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seaicesailor

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Re: The 2016 melting season
« Reply #3900 on: August 11, 2016, 11:39:04 AM »
There is no way that the 2012 record is going to be broken, but this is getting close to GAC-2012 levels, at least with regards to intensity, perhaps not longevity. I think all that ice in the ESS zone that I talked about last week is going to go now. This increases the chances of this year ending up second. Very exciting, as huge storms always are.

Neven, in the updated ECMWF the predicted minimum of the clyclone is not as low. I may be missing something since I only know how to access Wettersentrale and this does not indicate minima

slow wing

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Re: The 2016 melting season
« Reply #3901 on: August 11, 2016, 11:50:38 AM »
Seaicesailor, the updated ECMWF prediction I'm seeing is still at 969 hPa, and now at 4 days away rather than 5 so more likely to verify.
The plot below is from http://www.tropicaltidbits.com/analysis/models/?model=ecmwf&region=nhem&pkg=z500_mslp&runtime=2016081100&fh=12&xpos=0&ypos=0.

Just look at those equal-pressure lines (what is the correct technical name? EDIT: isobars, of course - I knew that!)!

The closer the lines, the steeper the pressure gradient and so the stronger the wind. That looks like it will wreck the ice anywhere near the centre! (And the predicted storm centre at that time is basically dead centre in the Arctic Basin - I don't know how it could be any more dead centre.)
« Last Edit: August 11, 2016, 12:02:50 PM by slow wing »

Neven

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Re: The 2016 melting season
« Reply #3902 on: August 11, 2016, 12:01:21 PM »
Just look at those equal-pressure lines (what is the correct technical name?)!

Isobars.

Quote
Neven, in the updated ECMWF the predicted minimum of the clyclone is not as low. I may be missing something since I only know how to access Wettersentrale and this does not indicate minima

It is slightly too far out, so things can definitely change. But it looks pretty certain that this is going to be the (third?) cyclone this year with a core pressure of below 980 hPa. It will have to get to 970 hPa or lower to be comparable to GAC-2012, and not fizzle out after just one day (GAC-2012 just kept going and going). Let's see how the forecasts evolve.

Either way, it will do some more damage to that ice in the ESS/CAB zone, maybe just enough to overtake 2007, 2011 and 2015.
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Quantum

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Re: The 2016 melting season
« Reply #3903 on: August 11, 2016, 12:07:36 PM »
Does anyone think that top melt could end quite early this year? The low, for the problems it will likely cause for the ice, is bringing unusually cold temperatures and widespread snowfall:


I'd expect during these conditions shallow melt ponds would freeze over and the final part of the melt season is almost entirely dominated by bottom melt.

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Re: The 2016 melting season
« Reply #3904 on: August 11, 2016, 12:25:32 PM »
Eric Holthaus:
Quote
Over the last day or so, a beautiful storm system has moved across Canada's Hudson Bay. Weather twitter has gone nuts for it. ...

The best animation of this storm I've seen is a compilation of images over the span of about 17 hours from polar orbiting satellites put together by Zack Labe, a PhD student at the University of California-Irvine.

The remarkable (and remarkably beautiful) development of this storm system—technically, a midlatitude cyclone—of course serves a purpose: To equalize this corner of the planet's temperature. In the wake of the system's cold front, temperatures on the shore of Hudson Bay dropped by about 35 degrees Fahrenheit, after reaching about 90 degrees a few days ago.

Animation here:  https://mobile.twitter.com/ZLabe/status/763394412021886976/video/1
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Re: The 2016 melting season
« Reply #3905 on: August 11, 2016, 01:27:18 PM »
Does anyone think that top melt could end quite early this year? The low, for the problems it will likely cause for the ice, is bringing unusually cold temperatures and widespread snowfall:

I'd expect during these conditions shallow melt ponds would freeze over and the final part of the melt season is almost entirely dominated by bottom melt.

I posted exactly that on the blog.

Early September top melt halt, third week before the bottom melt starts to become overcome by the temp drop.

That's if it follows 2006 to the bitter end.  Of course the upcoming storm could be a game changer but I see it as a post 2007 event driven by cyclical processes.  Prior to 2007 there simply wasn't enough open water to drive it and even if such a storm did occur, the ice was strong enough to resist it.

