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Messages - aslan

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Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 17, 2020, 11:25:02 PM »

(and you just have to change the WMO id : 20046 for Heiss, 20087 for Golommjannyj, 21432 for Kotel'Nyj, 20292 for Mys Tchelouskine -the best one, longest record and craziest anomalies !, etc...)

Currently I am already working on two differents ideas (not directly related to Arctic sea ice...) so I don't have time to work out on the anomalies on the Russian islands. But for sure something is happening... Also, question mark is the method for computing monthly mean. Pogodaiklimat uses the mean of the height three hourly synoptic time (00Z, 03Z, etc...) to my knowledge. Which can change a bit the end result, as others sites can compute from the mean of Tx and Tn, or mean of six hourly synoptic time (?). There is also some errors, at least for Pogodaiklimat. For example, early datas for Golommjannyj. Should be worth a look. But in the end, yeah something get totally broken in August, and it is still ongoing.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 17, 2020, 07:32:22 PM »
To be clear, because I am not sure I have state explicitly my point. I wanted to emphasize that an anomaly is not only stated by its absolute value. Deviation from normal is also a function of the normal spread. In winter in Arctic, an anomaly of 2-3°C is almost nothing while such an anomaly in the deep tropics could mean breaking a heat record. I did though that the heat could be more extreme than in 2016 for the Barents, but it was not fully the case. Heat is still extreme with some record (especially the 9.2°C reading of the Svalbard airport), but overall we are still within the boundary of the known climatology for this region in November. To the difference with August and September when anomalies expressed in absolute values were lower but were also way outside anything known.

P.S. : Or to put it more bluntly, in August and September, the red line was continuously way above the red dot at the top of the chart...

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 17, 2020, 06:50:42 PM »
19,5 °C positive anomaly yesterday on Golomyanny island

18,4°C positive anomaly on vize island
Thank you Positive retroaction.  Startling figures.  From my point of view, it would be great to know the absolute temperatures as well.

Yes, it's true
In golomany, yesterday had a minimum temperature of -3.5 ° C, an average temperature of -1.3 ° C and a maximum temperature of -0.9 ° C
On that day, November 17, the normal temperature was -21.5 ° C.

For the island of vize, the minimum temperature yesterday was -5.5 ° C
The average temperature was -0.3 ° C
The maximum 0.1 ° C
The normal average temperature is -18.7 ° C

More generally, anomalies between 9 and 11 degrees last for more than 1 month without stopping

To be fully exhaustive, August and September were more extreme than November as far as gap from the normal is considered. At Ostrov Vize, November 2020 is lagging a bit behind November 2016 for now, and no new record as been registered. Way above normal, but still within the (temporarily and for now...) known climatology. At Kotel'Nyj or Mys Tchelouskine there is a higher chance that November could be a record (especially Kotel'Nyj actually), but we are not fully at the same level of extreme than in 2016 overall. This said, winds are also in play. Even though no new wind record as been set to my knowledge, the Atlantic front has been battered for sure. Probably the most noteworthy is Ostrov Heiss with wind speed up to 30 m/s... The sea ice has been damaged, being highly fractured and locally reduced to a crumble of tiny floes :,-806019.2028485272,1669789.9532940923,39981.42069566273&p=arctic&t=2020-11-17-T02%3A00%3A00Z&l=Coastlines,AMSRU2_Sea_Ice_Concentration_12km(max=30),VIIRS_NOAA20_Brightness_Temp_BandI5_Night(palette=rainbow_2,min=227.6,max=277.2,squash=true),VIIRS_SNPP_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=227.6,max=277.2,squash=true),Reference_Labels(hidden),Reference_Features(hidden),VIIRS_NOAA20_CorrectedReflectance_TrueColor(hidden),VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 10, 2020, 10:34:17 PM »
So here's an image from Polarview, I think the AMSR2 Ice concentration from yesterday (9th Nov). Truthfully I don't know how accurate it is but if so how does everyone think the storm coming in that is due to hit exactly there in the next 48Hrs will have an effect ? According to Climate Reanalyzer it will drop to 967 running up the Greenland coast before having gusts up to 50mph. Earth null school  predicts waves 7m or so between Greenland and Svalbard though it does n't show what they are like nearer the Atlantic side ice edge. Which may not be as thick as could be if the AMSR2 is correct. Just throwing it in there. :@)

