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Jim Hunt

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Re: The 2018 melting season
« Reply #3200 on: August 30, 2018, 07:57:48 PM »
Not a lot of ice left in the Foxe Basin, actually.

Speaking of which, the Louis S. Saint Laurent is currently negotiating the Fury & Hecla Strait:

http://GreatWhiteCon.info/2018/08/the-northwest-passage-in-2018/#comment-245751

Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Phil.

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Re: The 2018 melting season
« Reply #3201 on: August 30, 2018, 08:13:05 PM »
I agree with the alarm re north of Greenland. I think this year we "discovered" that the thickest ice in the arctic is literally just around the corner from a vast encroaching ocean. And that rounding that corner can be a matter of small shift in currents, or eddies, or whatever.

I've been watching the large 'pear shaped' floe slowly drifting from Kap Morris Jessup after the opening up of the thick ice there.  In ten days it's drifted about 130km towards the Fram.

Steven

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Re: The 2018 melting season
« Reply #3202 on: August 30, 2018, 08:24:13 PM »
The first image is the latest GFS 10 day sea level pressure map. It has been more or less like this since the beginning of June, and gave that very long heatwave in Europe. It also sent a continuous stream of weather systems from the south into the North Atlantic and the Arctic, week after week, month after month.

So "my speculation that belongs to me" is that this has much to do with the Atlantic Front retreating sideways and export down the Fram being blocked..

It also shows up in the North Atlantic Oscillation index, which has been strongly positive this summer.  It's in stark contrast to the negative NAO values for the 2007-2012 period, when Fram export was strong.


Data from http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.shtml

RoxTheGeologist

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Re: The 2018 melting season
« Reply #3203 on: August 30, 2018, 09:26:24 PM »
What's so anomalous is that most of the flow out of the Arctic is not through the Fram strait, the Nares strait or the Bering strait. The channels of the CAA are where most of the water and ice is exiting the Arctic ocean. This is literally a sea change.

I thought that the FRAM would still have most of the flow, but clearly the ice isn't making it very far for whatever reason (Southerly Winds, thin, easy to melt ice, lots of extra mixing with the West Spitsbergen current, Warmer than normal Atlantic, Halocline breakdown)

If the deep water flow from the FRAM slowed dramatically it would have catastrophically serious consequences for the AMOC.
« Last Edit: August 30, 2018, 09:36:13 PM by RoxTheGeologist »

magnamentis

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Re: The 2018 melting season
« Reply #3204 on: August 30, 2018, 09:41:17 PM »
I think the volume of ice melted has been quite high. Despite heavy cloud cover, allegedly anomalously thick ice in Laptev and much of ESS has gone, Fram export melted before it got there, the Atlantic front retreated, Beaufort melted the string of MYI and thick ice in the Lincoln Sea has largely gone and as FOoW said, the circulation would appear to have changed, maybe temporarily.
Extent is quite high, so I think, once again, the ice is thinner.

Hycom SST mar21-aug29 (8bit, every4 days, 2.4MB)

what you're saying and then let's look at that arm protruding into the ESS, it's all extent but looking at it more closely there is very little left, probably less than 50% real cover if we were able to count 100% accurately.

what i'm wondering is how persistent that arm is, i mean it's pounded with rather strong winds in fast succession for weeks now and continuing and the winds are often quite warm at the periphery, hence to be honest i expected more damage in that region, while we still have about 10 days left for a kara-like event, after that i think that even extreme storms would be too cold to finish the job.

Dharma Rupa

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Re: The 2018 melting season
« Reply #3205 on: August 30, 2018, 09:46:00 PM »
If the deep water flow from the FRAM slowed dramatically it would have catastrophically serious consequences for the AMOC.

I probably should take the question over to the buoy thread, but, do we have any data on the subject?

magnamentis

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Re: The 2018 melting season
« Reply #3206 on: August 30, 2018, 09:52:09 PM »
I think instead of 15% concentration Extent we should focus on assessing 50% concentration Extent. 15% takes a lot of areas that are basically 85% ice- free into account.

People suggest that kind of thing pretty often, with various other thresholds.  One month ago I went back and reanalyzed all the NSIDC data using a 30% cutoff rather than 15%.  The effect was pretty much negligible -- it reduces the extent somewhat, but there's no long-term trend over time.

