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Gray-Wolf

Arctic Sea Ice Discussion 2017 - The Melt Season

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On 16/06/2017 at 22:09, knocker said:

The gfs and ecm still looking to develop quite a deep low for next weekend

ecm_mslp_arctic_9.thumb.png.5926cf0a6ed852693e212fcebb2a00e2.pnggfs_mslp_plev_arctic_33.thumb.png.a820c280c5de3285f05d5ce748c8ad87.png

The potential is certainly there as a cold low starts to mix in with a heat dome that is forecast over Siberia, these temperature contrasts certainly have the potential to produce a deep depression but even if it doen not rapidly deepen then all the models are trending a strong dipole like formation in the Chuckchi sea with pressure being high over Beaufort and much lower over Laptev, how long that lasts for is another matter but very strong winds will no doubt push that ice edge further Northwards yet again.

So potentially some interesting times ahead and even in the here and now, it will be interesting what this fairly deep low will do to the ice right now, is the air cold enough and the low not too deep enough not to cause damage to the ice or not?

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As much-maligned as the extent metric is, it's going to be interesting to see whether the predicted return of the Beaufort High and with above average airmass temperatures affecting large parts of the Arctic, starting a few days from now, will manage to send 2017 into uncharted territory for July.

It's a relief that the deep low didn't reach the ferocious intensity that was once predicted, but it was still only a few hPa off the June record low pressure, and in combination with a vigorous secondary low over the ESS seems to have managed to draw a deep wedge of relatively warm and moist air across the Pacific side of the Arctic, which has triggered the onset of a lot of melt ponds in a short space of time.

0_mslp850_arc.png?cb=565 

Melt ponds cropping up so widely just ahead of a strong Beaufort High arriving is not a good combination at all for ice integrity and duration, but the 12z ECM does at least offer some suggestion that it may not remain strong for long, or even manage to sustain an Arctic Dipole for more than a few days;

48_mslp500_arc.png?cb=565 120_mslp500_arc.png?cb=565 216_mslp500_arc.png?cb=565

In fact there are increasingly strong hints of a Scandinavian blocking pattern emerging in early July. This could see the main brunt of attack being borne by the Atlantic side, where unusually cool and cloudy weather has allowed a large lobe of sea ice to persist longer than has been the case since at least 2006 (I think - maybe only 2011?). This side can be attacked much more directly by warm air off the N. Atlantic, as well as undermined by the oceanic currents, so the ice lobe could disappear very rapidly if such a pattern change unfolds.

240_mslp850_arc.png?cb=565 240_mslp500_arc.png?cb=565

Come to think of it, ECM manages a 'worst of both worlds' solution on this particular run, as a fairly strong and 'warm' high becomes centred over the Pacific side at the same time as the Scandi blocking emerges.This model really seems to have it in for the Arctic this year!

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HI Knocks! I worry about the quality of the ice this year compared to all other years? It did not see the type of winter 'cold cycle' that other winters provide and this was compounded in areas by a deep snow cover from the succession of lows running up into our side of the basin?

If we had two 1m cubes of ice , one with an inner core temp of -25 and one of -20 would melt out times vary?

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It's fascinating how this year sees the vast majority of the volume situated on the Atlantic side of the Arctic, in stark contrast to recent years including, most notably, 2012.

In theory that means there's a lot more ice in a position exposed to oceanic melt-forcing that typically melts out all of the ice subjected to it by the minimum.

On the other hand, this year so far has displayed an impressive ability to keep the region much cooler than usual. So perhaps it will be an atmosphere v. ocean battle. Unfortunately water has vastly more heat capacity than air and the sub-surface heat reserves are relatively large even where surface temps are not that far above the long-term average. Any deep storms that cross the area such as we saw in late winter and early spring will cause some big problems.

According to predictive models working from the current situation, only an extreme retention-favourable Jul-Aug such as 2014 can prevent a record minimum in terms of sea ice extent this year.

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Interesting melt season thus far I got to say, ice extent across the pacific side looks very similar to 2007 but the CAB compared to 2016 from my observations looks more concentrated this year compared to last year and last year did see open water entering not too far away from the pole and a heavily fragmented CAB so there is maybe a case that this year we may even finish above 2016 despite so far weather conditions in general has been a bit more favourable for ice melt?

Looking ahead, it does look like high pressure will dominate the Pacific side and there are hints we may see a ridge entering from the Pacific to join up with the high in the Arctic which will cause strong southerly winds and bring in a lot of warm air again. As ever, its not always that plain sailing as this afternoon's GFS 12Z run shows which would be more favourable for the ice.

