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Sterks

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Re: The 2017 melting season
« Reply #4100 on: September 16, 2017, 01:30:37 PM »
5days out is unreliable, but as it's quiet here - GFS is predicting 978hpa
The ECMWF has it a little lower but in about the same position for the 20th. I think that it has been noted to be pretty reliable for a few days out. Not my cup of tea, reading these charts, but this looks like the makings for a strong gradient setup.
Le coup de grâce to this thread

uniquorn

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Re: The 2017 melting season
« Reply #4101 on: September 16, 2017, 08:47:22 PM »
Le coup de grâce to this thread

I hope you are right.
GFS forecast 975hPa moved forward to 19th

A-Team

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Re: The 2017 melting season
« Reply #4102 on: September 16, 2017, 09:39:01 PM »
GFS forecast 975hPa moved forward to 19th
RASM-ESRL sees that hitting a bit differently in nine GFS comparisons, notably somewhat stronger wind ('arctic24' in Reb_plot archive) late on the 18th. From the forecast melt, it seems like warmer water might get stirred up in the ESS-Laptev area.

NSIDC, back on Sept 6th so not yet calling a minimum (which for 3 km AMRS2 open water was on Sept 12th), notes "the ice edge in the Beaufort Sea is extremely far north. In parts of this region, the ice edge is farther north than at any time since the satellite record began in 1979."

They don't give distances to nearest land in km though that can be taken as 111 x degrees of latitude to shore (or more simply as a radial gradient out from the North Pole shown over continental shelf bathymetry, bottom). Walruses dive no deeper than 80 m to feed; there's next to nothing of that near the ice edge.

https://www.esrl.noaa.gov/psd/forecasts/seaice/

Arctic1    RASM-ESRL vs GFS ice area and snow depth
Arctic2    RASM-ESRL vs GFS 2m temp and surface pressure
Arctic4    RASM-ESRL vs GFS 850 hPa temp and precip
Arctic9    RASM-ESRL vs GFS 500-1000 hPa thickness and precip
Arctic12   RASM-ESRL vs GFS surface temp and LWP
Arctic13   RASM-ESRL vs GFS surface pressure + 850 hPa height
Arctic19   RASM-ESRL 500hPa height and wind vectors
Arctic22   RASM-ESRL vs GFS longwave flux + shortwave flux
Arctic24   RASM-ESRL vs GFS surface wind + energy flux


« Last Edit: September 16, 2017, 10:43:06 PM by A-Team »

Deeenngee

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Re: The 2017 melting season
« Reply #4103 on: September 17, 2017, 10:28:55 PM »
Probably my final 2017 descent to the min graph update. Probably.
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Re: The 2017 melting season
« Reply #4104 on: September 18, 2017, 12:47:55 PM »

F.Tnioli

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Re: The 2017 melting season
« Reply #4105 on: September 18, 2017, 01:24:41 PM »
Probably my final 2017 descent to the min graph update. Probably.
What makes you say this, i wonder. From A-team's post just above:


gerontocrat

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Re: The 2017 melting season
« Reply #4106 on: September 18, 2017, 02:23:35 PM »
Weather-forecast.com says a big weather system all this week over most of the Arctic Basin. If the image for tomorrow does not happen I give up on weather forecasts.
If a big weather system like this does not cause some melting somewhere is it time to say au revoir to this thread?
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Shared Humanity

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Re: The 2017 melting season
« Reply #4107 on: September 18, 2017, 02:33:55 PM »
This storm will certainly expose how fragile and mobile this ice is but it might actually serve to increase SIE as the ice moves about. That being said, this thread should remain active for those who would like to conduct a postmortem on this perplexing melt season.

jdallen

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Re: The 2017 melting season
« Reply #4108 on: September 18, 2017, 08:52:23 PM »
Probably my final 2017 descent to the min graph update. Probably.
I find it interesting that only 2007, 2011, 2012, 2015 and 2016 are lower, and we are in the "pack" for most of those save 2012.

In volume, we are lower, and in average ice quality, I think we have to go back to 2013 end of season to see anything approaching what we have now - but 2013 still had more thick ice than we have now.

A fascinating year so far, and one which may possibly reflect a new transitional pattern where feedbacks from increased water vapor like cloud cover and increased snowfall attenuate summer extent loss.

I think this will continue for some time, possibly even decades.  I think it will be punctuated at intervals by deeper meltouts to near or under 1M KM2 area, possibly under 1MKM2 extent, but will recover.

