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epiphyte

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Re: The 2015 melting season
« Reply #1100 on: June 04, 2015, 07:02:59 AM »
@jai_mitchell : "This shows that we might see rain on the CAB in the next few days"

...which oddly enough is the only thing that is keeping me ambivalent about where this season goes next. Whenever you get precipitation and the surface temp is close to freezing, in my experience it's a complete toss-up as to whether it falls as rain or snow. If it falls as rain IMO it will very likely be a record year. If it falls as snow it will give the ice a week or so of protection, which may be enough to keep things more or less intact until the weather changes.  If it does change, that is.

Either way, I get the feeling that the setup so far this year has been such that we're balanced on a knife-edge. IMO everything that needed to happen for a complete melt-out of everything <2m thick (which is most of it), has happened up to this point. Whether it will continue to do so has yet to be seen...

Michael Hauber

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Re: The 2015 melting season
« Reply #1101 on: June 04, 2015, 07:29:02 AM »
The forecasts in Neven's graph section suggest a mix of snow closer to the pole and rain closer to the Russian Siberian and Laptev regions.  I'm not sure why the same forecasts seem to show the entire Arctic warming to above freezing while a low moves in?

This low looks like it might stay a little while, which I would expect to cool things down enough to change this season from a very early start to at least an average start for the melt ponding for much of the central basin.
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S.Pansa

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Re: The 2015 melting season
« Reply #1102 on: June 04, 2015, 07:35:48 AM »
To add another point of view.

Here is an animation (click!) of the experimental HYCOM + CICE  model forecast for June 10th.
First pic is yesterday, second pic one week out - and the third image shows the situation one month ago (10th mai).
The forecasted thinning in the upcoming week is especially pronounced in the Chukchi, ES and Laptev Sea, but also the Kara, Hudson and even the Central Arctic get their faire share of "torching". And an animated Fram transport as the icing on the cake ....

It's just forecast, but boy that looks horrible

Edit: As I do not trust my animation-skills, I append the other images
« Last Edit: June 04, 2015, 08:21:18 AM by S.Pansa »

Jim Hunt

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Re: The 2015 melting season
« Reply #1103 on: June 04, 2015, 09:46:18 AM »
If it were only CT, the cause might be something with the algorithm or resolution or whatever, but like I said, Wipneus' graph shows the same (using more sophisticated and compatible data sets):

Comparing like with like then it suggests that at least part of the reason for the current record low JAXA extent is that (on average) the pack currently IS more compact than usual. I'm afraid I don't have much of a feel for how sensitive the assorted algos are to melt ponds, but there certainly looks to have been a substantial pale blue tinged area on MODIS recently. Perhaps not blue enough to confuse the sensors/algos as yet?
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Jim Hunt

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Re: The 2015 melting season
« Reply #1104 on: June 04, 2015, 11:05:14 AM »
The latest Arctic Sea Ice News is out:

http://nsidc.org/arcticseaicenews/2015/06/may-be-declining/

Quote
Overall, May was cooler than average over the central Arctic Ocean, the East Greenland Sea and the East Siberian and Laptev seas, notably north of the Greenland Ice Sheet where air temperatures at the 925 millibar level (about 3,000 feet above the surface) were 2 to 4 degrees Celsius (4 to 7 degrees Fahrenheit) below average. However, temperatures were 4 to 8 degrees Celsius (7 to 14 degrees Fahrenheit) above average in the Beaufort Sea and the Barents and Kara seas, with surface temperatures rising above the freezing point in Barrow, Alaska.

I was hoping for some reference to results from IceBridge 2015, but no such luck. There is discussion of a new paper though (paywalled):

Arctic Sea Ice Reemergence: The Role of Large-Scale Oceanic and Atmospheric Variability

Quote
A new study shows that when winter sea ice concentrations are above average in the East Greenland, Barents and Kara seas, ice concentrations tend to be below average in the Bering Sea. This spatial pattern of anomalies linking the North Atlantic and North Pacific is related to the sea level pressure pattern that drives surface winds and their associated movement of atmospheric heat. These conditions are in turn linked to cooler or warmer than average sea surface temperatures that provide memory, influencing regional sea ice concentrations the following autumn. Thus, while the atmosphere is critical in setting the spatial patterns of sea ice variability, the ocean provides the memory for reemergence.

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Michael Hauber

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Re: The 2015 melting season
« Reply #1105 on: June 04, 2015, 11:51:25 AM »
PIOMAS volume loss slower than last year.  Much of Arctic cooler than average for May according to NSIDC.  And the forecast looks like getting cooler rather than warmer.  Perhaps not the best year for those who think ice is melting faster the IPCC projections.  Or is the big low going to swap things around?  Watch and see.....