It will be interesting to see if it gets into top 3 territory.  My guess back in May was around 3-4.  Likely to be both passages open though.  If only for a little while.
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Re: The 2016 melting season
« Reply #3906 on: August 11, 2016, 02:14:36 PM »
Does anyone think that top melt could end quite early this year? The low, for the problems it will likely cause for the ice, is bringing unusually cold temperatures and widespread snowfall:

I'd expect during these conditions shallow melt ponds would freeze over and the final part of the melt season is almost entirely dominated by bottom melt.

I posted exactly that on the blog.

Early September top melt halt, third week before the bottom melt starts to become overcome by the temp drop.

That's if it follows 2006 to the bitter end.  Of course the upcoming storm could be a game changer but I see it as a post 2007 event driven by cyclical processes.  Prior to 2007 there simply wasn't enough open water to drive it and even if such a storm did occur, the ice was strong enough to resist it.

It will be interesting to see if it gets into top 3 territory.  My guess back in May was around 3-4.  Likely to be both passages open though.  If only for a little while.
Touch and go whether the northern route opens in my opinion.

What effect do you think the snowfall would have? I'd have thought that would be the best possible way of cooling down the sea at this time of year. Could the melt season itself end a few days, if not a week, early? Perhaps 5th-10th September?

magnamentis

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Re: The 2016 melting season
« Reply #3907 on: August 11, 2016, 03:26:20 PM »
There is no way that the 2012 record is going to be broken, but this is getting close to GAC-2012 levels, at least with regards to intensity, perhaps not longevity. I think all that ice in the ESS zone that I talked about last week is going to go now. This increases the chances of this year ending up second. Very exciting, as huge storms always are.



as you know we are in agreement as to second place, always were if i remember, while the term "NO WAY" caught my attention as to i would not sign that :-) most probable, most likely yes, but things always happen in a manner that nobody thought off. i can't see that anyone in 2012 thought that outcome possible, there were quite a few "there is no way" statement back then. pretty confident that you understand my point. keep it up, always a pleasure to follow :-)

AbruptSLR

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Re: The 2016 melting season
« Reply #3908 on: August 11, 2016, 05:39:19 PM »
It will have to get to 970 hPa or lower to be comparable to GAC-2012, and not fizzle out after just one day (GAC-2012 just kept going and going). Let's see how the forecasts evolve.

While it is even further out than the 96-hr forecast the attached 120-hr forecast showing reasonable strength after two days of cyclonic activity:
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epiphyte

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Re: The 2016 melting season
« Reply #3909 on: August 11, 2016, 05:41:17 PM »
There is no way that the 2012 record is going to be broken, but this is getting close to GAC-2012 levels, at least with regards to intensity, perhaps not longevity. I think all that ice in the ESS zone that I talked about last week is going to go now. This increases the chances of this year ending up second. Very exciting, as huge storms always are.



as you know we are in agreement as to second place, always were if i remember, while the term "NO WAY" caught my attention as to i would not sign that :-) most probable, most likely yes, but things always happen in a manner that nobody thought off. i can't see that anyone in 2012 thought that outcome possible, there were quite a few "there is no way" statement back then. pretty confident that you understand my point. keep it up, always a pleasure to follow :-)

Despite the prospect of snow and the relatively high concentrations in some areas, I think that the 2012 record might still be in danger. The surface granularity remains higher than ever before, and from several directions there are hundreds of miles of relatively open water across which waves might build - so IMO a late-season storm might stir things up more than we have seen in previous years. As we all know, there's an awful lot of energy lurking under the surface - if it ever was going to come into play, this would be the point in the season at which it would happen.

One more thought, and although it's simple, I don't think that's the same as simplistic. Storms are nature's way of redistributing atmospheric energy to remove an imbalance. Historically there have been multiple factors serving to reduce that tendency in the arctic - many of which depend on the existence of a contiguous ice sheet. IMO unusual storms at this time of year don't just have consequences, at least in part they are consequences, of these mechanisms starting to break down. When enough of them do so, I fear the collapse will come not with a whimper, but with a bang.

