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Messages - subgeometer

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1
Arctic sea ice / Re: The 2019/2020 freezing season
« on: September 25, 2019, 04:43:42 PM »
I disagree.

I agree with you! See #5:

http://GreatWhiteCon.info/2019/05/melt-pond-may-2019/

Not disagreeing but it also depends where the snow falls. Quebec vs Taymyr penisular for example. Its the stuff around the Arctic Basin that matters most here isnt it?

2
Arctic sea ice / Re: The 2019/2020 freezing season
« on: September 24, 2019, 08:36:16 AM »
Oe last look at the meltig seaso just past - I've posted a bunch of regional animations over on the test space thread , but here's one of the whole arctic drawn from Terra Modis on NASA worldview

3
Developers Corner / Re: Test space
« on: September 24, 2019, 08:32:19 AM »
Fram strait, A closer view of Nares Strait, the Pacific side and the Laptev Sea

I have some others but I might post those, with all these on youtube at full resolutio

4
Developers Corner / Re: Test space
« on: September 24, 2019, 08:27:45 AM »
These are a more reasonable size

The whole arctic basin through the course of the freezing season at 5.4MB by constraining bitrate to 500kbps

5
Developers Corner / Re: Test space
« on: September 24, 2019, 05:54:13 AM »
Nares Strait and Lincoln Sea over the 2019 melt season, encoded in the same batch as the "Beaufort Beard" animation above. Its about 3 times the size of the h265 version, though quality also seems a bit better. H265 outperforms on the bitrate setting while libx264 produces output a bit larger than requested, at least with these ice animations

6
Developers Corner / Re: Test space
« on: September 24, 2019, 05:17:21 AM »
A slightly longer version of the Beaufort Sea animation I posted on the melt thread a few weeks ago

This is at 720p  with h264 encoding. Its a bit large at 8MBfor ~150 images. I'll see how far I can push down the bitrate (doing 2pass encoding) without losing too much image quality. The alternative is to reduce size to 360p. I guess if you need the detail though, you pay in bitrate

EDit: Added the actual video

the h264 version here is twice the size of the h265 I made earlier though there are a couple of differences in -preset and -tune parameters - though the preset shd make it marginally more efficient. Its possible that "-tune animation" makes ffmpeg/libx264 consume heaps more bandwidth- I'll do some more experiments as time allows

Edit 2: Arggghhh padding. I added code to pad and force aspect ratio to deal with problems when sequencing clips for the video screens at the big Flea Circus show I mentioned in the post above, and which opens tonight, so I'll have to leave it for now. At least the H264 video displays fine on my system


7
Developers Corner / Re: Test space
« on: September 24, 2019, 02:36:01 AM »
I've been messing around downloading images from Worldview to make  video of the just concluded melting season to show at a Sydney Fringe Festival Cabaret called Museum of Fleas, as well as post here

I've also been learning a bit more about compressing video, and have been recording what I've learnt in some python functions so when I post some open source license/disclaimer on top of the 2 or 3  files I'll put them up on the forum.

In the meantime, since the melt season thread closed, videos of ice going down the gurgler in the Lincoln Sea into Nares strait,

Edit: This comes up with an error in my browser tho its fine to play locally on my system. It was encoded with libx265, it looks like back to libx264 for sake of compatibility. Also removed some late nite typos

8
Arctic sea ice / Re: The 2019 melting season
« on: September 14, 2019, 04:20:16 AM »
Another movie,( at a more reasonable 7MB) of the relentless conveyor feeding ice into the Beaufort Sea from 24-May through to 13 september. I should have gone a few weeks further back to breakup, and when I have time I'll grab the remaining frames to do so

9
Arctic sea ice / Re: The 2019 melting season
« on: September 14, 2019, 03:18:50 AM »
I have the chance to use a decent internet connection occasionally at the moment, so I've bodged a fix to my download script and begun downloading a bunch of sequences from Worldview to compile some movies with ffmpeg as I get to know the relevant encoding settings.

Here's a movie of most of the basin from May until the 11th(I was careless and missed the southern Beaufort and the Alaska coast). I'm not sure it will display here but should play fine on most any system. Hopefully the 15MB file size doesn't exceed a limit, if so I'll try resizing from 720 to 360p

Edit: that plays nicely on my barebones system after a considerable lag downloading, and reducing(naively) to 360p only gets file size down a few MB. It should be possible to get something like this down to half the size or a bit less  without any noticeable image quality loss or resorting to keyframing - I'll keep playing around

10
Arctic sea ice / Re: The 2019 melting season
« on: September 06, 2019, 05:03:37 AM »
August Area, Extent & Volume losses may have been low, but SST anomalies continued to climb and expand.