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JayW

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Re: The 2015 melting season
« Reply #1106 on: June 04, 2015, 12:05:38 PM »
Temp anomaly for May 2015 (first attachment)

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BornFromTheVoid

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Re: The 2015 melting season
« Reply #1107 on: June 04, 2015, 12:32:22 PM »
Temperature anomalies for the first and second half of May at 925hPa.



I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Neven

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Re: The 2015 melting season
« Reply #1108 on: June 04, 2015, 12:50:10 PM »
Nice, BFTV! It confirms what I suspected.
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seaicesailor

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Re: The 2015 melting season
« Reply #1109 on: June 04, 2015, 12:52:33 PM »
PIOMAS volume loss slower than last year.  Much of Arctic cooler than average for May according to NSIDC.  And the forecast looks like getting cooler rather than warmer.  Perhaps not the best year for those who think ice is melting faster the IPCC projections.  Or is the big low going to swap things around?  Watch and see.....



Where is the cooler weather for Kara, Laptev, CAA, Hudson?
Even under the storm temps at or above average. It may be even rainy

The question is how long will the storm last, to prevent June insolation, but that is beyond the five days of forecast.

Buddy

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Re: The 2015 melting season
« Reply #1110 on: June 04, 2015, 01:19:32 PM »
The DMI graph below certainly shows the cool May anomaly in the Arctic.  It also shows that June is starting out slightly above the average temp.  Will be interesting to watch and see how this plays out in June and July.

If the snow in the Arctic does get torched over the coming week...with the Bering Strait and Chukcsi opening up early.....and warm waters from the Pacific.  Could be an interesting couple of months.

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Rubikscube

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Re: The 2015 melting season
« Reply #1111 on: June 04, 2015, 01:20:21 PM »
The arctic sea ice snow cover is about to be torched.

Snow depth forecasts have proven notoriously unreliable time and time again, and I honestly don't see where the heat to melt all that snow should be comming from. According to ECMWF most of the central basin is going to be rather cold during the next 3 days, with the exception being Laptev and ESS, then the 96h-144h range is as unfavorable to melt as it can possibly get, LP activity and virtually no warm air intrusion at all. Only in the fantasy forecast range, 168h and beyond, does it seem like widespread melting will return to several important regions.

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Re: The 2015 melting season
« Reply #1112 on: June 04, 2015, 01:36:10 PM »
Looking at the last 4 yrs of DMI graphs (2015 on top, then 2014, 2013, 2012)....the last time the temperature was "above average" at this time of year (beginning of summer) was 2012.  You can see that the last 2 SUMMERS were cooler than average.  The temp in 2012 was just a "smidge" warmer (maybe 1 or 2 degrees K).

Also note...that May of this year was noticeably cooler than 2014 and 2013....and yet the melt still continues.  So it will be interesting to see what plays out....especially if the Arctic temps stay near or above average.




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plinius

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Re: The 2015 melting season
« Reply #1113 on: June 04, 2015, 01:54:47 PM »
May was not that cool: temperatures over central arctic do not matter at that time, because melt simply cannot reach the CAB at that time. However, we had significant melt over the rims, which is responsible for the low extent.

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Re: The 2015 melting season
« Reply #1114 on: June 04, 2015, 02:26:40 PM »
Quote
May was not that cool: temperatures over central arctic do not matter at that time, because melt simply cannot reach the CAB at that time.

The DMI graph shows the temps in the Arctic above the 80th parallel....so it does NOT include the periphery of the Arctic (obviously).

The points I was making was:  (1)  the CENTRAL Arctic was indeed cool in May (per the DMI graph...noticeably cooler than average), and (2) that we are now at a point much like 2012 with regards to the temperature in the central Arctic (above the 80th parallel).

Was there a "connection" between the warmer than average temperature of the central Arctic in 2012 from June through August.....AND the subsequent melt that year?  I don't have the answer to that one....I am ONLY OBSERVING WHAT I SEE.

And further.....is, or will there be, any connection between the temperature in the central Arctic over the next couple of months AND the amount of melting that will take place?  Again...I don't have the "answer" to that one.  Although....I would think that warmer than normal air temperatures would at least "coax" the ice to melt faster.  And combined with the fact that the Bering Sea/Chukchi is clearing early....may provide a means for warm Pacific waters to do additional "damage".

But again....the main point is that I was "observing" what I see has actually happened...and raising the question of what MIGHT happen over the next couple of months.....and looking at the similarities of the temperature of the central Arctic in 2012 and the START of summer in 2015.

Again...it will be INTERESTING to see how this plays out.

 

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plinius

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Re: The 2015 melting season
« Reply #1115 on: June 04, 2015, 02:56:40 PM »
Simply it hardly matters if the CAB is at -10C or at -5C in the month of May. There is no significant effect on ice growth and melt does anyway not happen. Heat capacity of the ice is also pretty small, apart from that everything is buffered by a 20cm snow cap. Hence, temperature has no say on what we observe in the CAB in May.
So, just do not bother with that and also no need to shout here.

