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TerryM

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Re: The 2015 melting season
« Reply #1200 on: June 08, 2015, 07:40:04 PM »
Plinius
The math, particularly in your second linked paper, is too much for me.

I have a much simpler model in mind.
As cyclonic winds react with <100% sea ice covered waters the water moves vertically upwards in the center and displace surface water, as well as anything floating in it, away from the center. This effect increases with wind speed, but is present at all velocities.
Sea ice, floating 90% submerged, is far more sensitive to water velocity and direction than to air and diffusion takes place more or less symmetrically.
Ignoring the ice for a moment, can you point to any literature showing an inward flow of water in a cyclonic situation at any wind speed? If not I think it reasonable to assume that anything floating heavily in this water will closely follow the outflowing currents generated by Ekman pumping/suction.
Terry

Neven

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Re: The 2015 melting season
« Reply #1201 on: June 08, 2015, 08:24:28 PM »
When I said in the latest ASI update that I thought the cyclone might get the ice in the Laptev and East Siberian Seas on the move, I wasn't expecting for the fast ice near the New Siberian Islands to break up already! From yesterday's Uni Bremen sea ice concentration map:



Looking at the concentration maps for June 6th this is extremely early. Other years, like 2010 and 2012, have some green and yellow showing up there, but none go blue until July. Back in 2011 I made an animation wherein it takes until Day 185 at least for some open water to show up:



We're on day 159 now, and this is just a first minor torch.

It might be an artefact, but I've never seen a blue artefact on the UB SIC maps, and clouds are blocking the view on LANCE-MODIS.
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Re: The 2015 melting season
« Reply #1202 on: June 08, 2015, 08:46:04 PM »
I think it is a misinterpretation of conditions, Neven. Even so, not necessarily good.  Peering intently at June 7ths worldview of the area NE of the Lena(?)  delta suggests wall-to-wall melt ponds and low albedo.  It may not have broken up, but from what I can see, it might as well have.
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Neven

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Re: The 2015 melting season
« Reply #1203 on: June 08, 2015, 09:35:23 PM »
I think it is a misinterpretation of conditions, Neven.

Probably, yeah. But I can't remember ever having seen fast ice being reported as blue. Not that I look that super-closely, but I still have 6 years of pretty intent watching.

I guess we'll know more tomorrow.  :)
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Rubikscube

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Re: The 2015 melting season
« Reply #1204 on: June 08, 2015, 09:49:28 PM »
When I said in the latest ASI update that I thought the cyclone might get the ice in the Laptev and East Siberian Seas on the move, I wasn't expecting for the fast ice near the New Siberian Islands to break up already!

It is certainly quite early, but not as much as it might seem. These melt pond related (i presume) low concentration areas are actually such an usual occurrence on the fast ice south of the New Siberian Islands that the average Uni-Bremen ice concentration there is significantly lower on 16. June than it is on 1. July.

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Re: The 2015 melting season
« Reply #1205 on: June 08, 2015, 09:55:10 PM »
It is certainly quite early, but not as much as it might seem. These melt pond related (i presume) low concentration areas are actually such an usual occurrence on the fast ice south of the New Siberian Islands that the average Uni-Bremen ice concentration there is significantly lower on 16. June than it is on 1. July.

Yes, but always green and yellow, not blue.

Anyway, I noticed it by accident while looking at the crushed ice in the Beaufort, because that isn't really usual either:

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Lord M Vader

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Re: The 2015 melting season
« Reply #1206 on: June 08, 2015, 10:10:59 PM »
Neven & Rubikcscube: if the current 12z run from GFS holds I don't think we'll have to think about any artefacts as a HUGE heat dome looks like it will reach Laptev Sea in about 3-4 days. Temps at 850 hPa will be about 10-15oC in the southern part of Laptev. Unclear at this moment if the warm air will be pushed the whole way to the New Siberian Islands (NSI). Looks like it will stay just west of the NSI..

Note that ECMWF 12z run isn't as agressive as the GFS is...

Just wait and see!! Personally, I think ECMWF is most reliable in this case...

Andreas T

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Re: The 2015 melting season
« Reply #1207 on: June 08, 2015, 10:34:18 PM »
sentinel from yesterday seems to confirm start of breakup southeast of lena delta but of course that is a bit of a guess, sentinel images can be ambiguous
It'll be interesting when the clouds clear

seaicesailor

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Re: The 2015 melting season
« Reply #1208 on: June 09, 2015, 12:32:00 AM »
Well, my apologies for having the conversation go opaque.
I think at 100% coverage, in the centre of the cyclone (low wind speed), and with thick ice your statement is definitely true.
At relatively thin ice, when it is broken, and at larger wind speeds the effect appears to reverse, because the turning angle of ice drift gets smaller than the turning angle of the wind (compared to the isobars).
I agree that we have seen declining concentrations under the centres of (weak) cyclones, but the above would also reason why, despite the stronger winds and breaking up, I am not aware of strongly lowering concentrations in the regions of higher wind speeds, where in a naive picture one would expect the largest effect.

