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plinius

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Re: The 2015 melting season
« Reply #1150 on: June 06, 2015, 03:51:15 PM »
@Michael: I can spin stories at Aristotelian level myself, they are not helpful though. There are equations describing Ekman transport, the Ekman spiral, coriolis forces etc. You may assume that I have solved them before (hope you did the same...). Would you mind pointing out on the equations, where your "outward" motion should come from? Wind stress is aligned with the surface wind, which is heavily directed inwards.

So, to attempt a solution: if we now combine this story (marvellous, did not know there are people still doing analytic Ekman transport):
http://www.the-cryosphere-discuss.net/9/2101/2015/tcd-9-2101-2015.pdf
with this:
http://www.gfz.hr/osobne_stranice/grisogono/QJ-2011-windturn_final_bg.pdf

The latter says that the wind turns 36 deg inwards, while the sea ice will have a complicated reaction. From the first paper Fig. 3, 4, I would hence take the message that the whole game will largely depend on sea ice thickness and concentration. So, a very weak low might hold the ice together, while at wind speed > 4m the low pressure system will actually start to strongly spread the ice.



TerryM

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Re: The 2015 melting season
« Reply #1151 on: June 06, 2015, 04:35:39 PM »
I don't think Ekman Pumping's effect of drawing large amounts of warmer deeper water towards the surface should be ignored.
Terry

plinius

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Re: The 2015 melting season
« Reply #1152 on: June 06, 2015, 05:02:25 PM »
@Terry: That was a different question. Of course Ekman pumping is intense there. However, I am again not sure what is worth: Pumping up 1.5C water from the bottom, or dragging surface waters from the rim under the ice (which a high pressure system would do). Probably the first but I think the jury is out on that...

Vergent

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Re: The 2015 melting season
« Reply #1153 on: June 06, 2015, 05:58:17 PM »
Actually, the strongest factor is the dew(get my point).  Latent heat of vaporization of water is 540 cal/g/°C. Freezing is 80cal/g. One gram of condensation melts 7 grams of ice. It takes half a liter of 1.0c water to that. That is a two orders of magnitude difference. Plus, there is a 0c layer of fresh water under the ice, so the rate constant is low. Water turbulence happens only at the edge. Condensation is happening everywhere in this storm. That is why the snow cover of the whole ice cap is going to be stripped away in the next few days. Area is two dimensional, the edge is one dimensional. That adds more orders of magnitude to the difference.

Verg


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Re: The 2015 melting season
« Reply #1154 on: June 06, 2015, 06:00:49 PM »

Nick Stokes has just made a much more flexible "DMI clone" available over at Moyhu, based on NCEP/NCAR data:

http://moyhu.blogspot.co.uk/2015/05/daily-arctic-temperatures.html

Neat gizmo! (gadget, ap)

Gray-Wolf

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Re: The 2015 melting season
« Reply #1155 on: June 06, 2015, 06:10:13 PM »
I've come across a few posters , on other sites, thinking this cyclone is a 'good' ( for ice retention) thing for the basin on the impacts of the cyclones over the past two years.

 I am not at all sure that this is 'good' at all or will just precondition our best ice for the melt season to come ( central basin) and lead to a big push toward Fram, from the CAA/N.Shore Greenland, along the fracture we saw form earlier in the week.

If the Laptev low follows on it might find a lot of disrupted ( easy to move) ice sat over Fram?

I'm gonna be glued to Worldview this week just to see what pans out.
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Andreas T

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Re: The 2015 melting season
« Reply #1156 on: June 06, 2015, 09:09:33 PM »
The buoy located with the pole-cams has been above freezing for at least 9 hours.

2/n - IMB 2015D reports (for 00:00 UTC on June 6th) 87.6487, -14.1647, -5.18°C, 998.86mb

It was above freezing not long ago however:

http://GreatWhiteCon.info/resources/ice-mass-balance-buoys/summer-2015-imbs/#2015D-Temp
the temperature sensors on the part of the pole above the ice should not be taken as air temperature. When exposed to sunlight they can be several degrees above air temperature which is measured on a shaded sensor which sits  on top of the pole.
http://www.chrispolashenski.com/docs/a57a149.pdf
mentions problems with warming of the buoy surface due to sunlight despite its white colour. The plastic material which minimizes conduction along the pole into the ice means that warming stays localized.
The readings on thermistors 1-5 have to be seen in this light :-). Further south you see clearer diurnal fluctuations on these exposed pole thermistors than in the dedicated air temperature readings. I just would not use these measurements as air temperatures even though in this case at 2015D the differences are small
I have thought of using the difference of say termistor2 and air temp as a rough indication of incoming radiation (it would be distorted by unknown wind cooling so probably not very meaningful)

Vergent

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Re: The 2015 melting season
« Reply #1157 on: June 06, 2015, 10:07:15 PM »
Andreas T,

This is not a mass balance buoy.