The Atlantic front will be hit hard for sure. Given the look it has, some massive melt and a big jump northward is even not out of question I fear. Perhaps I am a bit pessimistic, but forecast is looking grim I think. Models are predicting waves of 6 - 7 meters and periods of 10 - 12 seconds north of Svalbard on Thursaday, almost orthogonal to the ice edge. And the same in the Kara sea Friday and Saturday. With the heat advection (forecast are for a good 20mm of rain somewhere over the ice edge) and the wind, the Atlantic front will retreat for sure, but I fear that it could be more like a collapse than just a push to the North. We will see. Laptev is in for a good washing also, by the way. The sea is not closed and if the hole remain open, models are with values of up to 4m and 8 seconds on the 80th North directed against the ice edge...

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 10, 2020, 10:22:51 PM »
Er... I still don't know how to make it an other way.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 10, 2020, 10:21:34 PM »
It would be better to see also the 18GHZ and 37GHz but I don't know if there is an easy way to vizualise this data.<>
JAXA RGB uses 36H, 36V and 18V, nov1-9 shown split into the 3 component greyscale images.

Yep, so I decide to take my courage with my hands my two, and to look at the 37 GHz and 18 Ghz polarization. It is for the pass of the 08th of November, at 03 UTC something more or less. There is the horizontal 37 GHz (TB37H), the vertical 37 GHz (TB37V) and the horizontal 18 GHz. And there is the TB37V + TB37H and TB37V - TB37H. Usually, the ratio PR37 = (TB37V + TB37H) / (TB37V - TB37H). Again I'm not sure how JAXA put all of this in the mixer, but usually PR37 is between 0.05 and 0.01 for sea ice. And ice thickness increase with a lower PR37 (at ~0.05 more or less some decimals, we are at about ~20 cms of ice thickness, upper end of the detection). As uniquorn said, they probably also put the 18GHz in the mixer, as there is the TB37V, TB37H and TB18H on their website. With some specious algorithm, and a good deal of luke, we could probably emulate something.
This said.
Actually, there is really something on the 37 GHz, with TB37H being quite low for such a TB37V where JAXA thickness is showing open water. In any case TB37V is way higher than TB37H for water. But here we really have something looking a bit like open water with low TB37H and high TB37V. This leads to a high sum of TB (TB37V+TB37H) and a high difference (TB37V-TB37H). PR37 is the ratio of the two. North of the Svernaïa Zemlaïa, the ratio is something like 40K/450K which is almsot 0.1 while in Laptev the ratio is more like 10K/510K which is about 0.02. The PR37 of 0.1 is way outside of anything known about the ice thickness, so no suprise the algorithm go down to total meltdown... And so the ratio PR37 going trough the sky is exactly where JAXA has a hole. At least, we have the good thread in the hand...
Problem is, physically, I can't conceive that it is not a signal of really liquid water, like, I mean, liquid water. But in the same time, face values of TB37H and TB37V are good for the sea ice.