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Hi G.s.! I'm not sure thast the more favourable weather is as impacting as it was even 5 years back? The fragility of the pack allows swells to mix up warmer waters from below bringing melt to the base even if surface melt is curtailed? Open water areas obviously warm and this water can then flow through the Trans Arctic drift and under the ice on our side of the basin even if our side is sealed?

By months end we should have a better handle on what is occurring as the sub 1.5m ice will be gone over most of the basin. this open water will then be studded with the slightly thicker floes but will the open water prove too much for most of that? The lack of deep cold over winter may also show impact in ice melt out rates? Will warmer ice need as much energy to melt out?

It is a scary period ( for me) as it will either confirm my fears or save us from them!!!

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Well last year shown quite nicely how on paper more favourable looking set ups still made us 2nd lowest on record but traditionally reverse di-poles would tend to favour retaining ice and its something I rather see than a true dipole at this time of year.

I'm not too sure about this "warm ice" and "cold ice" theory but the ice is thinner this year and for me its ice thickness that will no doubt play a major role on where we will end up by the end of this melt season. The pacific side of the Arctic has been melting quite rapidly this year which is no surprise as weather patterns have favoured this but it has not exactly been a 2007/2011 style set up either where high pressure and warmth were quite dominant in those melt seasons.

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For ice to 'grow' over winter the cold needs to reach down through the ice to expand the floe down into the ocean. Put a warm blanket of snow over that surface and you insulate it from the cold above so no growth occurs? It is the same issue with the land that caught the WACCy snow? It might have taken longer to melt away but the land below was then ready to continue with its degradation as it was not placed in deep freeze over the winter. The explosion of the hillock on the june 28th might highlight this?

Apparently I mis spoke in claiming there were 700 more hillocks under investigation, apparently it is 7,000 more hillocks spotted and being monitored! It sounds very much like the 'blossoming' of the chimneys under the ESS earlier this decade ( which now see melt temps most of the year?).

As for 'thin ice' ? Well we have seen the old 07' record approached/matched by pretty average melt seasons just because the amount of FY ice as a proportion of the pack has grown so 'average melt seasons take it. this year we have the thinnest ice measured so surely even a slow year will see this ice melt? Late July/early Aug might be when we see this melt out occurring?

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12 hours ago, Gray-Wolf said:

As for 'thin ice' ? Well we have seen the old 07' record approached/matched by pretty average melt seasons just because the amount of FY ice as a proportion of the pack has grown so 'average melt seasons take it. this year we have the thinnest ice measured so surely even a slow year will see this ice melt? Late July/early Aug might be when we see this melt out occurring?

Well this thin ice towards the Pacific side of the Arctic will have an interesting 72 hours or so as we get a very warm plume heading in from the Pacific coupled with no doubt quite sunny skies to boot, we saw in 2015(around this time of year) the dramatic effects this had on the ice although thankfully it is not quite as severe and long lasting as it was back then as the pattern is forecast to break down quickly by low pressure over the CAB although the models kind of disagree on what happens next, most GFS runs had the low deepening but not one Euro run has backed this and some sort of reverse dipole looks the most likely and it will be interesting to observe what happens to the ice edge over Barents if the forecast Southerlies come to fruition as it looks a fairly potent southerly in store.

I think its fair to say whilst things do seem to be on a knife edge, we could be looking at a far worse situation when we saw those volume figures back in Spring and it is interesting what the final shape and extent of the ice will be come September.

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Well the 3 days of substantial of very warm air hitting the Pacific side of the Arctic is more or less over now as the reverse dipole takes shape but not without causing quite a lot of ice melt over the East Siberian/Chuckchi seas and the net result has been 3 consecutive century breaks in a row - not terribly unusual for July but goes to show, any real heat hitting this ice pack is causing substantial ice melt.

With the reverse dipole kicking in now and the weather forecast seem to be suggesting a fairly slack looking set up coming, extent figures could start to slow down somewhat, looks similar to the 2nd half of July 2014 but as it stands, not as cold in terms of upper air temps at least but if the favourable set ups last a good while then the ice pack has got a chance of not ending up too low but we shall see.

One thing to note is the definate trend of the Kara sea having a long heatwave which is already ramping up the SST's and the Atlantic side recieving warm southerlies although the strength at this stage is fairly slack but some retreat on the Atlantic side looks likely, one to watch for sure.

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10 days with no new posts in the height of the melt season?

That's unusual... no news is good news i guess.

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