NPEO 2015 Polar Area Weather Station ( PAWS ) Buoy ID 923840

http://psc.apl.washington.edu/northpole/PAWS923840_atmos_recent.html

Verg 8)
edit:
Besides, it's been heavily overcast and the wind has been blowing at 6-10 m/s. The effect you were supposing requires sunlight, still air, and the design compromises of a mass balance buoy.
« Last Edit: June 06, 2015, 10:31:20 PM by Vergent »

Neven

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Re: The 2015 melting season
« Reply #1158 on: June 06, 2015, 10:37:20 PM »
I'm gonna be glued to Worldview this week just to see what pans out.

I feel that good, old Arctic excitement too.  ;D
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werther

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Re: The 2015 melting season
« Reply #1159 on: June 06, 2015, 10:41:13 PM »
Since my last comment on 24 May I've been folowing MODIS/ECMWF and commenting. On the way to an opinion on this melting season by week 26, I can't resist making an entry.
Whatever this large Arctic Low may bring or signify for the characteristics of this season, at least it supports what ECMWF had prognosed. A catch-up effort in the Laptev/ESAS region. Rain and above freezing temps are having an impact. And its visible on MODIS near Vilkitsky Strait. Blueish hues are spreading. With near shore temps forecasted at + 20 dC next week Laptev will at least become supportive to get 2015 close to the 2012 decline. And that heat is being pulled in by the Low. It does seem to have another character than what was seen through '13 and '14.
As said by others, high ocean heat content is one factor that influences my judgment on what to expect.

Michael Hauber

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Re: The 2015 melting season
« Reply #1160 on: June 06, 2015, 11:06:09 PM »
@Michael: I can spin stories at Aristotelian level myself, they are not helpful though. There are equations describing Ekman transport, the Ekman spiral, coriolis forces etc. You may assume that I have solved them before (hope you did the same...). Would you mind pointing out on the equations, where your "outward" motion should come from? Wind stress is aligned with the surface wind, which is heavily directed inwards.

So, to attempt a solution: if we now combine this story (marvellous, did not know there are people still doing analytic Ekman transport):
http://www.the-cryosphere-discuss.net/9/2101/2015/tcd-9-2101-2015.pdf
with this:
http://www.gfz.hr/osobne_stranice/grisogono/QJ-2011-windturn_final_bg.pdf

The latter says that the wind turns 36 deg inwards, while the sea ice will have a complicated reaction. From the first paper Fig. 3, 4, I would hence take the message that the whole game will largely depend on sea ice thickness and concentration. So, a very weak low might hold the ice together, while at wind speed > 4m the low pressure system will actually start to strongly spread the ice.

If you'd bothered to read and understand what I'd wrote instead of dismissing it as an unhelpful story you would realise that the wind cannot be turned 36 degrees inwards by Ekman or Coriolos effect (relative to a low pressure system), but the turning must be outwards.
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Re: The 2015 melting season
« Reply #1161 on: June 06, 2015, 11:24:05 PM »
My only regret is that the cyclone isn't coupled with a nice 1040 hPa high on the American side of the Arctic, and then stay like that for a couple of days.  ;) ;D
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Re: The 2015 melting season
« Reply #1162 on: June 06, 2015, 11:34:43 PM »
Vergent - However 2015D is an ice mass balance buoy, which seems to fire off its acquired data somewhat more promptly than the nearby PAWS buoy?

Andreas - You may have noted my long conversation on the blog about IMB buoy thermistor strings with Wayne and the CRREL?

http://forum.arctic-sea-ice.net/index.php/topic,1149.msg52001.html#msg52001

The dedicated air temperature sensor on 2015D was hovering around 0 for quite a while before taking the plunge after lunch (UTC) on June 5th. I'm intrigued to discover what some of the other buoys in the far north ultimately report, but they seem rather taciturn just at the moment:

http://iabp.apl.washington.edu/maps_daily_table.html
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plinius

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Re: The 2015 melting season
« Reply #1163 on: June 06, 2015, 11:38:21 PM »
Gee, Michael, please revisit your signs. Surface winds are directed inwards in any low pressure system. This is by the way one of the reasons why hurricanes with clear eyes in the ground level are pretty rare.
So, next time please 1) first think and 2) then write a post.