So, to make my naive picture: If we have a relatively round storm with a wind maximum, the ice should have a net divergence in the centre, a less divergent (and probably convergent) region around the wind maximum and then increasing divergence again at the outskirts. That would thin the ice in the very centre, thicken inwards of the max wind radius, thin it in the outskirts (and relatively far in, due to the radial drift differential).

Not wanting to be beligerant, I was thinking if the storm is  a hurricane, then coriolis forces on the ocean-drifting flow are much weaker, being hurricanes close to Equator... Then it might happen what you say. But Arctic storms are not as strong as hurricanes, and at the same time Coriolis forces are maximum near the pole.






jdallen

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Re: The 2015 melting season
« Reply #1209 on: June 09, 2015, 12:39:39 AM »
It is certainly quite early, but not as much as it might seem. These melt pond related (i presume) low concentration areas are actually such an usual occurrence on the fast ice south of the New Siberian Islands that the average Uni-Bremen ice concentration there is significantly lower on 16. June than it is on 1. July.

Yes, but always green and yellow, not blue.

Anyway, I noticed it by accident while looking at the crushed ice in the Beaufort, because that isn't really usual either:

Very much agree with you there.  In this case, I think the state of the ice is at least a month ahead of similar conditions in the past; perhaps two.
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seaicesailor

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Re: The 2015 melting season
« Reply #1210 on: June 09, 2015, 01:14:11 AM »
 :DWithin the reliable margin pf predictions, this Thursday may be hot in Canada, Alaska, and Siberia Laptev sea, warm air from Pacific, and Fram export all ar once. What comes next looks even worse as pointed out by LMV and Neven. Area cliff...


plinius

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Re: The 2015 melting season
« Reply #1211 on: June 09, 2015, 01:38:42 AM »
Terry,

very interesting thoughts by your side that made me re-find that old Madsen paper, which I found quite instructive once upon a time:
ftp://io.usp.br/lado_20130322/papers/madsen_1977.pdf
That also shows that lovely struggle between Ekman's 45 degrees, and more "realistic" surface turning angles against the wind stress that are far smaller. If you combine that with the wind turning angle, you see again that the surface behaves different from your intuition (i.e. the very surface should then flow into a hurricane). Not a problem though on the large scale, because the climatology is made by the mean transport direction, which is at a large angle to the surface current. Similarly, you make the pumping worse for the hurricane, because it is far more effective if you dredge up  around the thermocline and then mix towards the surface by turbulence.
That paper also shows a bit the overall misery with Ekman transport, since that all depends on the vertical friction/shear terms, which are quite a mess (turbulent friction, viscosity, etc.).

I would point to that your view on the pumping poses a couple of problems: The horizontal scale is far larger than the vertical scale, so even if you have some stratification, you cannot just swap the driving agents: Ekman pumping happens because the mean surface transport has a divergence, not the other way round. Your surface waters will be forced down even at minimal differences in the wind stress. Not saying that it doesn't play a role, though.
You have a point about the flowing in deeper water: This is essentially the issue with the thicker ice that will have a larger turning angle as linked in the previous papers. However, I would like to be a bit picky and again stress that this effect is not caused _by_ the Ekman pumping, but it is the cause _of_ the Ekman pumping.
Also, concerning the ice: You have both a boundary towards the water (which exerts the stress on the water) and a boundary towards the air, which is why the previously linked paper introduced two turning angles at a surface. Never forget that the friction with the air might be lower, but that you have >10 times the velocity difference, which makes up for that... (or also think about that all motion of your surface and below must come from that friction, so your argument violates the cause-effect principle a bit).
So, sorry for the lengthy words from my side.

Plinius
The math, particularly in your second linked paper, is too much for me.

I have a much simpler model in mind.
As cyclonic winds react with <100% sea ice covered waters the water moves vertically upwards in the center and displace surface water, as well as anything floating in it, away from the center. This effect increases with wind speed, but is present at all velocities.
Sea ice, floating 90% submerged, is far more sensitive to water velocity and direction than to air and diffusion takes place more or less symmetrically.
Ignoring the ice for a moment, can you point to any literature showing an inward flow of water in a cyclonic situation at any wind speed? If not I think it reasonable to assume that anything floating heavily in this water will closely follow the outflowing currents generated by Ekman pumping/suction.
Terry

plinius

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Re: The 2015 melting season
« Reply #1212 on: June 09, 2015, 02:17:56 AM »
@seaicesailor: If my recollection does not fool me, in classic Ekman equations the Coriolis parameter should only impact the scale height of the spiral. Not sure about the various flavours though. And (as linked) you do not escape the turning angle issue by a high Coriolis parameter...