I have taken the 8th of November because it is a cloud free day and the IR channel allow use to spike at the surface:,358462.0295864898,905260.1729350943,702610.7856657819&p=arctic&t=2020-11-08-T02%3A00%3A00Z&l=Coastlines,AMSRU2_Sea_Ice_Concentration_12km(max=30),VIIRS_SNPP_Brightness_Temp_BandI5_Night(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_SNPP_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_NOAA20_Brightness_Temp_BandI5_Night(palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_NOAA20_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),AMSRU2_Sea_Ice_Brightness_Temp_89V(hidden),AMSRU2_Sea_Ice_Brightness_Temp_89H(hidden),Reference_Labels(hidden),Reference_Features(hidden),VIIRS_NOAA20_CorrectedReflectance_TrueColor(hidden),VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor

What I find curious is that this high PR is in connection with high IR temperatures. For the 1st and 2nd of November for example, where we can also see a highly fractured ice and open leads, IR temperatures are lower :,130120.98769930608,1046101.2498590265,511402.9195286478&p=arctic&t=2020-11-01-T10%3A00%3A00Z&l=Coastlines,AMSRU2_Sea_Ice_Concentration_12km(max=30),VIIRS_SNPP_Brightness_Temp_BandI5_Night(palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_SNPP_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_NOAA20_Brightness_Temp_BandI5_Night(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_NOAA20_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),AMSRU2_Sea_Ice_Brightness_Temp_89V(hidden),AMSRU2_Sea_Ice_Brightness_Temp_89H(hidden),Reference_Labels(hidden),Reference_Features(hidden),VIIRS_NOAA20_CorrectedReflectance_TrueColor(hidden),VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,-49112.767427918385,1270724.6748952155,436862.52663525497&p=arctic&t=2020-11-02-T10%3A00%3A00Z&l=Coastlines,AMSRU2_Sea_Ice_Concentration_12km(max=30),VIIRS_SNPP_Brightness_Temp_BandI5_Night(palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_SNPP_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_NOAA20_Brightness_Temp_BandI5_Night(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_NOAA20_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),AMSRU2_Sea_Ice_Brightness_Temp_89V(hidden),AMSRU2_Sea_Ice_Brightness_Temp_89H(hidden),Reference_Labels(hidden),Reference_Features(hidden),VIIRS_NOAA20_CorrectedReflectance_TrueColor(hidden),VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor

Excepted where JAXA is showing a melt fraction (in the buldge toward the Zemlya Frantza Yosifa), IR temp are lower.
I am not sure what to make of all of this. It is curious for sure. But overall, if the channel 37 GHz is reacting like there is liquid water, I can't think how this could not be the case.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 10, 2020, 02:34:02 PM »
I think Vince O means this, in the image he uploaded.
However I think it's an artifact that can be ignored, as it does not seem to appear in the other products posted here.
amsr2 shows lower concentration ice in the same area yesterday with some persistence over the last 3 days further east. It looks like the wet ice we see during the melting season but it has been too cold for that. Perhaps some fog related event from opening leads.
Brightness temperature bands are interesting to explore during winter night.
3 are shown below (click). The link provides 4 of them already set up.

It would be better to see also the 18GHZ and 37GHz but I don't know if there is an easy way to vizualise this data. To my knowledge, ice thickness is retrieved from ratio of polarisation for the band 37 GHz and 19 Ghz, perhaps others channels in the same vicinity (6, 7, 23 GHz). This is, while sea ice concentration is retrieved from the 89 Ghz band. I agree this is still worth a closer look, even though it is not really open ocean. I am wondering what the AMSR2 is seeing in the 37 GHz chanel... This said, ice thickness can't be calculated from brightness temperatures if the value is less than ~0.2m. Usually, this lead the algorithm to calculate a "melt fraction", which is not always very pertinent. It is thus likely that either way, the ice thickness is probably quite low, pushing the algorithm to the edge. With possible other effects like the open leads, the ocean being not so cold, etc... This can be an explanation.

Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: November 10, 2020, 12:55:39 PM »
Due to server maintenance, Arctic Data Archive System (ADS) was unable to access website from Nov. 10th 9:30 to 17:30 JST , 2020. We are sorry for the inconvenience this may cause.