@Michael: I can spin stories at Aristotelian level myself, they are not helpful though. There are equations describing Ekman transport, the Ekman spiral, coriolis forces etc. You may assume that I have solved them before (hope you did the same...). Would you mind pointing out on the equations, where your "outward" motion should come from? Wind stress is aligned with the surface wind, which is heavily directed inwards.

So, to attempt a solution: if we now combine this story (marvellous, did not know there are people still doing analytic Ekman transport):
http://www.the-cryosphere-discuss.net/9/2101/2015/tcd-9-2101-2015.pdf
with this:
http://www.gfz.hr/osobne_stranice/grisogono/QJ-2011-windturn_final_bg.pdf

The latter says that the wind turns 36 deg inwards, while the sea ice will have a complicated reaction. From the first paper Fig. 3, 4, I would hence take the message that the whole game will largely depend on sea ice thickness and concentration. So, a very weak low might hold the ice together, while at wind speed > 4m the low pressure system will actually start to strongly spread the ice.

If you'd bothered to read and understand what I'd wrote instead of dismissing it as an unhelpful story you would realise that the wind cannot be turned 36 degrees inwards by Ekman or Coriolos effect (relative to a low pressure system), but the turning must be outwards.

Neven

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Re: The 2015 melting season
« Reply #1164 on: June 06, 2015, 11:42:15 PM »
Cyclone is now at 971 hPa:
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johnm33

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Re: The 2015 melting season
« Reply #1165 on: June 06, 2015, 11:42:54 PM »
Looks to me like the western side above Greenland is going to see the ice accelerated south and carried off through Fram, any deep water brought up by Eckman pumping is going with it. The pressure of the ice driven south on the eastern side will prevent an influx from Kara so I expect an inflow from the Pacific. This probably wouldn't happen if the ice was full density, when I suspect it would be more difficult to move [less pumping] and would compact as it moves south and be replaced by rapidly freezing ice leading to an increase in area. Hopefully it'll be worthy of a Wipneus animation. where's that popcorn vid?

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Re: The 2015 melting season
« Reply #1166 on: June 06, 2015, 11:46:33 PM »
My only regret is that the cyclone isn't coupled with a nice 1040 hPa high on the American side of the Arctic

There's just no pleasing some people!

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Vergent

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Re: The 2015 melting season
« Reply #1167 on: June 06, 2015, 11:47:59 PM »
Gee, Michael, please revisit your signs. Surface winds are directed inwards in any low pressure system. This is by the way one of the reasons why hurricanes with clear eyes in the ground level are pretty rare.
So, next time please 1) first think and 2) then write a post.

@Michael: I can spin stories at Aristotelian level myself, they are not helpful though. There are equations describing Ekman transport, the Ekman spiral, coriolis forces etc. You may assume that I have solved them before (hope you did the same...). Would you mind pointing out on the equations, where your "outward" motion should come from? Wind stress is aligned with the surface wind, which is heavily directed inwards.

So, to attempt a solution: if we now combine this story (marvellous, did not know there are people still doing analytic Ekman transport):
http://www.the-cryosphere-discuss.net/9/2101/2015/tcd-9-2101-2015.pdf
with this:
http://www.gfz.hr/osobne_stranice/grisogono/QJ-2011-windturn_final_bg.pdf

The latter says that the wind turns 36 deg inwards, while the sea ice will have a complicated reaction. From the first paper Fig. 3, 4, I would hence take the message that the whole game will largely depend on sea ice thickness and concentration. So, a very weak low might hold the ice together, while at wind speed > 4m the low pressure system will actually start to strongly spread the ice.

If you'd bothered to read and understand what I'd wrote instead of dismissing it as an unhelpful story you would realise that the wind cannot be turned 36 degrees inwards by Ekman or Coriolos effect (relative to a low pressure system), but the turning must be outwards.