The positive anomalies nicely focussed on the Kara and Bering regions which are the places where one actually does get melt in May:

Source: www.karstenhaustein.com/climate

Temperatures in June are a different question. Now that there can be melt, we see significant WLA into that region. I suppose your question about higher temperatures in June-August and melt was rhetoric?

DavidR

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Re: The 2015 melting season
« Reply #1116 on: June 04, 2015, 03:03:21 PM »
May was not that cool: temperatures over central arctic do not matter at that time, because melt simply cannot reach the CAB at that time. However, we had significant melt over the rims, which is responsible for the low extent.
Plinius,
if you look at the entire Arctic, (http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries1.pl),  that is everything above 67N, temperatures in May  were not  in  the highest 20 years in the past  60. AND YET we are still at record low levels of extent! What is going on?
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Jim Hunt

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Re: The 2015 melting season
« Reply #1117 on: June 04, 2015, 03:30:46 PM »
What is going on?

Try the same exercise for Beaufort+Chukchi though. As plinius says, temperatures in May in the CAB are irrelevant. In June however.....
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Neven

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Re: The 2015 melting season
« Reply #1118 on: June 04, 2015, 03:43:01 PM »
I just wrote a second bulky update for the ASIB (I just hope it's not too much info that turns people off), and put in this animation showing the switch from cold to not so cold:



Like I wrote in the conclusion:

Quote
The Arctic has stopped being cold and is projected to stay warm for the coming week. At the same time it seems there is not much melt ponding happening, which is a crucial factor in building up melting momentum for the rest of the melting season. Extent numbers are very low, and area is catching up, because of early, fast and continued melt in Beaufort, Chukchi, Kara and Hudson, but on the other side the East Siberian and Laptev Seas are still asleep. That's where the action is moving to now, so let's see how many square kilometres of melt ponds can be squeezed in during Junction June.

Later this week I'm going to try and have a closer look at weather conditions in May 2015 compared to other years.
Because that's what it's all about: comparing, comparing, comparing. At least it is for me, who can't program a super computer to make sense of all the various parameters.
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Nightvid Cole

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Re: The 2015 melting season
« Reply #1119 on: June 04, 2015, 04:30:49 PM »
The arctic sea ice snow cover is about to be torched.



Here is the current snow cover.



Here is the forecast snow cover for the 12th.



Here was the snow cover on June 12, 2012.



Here is the snow cover on June 12, 2014



Here is June 12, 2013

My conclusion is that there will be high arctic melt pond formation even earlier than 2012. I think that this may be a really bad summer for the deniers and luke warmists.

Wow, nice illustration!!! What I find remarkable is how the snow cover as early in the season as June 12th seems to foretell the ice in September, not only extent, but also the shape of the pack.

In 2013 and 2014, it seems the "green" area's periphery for June 12 snow roughly matches the ice pack three months later, excluding the really low-concentration areas. However, in 2012 by that standard it looks like the whole ice pack is set to vanish - and we of course know that it didn't do so.

One possible explanation for this discrepancy is the double snowstorm that hit the central Arctic on June 16 and 20 or thereabouts. I wonder if we would see the snow cover maps for (say) June 23 or June 25 showing an inclination for that ice to likely survive the season.

Based on the extremely large amount of humid air projected to surround the Arctic by June 11th/12th according to CCI/GFS, it only takes one system to pull a plume of that over the arctic to result in an even bigger spike in surface melt than we already had - and though still too far out to really trust, the long range forecasts seem to call for the 12th and 13th to feature a low in Barents coupled with a high in the Pacific portion of the CAB. If this pans out, we will get a big tongue of "REALLY STEAMY" air (relatively speaking of course) injecting itself right into the heart of the central Arctic...

plinius

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Re: The 2015 melting season
« Reply #1120 on: June 04, 2015, 05:29:05 PM »
@DavidR: My apologies, the graphics I had linked somehow did not end up in the displayed message. Hope the attachment works to show the warm Beaufort and Kara.
If that does not work, you find the image at the bottom of Karsten's page.

epiphyte

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Re: The 2015 melting season
« Reply #1121 on: June 04, 2015, 06:40:28 PM »
For those watching EOSDIS/worldview, a reminder that the display projection switched on June 6th 2013, so  direct day-to day comparison with both 2014 & 2013 will be possible from then on...

anthropocene

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Re: The 2015 melting season
« Reply #1122 on: June 04, 2015, 09:56:42 PM »
I'm not sure why the same forecasts seem to show the entire Arctic warming to above freezing while a low moves in?