In other words, it makes it look like there's less ice across the board, but not that the ice is disappearing any faster.

See this post and following ones (the top of the next page includes a .csv file with the results):

https://forum.arctic-sea-ice.net/index.php/topic,2223.msg164660.html#msg164660

i was of the opinion that over the last 3 melting seasons the effect was bigger than before, further what we have seen in the kara earlier this year is exactly the kind of very fast vanishing of the reminder once the 100% extent which in reality was less than 50%  is reaching the now valid 15% threshold

as to your posted results i didn't see a reason to go back and forth with your findings but now i would at least say that the way you put it, that extent would be artifically lower, is exactly the opposite of the truth, IMO the 15% threshold puts extent artificially higher and not the other way around.

further, while it is great that you calculated that, perhaps you'd post the math behind it for verification and then nobody ever said that it must be 30%, perhaps the critical percentage is not 30% but another threshold. to follow this up it would take a few runs with different threshold to compare and the numbers to verify, after all, where are 30% numbers available, i did not find them which is why i was not able to do my own calculations?

problem with this topic is that nothing will change from using other numbers, hence it's somehow a bit of an overkill to fill pages with the topic. on the other hand it's still an interesting topic because if we have a huge area  of 50% ice and 50% water no-one can tell that the result do not differ by at least the 35% that are usually counted and now are not, after al 35% is about a third, hence cannot be insignificant to my understanding

FishOutofWater

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Re: The 2018 melting season
« Reply #3207 on: August 31, 2018, 12:56:40 AM »
My observations on flow out of the Fram are for sea ice and the surface layer only. Clearly, there is only one way in and out of the Arctic ocean at depths below about 100m.

The Norwegian Polar institute is monitoring the Arctic outflow through the Fram Strait.

http://www.npolar.no/en/projects/fram-strait-arctic-outflow-observatory.html

Here's a pretty recent article about the on the geologic history of the Arctic outflow.

https://www.nature.com/articles/ncomms15681

slow wing

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Re: The 2018 melting season
« Reply #3208 on: August 31, 2018, 07:15:31 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-08-30...

johnm33

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Re: The 2018 melting season
« Reply #3209 on: August 31, 2018, 10:27:00 AM »
We've had lows and more or less circumpolar winds accelerating the ice south for 5/6 days. The weakness of the ice is attested by it's failure to block the garlic press. The blob in south Beaufort is the result of any ice with a keel being pushed away from Amundsen by tidal forces then agglutinating through melt/freeze. The ice thins as it moves south, another indication of it's weakness is the lack of massive growth in extent, it's all being smashed by wave action. With the lows, mslp, persisting so long it's inevitable that more Atl. waters are drawn in to CAB, but what happens next? no clue. Worst case much of the thinned ice gets covered in snow.

oren

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Re: The 2018 melting season
« Reply #3210 on: August 31, 2018, 11:45:32 AM »
The central arctic (dark colour) appears to have thinned a lot in this week. Is that 'normal' to be expected at this point - or exceptional? thx
Perhaps heavy clouds came and went. It was certainly true on the Pacific side.

be cause

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Re: The 2018 melting season
« Reply #3211 on: August 31, 2018, 01:04:36 PM »
central Arctic thinning is certainly taking place north of Fram .. Worldview 30.08 shows openings in the ice to beyond 88'N .. worst condition I've seen since 2016 and worsening .. this stage in 2016 the gaps were filling in .. not opening up .. b.c.

ps .. looking at Sept 4th 2016 on worldview shows this year the ice is in better shape than then near the pole but much worse north of Greenland .
« Last Edit: August 31, 2018, 01:11:49 PM by be cause »
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

binntho

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Re: The 2018 melting season
« Reply #3212 on: August 31, 2018, 01:49:44 PM »
A rare glimpse through the clouds yesterday, Northern Greenland at the bottom, North Pole top left. There doesn't seem to be any snow on the ice (although I'm not really qualified to tell the difference), at least it hasn't snowed on land.