I wish I had saved the images from the beginning of the melting season. But I did not. mea culpa.

The interface at DMI's site  is set up to step back and forward through the time series

11
Arctic sea ice / Re: The 2019 melting season
« on: September 06, 2019, 04:57:22 AM »
A rare clear view of the North West Passage shows it more or less open now, though there still plenty of dispersed floes especially where it enters the Beaufort Sea(click to see in 500m resolation)

Skies are comparatively clear today in areas often completely obscured. so I've also attached a view of 86-88.5N on the Atlantic side of the pole showing a few holes and but also, reassuringly that most of the ice there is recognisable as considerable size floes and one of the Canadian sector  of the CAB, very dispersed, and not so reassuring

12
Arctic sea ice / Re: The 2019 melting season
« on: September 05, 2019, 04:35:55 AM »
A few frames from Climate Reanalyser (at 33, 99 and 186 hours out)with yesterdays Bremen extent map marked to show where I think melt will cease very soon and freezing perhaps begin(perhaps I've drawn the area a little too large?), and where melt will continue.

Its looking like we're for a series of massive influxes of warmth (and storminess - N Pacific storms are showing signs of penetrating the Arctic  basin more often, wrapping around Chukotka)from the Pacific, and some from the Atlantic as well

13
Arctic sea ice / Re: The 2019 melting season
« on: September 05, 2019, 03:19:50 AM »
.......everywhere on the other side of the pole will struggle to drop below freezing, so bottom melt will continue.


Please elaborate your opinion why surface temps would impact bottom melt ?

IMO bottom melt can continue even though the surface fresh waters or waters with poor salinity can show some freezing.

THX

Perhaps I should have said - "so bottom melt can continue unhindered"

What's unusual about the suggestion that there's a relationship between atmospheric temperatures and melting/freezing of sea ice? Once surface air temps drop below about -10C bottom-freezing will begin, at some surface air temp between that and -2C e is an equilibrium between freezing and melt, no doubt affected by any underlying warmth in the ocean waters.

Air has much lower heat capacity than water, so when temps aren't much above or below freezing its effects are muted, but when surface air temps are +4C(like the Lincoln has repeatedly experienced this season) or -40C(old-school winter) it most definitely has a significant effect

14
Arctic sea ice / Re: The 2019 melting season
« on: September 04, 2019, 02:10:38 AM »
GFS's 10 day outlook shows a story of 2 arctics. Inside a triangle with corners at Axel Heiberg FJI and Fram strait we can expect refreeze to commence and the holes to ice over whereas everywhere on the other side of the pole will struggle to drop below freezing, so bottom melt will continue.

I've attached the 10day average temperature map from Climate Reanalyzer

Eurasia will start to get seriously cold soon so I expect plenty of fireworks generated by the warm water surrounded by cold in the next couple of months

15
Arctic sea ice / Re: The 2019 melting season
« on: September 04, 2019, 01:48:43 AM »
A clear view of the northern CAA yesterday shows very little ice obstructing Parry Channel, winds have pushed it all to the southern side. And the hole that's been appearing in the Lincoln Sea is as large as I've seen it.

Todays EC/Windy forecast ups the winds a bit, and indicates another round of storms at the back end of the forecast. Still plenty of interesting things going on despite the lateness of the date

Edit: oops, I double posted the image of the CAA, and left out Lincoln Sea - fixed

16
Arctic sea ice / Re: The 2019 melting season
« on: September 02, 2019, 03:24:40 PM »
I am eyeballing Worldview daily for evidence of freezing between floes in the CAB, as temperatures are beginning to dip into that region.

None as of yet.

Looking at GFS 10 day forecasts at Climate Reanalyser you see a small area of cold form repeated going down to around -7C and then dissipated again by another warm influx, all the way through the forecast, so refreeze is going to be limited for now- and then theres the wind to come with storms . Eve if losses are limited  nad the pack freezes over the gaps, after the long August lag the waters around are all anomously warm, so significant extent increases are a long way off

17
Arctic sea ice / Re: The 2019 melting season
« on: August 31, 2019, 03:02:32 AM »
The dispersal to the Pacific and Eursian sides which has driven the extent stall looks likely to turn around given the forecasts, The CAB adjacent to the western Beaufort and eastern Chukchi sea will have 20 knot winds pushing the ice north which should lead to extent drops. Any export will be via Fram strait and the Barents between Svalbard and FJI. The storms that may follow also seem likely to drive ice north from the Laptev region.