Michael Hauber

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Re: The 2015 melting season
« Reply #1213 on: June 09, 2015, 03:01:22 AM »
Well, my apologies for having the conversation go opaque.
I think at 100% coverage, in the centre of the cyclone (low wind speed), and with thick ice your statement is definitely true.
At relatively thin ice, when it is broken, and at larger wind speeds the effect appears to reverse, because the turning angle of ice drift gets smaller than the turning angle of the wind (compared to the isobars).
I agree that we have seen declining concentrations under the centres of (weak) cyclones, but the above would also reason why, despite the stronger winds and breaking up, I am not aware of strongly lowering concentrations in the regions of higher wind speeds, where in a naive picture one would expect the largest effect.

So, to make my naive picture: If we have a relatively round storm with a wind maximum, the ice should have a net divergence in the centre, a less divergent (and probably convergent) region around the wind maximum and then increasing divergence again at the outskirts. That would thin the ice in the very centre, thicken inwards of the max wind radius, thin it in the outskirts (and relatively far in, due to the radial drift differential).

Ok I've read the stuff again and finally realised that geostrophic means the nearly parrellel wind field for the bulk atmosphere, and realised the distinction between that and the thin flow at ground level which will determine ice direction.

The first paper you linked to shows that the wind to ice angle falls below 35 degrees at about 15km/hour.  So that would mean that Ekman is causing sea ice to converge whenever wind is above 15km/hour, which is basically everywhere for anything but a very weak low, or very close to the center.  So either something is wrong with the numbers, or something other than Ekman causes ice to appear to diverge under a low pressure.
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JayW

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Re: The 2015 melting season
« Reply #1214 on: June 09, 2015, 04:21:55 AM »
Beaufort about to become a giant slush puppy?


http://www7320.nrlssc.navy.mil/hycomARC/beaufort.html
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epiphyte

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Re: The 2015 melting season
« Reply #1215 on: June 09, 2015, 06:22:45 AM »
Beaufort about to become a giant slush puppy?

...or maybe... Margaritaville ?
« Last Edit: June 09, 2015, 06:36:11 AM by epiphyte »

seaicesailor

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Re: The 2015 melting season
« Reply #1216 on: June 09, 2015, 08:27:38 AM »
I don't think this prediction is going to happen because it is so bad for the ice in all fronts.
It could even advance an ESS front


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Re: The 2015 melting season
« Reply #1217 on: June 09, 2015, 09:28:00 AM »
The 00z GFS has trended even warmer.

The cold air is stomped out with a mostly dipole like regime.

The WAA is underway and expands after day 2 into the central basin. 

The CAA and CAB get hit hard. 

A huge change from the last two years.

The Laptev gets smoked for a time.

The polar airmass gets split and sent to the NATL and Barents where it will modify.

While being replaced with warm contenential air. 

Of course this is inherent to ridging.

Bone crushing flow out of NPAC.  That air will be carrying moisture rich air and land based heating as well as some very strong winds and warming the NPAC and Southern Chuchcki.




Gigantic HP




Not. to forget the basin to basin flow. 

Thats gonna help open up water in the Kara and Laptev. 

But also Beaufort and Chuchki.
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Re: The 2015 melting season
« Reply #1218 on: June 09, 2015, 09:56:08 AM »
Wide spread warmth has taken over the arctic basin.

This is at 77N in the Western arctic CAB.

Melt ponds are just starting to form.

Temps are around 2C today there.

The CAB could be mostly snow free before peak Insolation.

In 2013 and 14 most of the CAB didn't go snow free. 




This year vigorous MAY WAA set things up differently.

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Re: The 2015 melting season
« Reply #1219 on: June 09, 2015, 10:03:57 AM »
Temps on banks Island are expected to reach 13-20C over the next 3-4 days with a Southerly flow blowing winds off the island right into the SW CAB ice. 

The NW passage is going to be under vigorous WAA and sun as well.

These are huge deviations from last year and 2013.

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Laurent

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Re: The 2015 melting season
« Reply #1220 on: June 09, 2015, 10:55:08 AM »
Complete wreckage near the pole !

