season
« Reply #1340 on: June 17, 2015, 05:33:23 AM »
And on transpolar drift.  I  get the impression that as far back as 2012 the transpolar drift has seemed to shift and is currently running much more Laptev to Canada, as opposed to Siberia to Fram Strait.  This has resulted in an increase in the Laptev bite feature, but a build up of thicker ice towards the Beaufort.  Even when we have been getting stronger Fram export in the last couple years the exported ice has been much more thinner ice from the Laptev region, and less of the thicker ice from the Siberian direction, more of which has been circulating into the Beaufort Gyre.

Although the Cryosat thickness observations seem to be at odds with this theory.  But not having Cryosat measurements from 2012 we don't know for sure whether the areas showing as thicker under the recent measurements have thickened or thinned relative to 2012.
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F.Tnioli

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Re: The 2015 melting season
« Reply #1341 on: June 17, 2015, 11:51:07 AM »
...
If there was more snow in 2012, I'd suspect that may result in more insulation of the ice over winter, making it harder for the ice to thicken, and resulting in a thinner ice sheet during 2012.  The thickness of 1st year ice at the end of winter is strongly influenced by a thermodynamic balance between heat escaping from the ocean below, and the cooling effect of the very cold air above.  Once the insulation from the thickening ice sheet grows high enough that the two are balanced no more thickening occurs.  Snow provides more insulation per litre of frozen water due to the air trapped in it.  The other factor is that higher amounts of snow will fall when temperature are close to freezing, which is poor conditions for ice thickening.  When temperatures are very cold the atmosphere cannot hold much moisture and less snow will fall.
Excellent paragraph! I feel the thing about "less snow when air is much colder than 0C" is not that simple, though. I know that there are certain cloud types which are not moisture, but ice (microscopic ice particles). Obviously those are not affected by how much moisture athmosphere can hold (directly). But IIRC, the process of actual snowflake formation is very much related to relative humidity, and as temperature drops, that changes. And another, probably much more important, thing - late autumn/winter, i think the cause is not "how cold athmosphere is", rather, it's "how much moisutre there is in the athmosphere". If lots of clouds come in (from anywhere else to a given region), that's lots of moisture alright, and one of major effects of it - is massive reduction of the loss of heat content of the athmosphere. I mean, clean skies (little/no moisture) -> surface and athmosphere radiate lots of heat out into ~3K near-Earth space, and things get real cold fast; but when it's lots of moisture, much of that radiation "stays" within the athmosphere.

I.e. the dropping temperature gradient between Arctic and moderate zone, most roughly speaking, should allow for more mixing - more Arctic air going much south and in return, more warm air going into Arctic, which means more moisture into the Arctic, which means slower cooling of the athmosphere late autumn/winter and, of course, more snow - and that like you said leads to slower /less ice thickening. Again, this all is extremely gross oversimplification, of course.
« Last Edit: June 17, 2015, 12:22:15 PM by F.Tnioli »
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JayW

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Re: The 2015 melting season
« Reply #1342 on: June 17, 2015, 12:41:14 PM »
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Re: The 2015 melting season
« Reply #1343 on: June 17, 2015, 01:16:06 PM »
This drone footage of an iceberg collapsing is sad, but cool.
http://grist.org/list/this-drone-footage-of-an-iceberg-collapsing-is-sad-cool/
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Re: The 2015 melting season
« Reply #1344 on: June 17, 2015, 02:13:57 PM »
Quote
This drone footage of an iceberg collapsing is sad, but cool.

I'm afraid there is going to be a LOT of "cool footage" over the next few years...and decades, especially in Greenland and the West Antarctic.

Now that the Arctic ice sheet is in the 14th round of a 15 round (year) fight.....the increasing heat being absorbed into the Arctic each summer will go to work on the Greenland ice sheet.  THAT will likely provide some exciting footage.

This year is just the "setup" for next year.  A possible (I think likely) new low ice level this year...sets up the ice to plunge to even much lower levels next year.  After that....the following years will allow the Arctic Ocean to absorb more and more heat that can go to work on Greenland...




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F.Tnioli

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Re: The 2015 melting season
« Reply #1345 on: June 17, 2015, 02:15:05 PM »
Yeah, this size, it's cool alright. Wait till you get slightly bigger "iceberg" called "Greenland ice sheet" to collapse - that would be even cooler. I wonder how big wave it'll produce and how far that wave will go.