A long lag in extent drops is usually followed by a catch up period, altough since its so late it may be reflected in an extended stall in the freezing season. But temps have failed to fall much below 1C above 80N so far, and have bounced back upto about -0.5C again today - there has been nothiung to halt bottom melt, so we might see some nasty surprises in some gauzy low concentration areas if winds get as strong as (or stronger than) forecast

18
Arctic sea ice / Re: The 2019 melting season
« on: August 26, 2019, 11:59:57 AM »
By cutting clouds from the top image I made a crude composite of the past 2 days from Worldview of The Eurasian side across to a bit past the pole. There must be a million km2 of dispersed rubble and/or slush between the Laptev sector(where the Atlantic water is?) and the Pacific fringe.

But unlike some earlier years  no Wrangel arms or anything beyond the ESS Big Blob exposed to attack from all sides. Quite a bit of this stuff could survive(barely), and then be covered by a big dump of snow in the next storm.

GFS is also hinting at a bomb cyclone around Kara/Laptev late in the run

19
Arctic sea ice / Re: The 2019 melting season
« on: August 24, 2019, 03:36:11 AM »
HYCOM Ice Thickness August 22 - August 29



I feel like HYCOM must have changed their scale or something because that literally looks like the end of ASI as we know it.

A hole by the pole at the end of the month? hmmm, not sure about that. While that area is almost always cloud covered it hasn't seemed to have had low concentration recently, although ice a few degrees further south on the Eurasian side does have fissures and holes.

The gap opening again east of the CAA storm all the way to the Atlantic is more plausible. There's lot of wind around the big high over Greenland, which is getting cold while almost surrounded by warm SSTs(Baffin Bay is verywarm, much of it with 4C+ anomaly on the DMI chart.

Anomalies continue edging up in the ESS as well, and DMI also shows a growing area of elevated SSTs across the wide swathe of thinning ice adjoining the Laptev Sea. If correct the freezing season will be brutal, right now there still remains plenty of energy for melt and to propel storms

20
Arctic sea ice / Re: The 2019 melting season
« on: August 24, 2019, 03:03:16 AM »
Ice north of Svalbard shows thinning between the pack and the blob pushed(further) into the Barents recently.

This region is in for a lot more 20-30 knot wind from a parade of lows starting in around 3 days if the forecasts are correct - and this area melts and freezes late/on its own schedule - its very far north, but under the influence of the salty warm Atlantic

21
Arctic sea ice / Re: The 2019 melting season
« on: August 24, 2019, 02:42:20 AM »



Temperature is dropping like a rock...

Temps are down around the freezing temp of seawater above 80N now, but may struggle to drop much further for a while, that's what GFS forecasts are suggesting, with continuing warm air advection(though it flips around as to the points of attack) There's all the high SSTs ringing the ice, and half the pack itself is full of holes and tears. They will have to freeze over for temps to go down a lot further

Edit: fixed typo and hopefully ungarbled my english

22
Arctic sea ice / Re: The 2019 melting season
« on: August 21, 2019, 06:25:16 AM »
Another of this season's weird extent loss slowdowns (eg the heatwave in June saw an absolute flatlining!) continues, only 20000km2 lost today on the JAXA graph, after 30K yesterday, now 370000km2 behind 2012 and about the same in front of 2016. Losses must pick up again though. 2016 and 2012 both lost ~900K after this date(which surely puts 2016 out of running for 2nd, its minimum now only 490K away.)