Neven

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Re: The 2015 melting season
« Reply #1221 on: June 09, 2015, 11:30:13 AM »
Okay, so the blue has turned green, yellow and purple again where the fast ice near the New Siberian Islands is. That's a first for me, so very instructive:
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Neven

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Re: The 2015 melting season
« Reply #1222 on: June 09, 2015, 01:10:05 PM »
Temps on banks Island are expected to reach 13-20C over the next 3-4 days with a Southerly flow blowing winds off the island right into the SW CAB ice. 

The NW passage is going to be under vigorous WAA and sun as well.

These are huge deviations from last year and 2013.

I agree. The first two weeks of May were actually colder than in 2013 and 2014 (more on that this week on the ASIB), which was probably because of open skies. But after that things have really taken off, and despite this short cyclonic reprieve, it seems things are going to continue in the same vein. By switching to the other side (hence the title of the second ASI update on the blog), the rate of decline has slowed down, but I think the 2015 trend line might be able to keep up somewhat with 2012's massive June plunge.

BTW, Friv, what's WAA again? Warm Air Anomaly/Attack/Assault?
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plinius

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Re: The 2015 melting season
« Reply #1223 on: June 09, 2015, 01:15:15 PM »
WAA = Warm air advection
WLA = Warm layer advection

Btw. May was not good for the ice, don't use mean T for that month, as the CAB can anyway not go into significant melt...

Temps on banks Island are expected to reach 13-20C over the next 3-4 days with a Southerly flow blowing winds off the island right into the SW CAB ice. 

The NW passage is going to be under vigorous WAA and sun as well.

These are huge deviations from last year and 2013.

I agree. The first two weeks of May were actually colder than in 2013 and 2014 (more on that this week on the ASIB), which was probably because of open skies. But after that things have really taken off, and despite this short cyclonic reprieve, it seems things are going to continue in the same vein. By switching to the other side (hence the title of the second ASI update on the blog), the rate of decline has slowed down, but I think the 2015 trend line might be able to keep up somewhat with 2012's massive June plunge.

BTW, Friv, what's WAA again? Warm Air Anomaly/Attack/Assault?

Yuha

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Re: The 2015 melting season
« Reply #1224 on: June 09, 2015, 02:36:12 PM »
WAA = Warm air advection

Whenever I read WAA I cannot help but think about this:  ;D

Neven

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Re: The 2015 melting season
« Reply #1225 on: June 09, 2015, 03:21:17 PM »
WAA = Warm air advection
WLA = Warm layer advection

Btw. May was not good for the ice, don't use mean T for that month, as the CAB can anyway not go into significant melt...

Thanks for the acronym. I hit myself on the head when realizing what it meant.

And like I said, first two weeks of May were cold, but then not so much (understatement). But again I'll have more on that on the ASIB this week.
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seaicesailor

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Re: The 2015 melting season
« Reply #1226 on: June 09, 2015, 03:31:13 PM »

[This was on May 6]

Beaufort is getting torched in the coming week:

Temps on banks Island are expected to reach 13-20C over the next 3-4 days with a Southerly flow blowing winds off the island right into the SW CAB ice. 

The NW passage is going to be under vigorous WAA and sun as well.

These are huge deviations from last year and 2013.

I agree. The first two weeks of May were actually colder than in 2013 and 2014 (more on that this week on the ASIB), which was probably because of open skies. But after that things have really taken off, and despite this short cyclonic reprieve, it seems things are going to continue in the same vein. By switching to the other side (hence the title of the second ASI update on the blog), the rate of decline has slowed down, but I think the 2015 trend line might be able to keep up somewhat with 2012's massive June plunge.

BTW, Friv, what's WAA again? Warm Air Anomaly/Attack/Assault?

I keep my skepticism about comparing temperature indicators between years, Neven. You correctly predicted Beaufort torching on May 8, a moment when temperatures at Central Arctic became very cold.

Yet because of that torching, Beaufort is open. Chuckchi too. And Hudson, Kara, Laptev now, and seems ESS soon. CAA getting hit. This is a huge difference with 2013 and 2014 and more in line with 2012 and 2007. There are open fronts all within the Arctic and that started in May if not earlier. In 2013 and 2014, not a chance.

My especulative hunch is that it is necessary to have all these fronts inside the Arctic to dive in June. However it is gonna be tough in July-August cause the CAB is cold and thick.

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Re: The 2015 melting season
« Reply #1227 on: June 09, 2015, 04:06:04 PM »
It is certainly quite early, but not as much as it might seem. These melt pond related (i presume) low concentration areas are actually such an usual occurrence on the fast ice south of the New Siberian Islands that the average Uni-Bremen ice concentration there is significantly lower on 16. June than it is on 1. July.

Yes, but always green and yellow, not blue.