This low looks like it might stay a little while, which I would expect to cool things down enough to change this season from a very early start to at least an average start for the melt ponding for much of the central basin.

On this blogsite it seems to be a common meme that High pressure= warm,   Low pressure =cold. Somebody like to provide evidence for this? IMHO this is by no means true all of the time - I suspect it is close to 50-50 for being correct or incorrect. The main factors deciding the temperature being the history, size and position of the highs and lows.
As an example, for a high pressure (i.e. almost calm conditions at sea-ice level) with clear skies and fixed in location above the ice-pack please explain the mechanism by which the air temperature at 2m is relatively "warm"

Nightvid Cole

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Re: The 2015 melting season
« Reply #1123 on: June 04, 2015, 11:37:24 PM »
I'm not sure why the same forecasts seem to show the entire Arctic warming to above freezing while a low moves in?

This low looks like it might stay a little while, which I would expect to cool things down enough to change this season from a very early start to at least an average start for the melt ponding for much of the central basin.

On this blogsite it seems to be a common meme that High pressure= warm,   Low pressure =cold. Somebody like to provide evidence for this? IMHO this is by no means true all of the time - I suspect it is close to 50-50 for being correct or incorrect. The main factors deciding the temperature being the history, size and position of the highs and lows.
As an example, for a high pressure (i.e. almost calm conditions at sea-ice level) with clear skies and fixed in location above the ice-pack please explain the mechanism by which the air temperature at 2m is relatively "warm"

If the source air is the same temperature, high pressure systems are warmer than low pressure systems due to adiabatic compression and expansion. Of course in actuality the source air can vary in both temperature and humidity and air can heat and cool due to lots of different sources of forcing, so it's a bit more complicated in the real world.

plinius

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Re: The 2015 melting season
« Reply #1124 on: June 05, 2015, 12:22:35 AM »
I'm not sure why the same forecasts seem to show the entire Arctic warming to above freezing while a low moves in?

This low looks like it might stay a little while, which I would expect to cool things down enough to change this season from a very early start to at least an average start for the melt ponding for much of the central basin.

On this blogsite it seems to be a common meme that High pressure= warm,   Low pressure =cold. Somebody like to provide evidence for this? IMHO this is by no means true all of the time - I suspect it is close to 50-50 for being correct or incorrect. The main factors deciding the temperature being the history, size and position of the highs and lows.
As an example, for a high pressure (i.e. almost calm conditions at sea-ice level) with clear skies and fixed in location above the ice-pack please explain the mechanism by which the air temperature at 2m is relatively "warm"

;-) Michael frequently seems to have a bit of an incomplete understanding that is a) not representative for the crowd here, and b) seems a bit politically coloured to me.

I think much of that misunderstanding derives from a misunderstanding of the maps. While high pressure has sinking quite warm air at the 850 hPa maps, low pressure systems sweep up the relatively cool boundary layer air by Ekman transport. So, they must have a cool core over the arctic, which has, however, not a lot of meaning for the 2m level due to the different lapse rate. Yet, people see a cold spot on their map...

By the way, as we are at that, I have a bit of a trouble to understand something: We know that hurricanes do Ekman pump, i.e. a cyclonic vortex would give rise to spreading/upwelling. Now, what I do not understand fully is: When a low pressure system is sitting over the arctic, the wind vectors should actually point inwards and the ice at the surface should be compressed?
Underneath there could be quite a bit of upwelling, in particular, since the ice will be forced in the idealized picture into near circular motion pushing out the water beneath it. Any mistake in this? What dominates here?



Michael Hauber

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Re: The 2015 melting season
« Reply #1125 on: June 05, 2015, 12:23:12 AM »
I'm not sure why the same forecasts seem to show the entire Arctic warming to above freezing while a low moves in?

This low looks like it might stay a little while, which I would expect to cool things down enough to change this season from a very early start to at least an average start for the melt ponding for much of the central basin.

On this blogsite it seems to be a common meme that High pressure= warm,   Low pressure =cold. Somebody like to provide evidence for this? IMHO this is by no means true all of the time - I suspect it is close to 50-50 for being correct or incorrect. The main factors deciding the temperature being the history, size and position of the highs and lows.
As an example, for a high pressure (i.e. almost calm conditions at sea-ice level) with clear skies and fixed in location above the ice-pack please explain the mechanism by which the air temperature at 2m is relatively "warm"

High pressure results sinking air and sinking air gets compressed and heats up.  High pressure also equals clear air which allows more sunlight in during the day, and lets more heat escape at night.  Its currently perpetual day time in the Arctic.