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Re: The 2016 melting season
« Reply #3910 on: August 11, 2016, 07:16:32 PM »
No way 2012 will achieved.
Even with worsest weather, 2012 was extreme.
Forecast ist cool in the Cab and -10 850er will be in big parts of the arctic.
I think that we see something like a very good (for the ice) end of the meltsaison, but with a slow refreeze afterit, just because of the high sst.
Then there will be cold air over the extreme warm water in the european part and this might have extreme effects, with very unusual high prediction after this and a cold winter in europe.
I think that bottom melt is still going on but the northern parts refreeze so this will be light a fight but if you look for the decreases actual and the temperature progged, i think we can still have a minimum over 2015 maybe, im pretty sure over 2007.

seaicesailor

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Re: The 2016 melting season
« Reply #3911 on: August 11, 2016, 08:21:54 PM »
Seaicesailor, the updated ECMWF prediction I'm seeing is still at 969 hPa, and now at 4 days away rather than 5 so more likely to verify.
The plot below is from http://www.tropicaltidbits.com/analysis/models/?model=ecmwf&region=nhem&pkg=z500_mslp&runtime=2016081100&fh=12&xpos=0&ypos=0.

Thank you!

Greenbelt

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Re: The 2016 melting season
« Reply #3912 on: August 11, 2016, 08:54:50 PM »
Some persistence, should set some winds and ice in motion.





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Re: The 2016 melting season
« Reply #3913 on: August 11, 2016, 10:20:05 PM »

NeilT

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Re: The 2016 melting season
« Reply #3914 on: August 11, 2016, 10:54:16 PM »
What effect do you think the snowfall would have? I'd have thought that would be the best possible way of cooling down the sea at this time of year. Could the melt season itself end a few days, if not a week, early? Perhaps 5th-10th September?

Not my area of observation but I'd doubt it will make that much difference.  It will protect the ice from cooling if the temps drop and there is so much heat already in the water, allied to pumping action bringing warmth from below, that I doubt the snow will have much of a positive action in slowing it.  Unless it manages to float on the top and is frozen in place.

Too many if's to be really sure.
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slow wing

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Re: The 2016 melting season
« Reply #3915 on: August 12, 2016, 12:38:53 AM »
Thanks for the ECMWF forecast plots of the storm, Greenbelt. ECMWF's 96h prediction is for the storm centre to bottom at 969 hPa at 12z Monday, 15 August 2016.

The GFS forecast has now come into close agreement, predicting the storm centre to drop to 972 hPa by 6z Monday 15 August 2016 (their 84h prediction).

In both forecasts the storm centre is smack bang in the centre of the Arctic basin and the storm persists for at least about a week, albeit weaker than on 15 August.

  What that should mean in practice is most of the Arctic sea ice will go on an excursion of up to a couple of hundred kilometres - counter-clockwise and heading away from the centre of the Arctic Basin (at around 45 degrees to a line from the Arctic Basin centre - isn't that how it works?). That should elevate the rate of bottom melt as the ice sweeps through the water.

  There should also be some epic Ekman pumping: an upwelling of water near the storm centre to replace the surface water being dragged outwards by the combined effects of the winds and ice. That might include some warmer, saltier water from the depths that can melt sea ice.

  After all the winds already, I expect this to be a very bad year for the ice.

  If 2007 was a trial by ocean current for the Arctic sea ice (specifically, arriving from the Pacific Ocean through the Bering Strait), and 2010, 2012 were trials by sun, then I would suggest 2016 is becoming a trial by wind  :P
« Last Edit: August 12, 2016, 12:53:15 AM by slow wing »

jai mitchell

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Re: The 2016 melting season
« Reply #3916 on: August 12, 2016, 12:52:14 AM »
there's an awful lot of energy lurking under the surface - if it ever was going to come into play, this would be the point in the season at which it would happen.

That is a very good point, watching the behaviour of Obuoy 14 it is clear that subsurface melt is a major factor.  I do not think we are capturing the potential for wind-driven mixing now that there is such a fractured ice pack.  Combine that with wave action and we could see significant melt.  However, I am, as yet, unconvinced that any of our current metrics (volume, area, extent) are capturing the extreme nature of the ice condition change that we are observing this season.   It is also unclear what drove the higher winter temperatures this year and if this may extend (or shorten!) the melt season this year.
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Re: The 2016 melting season
« Reply #3917 on: August 12, 2016, 01:27:45 AM »
I would think that the effect of a major low system would be to pull in energy from lower lattitudes - is this right?