Verg

plinius

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Re: The 2015 melting season
« Reply #1168 on: June 06, 2015, 11:52:16 PM »
Looks to me like the western side above Greenland is going to see the ice accelerated south and carried off through Fram, any deep water brought up by Eckman pumping is going with it. The pressure of the ice driven south on the eastern side will prevent an influx from Kara so I expect an inflow from the Pacific. This probably wouldn't happen if the ice was full density, when I suspect it would be more difficult to move [less pumping] and would compact as it moves south and be replaced by rapidly freezing ice leading to an increase in area. Hopefully it'll be worthy of a Wipneus animation. where's that popcorn vid?

I'd say that's a very small fraction. Also not sure if there is any significant upwards pumping near Greenland, since the main vector will be downwelling there (you have the coast on the right of quite coast-parallel isobars, which should force the surface water down, apart from nice high tides...). Pressure differential also helps accelerating the ice out of Fram. Main Ekman pumping region should be the whole area under the low. Will be interesting to see if it does some destruction. If I see MODIS right, the main beating has anyway happened on the Russian side. Laptev looks like a swiss cheese right now, Kara lost probably something like a third of its ice mass.

plinius

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Re: The 2015 melting season
« Reply #1169 on: June 06, 2015, 11:57:35 PM »
Indeed, Vergent. The analytic solution that I linked also points to a divergent motion in the centre of a low. Wind speed is low, so the turning angle will be large.

jai mitchell

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Re: The 2015 melting season
« Reply #1170 on: June 07, 2015, 04:21:01 AM »
Looks to me like the western side above Greenland is going to see the ice accelerated south and carried off through Fram, any deep water brought up by Eckman pumping is going with it. The pressure of the ice driven south on the eastern side will prevent an influx from Kara so I expect an inflow from the Pacific. This probably wouldn't happen if the ice was full density, when I suspect it would be more difficult to move [less pumping] and would compact as it moves south and be replaced by rapidly freezing ice leading to an increase in area. Hopefully it'll be worthy of a Wipneus animation. where's that popcorn vid?


The buoy tracks should tell in a few days if there has been significant acceleration. 
« Last Edit: June 07, 2015, 01:55:59 PM by jai mitchell »
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Michael Hauber

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Re: The 2015 melting season
« Reply #1171 on: June 07, 2015, 05:11:48 AM »
Gee, Michael, please revisit your signs. Surface winds are directed inwards in any low pressure system. This is by the way one of the reasons why hurricanes with clear eyes in the ground level are pretty rare.
So, next time please 1) first think and 2) then write a post.


Try these questions then:

Which direction would the air move if there was no coriolos effect?

Which direction does the air move when there is a coriolos effect?

Is the coriolos effect causing the air to move more or less inward than it would otherwise?
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Andreas T

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Re: The 2015 melting season
« Reply #1172 on: June 07, 2015, 11:33:29 AM »
.....

This is of interest to Wayne Davidson, but I don't know about anybody else! The CRREL tell me:

Quote
The top temperature sensors are indeed heating up from the sun.  If you look at it closely - you can see that they track the air temp, very well most of the time.  These readings are every 4 hours.  And if you look closely you can see that each day, the 20:00, 0:00 and 04:00  readings are always higher than air temperature and also would correspond to when the sun is beating down on that side of the buoy. I also am surprised that they are heating up that much. They are mounted inside the slotted white pipe for solar shielding and to allow air flow, and I would not have expected the temps to be that elevated...

This is the result of the sun heating up the slotted pipe that we hide the temperature sensors in to protect them from foxes chewing the cable, the wind from snow-blasting the cable during high winds - the snow would eat away at the cables..... Therefore the surface temperatures are installed in a "Well screen" - a slotted pipe that allows the air to infiltrate to the sensors, but prevents animals etc. from gaining access to chew on them (Has happened in the past and this was our solution).
Sorry I missed that conversation, being one anybody else who likes to get into the technical details, thank you for digging out that information, I  spotted this feature of the upper buoy sensors last year but its great to have this corroborated by more knowlegeable people. I should not have doubted your expertise. :-(
My comment was of a technical nature rather than questioning the validity of the values you quote. On the days you show air temps and upper buoy sensors are very similar, but can I suggest to include air temperature into your graphs, probably less crudely than I did here for 2015A (I made that table column an additional point in the graph)
In that example reading the bouy sensor graph as showing air temperatures above the ice would give the wrong impression.
Ignore data point#2 in my graph, this is just a meaningles column separating air temp and bouy temps.
« Last Edit: June 07, 2015, 11:39:11 AM by Andreas T »