When zooming in to full extent, the ice seems to consist of a few large floes (5-10 km diameter) floating in matrix of rubble.
because a thing is eloquently expressed it should not be taken to be as necessarily true
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Sterks

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Re: The 2018 melting season
« Reply #3213 on: August 31, 2018, 01:53:56 PM »
Interesting to see the effect of weather on bottom and lateral melting in the last 15 days. And let us agree the storms and winds were not very strong.
The weather keeps stirring. Laptev sea heat reserves are also playing a role.

uniquorn

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Re: The 2018 melting season
« Reply #3214 on: August 31, 2018, 03:09:24 PM »
Today's ecmwf waves and temps from windy

NeilT

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Re: The 2018 melting season
« Reply #3215 on: August 31, 2018, 03:48:21 PM »
Looking at the extent trend for the last 6 days, 2018 is looking at 7th or 8th place.

Time will tell though.

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Re: The 2018 melting season
« Reply #3216 on: August 31, 2018, 04:35:15 PM »
Looking at the extent trend for the last 6 days, 2018 is looking at 7th or 8th place.

6th, 7th or 8th place to me.

NeilT

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Re: The 2018 melting season
« Reply #3217 on: August 31, 2018, 04:38:05 PM »
6th, 7th or 8th place to me.

True it could drop below 2017.
Being right too soon is socially unacceptable.

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oren

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Re: The 2018 melting season
« Reply #3218 on: August 31, 2018, 05:29:40 PM »
2010 was mighty weird. I bet a lot of crow was eaten that year when extent had that late "mini-cliff".

Dharma Rupa

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Re: The 2018 melting season
« Reply #3219 on: August 31, 2018, 06:33:45 PM »
If you look at the ice front on the Atlantic side the lift-off North of Greenland looks a lot like a continuation of the same latitudinal line.

Niall Dollard

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Re: The 2018 melting season
« Reply #3220 on: August 31, 2018, 06:53:12 PM »
Looking at the extent trend for the last 6 days, 2018 is looking at 7th or 8th place.

Time will tell though.



You forgot 2008, which had a lower min than 2010 & 2017

A 9th place finish ? Now that would be weird  :o

Ned W

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Re: The 2018 melting season
« Reply #3221 on: August 31, 2018, 06:58:19 PM »
Looking at the extent trend for the last 6 days, 2018 is looking at 7th or 8th place.

6th, 7th or 8th place to me.
Odds of various ranks, per the predict-o-matic:

6th place: 61%
8th place: 23%
7th place: 12%
9th place: 2%
4th place: 1%
Everything else: negligible

Predicted minimum, 4.444 million km2 (yep, that's a lot of 4's)

Ned W

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Re: The 2018 melting season
« Reply #3222 on: August 31, 2018, 07:08:37 PM »
A month ago, GoSouthYoungins made this prediction (click link for original map attachment).

My prediction:  Black and Grey Sep 1. Black Sep 15   ish

Then a quick but thin and limited refreeze. If next year el ninos, it will be historically bad for ice.

Good, a prediction!  I love it.  FYI, that works out to an extent of 3.2 million km2 on 1 September, and 2.7 million km2 on 15 September.  (I reprojected your map onto an equal-area grid before calculating extent). 

So you're predicting that we'll smash the 2012 record, by nearly a half million km2.

September 1st is just around the corner now, and extent today is almost exactly 50% higher than GSY's Sept 1st prediction. 

(Not trying to discourage people here from making "hard" predictions ... quite the opposite, in fact -- I think it's great when people give it a try.  But it's good to look back and see how they turned out, retroactively... )

RoxTheGeologist

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Re: The 2018 melting season
« Reply #3223 on: August 31, 2018, 07:32:39 PM »
My observations on flow out of the Fram are for sea ice and the surface layer only. Clearly, there is only one way in and out of the Arctic ocean at depths below about 100m.

The Norwegian Polar institute is monitoring the Arctic outflow through the Fram Strait.

http://www.npolar.no/en/projects/fram-strait-arctic-outflow-observatory.html

Here's a pretty recent article about the on the geologic history of the Arctic outflow.

https://www.nature.com/articles/ncomms15681


FOOW, thanks for the article; it's really interesting! I couldn't find any current freshwater export data - I attached what I found on the Norwegian site.

Freshwater has to leave the Arctic somewhere. There has really been no increase in melt over the last view years (though the % of total ice being melt is increasing as volume decrease); the salinity of the melt will have increased with the reduction of MYI being melted; The input from rivers has gone up, 10%.