I think the transition to fully, seasonally "ice-free" Arctic conditions won't happen until we see water temperatures at depth in the basin rise at least a degree C.  At that point, there will be sufficient energy to continue vigorous bottom melt long enough that even the cloud and snow cover feedbacks won't reduce albedo enough to save the ice.

(Edit) A caveat to the ice's survival is tied to the refreeze rather than the melt season.  With Arctic amplification and the disruption the Hadley/Ferrell/Arctic cell circulation, winter temperatures will be crucial to the ice's survival.  If we start seeing winters which consistently follow 2015/2016 and 2016/2017 temperature pattern, the pack will be come far more vulnerable to factors which previously were marginal, such as Fram export which carries off the remaining thick MYI.  A bad refreeze leaving ice in the state it was this year in May then means that even what was a normal melt season prior to 2007 could become catastrophic.

We are very fortunate I think, that recent melt seasons have been anemic.
« Last Edit: September 18, 2017, 09:04:50 PM by jdallen »
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A-Team

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Re: The 2017 melting season
« Reply #4109 on: September 19, 2017, 12:11:00 AM »
Not too much impact is foreseen from the impending low pressure over the next 10 days in the ESRL wind over ice forecasts. The three animations, which seem fairly complex, can actually be updated daily using Dryland's archive parsing, an imported palette from UH AMSR2, Panoply scripting, and Gimp automation (BIMP or python-fu) as described today over at Developer's Corner (or at least that's the goal).
« Last Edit: September 19, 2017, 01:12:25 AM by A-Team »

F.Tnioli

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Re: The 2017 melting season
« Reply #4110 on: September 19, 2017, 01:50:04 PM »
...
A fascinating year so far, and one which may possibly reflect a new transitional pattern where feedbacks from increased water vapor like cloud cover and increased snowfall attenuate summer extent loss.

I think this will continue for some time, possibly even decades.  ...

We are very fortunate I think, that recent melt seasons have been anemic.
Not so simple. Summer extent loss being reduced by extra clouds and snow is a thing, yes; but also, winter/spring thickness loss is also a thing because of those same things, - extra clouds (preventing radiative heat loss from the surface to space basically) and extra snow (better insulation preventing normal thickness to form). One can quite count the latter effects as "preemptive loss of summer thickness and thus, also extent". Fortunate we are, yes.

Shared Humanity

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Re: The 2017 melting season
« Reply #4111 on: September 19, 2017, 02:17:10 PM »
Open water in the CAB at the end of the melt season is a new permanent feature of the Arctic. This is the biggest reason for the anomalously warm, stormy, and snowy Arctic, particularly in the early part of the freeze season IMHO. Less ice (volume) at the end of the freeze season is likely a new feature as well.

A cloudy cooler Arctic seems to be another feature during melt season. The Arctic use to have a bitter cold, desert climate. No longer, I fear.

Thomas Barlow

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Re: The 2017 melting season
« Reply #4112 on: September 19, 2017, 03:09:28 PM »
Here ends a very bad season.
Not being a Negative Nancy here, just realistic:
North Atlantic waters seeping into the Arctic are warmer than ever, the Nares was open all year since last year, the SSTs all around are warmer, the overall Arctic Ocean volume (ignoring thick ice crushed against land) is close to the worst state on record at start of freezing season, if not the worst, the ice itself is said to be poor quality, the fire seasons are pouring more soot over the Arctic than ever, and the fire seasons are longer than before.

This next paragraph was going to be the good news. I am trying really hard to see the good news here, and the idea that 'we dodged a bullet' being floated all over the internet now. I don't see it. “Extent” is not telling the true state the overall Arctic Ocean.
These general extent graphs are deceptive. I could be wrong, because I do think volume is the most important factor, and that volume in the overall Arctic Ocean to be the most important indicator, but the overall picture is very bad.

Ok, I'll try again to find something  positive ...
I'm trying... help me out here. The only positive I can think of is that bigger and bigger storms in the Atlantic could cool surface waters (but that's not very good news for those in the path of those storms). I would hope for a really cold winter over the Arctic, but that's not likely. The only good news is there might be more snow than previous years (due to warmer air), and that could shield the ice a little next Spring. Can it help volume by next Sept.? I doubt it.

So "dodging a bullet",  or "7th worst on record", it is not.
But wait for the science-deniers across the right-wing news to start shouting that ""the Arctic ice is in the best shape in years, and getting better.""

If anyone can think of a positive outcome from this melt season let me know. I may have missed it.
« Last Edit: September 20, 2017, 12:16:35 AM by Thomas Barlow »

Daniel B.