Bremen though has 2019and 2012 still neck and neck on the extent graph(and it is higher resolution), and on the corresponding map little holes are starting to appear in the interior of the Laptev sector, as the gossamer shreds in the warm breeze after near continuous dispersal,. With the storms on the horizon there could still be a few big days ahead, with considerablelosses just before the cold descends, like 2016

23
Arctic sea ice / Re: The 2019 melting season
« on: August 21, 2019, 06:02:42 AM »
Am I going crazy or is there a LOT of ice being exported thru the Fram and Svalbard right now? I feel like not that long ago the area was *somewhat* surrounded by blue water (except north) and now I see lots of ice being pushed into the region. Maybe I'm confused or misread what I saw earlier.
A lot of ice has been pushed either side of Svalbard, and 20 knot winds from a passing low will continue that over the next24 hrs. So much that some(a lot?) of the ice to Svalbard's east is very likely to survive into the freezing season (though it may melt then, especially if it travels any further south. Along Svalbard's north coast and especially to the west west the water is much warmer, any thing pushed there will melt

24
Arctic sea ice / Re: The 2019 melting season
« on: August 21, 2019, 05:49:48 AM »
Only 2 days now till this storm is predicted to start bombing out over the CAA, EC/Windy now has central pressure getting down to 969 a day or so later as it crosses to the CAB, witha huge wind field, with 30-40 knot winds gusting well over 50kt in places. Could this open Parry Channel and the main NW passage route? The Lincoln Sea and areasnorth of Ellesmre Island and Greenland are in for another (last?) bout of strong southerly wind, well above freezing. The gap may widen again before refreeze

Anyway, its an interesting climax to the season. Both models havethe CAA low taking over the Pacific and Canadian of the CAB. With a lot of wind, not quite as strong, but pressure remains around 980 for a while. As that goeshe GFS sees a narrow ridge from Greenland to the New Siberian Islands by D7 and a 'double diplole' as lows also swirl in the Barents and Atlantic fringe. Its dispersal vs melt vs the clock, as temps inevitably drop

25
Arctic sea ice / Re: The 2019 melting season
« on: August 19, 2019, 08:57:28 AM »
Anyway... Here's an updated version of the five day forecast. There's been an interesting development over the CAA, where that storm that smached itself to pieces on the Alaskan coast is reorganising itself on the other side over the CAA. 976 hPa is pretty low, and it seems to be strengthening. This could get interesting in the coming days!
976hPa is a serious storm, especially in contrast to the high pressure domes elsewhere over the region.

Depending on location and duration, this could stir up some heat from depth.

The storm over the CAA has been in the forecasts consistently for a few days now and like Freegrass says seems to becoming stronger as it gets a bit closer. The GFS is getting keener on the idea of increasing storminess in the basin after that, but flipping around as to where a low will intensify, currently it thinks a low will drop to around 980 between the Beaufort and CAB late in thge forecast, and current EC on Windy pretty much agrees

26
Arctic sea ice / Re: The 2019 melting season
« on: August 19, 2019, 08:45:53 AM »
A fractal swirl of more concentrated ice north of the the ESS gets stirred over the past week-now it being pushed into the warm SSTs in the wetern Beaufort Sea

27
Arctic sea ice / Re: The 2019 melting season
« on: August 19, 2019, 03:49:50 AM »
Just before cold air dominates the Arctic, this beautiful inverted dipole promises 40-80 km/h winds over the Laptev-ESS side for a couple of day. This is Thursday according to ECMWF.

assuming that the pressure gradient is 3000 Pa over 1 million meters, and that this is near enough to the NP, then the associated geostrophic wind is 3600x24/4/pi x 3000/1000000 = 20 m/s ~ 40 knot ~ 80 km/h, that’s a max. limit, near the surface it will drop considerably

As well as wind temps will be well over 0 and dewpoints of 0-3C the next few days over the Laptev sector and eastern Atlantic front, where the ice is looking bad, melting and dispersed and very grey. While freezing altitudes are up to 3km, there will be thick cloud so I am imagine a substantial longwave flux as vapour condenses within them, there's up to 30kg/m2 in these pulses coming in. Bremen's 'daygrid swathe' temporary shows holes appearing in the Laptev ice north west of the bite, so I guess they'll also be in their final AMSR2 for today

The Atlantic front is being turned by the conditions, advancing( into warm SSTs) around Svalbard, and rapidly retreating further east

I've attached an image of the Laptev sector, and one of ice east of Svalbard, and a gif of thinning ice north of the Laptev bite from 13-18August, doubleframed on the 18th, and skipping the 17th as it was solid cloud. I've also included Windy's dewpoint(not temperature - temps are generally about 0.5C higher!) forecast for thursday

Keep the forecasts coming Freegrass. It would be great though if we could collectively work out how to embed movies (eg MP4, avi) when possible rather than GIFs, which are great for encoding 8bit data, but don't compress efficiently. It would help limit server costs and energy consumption, and also those of us with crap internet connections. I've had difficulty in embedding them directly, I'll try using youtube sometime soon

28
Arctic sea ice / Re: The 2019 melting season
« on: August 16, 2019, 11:23:22 AM »
Laptev bite and ice north of it - 8 August and 16 August.