Neven

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Re: The 2015 melting season
« Reply #1173 on: June 07, 2015, 12:07:10 PM »
Our friend has bottomed out at 970 hPa:
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Neven

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Re: The 2015 melting season
« Reply #1174 on: June 07, 2015, 12:23:35 PM »
And the ice in M'Clure Strait is breaking up:

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Jim Hunt

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Re: The 2015 melting season
« Reply #1175 on: June 07, 2015, 01:36:48 PM »
Can I suggest to include air temperature into your graphs

My scripts used to simply plot the temperature profiles at 00:00 UTC each day. Whilst it's far from perfect, these days I try and pick a time when the top thermistors aren't sweltering under a hot sun. I include min/max air temperature on the Google maps though. For example:

http://GreatWhiteCon.info/resources/ice-mass-balance-buoys/summer-2015-imbs/#2015D-Map

Doing a single day plot including max/min for each sensor is an alternative, but plotting a whole season that way would get very messy, very quickly! Once you're aware of the problem it seems simplest to mentally block out the top few sensors, except when you're trying to work out where the snow/air interface is.
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Re: The 2015 melting season
« Reply #1177 on: June 07, 2015, 02:14:54 PM »
I can't remember ever seeing this pattern before, pretty intense:



Update: parallel typing with the previous post...
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Re: The 2015 melting season
« Reply #1178 on: June 07, 2015, 02:32:53 PM »
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Nick_Naylor

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Re: The 2015 melting season
« Reply #1179 on: June 07, 2015, 02:38:07 PM »
The thickness projection looks pretty dramatic starting tomorrow.
http://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticictn_nowcast_anim30d.gif

seaicesailor

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Re: The 2015 melting season
« Reply #1180 on: June 07, 2015, 03:13:16 PM »

2014 vs 2015 ocean surface temp anomalies
 

Wow, huge difference!
Could you do 2012 vs 2015 please? ::)

I wish I could. Not even with 2013. The coverage over Arctic started later.

seaicesailor

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Re: The 2015 melting season
« Reply #1181 on: June 07, 2015, 06:29:39 PM »
The thickness projection looks pretty dramatic starting tomorrow.
http://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticictn_nowcast_anim30d.gif

Last time HYCOM predicted a hole like that became real (persistent cyclone May 2013) Santa's lake)
Only that now it is over way thicker ice  ???

Correction: it was May 2013, see Neven's blog:
http://neven1.typepad.com/blog/2013/05/if-this-is-real.html

« Last Edit: June 07, 2015, 06:35:22 PM by seaicesailor »

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Re: The 2015 melting season
« Reply #1182 on: June 07, 2015, 06:38:29 PM »
The thickness projection looks pretty dramatic starting tomorrow.
http://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticictn_nowcast_anim30d.gif

Last time HYCOM predicted a hole like that became real (persistent cyclone May 2013) Santa's lake)
Only that now it is over way thicker ice  ???

Correction: it was May 2013, see Neven's blog:
http://neven1.typepad.com/blog/2013/05/if-this-is-real.html

I'm more impressed by what it shows happening to the protective arm of older, thicker ice in the Beaufort.  If HYCOM is close to being correct, that ice will not stop a new record.

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Re: The 2015 melting season
« Reply #1183 on: June 07, 2015, 06:49:08 PM »
The thickness projection looks pretty dramatic starting tomorrow.
http://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticictn_nowcast_anim30d.gif

Last time HYCOM predicted a hole like that became real (persistent cyclone May 2013) Santa's lake)
Only that now it is over way thicker ice  ???

Correction: it was May 2013, see Neven's blog:
http://neven1.typepad.com/blog/2013/05/if-this-is-real.html

I'm more impressed by what it shows happening to the protective arm of older, thicker ice in the Beaufort.  If HYCOM is close to being correct, that ice will not stop a new record.
Climate Reanalyzer shows a huge plume of moisture blasting into the Chukchi in about a week, on top of steady flows from Russia across the Kara, and on the other side, from Nunavit across the CAA.

I'd hazard a guess that all of the ice in the Beafort is doomed; not instantly, but almost certainly by mid August.
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plinius

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Re: The 2015 melting season
« Reply #1184 on: June 08, 2015, 12:09:04 AM »


I find that one from hycom even more impressive. The remnants of the low lign up with the rising pressure over the archipelago to spoon out the old, thick ice at about 0.3m/s through the FRAM strait. That's about 20-30 sqkm of ice per day going down the sink.