S.Pansa

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Re: The 2016 melting season
« Reply #3918 on: August 12, 2016, 06:18:53 AM »
GAC16 to-be and its possible aftermath - fortold by the transcendental gifts ot the mysterious TOPAZ4 :P Added for comparison, the TOPAZ4-state-of-the-ice from August, 1st.

seaicesailor

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Re: The 2016 melting season
« Reply #3919 on: August 12, 2016, 09:18:11 AM »
I would think that the effect of a major low system would be to pull in energy from lower lattitudes - is this right?
Indeed this will be dragging heat the first day or two (see Sleepy post at IJIS).
Last update makes it persistent for 3 days around 970's. Typically should cool down things a lot. It seems to spare Beaufort and CAA from the storm though.

seaicesailor

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Re: The 2016 melting season
« Reply #3920 on: August 12, 2016, 09:25:37 AM »
Somebody brought to attention at Neven's blog this paper by Zhang and others, and it is a very interesting piece of read for these days. An analysis of GAC effects using PIOMAS.
http://psc.apl.washington.edu/zhang/Pubs/Zhang_etal2013_cyclone_grl50190.pdf

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Re: The 2016 melting season
« Reply #3921 on: August 12, 2016, 12:21:18 PM »
Seaicesailor,

Indeed it is a fine and brief paper, in fact even better if you read it in conjunction with this paper: http://onlinelibrary.wiley.com/doi/10.1002/qj.1876/full ,
which covers a similar phenomenon in the Barents Sea some years ago, but with an entirely atmospheric perspective.

My take on the whole “GAC-2016” thing is that both atmosphere and ocean/sea ice will have to work together in order to come up with an unprecedented melting event this year:

1)   After a mild winter and a windy summer, the ice in the Arctic is now fragmented and well spread out
2)   After an excessive warm year globally, the SST anomalies around the Arctic are now extremely positive and the inflow of warm salty water has been at a maximum
3)   After a calm and dull July (no jet stream pertubations to speak of), the stratification of Artic water masses is now well developed and the pycnocline is near the surface
4)   On the back of a conventional low entering the Arctic this weekend, a new Persistent Arctic Cyclone (PAC-2016) is just about to develop
5)   The centre of the low will most likely position itself over a major ice island in the Arctic Ocean/perhaps the one over the Mendelejef Ridge
6)   The low will intensify through the release of heat from condensation in a number of spiral bands (similar to the recent Hudson Bay cyclone)
7)   The maximum wind speeds will occur over the Canadian Basin, and sporadic ice floes will help to set up a strong Ekman pumping of warm water from below
8)   The cyclone will maintain itself as long as the supply of warm water from below continues, i.e. as long as it stays away from the shores and the main ice pack near the N Pole
9)   Bottom melt will explode, when ice floes are driven by the wind over newly lifted, warm, salty waters; waves will batter the sides; sea spray will fill the air; and drizzle will erode the top surfaces of remaining floes
10)   In a couple of weeks, we will see whether a new record minima in sea ice volume, - extent and - area will have materialized themselves as predicted.


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Re: The 2016 melting season
« Reply #3922 on: August 12, 2016, 12:33:33 PM »
   ....
  What that should mean in practice is most of the Arctic sea ice will go on an excursion of up to a couple of hundred kilometres - counter-clockwise and heading away from the centre of the Arctic Basin (at around 45 degrees to a line from the Arctic Basin centre - isn't that how it works?). That should elevate the rate of bottom melt as the ice sweeps through the water.
   ....

Any guesses as to whether this storm causes a large detachment, as in 2012?  The expanse of ice NW of Wrangel looks vulnerable, though it's hard to disentangle the effects of rain and (some) compaction followed by dispersion.

slow wing

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Re: The 2016 melting season
« Reply #3923 on: August 12, 2016, 12:59:40 PM »
Iceman, just my guess but I'm guessing the ice NW of Wrangel Island will not survive the melt season. On the other hand, the ice in the Laptev Sea could separate from the main pack.

Lots of ice movement has already occurred as GAC-2016 builds, with compaction towards the North Pole. Time to bump that thread on the chances of an ice-free North Pole this season?
« Last Edit: August 12, 2016, 01:05:16 PM by slow wing »

seaicesailor

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Re: The 2016 melting season
« Reply #3924 on: August 12, 2016, 01:48:13 PM »
Yeah, with the upcoming storm we are losing sight to the current weakening dipole pattern. The drift map says it all

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Re: The 2016 melting season
« Reply #3925 on: August 12, 2016, 02:17:04 PM »
The 06z GFS has quite a strong storm lasting 36-48 hours before gradually filling out. It starts off around Laptev and gradually arcs over the Canadian side of the central Arctic, cutting right through the largest area of low concentration ice.