Answer is 8.13 km², an increase of 0.17 millions km², second lowest and 0.16 millions km² above 2016.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 10, 2020, 07:10:53 AM »
Guys could we please end this off-topic for this thread?
Oren, Gandul, JD, Aslan, etc. please let's keep the focus on the 2020 freezing season.
Gandul, you couldn't shup up could you? Valuable contrubutors are leaveing the thread, again.

Yes, even more as there is things to discuss. The weather is going to be extremely moist, mild and windy in the coming days. As grixm said, extent stall or even decline is likely. It is even more interessting because, by chance, the same happened at about this time of year in 2016. We will see the difference between the two years. In 2016, Arctic as a whole was warmer, but in 2020 the push is going to be stronger with a deeper low and a stronger heat advection. And even though extent does not stall, massive retreat of the Atlantic front from Svalbard to Svernaïa Zemlaïa is highly likely. Which is in the continuity with preceding posts, by the way, as the Atlantic front is already quite vulnerable... As uniquorn said, brightness temperature are usefull in winter, and the picture is not reassuring :,-475019.84206839127,2043200.5753692852,865155.2205587052&p=arctic&l=Reference_Features,AMSRU2_Sea_Ice_Brightness_Temp_89V(hidden),AMSRU2_Sea_Ice_Brightness_Temp_89H,Reference_Labels(hidden),Coastlines,VIIRS_NOAA20_CorrectedReflectance_TrueColor(hidden),VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor

It will be to seen also what happen to the Laptev hole, and to follow the heat records for the Russian islands...

P.S. : Sea state (colored arrows), winds at 10m (20kt threshold), sea level pressure, and isotherm -5°C at 850 hPa, for one weather model at 12Z Friday, from 00Z his morning.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 07, 2020, 10:36:17 PM »
And weather forecast is not encouraging. Likely not as worst as mid November 2016 (second picture), but still quite bad with a strong low and a massive heat advection.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 07, 2020, 09:56:09 PM »

Multiyear? So what happened in 2016 and in 2017. The Atlantification of the Laptev took a break??

I remember well both springs. 2016 was warm everywhere, but the Laptev coast melting suffered a delay due to the fact that a lot of ice drift streamlines had been converging during winter/spring toward ESS and Laptev, and the transpolar had been disrupted that winter not inducing as much peel-off on the Laptev coasts, leading to a high Laptev ice volume.

In 2017 spring simply started a few weeks late especially in Eurasia due to the high snow cover volume and late thaw. The whole summer was relatively cold.

I bet the relentless reduction of ice in Laptev can be explained by atmospheric climate change without having to resort to the obscure hypotheses of Atlantic Water effects. Global warming effects on oceans is slow and often counterintuitive. Reserves for heat are enormous given the dimensions and the heat capacity. Characteristic times of change are of the order of hundred years.

Granted, it is more entertaining and novel-esque to focus the attention on impossible to verify heat sources and impossible to measure methane time-bombs. To each their own.

Troll is for someone flooding the forum with the same argument over and over, ignoring the contributions of the others members.
Multi year does NOT mean it is monotonically worst year after year, but that it is a trend. The year 2012 was worst than the year 2007, the year 2016 was worst than the year 2012, and the year 2020 is worst than the year 2016. Perhaps 2021 will be even worst, perhaps not, who know. But only for you does a trend mean each year being monotonically and significantly worst than the preceding year.
And again, at some point which is now probably really not that far away, the trend will overwhelmed the Arctic and tip the Kara sea to a perenially open sea (and the Laptev and Chuckchi are next in line).
In your document, salinity is described as being in the range 22 to 32 PSU at surface, reaching 33 to 34.5 PSU at one hundred meters (100 meters). Just read...