This low will start on the edge of the Arctic, and pull in an injection of warm air in the Laptev region in particular.  Also a lot of wind, which in the next few days could be quite destructive for the ice.  Although the Laptev has had a slow start it has had a poor winter with lots of transport of ice away from this area resulting in ice that should be quite thin and vulnerable.  After this the system weakens and hangs around the central Arctic for a few days.  So the air will swirl around in the middle of the Arctic and much less warm air pulled in from outside.  And as it weakens the wind will die down so less waves and upwelling of warmer water from beneath etc.  The latest forecast also shows the low moving out towards the Bering strait reasonably quickly which would make the cool phase of the system relatively short and probably unimportant in the longer scheme of where this season ends up.

I judge temperatures by the 850hp temperature, and experience tells me that when 850hp goes below -8 nothing much tends to happen melt wise  (-12 or a bit lower for freezing).  The -8 line was  forecast to expand to cover much of the Arctic ocean in GFS (current forecast is showing maybe a third coverage).  Whereas the surface looks like warming up in GFS, so an apparent contradiction.  Knowing that surface temperatures can be problematic due to strong surface effects (impact of melting ice, solar radiation etc), and based on past experience I would put my money on the cooler outlook shown by the 850hp forecast.  But so many times the Arctic throws up surprises, so wait and see....
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seaicesailor

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Re: The 2015 melting season
« Reply #1126 on: June 05, 2015, 01:13:28 AM »
I'm not sure why the same forecasts seem to show the entire Arctic warming to above freezing while a low moves in?

This low looks like it might stay a little while, which I would expect to cool things down enough to change this season from a very early start to at least an average start for the melt ponding for much of the central basin.

On this blogsite it seems to be a common meme that High pressure= warm,   Low pressure =cold. Somebody like to provide evidence for this? IMHO this is by no means true all of the time - I suspect it is close to 50-50 for being correct or incorrect. The main factors deciding the temperature being the history, size and position of the highs and lows.
As an example, for a high pressure (i.e. almost calm conditions at sea-ice level) with clear skies and fixed in location above the ice-pack please explain the mechanism by which the air temperature at 2m is relatively "warm"

;-) Michael frequently seems to have a bit of an incomplete understanding that is a) not representative for the crowd here, and b) seems a bit politically coloured to me.

I think much of that misunderstanding derives from a misunderstanding of the maps. While high pressure has sinking quite warm air at the 850 hPa maps, low pressure systems sweep up the relatively cool boundary layer air by Ekman transport. So, they must have a cool core over the arctic, which has, however, not a lot of meaning for the 2m level due to the different lapse rate. Yet, people see a cold spot on their map...

By the way, as we are at that, I have a bit of a trouble to understand something: We know that hurricanes do Ekman pump, i.e. a cyclonic vortex would give rise to spreading/upwelling. Now, what I do not understand fully is: When a low pressure system is sitting over the arctic, the wind vectors should actually point inwards and the ice at the surface should be compressed?
Underneath there could be quite a bit of upwelling, in particular, since the ice will be forced in the idealized picture into near circular motion pushing out the water beneath it. Any mistake in this? What dominates here?

Ice drift vectors are not completely aligned with surface wind vectors. Ice drift is much slower, and Coriolis force acts on a given ice element making it deviate to its left right w.r.t. the dragging wind, so the ice acquires a diverging spiral trajectory. Ice drags water beneath in its rotating motion, and because of the divergent flow, ocean water must acquire an upwards motion to keep continuity of mass (no void can appear at the rotation center because of divergence).

So long story short, divergence of ice drift due to Coriolis dominates.

The opposite happens under HP.
« Last Edit: June 05, 2015, 01:21:19 AM by seaicesailor »

plinius

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Re: The 2015 melting season
« Reply #1127 on: June 05, 2015, 02:30:41 AM »
I was not seeking an explanation to Ekman (known), but more of a robust quantification. Your simple explanation is void because the surface wind vectors already turn inward by the same Ekman spiral. That's then the reason why net ocean transport is again roughly aligned with the isobars. The issue is, however, that ice is directly on the surface, so it is not evident to me why it should spread out...

Sleepy

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Re: The 2015 melting season
« Reply #1128 on: June 05, 2015, 05:51:57 AM »
I'm not sure why the same forecasts seem to show the entire Arctic warming to above freezing while a low moves in?

This low looks like it might stay a little while, which I would expect to cool things down enough to change this season from a very early start to at least an average start for the melt ponding for much of the central basin.

On this blogsite it seems to be a common meme that High pressure= warm,   Low pressure =cold. Somebody like to provide evidence for this? IMHO this is by no means true all of the time - I suspect it is close to 50-50 for being correct or incorrect. The main factors deciding the temperature being the history, size and position of the highs and lows.
As an example, for a high pressure (i.e. almost calm conditions at sea-ice level) with clear skies and fixed in location above the ice-pack please explain the mechanism by which the air temperature at 2m is relatively "warm"

Here in Sweden we actually have a fifth season we call vårvinter (spring-winter). That's when we have a long period during late winter characterized by lots of high pressure, sunshine and really chilly days and nights. Of course the days will be warmer and often really pleasant, but not enough for actual melting, rather sublimation of ice.