Anyway, I noticed it by accident while looking at the crushed ice in the Beaufort, because that isn't really usual either:

Very much agree with you there.  In this case, I think the state of the ice is at least a month ahead of similar conditions in the past; perhaps two.

With all respect I think you both need to freshen up your memories :). This one, from 2006, is one of the more extreme examples, but if you go through the archives and cherry pick the right dates you can make similar comparisons involving sizable areas of >50% and even >20% concentration from virtually any year. 7th June is rather early though, and the breakup of M'Clure Strait fits in the same category; early, but not totally unprecedented. Thus, I would rather say we are a week or two ahead of most years.

That said, things seem to be speeding up dramatically at the moment. I really didn't expect to see every buoy report such heavy melting during the past 24 hours, and according to ECMWF it might soon be time to issue a "dipole alert". I'm actually going to revise my minimum votes down a couple of notches.
« Last Edit: June 09, 2015, 04:11:16 PM by Rubikscube »

Neven

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Re: The 2015 melting season
« Reply #1228 on: June 09, 2015, 04:12:34 PM »
That said, things seem to be speeding up dramatically at the moment. I really didn't expect to see every buoy report such heavy melting during the past 24 hours, and according to ECMWF it might soon be time to issue a "dipole alert". I'm actually going to revise my minimum votes down a couple of notches.

Yes, me too. I'll have to remember voting closes on June 14th.  :)
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Re: The 2015 melting season
« Reply #1229 on: June 09, 2015, 05:08:08 PM »
Regarding the average temp during May, it seems averaging above-freezing and below-freezing temps together is somewhat problematic. If the Beaufort is +3DC and the CAB is -5DC, there will be much more melt than if both areas are -1DC. This is especially true in May where the -5DC is not going to cause almost any ice thickening/refreezing.

seaicesailor

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Re: The 2015 melting season
« Reply #1230 on: June 09, 2015, 05:26:56 PM »
Regarding the average temp during May, it seems averaging above-freezing and below-freezing temps together is somewhat problematic. If the Beaufort is +3DC and the CAB is -5DC, there will be much more melt than if both areas are -1DC. This is especially true in May where the -5DC is not going to cause almost any ice thickening/refreezing.

You hit the nail. Because if all slightly below freezing, no melting will start. But if as you say, part is +2 and rest well below freezing, no matter what melting starts, melt front is established, and albedo feedback will kick in and finish with it all.

Lord M Vader

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Re: The 2015 melting season
« Reply #1231 on: June 09, 2015, 08:34:52 PM »
LOOK AT GFS 12z run!!! GFS 12Z BACKED FROM ITS EARLIER TORCH FORECAST! SIBIRIAN HEAT DOME IS MORE OR LESS MISSING THE LAPTEV SEA!!!

What we'll see is a strong tempgradient at 850 hpa. At the New Sibirian Islands the temps at 850 hpa level will be around -5 to -10C while at the western edge of the Laptev Sea about 5-10C..

//LMV

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Re: The 2015 melting season
« Reply #1232 on: June 09, 2015, 10:33:52 PM »
Looking at EOSDIS channel 3-6-7 and assuming red ice is surface melt:

2012- surface melt start to dominate most of the Arctic from today.
2013- significant surface melt on the Pacific side by the 20th, but probably only about 1/3rd of entire Arctic.
2014 - most of Arctic seems to show surface melt by the 20th.
2015 - currently surface melt is limited to the fringe areas - we seem a long way behind 2012, but the forecast looks good to put us ahead of 13 and 14.
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Re: The 2015 melting season
« Reply #1233 on: June 09, 2015, 11:57:24 PM »
Looking at EOSDIS channel 3-6-7 and assuming red ice is surface melt:

2012- surface melt start to dominate most of the Arctic from today.
2013- significant surface melt on the Pacific side by the 20th, but probably only about 1/3rd of entire Arctic.
2014 - most of Arctic seems to show surface melt by the 20th.
2015 - currently surface melt is limited to the fringe areas - we seem a long way behind 2012, but the forecast looks good to put us ahead of 13 and 14.

Isn't this based on visible light data? There seems to be a big overcast over most of the CAB today, so I wouldn't read too much into this...

JayW

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Re: The 2015 melting season
« Reply #1234 on: June 10, 2015, 01:07:19 AM »
LOOK AT GFS 12z run!!! GFS 12Z BACKED FROM ITS EARLIER TORCH FORECAST! SIBIRIAN HEAT DOME IS MORE OR LESS MISSING THE LAPTEV SEA!!!

What we'll see is a strong tempgradient at 850 hpa. At the New Sibirian Islands the temps at 850 hpa level will be around -5 to -10C while at the western edge of the Laptev Sea about 5-10C..