P.S.: @Michael, just forget it, pity that you did not even grasp the point that this discussion was not about explaining coriolis forces.

johnm33

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Re: The 2015 melting season
« Reply #1185 on: June 08, 2015, 10:51:11 AM »
Plinius Just to be clear what i expect to see is a more intense version of the movement as illustrated by Wipneus in 1505 and 1548 in 'Home brew' http://forum.arctic-sea-ice.net/index.php/topic,382.1500.html or the one by Neven at 1524,

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Re: The 2015 melting season
« Reply #1186 on: June 08, 2015, 11:27:04 AM »
The latest Arctic Sea Ice News is out. I was hoping for some reference to results from IceBridge 2015

It seems a lot of information has been released, albeit without a mention in ASIN.

http://nsidc.org/data/sipn/data-sets.html

For starters see the IceBridge:

http://nsidc.org/data/docs/daac/icebridge/evaluation_products/sea-ice-freeboard-snowdepth-thickness-quicklook-index.html

and CryoSat overview pages:

http://nsidc.org/data/docs/daac/icebridge/evaluation_products/cryosat-2-sea-ice-frebrd-thick-snowdepth-quicklook-index.html

I haven't spotted any visualisations of IceBridge thickness as yet, But Nathan Kurtz's CryoSat manual:

ftp://n5eil01u.ecs.nsidc.org/SAN2/ICEBRIDGE_FTP/Evaluation_Products/CryoSat-2_Sea_Ice_Freeboard_Thickness_and_Snow_Depth_Quick_Look/Documentation/cryosat_ql_product_2015.pdf

includes this "alternative" CryoSat 2 thickness map and IceBridge/MERRA snow depth map for March 2015:
« Last Edit: July 11, 2015, 10:16:35 AM by Jim Hunt »
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Re: The 2015 melting season
« Reply #1187 on: June 08, 2015, 01:08:31 PM »
Quote

P.S.: @Michael, just forget it, pity that you did not even grasp the point that this discussion was not about explaining coriolis forces.

It was all about Coriolis forces.
And pressure gradient, and planetary and ocean turbulent friction.

In storm wind direction is perpendicular to pressure gradient because of Coriolis but closer to surface, winds turn inwards due to surface friction.

In ocean, drift is caused by wind drag but floe will drift outwards because of Coriolis.

The outwards angle of drift is greater than the inward angle of wind direction. Therefore ocean drift (or ice on top of it) is divergent

Sorry I repeat myself but to make it clear IT IS THE CORIOLIS. Whether I am right or wrong, it is.

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Re: The 2015 melting season
« Reply #1188 on: June 08, 2015, 01:14:15 PM »
Besides an increase in Fram Strait transport, the GFS and ECMWF forecasts are more and more showing increased high pressure over the American side of the Arctic again, where all the multi-year-mix is. I'm not going post any images or animations, as it's still far too out to be reliable, but anyone so inclined can check it at the ASIG Forecasts page.

Things are really getting interesting now, with extent returning to the pack of trend lines (probably due to the cyclone), but lots of other stuff getting developed in the meantime, like above freezing temperatures Arctic-wide for the coming week, especially in the CAA. Or to be more precise: the CAA is going to get torched, and possibly the Beaufort as well.
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plinius

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Re: The 2015 melting season
« Reply #1189 on: June 08, 2015, 01:19:40 PM »
@seaicesailor: On the danger of repeating myself - everybody should know what Coriolis forces are. The discussion here was about the turning angle.
If you had the patience to read the two papers I linked above, you could see that the question if the ice is pushed outwards will depend on the wind speed (higher wind speed, more inwards), ice thickness (the thinner the ice, the more inwards), and ice concentration (the lower the coverage, the more inwards). The hyperplane of sign change between inwards and outwards drag in this parameter space is (if those papers are correct) entirely within the parameters of the current arctic sea ice.
You can of course try to hammer your point by repeating the same claim over and over, but the appropriate discussion style would be to show why those papers do not apply and what should be used instead, if you have reason to dismiss them.

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Re: The 2015 melting season
« Reply #1190 on: June 08, 2015, 01:29:12 PM »
@plinius: That's about 20-30 sqkm of ice per day going down the sink.
How did you calculate that? It seems a small number to me ... thanks.