29
Arctic sea ice / Re: The 2019 melting season
« on: August 16, 2019, 06:16:26 AM »
3 images of the western Laptev sea, and CAB north of it to the Atlantic side of the pole, showing disintegration in the south and fraying as far north as 88N. I've included an imae of the whole area, and 2 higher-res details, one of the ice by the bite that's being totally hammered, and one of some of the holes beween 86 and 88N, and 104 and 141E

30
Arctic sea ice / Re: The 2019 melting season
« on: August 16, 2019, 04:53:44 AM »
There's been an (at least for me) striking drop in Chukchi and some Bering SSTs that continues since they peaked in mid July Norton Sound peaked around 20C, and is now down to around 14-15C. Large areas of the Chukchi sea have also dropped ~3C. In more northern areas energy might be going into ice melt, with currents bringing cold surface water from under the ice.

But this region is a long way south, some of it outside the Arctic Circle entirely, so insolation does not drop off as sharply as at the pole. This leads me to suspect there's been some vertical mixing going on, which would raise salinity

31
Arctic sea ice / Re: The 2019 melting season
« on: August 16, 2019, 04:41:32 AM »



There's also a pressure gradient and strong winds from the North Pacific and Bering, which will continue, which may have an impact on the Bering Strait throughflow. Some very warm water in the N. Pacific. Not a huge deal, but may be interesting to consider.

Water is also very warm inside the straits, 8-11C for hundreds of km north. The water flowing in is much more saline though. Uniquorn posted some salinity model charts from Mercator earlier in the season that matched closely with melt patterns there in recent years(2016 and after?) and help to explain why the Chukchi struggles to freeze, and especially, why (expanding)parts of it melt out so easily even in mid winter.

Pressure builds to over 1040 for a couple of days, as the high moves to hover over the Chukchi Sea

32
Arctic sea ice / Re: The 2019 melting season
« on: August 16, 2019, 04:26:13 AM »
There's only one place for the ice to go, into hot water...

This will restrain the advance of the melt edge, and the hot water, at least at the surface. And areas with cold surface waters and remnant ice can refreeze quickly once atmospheric temperatures drop sufficiently. If the weather is kind in a couple of weeks maybe the freezing thread can get off to a good start with a larger than normal dump of energy to space as a large amount of new ice forms. That requires high pressure and minimal clouds though.

In the meantime the disprsal can only further expand the holes and  ragged tears in the interior of the pack. Eg at 87N on the Eurasian side its already looking pretty bad, as we approach minimum the pack will look worse than we've ever seen it.

EC sees another 7 days of warm air from Eurasia pushing right across the pack, before(finally) indicating an end to it, to be replaced by the low over the pack sucking in other lows from Europe and the Atlantic, one of which may well bomb out. The N Atlantic cyclone cannon has been silent till now

33
Arctic sea ice / Re: The 2019 melting season
« on: August 15, 2019, 10:31:51 AM »


Heat blowing in from the continents will have a minimal effect, as it isn't accompanied by significant insolation or long-wave radiation.

All hinges now on bottom melt, and to a certain degree, on how much heat is pulled from depth by wind.

I think a 2nd place finish is pretty close to being "in the bag".  I'm doubtful that we will pass 2012 - *UNLESS* the melt season continues into late September, driven by bottom melt.

Unfortunately, that store of heat - what's already in the water - is an aspect of the Arctic we probably have the least information on.  We can only wait and see what transpires.