//LMV

NWS Alaska, bolded for emphasis.
Quote

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
128 PM AKDT TUE JUN 9 2015
.DISCUSSION...

UPPER AIR...
A COLD TROUGH WEST OF THE CHUKCHI SEA WILL BECOME SHARPER BY
WEDNESDAY MORNING AS IT MOVES TO THE ALASKA WEST COAST. THE TROUGH
WILL CONTINUE TO SWEEP EASTWARD ACROSS NORTHERN ALASKA THROUGH
THURSDAY...BRINGING COOLER TEMPERATURES. AFTER THE TROUGH EXITS
EASTWARD INTO CANADA...RIDGING WILL REBUILD NORTHWARD ACROSS
NORTHERN ALASKA...ACCOMPANIED BY A RETURN OF WARMER TEMPERATURES.
FORECAST CONFIDENCE REMAINS GOOD THROUGH MONDAY...GFS AND ECMWF
HAVE SIMILAR SOLUTIONS AND GOOD RUN TO RUN CONTINUITY. ENSEMBLE
MEANS ARE PREFERRED FOR THE LATTER PART OF THE MEDIUM RANGE
PERIOD KEEPING SOME UPPER LEVEL RIDGING IN PLACE...THE 12Z GFS
APPEARS TOO AMBITIOUS IN LOWERING HEIGHTS AND TEMPERATURES.
THE GFS DAY 10 OUTLOOK OF A WINTER-LIKE DEEP UPPER LOW PUNCHING
SOUTHWARD INTO THE NORTHERN ALASKA MAINLAND LOOKS RATHER
EXTREME. RECENT RUNS OF THE ECMWF HAVE SHOWN GENERALLY BETTER RUN
TO RUN CONTINUITY THAN THE GFS LATER IN THE EXTENDED PERIOD.


http://www.arh.noaa.gov/wmofcst.php?wmo=FXAK69PAFG&type=public
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plinius

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Re: The 2015 melting season
« Reply #1235 on: June 10, 2015, 02:47:14 PM »
@Michael: For someone who does not know the meaning of "geostrophic", you present us with an impressively big mouth here, don't you think?


Well, my apologies for having the conversation go opaque.
I think at 100% coverage, in the centre of the cyclone (low wind speed), and with thick ice your statement is definitely true.
At relatively thin ice, when it is broken, and at larger wind speeds the effect appears to reverse, because the turning angle of ice drift gets smaller than the turning angle of the wind (compared to the isobars).
I agree that we have seen declining concentrations under the centres of (weak) cyclones, but the above would also reason why, despite the stronger winds and breaking up, I am not aware of strongly lowering concentrations in the regions of higher wind speeds, where in a naive picture one would expect the largest effect.

So, to make my naive picture: If we have a relatively round storm with a wind maximum, the ice should have a net divergence in the centre, a less divergent (and probably convergent) region around the wind maximum and then increasing divergence again at the outskirts. That would thin the ice in the very centre, thicken inwards of the max wind radius, thin it in the outskirts (and relatively far in, due to the radial drift differential).

Ok I've read the stuff again and finally realised that geostrophic means the nearly parrellel wind field for the bulk atmosphere, and realised the distinction between that and the thin flow at ground level which will determine ice direction.

The first paper you linked to shows that the wind to ice angle falls below 35 degrees at about 15km/hour.  So that would mean that Ekman is causing sea ice to converge whenever wind is above 15km/hour, which is basically everywhere for anything but a very weak low, or very close to the center.  So either something is wrong with the numbers, or something other than Ekman causes ice to appear to diverge under a low pressure.

Neven

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Re: The 2015 melting season
« Reply #1236 on: June 10, 2015, 02:55:49 PM »
Shall we discuss the melting season in progress?

The forecast is looking more and more certain, with highs taking over the American/Pacific side of the Arctic in three days from now. The only questions remaining are how long and how much/bad. I expect IJIS SIE to continue decreasing again, after a stand still these past three days. But whether it will be able to keep up with 2012...
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Re: The 2015 melting season
« Reply #1237 on: June 10, 2015, 05:45:35 PM »
Shall we discuss the melting season in progress?

The forecast is looking more and more certain, with highs taking over the American/Pacific side of the Arctic in three days from now. The only questions remaining are how long and how much/bad. I expect IJIS SIE to continue decreasing again, after a stand still these past three days. But whether it will be able to keep up with 2012...

The CT maps for 6/7 and 6/8 suggest some melt ponding in the CAB (see circled areas):



Today, and in the near term, there is dry air over much of the area:



Later on in the forecast, a moist air mass enters from the Alaskan side:



The high latent heat content of this air mass, if the forecast comes to pass, will cause pond coverage to increase dramatically...