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Re: The 2015 melting season
« Reply #1191 on: June 08, 2015, 01:56:57 PM »
Add a k behind my numbers. And actually it seems a bit high ex post... think it was too late for me and I had doubled the Fram strait width.
400km*35km/day - so only ~14k sqkm/day, assuming that it is being pressed out along the entire front, assuming that the W Spitzbergen current is getting run over.


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Re: The 2015 melting season
« Reply #1192 on: June 08, 2015, 02:32:40 PM »
@Plinius
You reverse the sign of the modification of direction of the movement of the ice compared to the direction of the wind: figure 6 of the article "An analytical model for wind-driven Arctic
summer sea ice drift" clearly shows that the movement of the ice is outwards for low pressure and inwards for high pressure
 ;)

plinius

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Re: The 2015 melting season
« Reply #1193 on: June 08, 2015, 03:51:13 PM »
@ Paolo: You forgot to apply the inward turn of the surface winds (36 degrees, typically) before using their numbers.

Do you understand the sign reversal for different parameters now?

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Re: The 2015 melting season
« Reply #1194 on: June 08, 2015, 04:21:52 PM »
I'm sorry, I haven't been reading the Ekman/Coriolis discussion very attentively, but are you saying that the ice pack isn't diverged under a cyclone, plinius? I mean, we've seen that happen in action. I apologize if that's not what you're saying.
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plinius

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Re: The 2015 melting season
« Reply #1195 on: June 08, 2015, 04:38:24 PM »
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).

Lord M Vader

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Re: The 2015 melting season
« Reply #1196 on: June 08, 2015, 06:32:03 PM »
However, if the current GFS 06z run do hold for the next three days I think it's fair to say that Hudson Bay and Kara Sea will see some real damage of the ice there due to warm air intrusion there. Baffin/Newfoundland Bay should also see an ice loss in the periphery there.

The real interesting thing is what will happen to the "heat blob" in Central Siberia when/if it reaches Kara and Laptev Sea.. The 850 hPa temps are somewhere in the range of 10-15 degrees! THAT my freinds should mean a lot of warm melt water to the Arctic. Of course, the temps might be low if there will be an inversion forming there with a lot of fog which is quite usual as warm air enters cold waters.

In "fantasyland" at +168 hours at GFS 06z run the North Pole will see temps at 850 hPa being at 0-6oC...

Let's see what the next couple of forecast runs says!!

Best, LV

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Re: The 2015 melting season
« Reply #1197 on: June 08, 2015, 06:56:26 PM »
The thickness projection looks pretty dramatic starting tomorrow.
http://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticictn_nowcast_anim30d.gif

Last time HYCOM predicted a hole like that became real (persistent cyclone May 2013) Santa's lake)
Only that now it is over way thicker ice  ???

Correction: it was May 2013, see Neven's blog:
http://neven1.typepad.com/blog/2013/05/if-this-is-real.html

I'm more impressed by what it shows happening to the protective arm of older, thicker ice in the Beaufort.  If HYCOM is close to being correct, that ice will not stop a new record.

HYCOM is looking really good right now, I think it probably is correct and it does open up the prospects of serious loss in the Pacific sector of the Arctic Ocean. That would open up the possibility of a re-run of 2012 or 2007.  :)

But perhaps more importantly, it would really rub Osteopop's nose in it.  ;D

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Re: The 2015 melting season
« Reply #1198 on: June 08, 2015, 07:13:51 PM »
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).

Okay, thanks, you might be right, I know nothing of the subject.
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ChrisReynolds

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Re: The 2015 melting season
« Reply #1199 on: June 08, 2015, 07:25:43 PM »
I still think the thinning due to the storm as seen in HYCOM could mean preconditioning from lower ice concentration, meaning a good loss of ice through the summer. But when I posted that I had a nagging feeling I had read something relevant. Now I have found it.

Screen et al 2011
Dramatic interannual changes of perennial Arctic sea ice linked to abnormal summer storm activity.
http://onlinelibrary.wiley.com/doi/10.1029/2011JD015847/abstract
Quote
fewer cyclones over the central Arctic Ocean during the months of May, June, and July appear to favor a low sea ice area at the end of the melt season.

So perhaps not contributing to a record low, but it still seems to hold a reasonable prospect of good ice loss in Beaufort and Chukchi. That would open up the ESS, especially as Laptev compactness has dropped significantly over the last week.