The northern polar circle has the most sunshine days per year on the planet. Attached is a diagram that shows the number of days per year with at least half the sun over the horizon without clouds.

epiphyte

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Re: The 2015 melting season
« Reply #1129 on: June 05, 2015, 06:24:55 AM »
The way I see it, high pressure (usually) means clear skies, and air moves from high to low - so if there's a low in the arctic, the significant question is question is "is the incoming air warm (and/or wet) enough to melt ice?", and if there's a high, it's "is the energy from the sun being used to melt ice, or is it leaving the area?"

...[edit]  - and right now we seem to be looking at a low which will be kind of warm and soggy other than maybe one day drawing the cold out of Greenland. So possibly a great opportunity to get out there and drill for oil is on the horizon :(
« Last Edit: June 05, 2015, 07:19:47 AM by epiphyte »

jdallen

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Re: The 2015 melting season
« Reply #1130 on: June 05, 2015, 07:14:35 AM »
This low will start on the edge of the Arctic, and pull in an injection of warm air in the Laptev region in particular.  Also a lot of wind, which in the next few days could be quite destructive for the ice.  Although the Laptev has had a slow start it has had a poor winter with lots of transport of ice away from this area resulting in ice that should be quite thin and vulnerable.
... a point I've been ruminating over. 

Numbers tend to bear you out; lots of that ice is well under 2M thickness.

I'm not sure the late start necessarily will save anything.  No snow cover, lots of heat blasting in across the now overheating tundra...

It's hard to imagine worse conditions for ice retention.
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Re: The 2015 melting season
« Reply #1131 on: June 05, 2015, 12:12:08 PM »
Some large holes have appeared in the ice north of Ellesmere Island:

http://GreatWhiteCon.info/resources/arctic-sea-ice-images/summer-2015-images/#CAB

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seaicesailor

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Re: The 2015 melting season
« Reply #1132 on: June 05, 2015, 12:21:03 PM »
I was not seeking an explanation to Ekman (known), but more of a robust quantification. Your simple explanation is void because the surface wind vectors already turn inward by the same Ekman spiral. That's then the reason why net ocean transport is again roughly aligned with the isobars. The issue is, however, that ice is directly on the surface, so it is not evident to me why it should spread out...

Sorry thats all I know. I believe though that the angle the wind vector turns inward is smaller than the angle the ice floe (or surface water in its absence) speed vector turns outward. Think that pressure gradient much less important than turbulent stress and coriolis in the balance of forces for water than for air (which is 1000 times less dense). Therefore, the pressure gradient will not be able to deviate surface water or ice inwards as strongly as coriolis deviates it outwards. Actually a decent ocean Ekman transport model neglects pressure gradients altogether, while in atmosphere pressure gradients are on par to Coriolis as the driving forces.

For better explanation, you always have the ggogle
http://en.m.wikipedia.org/wiki/Ekman_transport
« Last Edit: June 05, 2015, 12:26:32 PM by seaicesailor »

seaicesailor

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Re: The 2015 melting season
« Reply #1133 on: June 05, 2015, 12:38:53 PM »
Some large holes have appeared in the ice north of Ellesmere Island:

http://GreatWhiteCon.info/resources/arctic-sea-ice-images/summer-2015-images/#CAB

Wow. Well the storm is scheduled to stir that up in two days. I wonder what will happen

JayW

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Re: The 2015 melting season
« Reply #1134 on: June 05, 2015, 01:40:56 PM »
The way I see it, high pressure (usually) means clear skies, and air moves from high to low - so if there's a low in the arctic, the significant question is question is "is the incoming air warm (and/or wet) enough to melt ice?", and if there's a high, it's "is the energy from the sun being used to melt ice, or is it leaving the area?"

...[edit]  - and right now we seem to be looking at a low which will be kind of warm and soggy other than maybe one day drawing the cold out of Greenland. So possibly a great opportunity to get out there and drill for oil is on the horizon :(

I agree, looking at the current conditions, temperatures to the northwest of the low pressure (where one would *normally* be drawing in colder air) it seems pretty warm. 

MSLP


Temps

http://ocean.dmi.dk/arctic/weather/arcticweather.uk.php

In fact buoy 2015D http://imb.erdc.dren.mil/2015D.htm has been hovering near that freezing mark. And it looks like liquid on the camera that's located with it.
http://psc.apl.washington.edu/northpole/index.html
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Re: The 2015 melting season
« Reply #1135 on: June 05, 2015, 04:28:27 PM »
I was not seeking an explanation to Ekman (known), but more of a robust quantification. Your simple explanation is void because the surface wind vectors already turn inward by the same Ekman spiral. That's then the reason why net ocean transport is again roughly aligned with the isobars. The issue is, however, that ice is directly on the surface, so it is not evident to me why it should spread out...