Lord M Vader

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Re: The 2015 melting season
« Reply #1238 on: June 10, 2015, 06:12:50 PM »
CC Reanalyzer depicts a shrinking snow cover which by June 17 is foreseen to be virtually non-existent through the Arctic basin.

As Nightvid Cole says, more moist air is going to intrude into the Arctic basin but if one look in the close time the heat dome which is narrowly missing the Arctic the next few days will have a rather decent effect on the ice in Kara Sea as it is very moisty.. The ice east of Novaya Zemlya and west of Novaya Severnaya should take a great punch...

Neven & Co: is this the day for melt onset if one consider the DMI graph? Looks like it was touching freeze point yeaterday...

Of some notes, Nick Stokes or whatever his name is at "moyhu" indicates that June 2-7 hall have been above 0,3C over the normal for, was it 1984-2013?, which surely is a really warm start of June... On his page, HADSST3 was +0,593 for the Globe which can be compared to +0,557 in April.. Further, Stokes predict May 2015 to be around +0,8C.. Sorry Neven, I know this should be in the thread of Global Temperatures but I just thought it was worth to mention here...

//LMV

plinius

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Re: The 2015 melting season
« Reply #1239 on: June 10, 2015, 06:27:08 PM »
Nice find! Though I do not think it is melt-ponding, but at least in the latter case significant divergence.
GLB/Hycom has been predicting this spot for days already:
http://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticictn/nowcast/ictn2015060812_2015061000_924_arcticictn.001.gif

Created by a pretty impressive local divergence:


Obviously ice drifting down the Siberian coast on one side and the remainder of the cyclonic motion on the other. Bad spot for the ice...

Shall we discuss the melting season in progress?

The forecast is looking more and more certain, with highs taking over the American/Pacific side of the Arctic in three days from now. The only questions remaining are how long and how much/bad. I expect IJIS SIE to continue decreasing again, after a stand still these past three days. But whether it will be able to keep up with 2012...

The CT maps for 6/7 and 6/8 suggest some melt ponding in the CAB (see circled areas):



Today, and in the near term, there is dry air over much of the area:



Later on in the forecast, a moist air mass enters from the Alaskan side:



The high latent heat content of this air mass, if the forecast comes to pass, will cause pond coverage to increase dramatically...

Lord M Vader

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Re: The 2015 melting season
« Reply #1240 on: June 10, 2015, 08:28:09 PM »
It's official now!! June 10 marks the melt onset for the Arctic! This due to DMI temp graph for +80N. As the graph clearly visualize the temp now is above freeze point..

Which days in June (May) have marked the melt onset for the CAB in earlier years?

//LMV

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Re: The 2015 melting season
« Reply #1241 on: June 10, 2015, 09:36:09 PM »
The forecast has stayed the same for days, and just crept closer and closer. Now it looks like Beaufort and Chukchi are about to receive a second punch in the face in coming days.

Temperature anomaly so far in June:
« Last Edit: June 10, 2015, 09:44:16 PM by Neven »
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Re: The 2015 melting season
« Reply #1242 on: June 10, 2015, 10:30:23 PM »
39 F (4 C) at Alert, 70 F (21 C) at Tuktoyaktuk!
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Re: The 2015 melting season
« Reply #1243 on: June 10, 2015, 11:32:14 PM »
Whatever ‘meltpond-june’ may or may not bring, the recent large Low has had an effect on ice distribution in the CAB.



This 500 km radius circle around the pole is from today’s MODIS, enhanced picture (bright -10/contrast +22/mid-tones -64). It shows a lot of torn leads and open water, as the surface winds have dispersed  while compacting elsewhere. It looks like the large swath of thinner ice in the ‘Laptev-bite-to-come’ has been messed up most.

Within two weeks a first assessment on this melt season can be made, at least, IMHO. I’m looking forward to do a first good analysis.
The early range of lowest extents hasn’t convinced me that an extreme low is in the box. The range was related to an anomalously warm Pacific. There’s a good chance Pacific influx will continue. There’s also reason to expect warmer air temps, as have occurred lately over the Kara/Barentsz Seas. There’s a lot of, quite early, melt-ponding on fringes in the peripheral seas. Much depends now on the return of sunny weather and southern winds , especially over the Laptev Sea.