Edit: beaten. :D Also, found a paper (the .pdf can be downloaded here) which is quite interesting.
« Last Edit: June 17, 2015, 02:33:11 PM by F.Tnioli »
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Re: The 2015 melting season
« Reply #1346 on: June 17, 2015, 02:18:57 PM »
Nightvid and Vergent.

I find it annoying that you guys always pick a 7-10 day forecast when examining the TOPAZ4 snow cover data, especially when making comparisons to previous years. Even more so when you never revisit those forecasts 7-10 days later to see what the result actually was. It is great that someone posts this data so we can discuss it, but the way the data has been presented by you border to cherry picking and comparison on unequal terms, the kind of unserious approaches I usually associate with deniers.

Nightvid Cole

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Re: The 2015 melting season
« Reply #1347 on: June 17, 2015, 02:33:41 PM »
I would put the transition to mostly red on MODIS to be about a week behind 2012.  I would also say that 2013 and 2014 were only a little far behind on this date, however 2013 gets colder and cloudier with lots of clouds, and bits of orange visible between the cloud for the rest of June.  2014 does much better, and I estimate reaches about the same level as today about the 21st, and continues to show significant areas of deep red for the rest of June, alongside moderate areas of cloud, with no orange ice easily visible.

Earlier surface melt in 2012, but earlier loss of snow in 2015?  Is the snow data wrong?  Or perhaps there was a lot more snow to begin with in 2012?  Once the surface is melting does it make any difference whether the surface is snow or ice for albedo?  Will the fact that salty ice melts at a lower temperature than fresh snow make enough difference to be noticeable?

If there was more snow in 2012, I'd suspect that may result in more insulation of the ice over winter, making it harder for the ice to thicken, and resulting in a thinner ice sheet during 2012.  The thickness of 1st year ice at the end of winter is strongly influenced by a thermodynamic balance between heat escaping from the ocean below, and the cooling effect of the very cold air above.  Once the insulation from the thickening ice sheet grows high enough that the two are balanced no more thickening occurs.  Snow provides more insulation per litre of frozen water due to the air trapped in it.  The other factor is that higher amounts of snow will fall when temperature are close to freezing, which is poor conditions for ice thickening.  When temperatures are very cold the atmosphere cannot hold much moisture and less snow will fall.

I'll admit that the discrepancy seems a bit puzzling, though part of it may be explicable by cloud cover, since we don't have de-clouded comparison images yet (AFAIK.)

This is one of the advantages of microwave-based data, rather than visible light, although at higher frequencies (e.g. 89 GHz), microwaves are often not much better than visible light. It's the low frequencies such as 19 GHz and 37 GHz where microwaves really excel, though even at those frequencies, a very thick cloud or a cloud with large droplets or precipitation can still block the signal. In order to penetrate everything including heavily precipitating clouds 100%, you'd need to go down into radio waves around 100-200 MHz, but then you'd have poor resolution without a very large sensor to compensate for the diffraction limit.

So we are limited to being affected by atmospheric conditions to some degree, but even so, it seems there is plenty of surface melt in the central Arctic according to OSISAF:




Nightvid Cole

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Re: The 2015 melting season
« Reply #1348 on: June 17, 2015, 02:45:38 PM »
Nightvid and Vergent.

I find it annoying that you guys always pick a 7-10 day forecast when examining the TOPAZ4 snow cover data, especially when making comparisons to previous years. Even more so when you never revisit those forecasts 7-10 days later to see what the result actually was. It is great that someone posts this data so we can discuss it, but the way the data has been presented by you border to cherry picking and comparison on unequal terms, the kind of unserious approaches I usually associate with deniers.

I have checked back to see the reanalysis maps for the snow data, and they do line up reasonably well with the former forecasts. You're being very uncharitable to assume that I never even looked and to equate this to denialism, but just to give one example (upper image is forecast with 7-day lead time, lower image is reanalysis):











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Re: The 2015 melting season
« Reply #1349 on: June 17, 2015, 03:11:51 PM »
Quickly browsing through Neven's forecast page, anyone thinks, despite Arctic low pressure, the ice edge from Beaufort to Laptev is going to advance with some severe melting? CAA and then Hudson may contribute later too.

The Navy sea temperature anomalies seem to indicate albedo feedback is on, and will be helping push the edge too.