This is roughly what the path looks like on the latest sea ie concentration image



We could well see that ice toward Chukchi get separated from the main pack.
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Re: The 2016 melting season
« Reply #3926 on: August 12, 2016, 02:24:09 PM »
Really stupid question but why exactly does LP cause divergence and expansion? Intuitively one would expect the opposite since winds converge in a LP system and diverge in an anticyclone.

slow wing

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Re: The 2016 melting season
« Reply #3927 on: August 12, 2016, 02:34:55 PM »
Really stupid question but why exactly does LP cause divergence and expansion? Intuitively one would expect the opposite since winds converge in a LP system and diverge in an anticyclone.
It's because of the Coriolis effect.

Consider a low pressure system centred on the North Pole. Its winds are counter-clockwise, which is the same direction as the Earth is rotating. So it is speeding up the rotating ice and, consequently, the ice drifts outwards.

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Re: The 2016 melting season
« Reply #3928 on: August 12, 2016, 02:38:40 PM »
Really stupid question but why exactly does LP cause divergence and expansion? Intuitively one would expect the opposite since winds converge in a LP system and diverge in an anticyclone.
Winds in an LP move counter-clockwise, Coreolis forces tend towards the right, hence dispersion. At least that's how I understand it!
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seaicesailor

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Re: The 2016 melting season
« Reply #3929 on: August 12, 2016, 02:45:47 PM »
Really stupid question but why exactly does LP cause divergence and expansion? Intuitively one would expect the opposite since winds converge in a LP system and diverge in an anticyclone.

I opened a thread to gather answers about the same last year
http://forum.arctic-sea-ice.net/index.php/topic,1344.msg58904.html#msg58904
You may find answers there but looking thoroughly.
Long story short: coriolis force causes ice to move laterally toward its right (away from the storm center) with respect to the surface wind that is pulling the ice; the tendency of the ice to drift away from the center of the storm is greater than the tendency of the surface wind to converge toward the center of the storm. The resulting effect is that ice floes tend to diverge away from the storm center.

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Re: The 2016 melting season
« Reply #3930 on: August 12, 2016, 03:08:31 PM »
I know that this model has not very good reputation, but I would like to ask: how good are these archived images? According to these maps, we are faced with the same kind of storm


seaicesailor

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Re: The 2016 melting season
« Reply #3931 on: August 12, 2016, 03:37:24 PM »
You opened pandorax box.
Qualitatively ok
Quantitatively distrust the drift near the center, they cause too low concentration predictions.
These two models you show are years apart and different.
It is early to get a reliable prediction,
From the pics it seems there is quite a difference, this time not nearly as strong. But for all reasons above, it is worthless assessment

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Re: The 2016 melting season
« Reply #3932 on: August 12, 2016, 03:55:55 PM »
I believe the ACNFS drift maps are pretty decent. It's the concentration and volume maps that often have issues.
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Re: The 2016 melting season
« Reply #3933 on: August 12, 2016, 04:15:05 PM »
Temperatures remain anomalously cold in the arctic.





The upcoming storm will serve to reinforce/intensify these anomalies. A fifth place finish in sea ice extent is looking likely, with an early minimum.






seaicesailor

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Re: The 2016 melting season
« Reply #3934 on: August 12, 2016, 04:31:03 PM »
Temperatures remain anomalously cold in the arctic.
...
The upcoming storm will serve to reinforce/intensify these anomalies. A fifth place finish in sea ice extent is looking likely, with an early minimum.
...

Considering your assessment same time last year using the 925 hpa plots, when you predicted a "significant slowdown" that might lead 2015 be above 2013 and 2014,

http://forum.arctic-sea-ice.net/index.php/topic,1149.msg59717.html#msg59717

I should put all my chips this year finish record low.

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Re: The 2016 melting season
« Reply #3935 on: August 12, 2016, 05:02:09 PM »
Temperatures remain anomalously cold in the arctic.
...
The upcoming storm will serve to reinforce/intensify these anomalies. A fifth place finish in sea ice extent is looking likely, with an early minimum.
...