The evidence is on worldview that this longlasting atmospheric infkux is adding extra oomph to bottom melt. The warmth comes with a high dewpoint, significant atmospheric moisture and wind( which is also moving the ice around and enhancing bottom melt. The longwave from clouds can take cm oiff even in midwinter. It all enhances and extends the momentum - aka bottom melt. Apart from enough ice melt, atmospheric cooling is about the only way to stop momentum

2016 is totally in the bag, its only 750K away on JAXA

Edit: JAXA is 750K behind 2019 minimum, not 720 , an average 37500 km2/day for the next 20 days to tie if minimum comes really early, as in 2016.We need a major slowdown right now and even then I can't see the minimum not going below 4 million km2. In the absence of major storms 2019 might bottom out a bit above 3.5 million, but I wouldnt bet my house on it

34
Arctic sea ice / Re: The 2019 melting season
« on: August 15, 2019, 05:53:39 AM »
A couple more tantalising cloudless images of the edge of the pack around 78-80N on Eurasian and Canadian sides, with their locations marked on today's Bremen extent  concentration map. The ice north of the Laptev is a strange brown, I don't know if this is an effect from smoke haze above, tkinness, or what. The area between the Laptev and Barents seas is likely to soon start looking equally ragged from melt, if not already

35
Arctic sea ice / Re: The 2019 melting season
« on: August 15, 2019, 04:13:17 AM »
SST's north of laptev are turning orange. That would be under the ice. Could this be a result of all that hot rain hitting this area? How does this get measured? By buoys?

Edit; The rain actually hit the ice more to the west of this area, so probably not because of the rain. Just hot temperatures.

The ice is dspersed and melting there. Open water between the rubble could be observed by a microwave instrument, maybe.though it seems unlikely the SST could be above -1.5C with so much ice around, even if the water some metres beneath was considerably warmer.

I think its probably spurious, unlike ESS SSTs which have increased significantly over the past week since most of the ice melted, now showing lots of positive anomalies on the same DMI mapsSome of that must be warmth beneath the surface accumulated in June and July and now raising the surface temp once the ice is gone

36
Arctic sea ice / Re: The 2019 melting season
« on: August 15, 2019, 03:57:56 AM »
Some nasty surprises are starting to wink thru the cloud as heat keeps pouring in from Eurasia.

A worldview image of ice near Severnaya Zemlya, showing rapid retreat and melt in a spot where thick ice apparently was just recently.

The various extent and especially area graphs are all over the place, they don't seem equipped to handle a state where so much of the pack is in a state of melt, cascading into rubble as it disperses. There's very little 95% coverage on the maps

The forecasts don't let up. DEwpoints over the ice are close to the surface temp, at the spot indicated on the Windy screenshots dewpoint ranges from 0-2C for the next week with temps about a degree higher. Both GFS and EC show the heat continuing, and hint at the beginning of some weather action from the Barents and Atlantic. One big difference is that GFS appears to be modelling a lot of ghost ice in the ESS, temps in the southern part are much cooler than on the ECMWF. Adjacent regions in Chukotka are ~10 degrees different in the 2 models, freezing in GFS, ranging from 7-15 on EC.



This all as the basin should be cooling - 80N is due to go through 0C on the DMI graph in another day, but, surprise, surprise, temperatures have gone back above the green line and it looks like another week before we go through the freezing point of water in that region

There's not much to slow momentum anytme soon

37
Arctic sea ice / Re: The 2019 melting season
« on: August 12, 2019, 07:52:28 AM »
Can this ice around 85-6N survive another month? If the waether cools quickly, and its calm, maybe, though it will look awful.

JAXA dropped 110K to 5million km2 today. The average drop from now to minimum in 2010s has been about 1.3 million, so its unlikely to not beat 2016 (4.03million)into 3rd. We're currently 110K above 2012 on this chart(about even on NOAAs, and 2019 retains a dwindling lead according to Bremen), so 2019 remains in the hunt for the record.

There's a lot of vulnerable ice. I've included an edited Bremen map from 11 August to show the location of the Worldview image(red square) and the ice that I think will likely survive(inside purple line) and that which is at risk of melting out, as a tentative stab at a minimum projection

38
Arctic sea ice / Re: The 2019 melting season
« on: August 12, 2019, 04:57:46 AM »
Area data is notoriously difficult to interpret this time of the year. The graphs that Gerontocrat posts show what they show, but it is difficult to draw conclusions about melting or freezing based solely upon the graphs. 