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Re: The 2017 melting season
« Reply #4113 on: September 19, 2017, 03:25:39 PM »
Probably my final 2017 descent to the min graph update. Probably.
I find it interesting that only 2007, 2011, 2012, 2015 and 2016 are lower, and we are in the "pack" for most of those save 2012.

In volume, we are lower, and in average ice quality, I think we have to go back to 2013 end of season to see anything approaching what we have now - but 2013 still had more thick ice than we have now.

A fascinating year so far, and one which may possibly reflect a new transitional pattern where feedbacks from increased water vapor like cloud cover and increased snowfall attenuate summer extent loss.

I think this will continue for some time, possibly even decades.  I think it will be punctuated at intervals by deeper meltouts to near or under 1M KM2 area, possibly under 1MKM2 extent, but will recover.

I think the transition to fully, seasonally "ice-free" Arctic conditions won't happen until we see water temperatures at depth in the basin rise at least a degree C.  At that point, there will be sufficient energy to continue vigorous bottom melt long enough that even the cloud and snow cover feedbacks won't reduce albedo enough to save the ice.

(Edit) A caveat to the ice's survival is tied to the refreeze rather than the melt season.  With Arctic amplification and the disruption the Hadley/Ferrell/Arctic cell circulation, winter temperatures will be crucial to the ice's survival.  If we start seeing winters which consistently follow 2015/2016 and 2016/2017 temperature pattern, the pack will be come far more vulnerable to factors which previously were marginal, such as Fram export which carries off the remaining thick MYI.  A bad refreeze leaving ice in the state it was this year in May then means that even what was a normal melt season prior to 2007 could become catastrophic.

We are very fortunate I think, that recent melt seasons have been anemic.

We may simple by in a holding pattern.  The summer minimum in extent may be constrained by the water and air temperatures and circulation.  Barring a significant change, such as the one you mentioned, we may see several years (decades) of annual ice minimums in the "pack."

Dharma Rupa

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Re: The 2017 melting season
« Reply #4114 on: September 19, 2017, 05:15:19 PM »
...
A fascinating year so far, and one which may possibly reflect a new transitional pattern where feedbacks from increased water vapor like cloud cover and increased snowfall attenuate summer extent loss.

I think this will continue for some time, possibly even decades.  ...

We are very fortunate I think, that recent melt seasons have been anemic.
Not so simple. Summer extent loss being reduced by extra clouds and snow is a thing, yes; but also, winter/spring thickness loss is also a thing because of those same things, - extra clouds (preventing radiative heat loss from the surface to space basically) and extra snow (better insulation preventing normal thickness to form). One can quite count the latter effects as "preemptive loss of summer thickness and thus, also extent". Fortunate we are, yes.
I tend to go with this analysis, and with the general WACC prognosis and maritime climate.  I think we have "warm" wet winters and "cold" wet summers until the point is reached where there is no longer enough ice to maintain a fresh-water cap, at which point the thermocline breaks down and the ocean melts out.

Adam Ash

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Re: The 2017 melting season
« Reply #4115 on: September 20, 2017, 04:45:20 AM »
It is likely that humanity will insist on adding more carbon to the atmosphere (probably at increasing rates for a few years yet), and so the overall global forcing on the energy balance will continue to get worse.

For the Arctic I think that the present trend in deteriorating ice condition and volume will persist, although things will get interesting when Greenland ice sheet melt starts to increase the extent of fresh surface water to the degree that the overturning circulation is slowed.  Once the MOC slows, then under-water heat transport north will decline, tho it is unclear whether any increased heat content of the northbound currents will offset effect of flow reduction for a while.

As Hansen's Storms of Our Children indicates, the melt of Greenland ice will cause increase energy gradients, which will (among other nasty things) cause increased intensity of storms in the Atlantic, particularly. 

So in my view, the short term picture for the Arctic ice is not quite as clearly 'a steady decline to ice free' as it may seem.  There could be a 'pause' (dare I use that term?!) in volume loss due to changes in global energy distribution until the land-based ice reaches a new equilibrium and the surface fresh water re-mixes.  Whereupon, with the main heat sink gone, all hell will break loose.

cesium62

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Re: The 2017 melting season
« Reply #4116 on: September 20, 2017, 05:13:03 AM »
We may simple by in a holding pattern.  The summer minimum in extent may be constrained by the water and air temperatures and circulation.

There could be a 'pause' (dare I use that term?!) in volume loss due to changes in global energy distribution

It's not clear to me how the Pacific and Atlantic can both get hotter without that heat transferring to the Arctic, but assuming it can happen, the Antarctic is screwed worse than I thought.

jdallen

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Re: The 2017 melting season
« Reply #4117 on: September 20, 2017, 06:01:31 AM »
We may simple by in a holding pattern.  The summer minimum in extent may be constrained by the water and air temperatures and circulation.