A low density layer will flow over a higher density layer to form an layer of equal thickness, so the freshwater will flow out of the FRAM and the CAA simply driven by it's density difference. I would think that the energy driving this flow has dropped, even with the increased input from rivers; 2 PSU ice/melt has a lot more potential energy than 8 PSU ice/melt (20% more compared to 32 PSU surface waters).

I would think that the FRAM freshwater output has dropped, and not just because of the output through the CAA, but also because the forces driving the export have also been reduced. Perhaps that is a contributing factor as to why we aren't seeing as much FRAM export of ice...



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GoSouthYoungins

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Re: The 2018 melting season
« Reply #3225 on: August 31, 2018, 11:28:06 PM »
A month ago, GoSouthYoungins made this prediction (click link for original map attachment).

My prediction:  Black and Grey Sep 1. Black Sep 15   ish

Then a quick but thin and limited refreeze. If next year el ninos, it will be historically bad for ice.

Good, a prediction!  I love it.  FYI, that works out to an extent of 3.2 million km2 on 1 September, and 2.7 million km2 on 15 September.  (I reprojected your map onto an equal-area grid before calculating extent). 

So you're predicting that we'll smash the 2012 record, by nearly a half million km2.

September 1st is just around the corner now, and extent today is almost exactly 50% higher than GSY's Sept 1st prediction. 

(Not trying to discourage people here from making "hard" predictions ... quite the opposite, in fact -- I think it's great when people give it a try.  But it's good to look back and see how they turned out, retroactively... )

So, I don't mind being called out for incorrect predictions. I think more attention towards bias, etc. is a good thing. But, I didn't put a number on it (although a month ago I was expecting more melt overall, with less North of greenland, and made some numerical predictions accordingly). You put a number on it.

Personally, I think basic logic dictates that if an area is more water than ice, then it should be considered water. 15% as an arbitrary threshold is bizarre. If you look at my map prediction for Sep 1, a 50% threshold will be almost exactly as I predicted. I was not trying to make a hard prediction. It was fairly obvious at that point that it would be something very similar to what I posted. The first half of September melt is much more dubious.
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be cause

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Re: The 2018 melting season
« Reply #3226 on: September 01, 2018, 12:36:53 AM »
looking thru Worldview today I see more disintegration / bottom melt around the pole .. it is a rare opportunity to see below the clouds . It looks like the Lincoln sea disease has spread north . This is in keeping with dmi 80 surface temps having been above normal the whole of August , definately the warmest August in the satellite era in the region . A warm stormy autumn could yet extend the melt season . b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

Ned W

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Re: The 2018 melting season
« Reply #3227 on: September 01, 2018, 01:19:12 AM »
It's that time of year again, when we see that extent hasn't dropped as low as we feel it ought to have, and so we try to change the definition...

I think instead of 15% concentration Extent we should focus on assessing 50% concentration Extent. 15% takes a lot of areas that are basically 85% ice- free into account.

[... snip ... Discussion of posts where Ned W compares the standard extent data to what it would look like with a 30% threshold instead of 15% ...]

further, while it is great that you calculated that, perhaps you'd post the math behind it for verification and then nobody ever said that it must be 30%, perhaps the critical percentage is not 30% but another threshold. to follow this up it would take a few runs with different threshold to compare and the numbers to verify, after all, where are 30% numbers available, i did not find them which is why i was not able to do my own calculations?

[...] if we have a huge area  of 50% ice and 50% water no-one can tell that the result do not differ by at least the 35% that are usually counted and now are not, after al 35% is about a third, hence cannot be insignificant to my understanding

Personally, I think basic logic dictates that if an area is more water than ice, then it should be considered water. 15% as an arbitrary threshold is bizarre. If you look at my map prediction for Sep 1, a 50% threshold will be almost exactly as I predicted.

This comes up every year.  15% is what the community uses, all of the data (except older DMI) are based on it.  If we start making predictions about a 30 or 40 or 50% threshold, all it does is ensure that it will be prohibitively difficult to compare them to anything else, quantitively.