Considering your assessment same time last year using the 925 hpa plots, when you predicted a "significant slowdown" that might lead 2015 be above 2013 and 2014,

http://forum.arctic-sea-ice.net/index.php/topic,1149.msg59717.html#msg59717

I should put all my chips this year finish record low.

might

Quote
The rapid pace of daily ice loss seen in late July 2015 slowed somewhat in August.
http://nsidc.org/arcticseaicenews/2015/09/steady-decline-summer-minimum-approaching/

Considering members here were predicting 2015 would beat 2012 I rest my case. Seaicesailor, how about you make a prediction we can judge your accuracy? (We can see who is closer and we will find out in 45 days or less) The anomalously cold weather, cloud cover, and physical forces of low pressure with regards to ice dispersion will be extremely favorable for ice preservation. 2012 featured anomalously warm weather leading up to and following the storm. (This is nothing like the 2012 GAC)

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BornFromTheVoid

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Re: The 2016 melting season
« Reply #3937 on: August 12, 2016, 06:22:57 PM »
According to the graphs here http://cires1.colorado.edu/~aslater/ARCTIC_TAIR/ 2012 was largely close to average during August, with a short sharp spike at the end of the month. The August temps leading up to the storm weren't much different to now, and the forecast for after the storm doesn't appear massively much cooler than 2012 either, at least to me.

Guess we'll have to wait and see how the month pans out
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Re: The 2016 melting season
« Reply #3938 on: August 12, 2016, 07:54:12 PM »
The 06z GFS has quite a strong storm lasting 36-48 hours before gradually filling out. It starts off around Laptev and gradually arcs over the Canadian side of the central Arctic, cutting right through the largest area of low concentration ice.
We could well see that ice toward Chukchi get separated from the main pack.
Makes sense it would follow the areas with the most open water...  more energy to sustain the storm there.  Food for thought when thinking about the future.
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Re: The 2016 melting season
« Reply #3939 on: August 12, 2016, 08:15:51 PM »
Temperatures remain anomalously cold in the arctic.
...
The upcoming storm will serve to reinforce/intensify these anomalies. A fifth place finish in sea ice extent is looking likely, with an early minimum.
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Considering members here were predicting 2015 would beat 2012 I rest my case. Seaicesailor, how about you make a prediction we can judge your accuracy? (We can see who is closer and we will find out in 45 days or less)

Now just hold on a second here... you are cherry picking a bit and by extension implying that because a few people overestimated melt in 2015, your predictions should be considered accurate?  Try again with better supporting data please.

This is not "who's smarter than who" contest.  You've been challenged.  Marshal your own supporting facts.  Pointing out other people's inaccuracies won't help there.  Neither will challenging someone else to some sort of intellectual duel.

The anomalously cold weather, cloud cover, and physical forces of low pressure with regards to ice dispersion will be extremely favorable for ice preservation. 2012 featured anomalously warm weather leading up to and following the storm. (This is nothing like the 2012 GAC)
I believe BFTV just pointed out 2012 wasn't particularly warm, so I think you may need to revisit your logic.
Storms and dispersion are not favorable for ice retention.  With large areas of open water and opportunity for large stretches of broken ice to move, it actually increases exposure to heat via disturbing the near surface "lens" of fresher melt and Ekman pumping bringing warmer water up from depth.

I will hasten to add that any ice dispersed to the Beaufort or "Atlantic Front" is doomed due to sea surface temperatures hot enough to strip 5-10CM/day or more off of ice that drifts there.  Ice pushed into the ESS or Chukchi isn't much better off.

In short, a storm in June or July when insolation is at its peak is helpful to preservation (presumption: it's not bringing rain with it...) because of how it decreases heat acquired via insolation.  A storm in August, with mobile ice when bottom melt is dominant, decidedly is not.
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RoxTheGeologist

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Re: The 2016 melting season
« Reply #3940 on: August 12, 2016, 08:56:13 PM »

In short, a storm in June or July when insolation is at its peak is helpful to preservation (presumption: it's not bringing rain with it...) because of how it decreases heat acquired via insolation.  A storm in August, with mobile ice when bottom melt is dominant, decidedly is not.

Especially with the lack of Barents sea ice to cool off the incoming Atlantic Waters over the last few years.

Neven

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Re: The 2016 melting season
« Reply #3941 on: August 12, 2016, 10:01:24 PM »
This is really starting to look like the real deal, not just the intensity, but longevity too now. It's no GAC-2012, but I think it's the second strongest summer storm I have seen since 2010.