There could be a 'pause' (dare I use that term?!) in volume loss due to changes in global energy distribution
I think it will transfer, and that's will be what kills the pack.

I think it will take some time - possibly decades as others have suggested.

Even without a sub 1 million KM2 melt year, I think the trend is going to be very bad for life in the northern hemisphere.

I think we are starting to see the wild oscillations in climate that will by typical until the heat redistributes propotionately in the system.

It's not clear to me how the Pacific and Atlantic can both get hotter without that heat transferring to the Arctic, but assuming it can happen, the Antarctic is screwed worse than I thought.
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Adam Ash

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Re: The 2017 melting season
« Reply #4118 on: September 20, 2017, 06:34:02 AM »
I'm sure you have every nuance at your fingertips, but it may pay to re-read Hansen's paper to get a handle on what is in store...

http://www.columbia.edu/~jeh1/2015/20150704_IceMelt.pdf
Ice Melt, Sea Level Rise and Superstorms: Evidence from Paleoclimate Data, Climate Modeling, and Modern Observations that 2°C Global Warming is Highly Dangerous.

During the melt phase, increased extent of Antarctic sea ice is assured.  What happens to Arctic ice is less obvious, due to the aforementioned slowing (stopping!) of the AMOC and hence of ocean heat transport towards the northern seas.
 
As I understand it, the accumulating energy surplus will be temporarily accommodated in the equatorial regions (ocean and atmosphere)while the melting ice sheets spread their cold fresh water onto polar seas.  The resulting increased temperature gradients between equator and poles will be bad for most things (if I may understate the impacts!).

I would appreciate any clarifications.

mmghosh

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Re: The 2017 melting season
« Reply #4119 on: September 20, 2017, 06:57:46 AM »
Any possible connection between the slow Arctic melt and the active Caribbean hurricane season?

Adam Ash

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Re: The 2017 melting season
« Reply #4120 on: September 20, 2017, 10:52:19 AM »
Well, to a layman, it looks like a dog, barks and wags its tail!  So....?!

F.Tnioli

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Re: The 2017 melting season
« Reply #4121 on: September 20, 2017, 01:14:06 PM »
It is likely that humanity will insist on adding more carbon to the atmosphere (probably at increasing rates for a few years yet), and so the overall global forcing on the energy balance will continue to get worse.

...

So in my view, the short term picture for the Arctic ice is not quite as clearly 'a steady decline to ice free' as it may seem.  There could be a 'pause' (dare I use that term?!) in volume loss due to changes in global energy distribution until the land-based ice reaches a new equilibrium and the surface fresh water re-mixes.  Whereupon, with the main heat sink gone, all hell will break loose.
There will not be any much "pause" any longer than few years (not decades; and few years is much about seasonal variabilities, too). Reason? CH4. You forget about CH4 here, entirely. Well, don't. CH4 is about 120 times more efficient GHG than CO2 within 1st year of release, per-particle. Which is when (1st year) much of released CH4 remain in the Arctic. And whomever doubts Arctic CH4 emissions are substantial and accelerating - better and reconsider.
« Last Edit: September 20, 2017, 01:20:32 PM by F.Tnioli »

Daniel B.

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Re: The 2017 melting season
« Reply #4122 on: September 20, 2017, 03:35:46 PM »
Any possible connection between the slow Arctic melt and the active Caribbean hurricane season?

Thus far there has been no established link.  There is still considerable debate on whether the melt has influenced mid-latitude weather.

https://www.wunderground.com/cat6/whats-arctic-doing-to-midlatitude-weather-vice-versa

F.Tnioli

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Re: The 2017 melting season
« Reply #4123 on: September 20, 2017, 04:26:18 PM »
The debate is existing, yes. But the point of such debate is not about whether such connection exists: "What happens in the Arctic does not stay in the Arctic" report clearly mentions that global climate system is being affected by changes of Arctic sea ice, and explains (some of the reasons) why. The connection definitely exists, as any Polar Vortex specialist will confirm. The only debate possible is about magnitude and importance of such connection at present and/or future time.

I'll exceed my usual length to add this key quote from the above mentioned report:

"Recent scientific literature suggests that there are direct causal links between the decline of sea ice and more extreme temperature fluctuations than have been previously recorded in the Northern Hemisphere".