 

Yesterdays Bremen AMSR2 also shows high concentration north of the Laptev bite, despite the clear fraying visble on earlier days on the map and worldview, and the warm temps under thick cloud. The cloud is fooling the instrument - weather artifacts are often visible. Animations by Aluminium etc show the passage of cloud bands as areas of fleetingly increased concentration- phantom area

Temps have to drop well below freezing for new ice to form, -11C is the figure usually quoted, and nowhere has been anywhere near that cold yet, and won't be for at least a couple of weeks yet. Regional area increases can come from transport. Any absolute area increases now are spurious, solid floes collapsing to rubble, and the effects of dispersal combined with quirks of the algorithm and low resolution of the instruments, as well as the effects of thick clouds

39
Arctic sea ice / Re: The 2019 melting season
« on: August 12, 2019, 04:40:52 AM »
2worldview images from9 August

...The second shows the immense Siberian smoke plume... heading over Severbaya Zemlya and the ice edge

Now *that's* interesting. Nothing like sprinkling something dark over the ice to induce melt.

It's lucky this is happening as the sun is on the wane - climatologically we are only a few days from going under 0C north of 80 degrees, if it were June or the first half of July the effects on energy accumulation from insolation would be a lot worse. Just how much it would darken the ice I'll leave to those who have the expertise

As it is this vast influx will continue through the week, and smoke is likely to appear in every corner of the Arctic Ocean. For example smoke dense enough to block out the sun is forecast off North Greenland in 2 days. Right now a large area of the CAB adjacent to the Laptev s under a cloud whose aerosol density s up to 4.5 AOD(1 AOD is enough to block the sun if I understand correctly). Any polar bears out there on the dwindling ice are in for a weird eerie experience. Pink skies and blood red light?

I've attached 2 Wndy/Coperncus Aerosol forecast maps, as well as the smoke hosing the Laptev on Worldvew yesterday, and a vew of the ice edge near Severnaya Zemlya, showing strong melt after the first couple of days of warmth

40
Arctic sea ice / Re: The 2019 melting season
« on: August 10, 2019, 05:37:50 AM »
I post 6 to 10 day forecasts when the models are indicating a large scale phenomenon such as a a change in the Arctic oscillation. I know that the models are unlikely to get the details right and will the ECMWF often overdevelops storms and ridges near the pole in those forecasts, but I find that the European model does pick up large scale features pretty well on the 5 to 10 day scale.

We have reached the point in the melting season where bottom melt dominates and heat in the ocean has more impact than insolation in the central Arctic. There is sufficient ice around the pole that we can now be certain that there will be no "blue ocean event" this year.

The heatwaves the models saw coming well out, since the Mackenzie in May. Even if they turn out wrongI think its worth posting the far off forecasts when something big is signalled.

A BOE is totally improbable from here, too much ice. Perhaps if conditions didn't ease off at times in July. But there is a lot of vulnerable ice on the Eurasian and Pacific sides, pretty much to the pole. There's a huge amount of rubble, vulnerable to bottom and side melt Then there's the gap, and thinning Lincoln Sea etc.The next week will see rapid advances in the Laptev region and the thinning ice north of there. It's going to start looking very ragged as all the FYI struggles to survive. And there is still plenty of time before the minimum for serious storms to wreak havoc, something the forecasts seemingly aren't so good at predicting

41
Arctic sea ice / Re: The 2019 melting season
« on: August 10, 2019, 03:24:17 AM »
2worldview images from9 August

The first shows fraying ice at 85-86N, north of the Laptev Sea. Similar ice can be seen thru the odd hole in cloud further north.

The second shows the immense Siberian smoke plume merging with (rain?) clouds before heading over Severbaya Zemlya and the ice edge

42
Arctic sea ice / Re: The 2019 melting season
« on: August 10, 2019, 02:34:36 AM »
August 3-7.

2018.

Ice between the Laptev sea and the pole seems to be getting to a critical point. Cracks and holes are visible in every break in the clouds on Worldview.

Edit: Dispersion is still notable towards Beaufort, Barents Kara and Laptev, somewhat disguising the massive collapse in the ESS, and making the extent numbers hold up

43
Arctic sea ice / Re: The 2019 melting season
« on: August 08, 2019, 05:55:20 AM »
Seriously ugly forecast today on EC/Windy. From D2 a continuous stream of heat from central asia over the Laptev Sea, and the most of the basin again progressively cleared of below below freezing air to 800hPa and above. Surely for the last time this season? Dewpoints are above freezing well over the ice. And wind, did I mention the wind - tight isobars between a high over ESS and lows over the Kara and Beaufort will push ice to open water, and heat on the fragile Eurasian side of the CAB

It starts with a few days of 20-30knot winds between Svalbard and FJI. Expect the front to advance in that direction -but into the teeth of warm SSTs. And the reserves are dwindling in the rear. Tears and cracks can be seen all the way to 87N yesterday on worldview, and a few troubling cracks very close to the pole in a rare gap in cloud. Dispersal and the warm advection may play havoc with that half of the pack

44
Arctic sea ice / Re: The 2019 melting season
« on: August 07, 2019, 04:03:38 AM »
A huge smoke plume over the Laptev sea yesterday. The coming massive heatwave there will likely drive more large smoke clouds over the basin , especially if fires intensify with the heat. Some are very far north, within 100km of the Laptev sea coast`.