Neven

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Re: The 2015 melting season
« Reply #1244 on: June 10, 2015, 11:51:40 PM »
I've been so busy with melt ponds, temp anomalies and looking at the forecast (oh yeah, and working and building fences  ;)), that I had forgotten there was a 970 mb cyclone just two days ago!  ::) ;D

Great stuff, Werther, thanks for keeping an eye on the consequences of the cyclone. Looking forward to your analysis.
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Re: The 2015 melting season
« Reply #1245 on: June 11, 2015, 12:11:51 AM »
The forecast has stayed the same for days, and just crept closer and closer. Now it looks like Beaufort and Chukchi are about to receive a second punch in the face in coming days.

Temperature anomaly so far in June:

Both look pretty blueish in MODIS today. Preconditioned by previous blow.

Michael Hauber

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Re: The 2015 melting season
« Reply #1246 on: June 11, 2015, 12:22:03 AM »
Earlier I discussed my theory that La Ninas tend to produce more frequent dipole type events in the north Pacific.  The current forecast shows the type of set up I mean.  At about the 48 hour point a high pressure system sets up in the far NE Pacific, and a low in the far NW Pacific, resulting in a significant influx of warm air into the Arctic.  This influx looks to be much more effective in spreading heat throughout the Arctic then the warm influx a week or two ago.  That would be partly due to being later in the season, but I suspect it is also due to the greater amount of moisture in the air of the Pacific, which makes the air mass harder to cool down due to the latent heat.  In contrast the previous heat influx was much more off land, and although the temperatures near the coast were impressive, and looked much more significant on the 850hp forecast charts than the current influx does, they had minimal impact on the rest of the Arctic.

While I am saying that this pattern is typical of a La Nina/cool PDO and we are currently in an el nino, it is interesting to note that we are seeing this pattern at the same time that some atmospheric indicators take on a more La Nina characteristic.  The MJO is amplifying in the Indian Ocean and trade winds increasing over the Pacific.  (Probably only a short term hiccup in the development of the current El Nino, but we'll see)
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Michael J

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Re: The 2015 melting season
« Reply #1247 on: June 11, 2015, 02:05:29 AM »
Hi, I've just started following this forum. I can see how weather conditions have a large effect on the ice melt. I was curious whether it is currently possible to have an ice free Arctic through a series of unfortunate weather patterns or hasn't the earth warmed up enough as yet.

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Re: The 2015 melting season
« Reply #1248 on: June 11, 2015, 05:41:51 AM »
Whatever ‘meltpond-june’ may or may not bring, the recent large Low has had an effect on ice distribution in the CAB.



This 500 km radius circle around the pole is from today’s MODIS, enhanced picture (bright -10/contrast +22/mid-tones -64). It shows a lot of torn leads and open water, as the surface winds have dispersed  while compacting elsewhere. It looks like the large swath of thinner ice in the ‘Laptev-bite-to-come’ has been messed up most.

Within two weeks a first assessment on this melt season can be made, at least, IMHO. I’m looking forward to do a first good analysis.
The early range of lowest extents hasn’t convinced me that an extreme low is in the box. The range was related to an anomalously warm Pacific. There’s a good chance Pacific influx will continue. There’s also reason to expect warmer air temps, as have occurred lately over the Kara/Barentsz Seas. There’s a lot of, quite early, melt-ponding on fringes in the peripheral seas. Much depends now on the return of sunny weather and southern winds , especially over the Laptev Sea.
Very interesting image!

How unusual is that level of break-up around the pole at around this date?
For how many years back do we have the satellite images to know that?
Do we know how broken up the ice actually is?
For example, a ripple pattern with a period of a couple of km can been in the segment from 10-12 o'clock. Does that mean a whole lot of parallel leads but with the ice maintaining integrity inbetween? Or not?
And in the 'Laptev bite' region, what can we see about the size distribution of ice chunks? Could it go all the way down to 'slushee' in some places?
Are there higher resolution images available to determine this?

At first look it is very interesting to see such an image this early in the melting season, so thanks in advance to anyone who can answer any of these questions.

Michael Hauber

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Re: The 2015 melting season
« Reply #1249 on: June 11, 2015, 06:24:45 AM »
You can look at satellite images at EOSDIS Worldview.  In my opinion 2013 was worse at this date (I linked 3 days later to get a more cloud free view), and 2014 about the same.  Use add base layer to choose bands 3-6-7 to get a false colour (enhanced or filtered colour?) view which shows red for melting, orange for dry frozen snow/ice, and paler oranges to white for clouds.  This helps show that the ripple pattern is probably clouds.  Images at this site go back to 2012.  The MODIS equivelant used to go back to 2008 or 2009, but a hard drive failure wiped out the history.  I've also seen images going back to 2006 and 2007 but I don't know if anyone actually stitched the individual satellite snapshots of a small area together for a wider view of the Arctic.
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