Obviously more extreme temperature fluctuations - is one definite driver for more and more powerful storms. Those temperature gradients is what creates storms in the 1st place.
« Last Edit: September 20, 2017, 04:32:22 PM by F.Tnioli »

Lord M Vader

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Re: The 2017 melting season
« Reply #4124 on: September 20, 2017, 09:44:21 PM »
While the melting season is virtually over, it could be interesting to note that a seemingly extremely high value of almost 13oC was measured at Longyearbyen at Svalbard this monday. Yeaterday, the temps were almost equal high but came just shy at 12oC. This was a result of warm southerlies. I don't know what the record high for September is there.

A-Team

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Re: The 2017 melting season
« Reply #4125 on: September 20, 2017, 10:38:44 PM »
extremely high 2 m air temperature of almost 13ºC was measured at Longyearbyen
The water surface temperature is also toasty and some slow adjacent bottom melt is ongoing underneath. Per RASM-ESRL_2017-08-19-00_t024.nc. Here -1.8ºC is the freezing point of seawater at the applicable salinity.
« Last Edit: September 21, 2017, 03:00:08 AM by A-Team »

morganism

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Re: The 2017 melting season
« Reply #4126 on: September 20, 2017, 10:46:47 PM »
Holy Scandinavia Ridge. A complete monster of a block forecast to build across Scandinavia during the upcoming 10 days.

https://twitter.com/MJVentrice/status/910494303222452224

Niall Dollard

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Re: The 2017 melting season
« Reply #4127 on: September 23, 2017, 02:05:44 AM »
While the melting season is virtually over, it could be interesting to note that a seemingly extremely high value of almost 13oC was measured at Longyearbyen at Svalbard this monday. Yeaterday, the temps were almost equal high but came just shy at 12oC. This was a result of warm southerlies. I don't know what the record high for September is there.

Yr.no list the temperature extremes at Longyearbyen from 1975 to present. The 12.9 C this year puts it in second place but well below the Sept record of 15.2 C set in 1990.

Models are forecasting a big high over northern Europe soon and temps could go very high over Svalbard at the end of next week. Possible October record maybe?

For the record here are Sept maxes of 12 C or more between 1975 and 2017

1990 15.2
2017 12.9
1999 12.5
2004 12.5
2008 12.4
2013 12.0
« Last Edit: September 23, 2017, 02:35:23 AM by Niall Dollard »

Niall Dollard

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Re: The 2017 melting season
« Reply #4128 on: October 01, 2017, 01:02:50 AM »
Maybe getting slightly O/T with this but continuing with request for info on the mild September in Svalbard. Since last post, the September 2017 max temperature at Longyearbyen was beaten yet again. It managed to get to 13.3 C on Sept 26th.

The mean temperature for Sept 2017 was second warmest (second to Sept 1990) in a series going back to 1898. Below are the stats (cropped from yr.no). 

   

Shared Humanity

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Re: The 2017 melting season
« Reply #4129 on: October 04, 2017, 02:38:56 PM »
Niall....

Was Svalbard temperatures at near record highs throughout this melt season? If so, how do we explain the persistent ice on the Atlantic side of the CAB? Could it be that insolation is far more important to melt than air temperatures?

oren

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Re: The 2017 melting season
« Reply #4130 on: October 04, 2017, 03:27:44 PM »
Niall....

Was Svalbard temperatures at near record highs throughout this melt season? If so, how do we explain the persistent ice on the Atlantic side of the CAB? Could it be that insolation is far more important to melt than air temperatures?
Or that wind and waves (or lack thereof) matter.

Niall Dollard

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Re: The 2017 melting season
« Reply #4131 on: October 04, 2017, 10:02:34 PM »
Here are the Svalbard Airport mean temperature anomalies for May to Sept this year (with 2016 anomalies in brackets for comparison):

May +0.3 (+5.6)
June +4.6 (+1.1)
July +1.0 (+3.1)
August +1.4 (+1.1)
Sept +4.6 (+3.8 )

For Svalbard, a synoptic pattern bringing warm southerlies will serve to bring both warm temperatures and push the ice edge back. The proximity of the ice edge to the islands has a strong effect on mean temperatures. The West Spitzbergen Current keeps the ocean to the west, ice free. In more recent years the ice edge has stayed well back from practically all of Svalbard, for many months 

Starting the melt season in May, air temperatures were low across much of the far north Atlantic and there was not much movement of the ice edge.
June was a warm month in Svalbard and on the face of it you would think this could imply considerable ice melt. However to the east across much of the Barents we still had cold anomalies. To the west Wipeneus reported there was still some Fram export ongoing through June - so it's possible the export south would give the impression of little ice retreat.
July and August showed only modest warmth (modest for Svalbard that is, where all summer months this century have shown positive anomalies  :o ).
The big anomaly was in September and with Fram export flatlining there was considerable ice retreat to the north of Svalbard during this month. This can seen quite well in A Team's animations.

magnamentis

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Re: The 2017 melting season
« Reply #4132 on: October 05, 2017, 12:02:53 AM »
Niall....