I'm not sure how much flash melting this is going to cause, but probably enough to stay near 2007/2011/2015, given current SSTs (more than comparable to 2012).
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jdallen

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Re: The 2016 melting season
« Reply #3942 on: August 12, 2016, 10:02:14 PM »

In short, a storm in June or July when insolation is at its peak is helpful to preservation (presumption: it's not bringing rain with it...) because of how it decreases heat acquired via insolation.  A storm in August, with mobile ice when bottom melt is dominant, decidedly is not.

Especially with the lack of Barents sea ice to cool off the incoming Atlantic Waters over the last few years.
While notable, that has more implications for winter generally than melt now.

More relevant than both 80N DMI temperatures and Barents or other peripheral sea's SST's are water temperatures inside the pack, as shown by the attached NOAA anomaly map.

Generally, it appears they are 0.25-0.5C higher than normal.  That over time is an additional 0.3 to 1.1CM of melt per day, depending on which end of the range you are. 

[edit:  this higher temperature represents a significant increase in net enthalpy across the Arctic Ocean.  It may seriously affect the refreeze and 2017 season, unless we have an amazingly favorable winter.  By implication, it also indicates a great deal more heat is available for bottom melt, especially in view of the coming storm.]

It adds up, and where temps are just a little warmer, in close to the pack, as in the near Chukchi portions of the CAB and along the ESS/Laptev ice front, it's potentially 2CM/day.

Even if that addition isn't enough to fully tear down area and extent, it will turn large swaths of the pack into brash - something we've seen a lot of this year - which is pretty disheartening.

We may not make it to 2012.  We may not make it to 2007, though that is very much possible if not probable.  Regardless, even if we don't hit those metrics, I argue the ice has taken a terrible beating this year, and will be left as or more vulnerable than it was in 2007, possibly worse than 2012.  I suspect we will have less 2+MYI than ever before, and most of what we will have will be below or near 1.5M in thickness at the end of the season.  I'm not feeling particularly optimistic.
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Greenbelt

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Re: The 2016 melting season
« Reply #3943 on: August 12, 2016, 11:20:03 PM »
4 days in 970s





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Re: The 2016 melting season
« Reply #3944 on: August 12, 2016, 11:26:37 PM »
August 7-12.  130 hours.  Those winds should really move some ice around, as this ice looks very mobile.

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seaicesailor

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Re: The 2016 melting season
« Reply #3945 on: August 13, 2016, 12:04:31 AM »
On Wednesday coupled with a 1023 hpa high over Beaufort. That'd be something.

jdallen

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Re: The 2016 melting season
« Reply #3946 on: August 13, 2016, 02:14:25 AM »
On Wednesday coupled with a 1023 hpa high over Beaufort. That'd be something.
What I'm intensely interested in, is the size of the swells that will be generated.

There could be waves of size - 2-4 Meters - across wide areas of the CAB.  I'm waiting with great expectation to see what that does to the ice in its current extremely fragmented state.
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Michael Hauber

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Re: The 2016 melting season
« Reply #3947 on: August 13, 2016, 03:59:07 AM »
GFS thinks this low is going to get pretty cold.  The first couple days pulls in a pulse of warm air from Siberia, so storm + warm winds + weak ice could make some serious damage.  But as far as warm air pulses into the Arctic I'd say this one is pretty mediocre.  Less than half of the size of what we saw with the recent dipole which we some of us were excited about, but did nothing obvious in terms of say ADS extent drop.  Then the area of -8 at 850hp grows to cover quite a lot of the storm, and towards the end areas of -12 make an appearance.  A very rough rule of thumb I've used is that 0 is strong surface melt, at -8 surface melt pretty much stops, and at -12 its about when refreeze starts, although being still early enough in summer ocean temps and solar radiation may stop this, or it may not end up as cold as currently forecast, or maybe it needs to get a bit colder than -12.  I don't think refreeze is likely to start this early, even towards the pole.  And of course there is still bottom melt and Ekman pumping to consider.
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icy voyeur

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Re: The 2016 melting season
« Reply #3948 on: August 13, 2016, 04:26:17 AM »
What I'm intensely interested in, is the size of the swells that will be generated.

Indeed. I "feel" that this is where the principle vulnerability lays. Increased swell that both resurrects subsurface heat and mixes low salinity layers could do serious damage. Or so I fear. I'm fascinated whatever occurs.

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Re: The 2016 melting season
« Reply #3949 on: August 13, 2016, 06:27:43 AM »
So there is a denier sight that has the following GIF comparing sea ice thickness between 2012 and 2016 on the same day in August.  Where did this come from and is it wrong?
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