If this year's "50%-extent" is X million km2 ... Is that low, high, or average?  Nobody will know!  Because for every previous year, we have "15%-extent" data.

However ... As noted above, I did go back and reprocess all the NSIDC concentration maps to calculate a "30%-extent", and posted the results in the other thread here:

https://forum.arctic-sea-ice.net/index.php/topic,2223.msg164660.html#msg164660

On the next page following that one there's a post by me with a csv file with the results.

Magnamentis wants that redone for other thresholds, and wants me to post "the math" for verification purposes.  The "math" involved is merely (a) reprojecting all the ice concentration maps into an equal-area projection, and then (b) counting up the number of grid cells that exceed whatever threshold you want.  (A further complication is the "pole hole" whose size changes...) If there's a lot of interest I'd be willing to rerun the processor for different thresholds.

The thing is, though, so far at least it doesn't have any non-trivial effect on the long-term trend in extent.  As Neven predicted...   So the payoff for doing it is pretty small.


Niall Dollard

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Re: The 2018 melting season
« Reply #3228 on: September 01, 2018, 03:17:53 AM »
It's that time of year again, when we see that extent hasn't dropped as low as we feel it ought to have, and so we try to change the definition...


So in other worlds the bullshit begins, in earnest,

Ned W

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Re: The 2018 melting season
« Reply #3229 on: September 01, 2018, 03:27:33 AM »
It's that time of year again, when we see that extent hasn't dropped as low as we feel it ought to have, and so we try to change the definition...


So in other worlds the bullshit begins, in earnest,

That's not quite how I would put it, but ... YMMV.

Edited to add:  I think there is a natural human tendency to cast about for explanations when things don't go the way that we expect.  Sometimes that is productive, if it involves re-evaluating wrong assumptions or whatever.  Other times it's not so productive.  But one way or another, we probably all do this.
« Last Edit: September 01, 2018, 03:34:44 AM by Ned W »

FishOutofWater

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Re: The 2018 melting season
« Reply #3230 on: September 01, 2018, 03:40:26 AM »
We have known for a month that June and July were cool, stormy and cloudy. No one should be surprised that the extent at the beginning of September is higher than years in this decade that had sunnier and warmer summers. Moreover, there has been almost no ice transport out of the Fram strait this summer, nor has much ice been pushed towards the warm water on the Atlantic side. Changing the definitions won't change the facts.

jdallen

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Re: The 2018 melting season
« Reply #3231 on: September 01, 2018, 04:28:29 AM »
looking thru Worldview today I see more disintegration / bottom melt around the pole .. it is a rare opportunity to see below the clouds . It looks like the Lincoln sea disease has spread north . This is in keeping with dmi 80 surface temps having been above normal the whole of August , definately the warmest August in the satellite era in the region . A warm stormy autumn could yet extend the melt season . b.c.

There are ways in which the ice quality is reminding me of the end of 2013.  That was another year which was absolutely saved by the weather, as huge portions of the map looked like it had broken out with white freckles.
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slow wing

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Re: The 2018 melting season
« Reply #3232 on: September 01, 2018, 05:26:00 AM »
U. Bremen's false colour ice concentration maps show a week's action in the Arctic basin, ending on the map just released, 2018-08-31...

Aluminium

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Re: The 2018 melting season
« Reply #3233 on: September 01, 2018, 07:56:03 AM »
August 27-31.

oren

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Re: The 2018 melting season
« Reply #3234 on: September 01, 2018, 08:55:54 AM »
Looking at the huge region of slush north of the Chukchi and in the ESS, extent can still drop significantly if the melting season extends to 3 more weeks. I wouldn't be surprised if that happened.

jdallen

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Re: The 2018 melting season
« Reply #3235 on: September 01, 2018, 08:58:10 AM »
I just poked around 2013 using Worldview.  The quality of the ice this year is reminding me more and more of 2013 - the same kind of isolated rounded floes, somewhat filled in around them by much smaller brash and almost "foamed up" extent of the kind we see in areas a week or two away from melting out.