Sorry thats all I know. I believe though that the angle the wind vector turns inward is smaller than the angle the ice floe (or surface water in its absence) speed vector turns outward. Think that pressure gradient much less important than turbulent stress and coriolis in the balance of forces for water than for air (which is 1000 times less dense). Therefore, the pressure gradient will not be able to deviate surface water or ice inwards as strongly as coriolis deviates it outwards. Actually a decent ocean Ekman transport model neglects pressure gradients altogether, while in atmosphere pressure gradients are on par to Coriolis as the driving forces.

For better explanation, you always have the ggogle
http://en.m.wikipedia.org/wiki/Ekman_transport

NSIDC also cover this, for example:
"The dominant change in the climate pattern of Antarctica has been a gradual increase in the westerly circumpolar winds. Models suggest that both the loss of ozone (the ozone hole that occurs in September/October every year) and increases in greenhouse gases lead to an increase in frequency of this climate pattern. When winds push on sea ice, they tend to move it in the direction they are blowing, but the Coriolis effect adds an apparent push to the left. In the unconfined system of Antarctic sea ice, this pushes the ice northward away from the continent."
In the Arctic it will be to the right.
During pilot training the influence of the Coriolis effect was something that needed to be considered in navigation.

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Re: The 2015 melting season
« Reply #1136 on: June 05, 2015, 06:46:09 PM »
Watching the all-important weather this week, it looks like the prior forecast of a sprawling low pressure area entering the central Arctic from Russian Atlantic side, with a high pressure ridging from Eastern Siberia to the Canadian side is coming to pass as predicted.



The next big pattern suggestion seems to that the big low pressure stays over the central arctic for quite a while, with fairly warm temperatures beneath, but lots of clouds and some snow and rain on the pacific side of the low, with relatively warm humid air coming in on southerly winds from Russia.





The EC model seems to agree with this pattern, and also shows a lot of heat entering the central arctic from the Russian side as the low pressure migrates back toward the European side after a week or so.




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Re: The 2015 melting season
« Reply #1137 on: June 05, 2015, 07:00:31 PM »
@Phil: The surface winds themselves are already turned inwards by the analogous Coriolis/Ekman effect. Net ocean transport realigns with the isobars because the deeper water (see Ekman spiral....) corrects for the surface motion. So, no, from a handful of weblinks there is no evidence if and (if yes) why ice would be spread out under a cyclone. I also suppose the infamous upwelling under hurricanes is so bad because a lot of the divergent portion gets right above the thermocline region, not because of a mere surface effect...

@sea ice sailor: Not really, the water mountains, e.g. in the Sargasso are held together by geostrophic flow, so such effects do play quite a role in the oceans. The turbulence decides though over the scale height of the Ekman spiral, which will be different from air.

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Re: The 2015 melting season
« Reply #1138 on: June 05, 2015, 07:32:12 PM »

2014 vs 2015 ocean surface temp anomalies
 

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Re: The 2015 melting season
« Reply #1139 on: June 05, 2015, 07:45:51 PM »

2014 vs 2015 ocean surface temp anomalies
 

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

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Re: The 2015 melting season
« Reply #1140 on: June 05, 2015, 10:55:44 PM »
CT's global sea ice area anomaly has just entered negative territory for the first time in quite a while.

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Re: The 2015 melting season
« Reply #1141 on: June 06, 2015, 01:35:26 AM »
@Phil: The surface winds themselves are already turned inwards by the analogous Coriolis/Ekman effect. Net ocean transport realigns with the isobars because the deeper water (see Ekman spiral....) corrects for the surface motion. So, no, from a handful of weblinks there is no evidence if and (if yes) why ice would be spread out under a cyclone. I also suppose the infamous upwelling under hurricanes is so bad because a lot of the divergent portion gets right above the thermocline region, not because of a mere surface effect...

@sea ice sailor: Not really, the water mountains, e.g. in the Sargasso are held together by geostrophic flow, so such effects do play quite a role in the oceans. The turbulence decides though over the scale height of the Ekman spiral, which will be different from air.