Was Svalbard temperatures at near record highs throughout this melt season? If so, how do we explain the persistent ice on the Atlantic side of the CAB? Could it be that insolation is far more important to melt than air temperatures?

that relatively thick ice drifted in from the CAB during last winter and was replenished far into this melting season. it was not "stationary" ice that just did not melt.

further the presence of every freshly "imported" ice into the region throughout winter and spring kept the directly surrounding waters relatively cool and the permanent melt kept it at relatively low salinity which. all these factors add to persistent ice cover in the region despite warm temps and warm oceans in the wider neighbourhood.

however that was, it will sooner or later have an impact because the "imported" ice from the CAB will reduce average thickness in the CAB and eventually in the beaufort/chucky region while a really cold winter with conditions that are good to build a lot of new ice could neutralize that effect.

as usual, predictions are difficult and mostly proven wrong/useless but interesting it is nevertheless.
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A-Team

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Re: The 2017 melting season
« Reply #4133 on: October 05, 2017, 12:08:50 AM »
Svalbard temperatures at near record highs throughout this melt season? How do we explain the persistent ice on the Atlantic side of the CAB? Insolation? air temperatures? lack of wind? waves?
I have been wondering too about that strip of shallow bathymetry north of Svalbard -- where the heck were Atlantic Waters and Yermak Plateau this year? The reanimation below goes from the open water minimum up to Oct 3rd. Fram export is still nil as Niall notes.

Mag observes rightly that melt is difficult to observe when it's being overwritten by fresh oncoming ice that may also impeded wind mixing by providing a cover.

We may see some persistence yet or even some localized AW-induced further melt. For those who can't wait, there's always the ESRL forecast graphics out to mid-Oct for sea surface temperature and net anticipated melt.
« Last Edit: October 05, 2017, 12:18:41 AM by A-Team »

Ninebelowzero

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Re: The 2017 melting season
« Reply #4134 on: October 05, 2017, 09:10:58 AM »
Some fast ice being scoured off or detaching amidst the broken sea ice in this late season Worldview picture (28th September) showing 100km of coast.


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Re: The 2017 melting season
« Reply #4135 on: October 08, 2017, 04:49:19 PM »
Not precisely on topic, but perhaps of interest here.  From Zack Labe:

Monthly Arctic air temperature (925hPa) rankings over the satellite era (from 1979)

Additional temperature graphics  http://sites.uci.edu/zlabe/arctic-temperatures/
https://twitter.com/ZLabe/status/915964532282974208
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Shared Humanity

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Re: The 2017 melting season
« Reply #4136 on: October 08, 2017, 07:46:50 PM »
If I am reading this chart correctly every single month of 2017 has been cooler than the corresponding month in 2016 with the exception of August.

The chart also shows a distinct cooling of summer months (May thru August), beginning in 2013.
« Last Edit: October 08, 2017, 09:42:59 PM by Shared Humanity »

Martin Gisser

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Re: The 2017 melting season
« Reply #4137 on: October 08, 2017, 08:33:02 PM »
Not precisely on topic, but perhaps of interest here.  From Zack Labe:

Monthly Arctic air temperature (925hPa) rankings over the satellite era (from 1979)

Additional temperature graphics  http://sites.uci.edu/zlabe/arctic-temperatures/
https://twitter.com/ZLabe/status/915964532282974208
As if we aren't bugged enough by Fahrenheit etc.

Couldn't find Zach's email, so I complain here:
While his graphics are great... my first reaction to this one is: "What are those stupid numbers? Celsius? Fahrenheit? WTF?". OK, one can guess from the "1"s that they are a ranking. Now search the biggest number...
Good there's Zach's page to look: "Temperature rankings (1 = warmest, 39 = coldest)". That should be included.
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A-Team

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Re: The 2017 melting season
« Reply #4138 on: October 08, 2017, 10:41:01 PM »
As if we aren't bugged enough
Sometimes it helps to remove ranking details, step back and look for trends (it's getting warmer!) and anomalies (cool-neutral block May-Sept in 2013-14). Oct-Nov-Dec for 2017 come in at 7, 8 and 10 using averages for the last seven years.