What we may be seeing is a new transitional ice regime which may persist a few years until we start regularly seeing BOE's.
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uniquorn

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Re: The 2018 melting season
« Reply #3236 on: September 01, 2018, 12:54:22 PM »
Today's ecmwf waves and temps from windy

Jim Hunt

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Re: The 2018 melting season
« Reply #3237 on: September 01, 2018, 01:25:11 PM »
The barrage of assorted swells has begun:

http://GreatWhiteCon.info/2018/08/the-great-arctic-cyclone-of-2018/#Sep-01

Extent decline seems to have stalled. Meanwhile "high res" AMSR2 area is falling fast:
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

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Re: The 2018 melting season
« Reply #3238 on: September 01, 2018, 05:43:17 PM »
Unless we see a larger than average drop in September, an 8th place finish is looking likely.

Dharma Rupa

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Re: The 2018 melting season
« Reply #3239 on: September 01, 2018, 08:31:49 PM »
Blue line, Green line -- decisions...decisions.

[BTW -- in Boston the subways are known by color, and there are all of Red Line, Green Line, and Blue Line.]


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Re: The 2018 melting season
« Reply #3240 on: September 01, 2018, 09:56:28 PM »
From the very first post in this thread, way back in March:

Personally, I think we will end up somewhere around 4,5 Mn km2 by the middle of September.

FWIW, it's now September and the current projected JAXA minimum (rounded to one decimal place) is in fact 4.5 million km2.  Not bad!

Jim Hunt

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Re: The 2018 melting season
« Reply #3241 on: September 02, 2018, 01:45:28 AM »
Here's the wave/swell forecast for the Laptev/ESS at 09:00 UTC tomorrow, with the remnants of yesterday's still visible in the Kara Sea, albeit no longer directed at the ice edge:
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

uniquorn

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Re: The 2018 melting season
« Reply #3242 on: September 02, 2018, 01:13:00 PM »
Update on the Mclure Strait, amsr2-uhh jul18-sep1. (arctic, small 2.3MB)

Sterks

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Re: The 2018 melting season
« Reply #3243 on: September 02, 2018, 02:10:28 PM »
Wow, see real chances of the ESS arm to finally disappear, at least the area that seems to becoming detached. Quite a lot of ice a month ago, anomalously thick then, according to PIOMAS. I assume PIOMAS anomalies will remain virtually flat because of this.

Aluminium

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Re: The 2018 melting season
« Reply #3244 on: September 02, 2018, 03:25:53 PM »
June and August were the warmest on Kotelny Island (2.1°C and 6.3°C). July (3.6°C) was slightly above normal (2.9°C). I assume some extra heat has accumulated in the sea around.

oren

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Re: The 2018 melting season
« Reply #3245 on: September 02, 2018, 05:06:17 PM »
Wow, see real chances of the ESS arm to finally disappear, at least the area that seems to becoming detached. Quite a lot of ice a month ago, anomalously thick then, according to PIOMAS. I assume PIOMAS anomalies will remain virtually flat because of this.
Yes. The ESS has shrunk considerably. (So has Little Blob in the Beaufort Sea.) Now it's a race against time.

Phil.

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Re: The 2018 melting season
« Reply #3246 on: September 02, 2018, 06:48:57 PM »
The Bremen is currently off Wrangell island and the temperature is 13ºC, the last several days the weather has been good, temperatures up to 10 or so and sunny at times.

jdallen

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Re: The 2018 melting season
« Reply #3247 on: September 02, 2018, 08:50:16 PM »
The Bremen is currently off Wrangell island and the temperature is 13ºC, the last several days the weather has been good, temperatures up to 10 or so and sunny at times.

That's way, *WAY* too hot.  Like 10C above normal.  Like a new September high temperature record too hot.
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Jim Hunt

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Re: The 2018 melting season
« Reply #3248 on: September 02, 2018, 08:55:41 PM »
The Lincoln Sea and thereabouts still looks a mess. This via Aqua yesterday:
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gerontocrat

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Re: The 2018 melting season
« Reply #3249 on: September 02, 2018, 09:41:23 PM »
Wow, see real chances of the ESS arm to finally disappear, at least the area that seems to becoming detached. Quite a lot of ice a month ago, anomalously thick then, according to PIOMAS. I assume PIOMAS anomalies will remain virtually flat because of this.
Yes. The ESS has shrunk considerably. (So has Little Blob in the Beaufort Sea.) Now it's a race against time.
NSIDC area and extent graphs for the ESS attached
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