The temperature and salinity fields show large gradients between the mixing zones of river and sea water and the uniform thermohaline structure of the northern Laptev Sea. In the wintertime, due to a sharp decrease in runoff, increase in ice cover, and decrease in convection processes, the thermohaline structure is relatively homogenous. The water temperature varies from -1.4° in the eastern sea, up to -0.8° in the northwestern sea. The water salinity in the southwestern sea has values of 22-24 0/00, smoothly increasing northward and to the northwest up to 32-34 0/00. Figure 7 shows the vertical temperature and salinity profiles for the western, southeastern, and northern regions of the Laptev Sea in the summertime. In summer the southwestern upper 15 meter layer is warmed to a temperature of 5 ° - 7° . In the southeastern part, temperatures increase to 1° and remain about -1° in the northern areas. In winter a vertical temperature and salinity distribution in the shallow area is quite uniform, the salinity weakly increasing with depth and the temperature being within -0.5° - 1.9° C, depending on the region. In the deep northern Laptev Sea a temperature maximum is observed at a level of 100-400 m, the salinity dramatically increases from the surface to a 100 m level from 29 to 33-34.5 0/00 and changes little at greater depths.

This year, we are speaking of salinity significantly above 34 PSU, nearing 34.5 PSU if we trust MERCATOR, at surface, in winter, in Laptev. Not at a depth of 100 or 800 meters, at surface.
And you don't answer the question, why then the ice boundary is set northward of 81 - 82°N or something like this, from Svalbard to Severnaïa Zemlaïa, if this is just some direct consequence of huge inertia from the Spring heat wave over Siberia (and by the way why there is still probably some bottom melt ongoing there, to be exhaustive).

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 07, 2020, 12:42:57 PM »
In the end, could you please stop trolling this forum... Yes, record warmth during the Spring leads to an early break up of the sea ice. A lot of heat has been absorbed by Siberian seas. But, no, this is not just one fluke explaining everything! For one part this is taking place in the general trend of the global warming. And the salinity anomaly, the persistence of the heat anomaly up to now, the fact that the southern Chukchi sea is in an even worst shape, the Atlantic front being fixed north of Svalbard and Severnaya Zemlya etc... All of this is not a direct consequence of a large build up of heat in the Siberian seas in the Spring and Summer.  And yes, this will have long lasting consequences. For example, Ostrov Kotel'Nyj mean temperature is currently (as of the 7th included) a f*****g 7.3°C above the previous record for November (-7.7°C as of the 7th vs -15°C for the whole month of November 2012). Even though the temperatures turn back to average, a new record is virtually certain (small detail, but the SYNOP are still coding CBs at this time of year, which is even more extraordinary). Even more extraordinary is the heat record for Cape Tchelouskyne. Freezing degree days are near the record low level of 2016 for the whole Arctic bassin, and as the sea ice is slow to build up, this means that a weak and vulnerable first year ice next Spring is already locked in. This does not mean that there will be a catastrophe next Spring. Only that this increase greatly the probability of such a catastrophe, even with a more average Spring.
Things are not as simple as : some heat wave happening by chance in Spring -> oh a warm Autumn ! -> Yeah but evrything will ease back to average this Winter, we are fine for the next Spring.

P.S. : If Mercator bulletin is of any usefulness, Laptev salinity is around 34 PSU from top to bottom, and it remains to prove that a heat wave can lead to such a salinity anomaly...

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 30, 2020, 10:40:08 AM »
P.S. : About this subject also, CBs -and confirmed by satellites- and snow shower under CB at Kotel'Nyj and Vrangel, wich at this time of year is rare (especially as it is the same kind of weather since 3 days with continous reports of CB...):

No thunderstorm but it was not far away... (models were also hiting at this possibility).

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 30, 2020, 10:08:24 AM »

I haven't counted them.  oct29
If the quote above is correct then the inversion layer is pretty low.