The average temperature distribution map for 04-14 Oct 17 is shown below (ESRL forecast, 40x6 hr increments, not available earlier years) with -1.8ºC sea water freezing point contour shown.

Technical note: This two-click map is made using a linear grayscale gradient in Panoply so that when 'Average Layers' is applied in Gimp, the outcome is indeed the numeric average of the temperature at each fixed vertical stack of pixels. Most copy-paste maps on the forums do not allow averaging because of poorly constructed palettes that do not desaturate properly. Contouring is helpful here -- the cold pole is along the eastern CAA rather than the north pole (small dot) and temperature contours are nested, very much like those of ice thickness.

Suppose now that weekly (or daily!) ranks had been used instead of monthly. That would add resolution as well as noise. Much of that noise would wash out upon downsizing to the same dimensions as the monthly. Somewhere sometime in some statistics journal far far away someone said just how to do this optimally. I'm skeptical that improved takeaways would emerge in this instance.
« Last Edit: October 09, 2017, 12:21:53 AM by A-Team »

Neven

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Re: The 2017 melting season
« Reply #4139 on: October 08, 2017, 10:49:55 PM »
OK, one can guess from the "1"s that they are a ranking.

You can also guess it from the 'Air Temperature Rank By Month' in big letters below the graph.  ;)

I for one find it very useful, now that the monthly rankings are no longer updated on Andrew Slater's website.
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Dharma Rupa

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Re: The 2017 melting season
« Reply #4140 on: October 09, 2017, 01:39:40 AM »

A-Team, can you smear that first graph even more?...a lot of smoothing, please.

"What are those stupid numbers? Celsius? Fahrenheit? WTF?"

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Re: The 2017 melting season
« Reply #4141 on: October 09, 2017, 09:16:26 AM »
The ranking for July was 29th. Preceded by 16th for May and 15th for June. The (co)incidence of this cold summer with the thin ice out of the previous winter is remarkable, and final extent just reflects so.
Great graph, Zach.

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Re: The 2017 melting season
« Reply #4142 on: October 09, 2017, 03:47:54 PM »
can you smear that first graph even more?...a lot of smoothing, please.
First the rankings graphic has to be cleared of its dithering, internal and external borders, and text. Then, after filling in Oct Nov Dec 2017 with recent means, the outer cells need to be expanded a cell's width to reduce edge effects. Then a (gaussian) blur radius must be selected, here a 0.5, 1.0, 1.5 multiples of cell dimensions. Then the blur can be iterated until effective stabilization. Because the forum does not support png animations, just some snapshots of the process are shown below. (A gif animation is restricted to 256 colors per frame and the blurring creates far more, necessitating reduction, which results in forced contouring.)
« Last Edit: October 09, 2017, 04:13:28 PM by A-Team »

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Re: The 2017 melting season
« Reply #4143 on: October 09, 2017, 03:49:40 PM »
Here are twenty rounds of gaussian blurring at the 3 radii mentioned above, along with contouring forced by the gif format of 1989.

Since patterns will inevitably emerge, with no a priori justification at hand for blur radius or number of iterations, it's better just to sample the parameter space to see if these patterns are robust. It would be no more effort to look at 6,000 combinations than the 60 settings tested here but those are already enough to suggest the outcome.

remarkable correlation of summer and winter?
No. A statistically suggestive correlation coefficient takes vastly more data. As mentioned many times up-forum, gregorian months are an arbitrary and unfortunate papal unit, not synched with solstices or equinoxes (or ice maxima and minima); cutting ranks down to weekly would help some, yet ranks are awkward statistically and here all regional information is lost. So it would be better to use actual weekly temperature 2D maps and color by std deviations from climate. That data is readily available as reanalysis.

Nonetheless, Zach's graphic communicates two important points effectively to the average person by understandable (ie trustworthy) methods. People know a pattern when they see one. And, except for regionality, those would likely be the very same points emerging from a fancier statistical approach that would not be understandable outside of climate science circles.