Maybe this attempt at explaining will be clearer.  The coriolis effect deflects motion towards the right due to rotation effects (if you are moving towards the north pole angular momentum must be conserved, rotation around the north pole must speed up as you get closer and so you get deflected towards the right).  Imagine if the low pressure is directly north.  The air tries to respond by moving directly north.  The coriolis effect diverts this motion towards the East-north east (i.e. almost but not quite parrallel with the isobars).  The water or ice at the surface does not feel the pressure difference pushing to the north, but feels a wind pushing it to the ENE.  The deflection of the coriolis effect to the right then results in water or ice movement that is towards the ESE, and hence the water or ice surface tends to move away from a low pressure system and not towards it.
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Re: The 2015 melting season
« Reply #1142 on: June 06, 2015, 03:16:36 AM »
06/04/2100Z  87.776°N   15.522°W   0.4°C  1011.9mb  028°  7.0m/s
06/04/1800Z  87.787°N   15.447°W   0.1°C  1012.0mb  060°  7.0m/s
06/04/1500Z  87.797°N   15.328°W   0.3°C  1012.0mb  056°  6.0m/s
06/04/1200Z  87.809°N   15.206°W   0.2°C  1011.6mb  046°  6.0m/s

The buoy located with the pole-cams has been above freezing for at least 9 hours.

Verg
 

Sleepy

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Re: The 2015 melting season
« Reply #1143 on: June 06, 2015, 04:52:44 AM »
@Phil: The surface winds themselves are already turned inwards by the analogous Coriolis/Ekman effect. Net ocean transport realigns with the isobars because the deeper water (see Ekman spiral....) corrects for the surface motion. So, no, from a handful of weblinks there is no evidence if and (if yes) why ice would be spread out under a cyclone. I also suppose the infamous upwelling under hurricanes is so bad because a lot of the divergent portion gets right above the thermocline region, not because of a mere surface effect...

@sea ice sailor: Not really, the water mountains, e.g. in the Sargasso are held together by geostrophic flow, so such effects do play quite a role in the oceans. The turbulence decides though over the scale height of the Ekman spiral, which will be different from air.

Maybe this attempt at explaining will be clearer.  The coriolis effect deflects motion towards the right due to rotation effects (if you are moving towards the north pole angular momentum must be conserved, rotation around the north pole must speed up as you get closer and so you get deflected towards the right).  Imagine if the low pressure is directly north.  The air tries to respond by moving directly north.  The coriolis effect diverts this motion towards the East-north east (i.e. almost but not quite parrallel with the isobars).  The water or ice at the surface does not feel the pressure difference pushing to the north, but feels a wind pushing it to the ENE.  The deflection of the coriolis effect to the right then results in water or ice movement that is towards the ESE, and hence the water or ice surface tends to move away from a low pressure system and not towards it.

Regarding the Coriolis force, I'd like to add a couple of articles written by Anders Persson which might be useful?
http://empslocal.ex.ac.uk/people/staff/gv219/classics.d/persson_on_coriolis05.pdf
http://empslocal.ex.ac.uk/people/staff/gv219/classics.d/Persson98.pdf

And a couple of pictures from the first link. The second picture with movements of drifting buoys after a windy day.

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Re: The 2015 melting season
« Reply #1144 on: June 06, 2015, 05:04:46 AM »
The low is currently down to 977hp according to Canada weather office, and looks to be dropping further.  This is about as strong as they persistent cyclone in 2013 at its strongest.  Looking at the current ECMWF forecast.  and the forecast referenced in Neven's cyclone warning blog post for the GAC 2012 I can't tell which is bigger or more intense.  There are some hints of a second decent cyclone forming over Kara, and/or a strong ridge east of Laptev, although models keep chopping and changing this far out.  Laptev is getting a lot of heat and wind from this event, and there looks like a fair chance of significant follow up.

This could be interesting to watch....
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Re: The 2015 melting season
« Reply #1145 on: June 06, 2015, 10:10:20 AM »
The low is currently down to 977hp according to Canada weather office, and looks to be dropping further. 

Indeed, at 975 hPa now:



I somehow overlooked this in my update. It's somewhat stronger than expected. Interesting, for sure.
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Jim Hunt

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Re: The 2015 melting season
« Reply #1146 on: June 06, 2015, 11:46:20 AM »
The buoy located with the pole-cams has been above freezing for at least 9 hours.

1/n - I figure this is worth cross-posting from IJIS (which is down BTW):

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

It currently only has data for 2015. Here's one I prepared earlier:

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Jim Hunt

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Re: The 2015 melting season
« Reply #1147 on: June 06, 2015, 12:16:35 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
« Last Edit: June 06, 2015, 02:08:55 PM by Jim Hunt »
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Jim Hunt

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Re: The 2015 melting season
« Reply #1148 on: June 06, 2015, 12:25:46 PM »
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Re: The 2015 melting season
« Reply #1149 on: June 06, 2015, 12:59:51 PM »
For those watching EOSDIS/worldview, a reminder that the display projection switched on June 6th 2013, so  direct day-to day comparison with both 2014 & 2013 will be possible from then on...

Today's the day  :)