The ice piled up against Severnaya Zemlya is in danger of being cut off from the pack, as the Laptev bite grows and ice is pushed once more towards the Barents Sea. The ice to its east is already reduced to ribbons as can be seen in the image

45
Arctic sea ice / Re: The 2019 melting season
« on: August 05, 2019, 05:13:30 AM »

 while some CAB ice is constantly driven south to melt in the warm waters of the Chucki.


With the exception of a narrow band of water extending over the shallow Chuchki Plateau, the warm water in the Chuchki hasn't reached the 75N line.

CAB ice N of 80N will need to make a journey of at least 300km and perhaps over 600 km to reach warm water in the Chuchki.

It takes a lot of wind for a lot of days to push ice that far.

Currents from the Chukchi are pushing directly at the ice edge in the western Beaufort. More importantly I think, for the atmosphere 800km is not so far. Being ringed by warm SSTs will extend the melt season in the centre of the pack as the air above will struggle to cool. At the same time the warm water will likely feed storms

46
Arctic sea ice / Re: The 2019 melting season
« on: August 05, 2019, 04:54:54 AM »
GFS and EC are both forecasting another monster heatwave rolling over the Laptev sea pushed by a high on one flank, and another strong low advancing into the Kara sea, which also drives a large area of 20-30 knot winds pushing ice into the Barents sea. The Laptev bite will advance rapidly for a few days if it plays out.

The real action starts about 5 days out, so its still a bit far off.

A bunch of Pacific typhoons are forecast this week, hopefully none of them head our way next week

47
Arctic sea ice / Re: The 2019 melting season
« on: August 05, 2019, 03:46:02 AM »
Unfortunately Sentinel doesn't have coverage of the Arctic Ocean much beyond land (or above 82.8 degrees) with the partial exception of the CAB north of the CAA. I went out as far as I could to sea to find a recent clear image. I've included a gif comparing July28 and 31 at about 82.6, -119, showing the ice spreading a little in the interval, (and moving from top right towards bottom left)

click to play

48
Arctic sea ice / Re: The 2019 melting season
« on: August 05, 2019, 03:36:39 AM »
The crack, the persistent southerlies and the warmth released by descending air(foehn winds and high pressure ridges) are enough to explain the thinning on the Greenland/CAA edge of the basin, though warm water seems to be affecting NE Greenland, EC shows 2C water in part of the crack there, right at NE tip of Greenland..

I had a bit of a look on Sentinel.  I've attached a close up and wider view of ice in the Lincoln Sea, near the open water on its west shore, showing worn pebble shaped floes peppered with open water.

I also attached a couple of views centred on about 82.6,-102, about 100km NW of Axel Heiberg Island, also showing somewhat dispersed ice

Edit: The closeups are at Sentinels 500m resolution, I hadn't realised its screenshot tool left the scale out

49
Arctic sea ice / Re: The 2019 melting season
« on: August 02, 2019, 07:45:48 AM »
July 28 - August 1.

2018.

The pack continues to spread toward the encroaching melt edge. A lot of ice on death row, anything south of 80N on Eurasian and Pacific side, with areas to 85N soon to join it I think.

50
Arctic sea ice / Re: The 2019 melting season
« on: August 02, 2019, 07:19:52 AM »
If the Uni Bremen extent graph is to be believed 2012 has a lot of catching up to do, 2019 leads by a country mile. I'm not sure if its correct about this, but it goes with the map we follow.

JAXA extent losses have slowed over the past 2 days, but here 2019 still leads by 170000km2, up 10K  yesterday.

A few days slow down on extent or even the weird flatlining on area can't be read to signal anything definitive about the season or its ongoing momemtum - 2012 also went really slow about this time - at least on measures like extent, though Wipneus melt ratio graphs show a spike in melt at the same time, the prelude to the massive drop to follow with the GAC. I only hope Friv is right about the CAA and Atlantic front


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