Assuming that the ranking data refers to 2m average temperatures over the Arctic Ocean proper (Inner Basin) rather than its official boundary which includes the Barents or the Arctic Circle latitudinal boundary, it's worth recalling the pronounced lopsidedness of this ocean relative to the North Pole, Cold Pole (west of Ellesmere), current land distribution, adjacent ice sheets, flux gates, ocean currents and continental shelves will possibly lead to an imbalance of latitudinal contributions to this average. How ever all of these are put together, they wouldn't undo the strong pattern seen from simple ranking.
« Last Edit: October 09, 2017, 05:33:16 PM by A-Team »

Dharma Rupa

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Re: The 2017 melting season
« Reply #4144 on: October 09, 2017, 04:00:13 PM »
can you smear that first graph even more?...a lot of smoothing, please.
First the rankings graphic has to be cleared of its dithering, internal and external borders, and text. Then the outer cells need to be expanded a cell's width to reduce edge effects. Then a (gaussian) blur radius must be selected, here a 0.5, 1.0, 1.5 multiples of cell dimensions. Then the blur can be iterated until effective stabilization. Because the forum does not support png animations, just some snapshots of the process are shown below. (A gif animation is restricted to 256 colors per frame and the blurring creates far more, necessitating reduction, which results in forced contouring.)

Thank you!  Aside from the obvious warming, there seems to be the beginnings of a trend to comparatively cool summers in the last few years.   Too early to call it a demonstrated pattern.

Sterks

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Re: The 2017 melting season
« Reply #4145 on: October 09, 2017, 04:06:38 PM »
Amazing work, thank you.
I am intrigued not only by the blob of recent summers, warm yet cooler than 2012 and prior, but by some diagonals that appear crossing many years and survive even the strongest filtering. Difficult to ascertain what they could mean.

A-Team

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Re: The 2017 melting season
« Reply #4146 on: October 09, 2017, 05:31:49 PM »
The other thing worth noticing is the palette. A palette can be chosen to load the visualization dice (often inadvertently) but here it wasn't. The centrally hinged palette diverges from the mid-rank white towards blue and red in line with viewer perceptual expectations.

It's not grandfather's rainbow palette but instead one that separates properly when RGB channels are decomposed to HSL, meaning the lightness channel is divergently monotonic and probably linearly so. 

That's important for two reasons: (1) even-handed viewer perception of rank colors and so patterns and (2) enabling interactive surface plots and indeed easy animations of them for levels of blur. In other words, the height above the base plane is proportional to rank so it displays properly without even loading colors as a texture.

The graphic below shows the palette, its desaturation, and a static image of near-terminal blurs taken from the one-click interactive 3D surface plot in ImageJ. (Forum software does not allow the interactive display.) Some hills and valleys are consistently present that aren't so evident in flat images.

Such displays allow compression of information (multiplexing), for example ten day ESRL forecasts of snow thickness over ice thickness (not shown) where the latter is grayscale and the former any suitable palette.

It's convenient to build these palettes directly within HSL, or use online tools, or run makecpt, or take from a gallery (listed at Dev Corner), so there's no good reason to still be using rainbow.
« Last Edit: October 09, 2017, 05:46:21 PM by A-Team »

Dharma Rupa

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Re: The 2017 melting season
« Reply #4147 on: October 09, 2017, 07:05:06 PM »
The graphic below shows the palette, its desaturation, and a static image of near-terminal blurs taken from the one-click interactive 3D surface plot in ImageJ. (Forum software does not allow the interactive display.) Some hills and valleys are consistently present that aren't so evident in flat images.

I'm going to have the problem of not knowing the vocabulary very well, but I think the hills and valleys are basically represented by the grey scale (saturation?).  What would happen if you were to keep the hills and valleys as a monochromatic and replace the "normalized" color signal with a different measure -- for example ENSO?  That is a reduction of the relative warmness to the status of background fabric and presentation of the other signal overlayed.  (Of course, ENSO might turn out to be a meaningless choice, with some other signal showing a significant and possibly unusual correlation.)


liefde

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Re: The 2017 melting season
« Reply #4148 on: October 10, 2017, 11:54:32 AM »
The chart also shows a distinct cooling of summer months (May thru August), beginning in 2013.
Yes, this is due to the global rise of water vapor (and other greenhouse gases). Seasonal changes are going to diminish within the blanket of GHGs. At some point, and we don't know when, it even reaches a level of equalization because of the shielding effects. Less heat is getting in, but the heat energy that does get in, stays there and spreads out evenly globally, regardless of lower layer content. This is best seen with this correlation: https://www.facebook.com/photo.php?fbid=10155019017687201&l=59fe6bcf60

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Re: The 2017 melting season
« Reply #4149 on: October 10, 2017, 01:26:06 PM »
That sounds ominous!  So are you saying that - with smaller seasonal variation under a thicker GHG blanket - in the summer at each pole it will be cooler but (probably) above freezing point while in winter each pole will be warmer.  So slightly slower summer melt (tho it is melting anyway already) but potentially fewer freezing-degree-days.  All of this adding to the general warming trend experienced already.  Right?