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Author Topic: The 2017 melting season  (Read 660253 times)

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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nukefix

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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: Today at 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: Today at 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: Today at 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.

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Re: The 2017 melting season
« Reply #4117 on: Today at 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: Today at 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: Today at 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: Today at 10:52:19 AM »
Well, to a layman, it looks like a dog, barks and wags its tail!  So....?!