Not a lot of time again, sorry, but if models are of any usefulness. From North to South, following more or less the flow : 83.30°N 138.30°E at 03Z the 29th ; 81.00°N 144.00°E at 03Z the 29th ; 77.00°N 145.00°E at 06Z the 29th and same hour 74.30°N 146.00°E

Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: October 28, 2020, 09:30:24 AM »
NSIDC Extent graphs - compare and contrast the Beaufort with the Laptev and the ESS

We can also look at it from the standpoint of a specific day to see the crash. Here it is the sum of Laptev, East Siberian and Kara seas 5 day mean of sea cie extent from NSIDC.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 26, 2020, 04:52:35 PM »
Last sounding

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 26, 2020, 04:47:55 PM »
Quick and dirty sorry, but about the storm of tomorrow, to illustrate again. Map is wind speed (orange and yellow) at 500m (about 925 hPa), wind at same height (I hope...), theta (potential temperature) in black, surface temperature at -2°C in blue for an approximate ice edge, vertical velocity at 925 hPa (max threshold at -10 Pa/s) in gray and convective rainfall in transparence. And when I say convective rainfall, yeah I really meant that models are forecasting CBs all over the Arctic in the coming day. Next step, a subtropical storm in the Arctic.... This said. If we follow the wind, we hit a wall of theta which is the inversion over sea ice. There is surface based CAPE north to Kotel'Nyj (For central Arctic in late October, this qualify as a "holy mother of Einstein, what the f*** is going on" level on the crazyometer). This layer of unstable air is forced to rise over the ridge of theta, bringing mid level CBs over ice pack. We are swimming in a pool of craziness. This advection can be followed on soundings as the theta at the top of the inversion is the same that theta at surface north of Kotel'Nyj. We really have an isentropic lift forced by the temperature inversion over the pack, forcing ascents and instability... And on top of that, we can see that LLJ can't descend to surface over ice pack.
Soundings are from south to north (77°N, 81°N, 82°N)
Of course there is also and mostly synoptic scale forcings, etc... but there is really some things going on at the interface between sea ice and ocean, and we are to the point we need a good swath of CBs to cool down the Arctic Ocean. On top of that, in the Arctic night, CBs are powerfull at isolating the surface, radiating a lot of heat toward he surface in longwave (and sea ice is not white in IR...)

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 26, 2020, 03:28:54 PM »
This is Arctic. Even though on its own a wave period of 10 seconds is not extraordinary (in the Pacific, period of 20 seconds are possible...), it is not the way it must work. For the depth of the mixing, I don't know and I am not sure there can be an answer. It depends on different factors, and especially the stratification of ocean. During the storm of 2012, mixing occurs over a depth of about 10 to 30 meters : And during a storm in October 2015, it was about the same idea :
But it is really hard to give some numbers. It depends a lot on the stratification of the ocean. Either way, even though it does not sound a lot, wave period of 10 seconds and mixing depth of 30 meters are really significant in the Arctic.

P.S. : Worth to read also :

(but there is also the question of the reduced stratification of the atmosphere which should promote higher wind speed at surface, no matter the change in the pressure field. I am not aware of anay studies about this subject)

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 26, 2020, 10:29:55 AM »
Big waves are again forecasted for the siberian side. Strong winds are usual at this time of the year, but the fetch should be zero or almost zero. Here, winds are blowing over open water. As a consequences, waves of 4 - 6 meters with a period of 8 - 10 seconds for Chukchi and Kara sea... A good washing again.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 26, 2020, 08:22:03 AM »
Temperature on Kotelny Island finally falls below -10°C. Winter is coming.

Not wanting to sound disparaging, but -10°C at Kotel'nyj at this time of year is barely the normal high, and temperatures are already back to -2°C :

Of course it is cooling. Even with all the warming possible, October is bound to be a month of rapid decline of the temperatures in  the NH. But anomalies are still extreme and the seasonal cooling not so strong. Even though we are not going to see a repeat of the month of Septemebr, with monthly mean temperatures higher than the preceding records by many °C over millions of square kms ; October is still going to book new records. As of now for exemple, mean temp' at Kotel'Nyj is -2.8°C and the record is -3.2°C in 2018. We will need more than one or two "mornings"(ok, Tn  ;D ) at -10°C for not breaking the record.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 23, 2020, 03:18:35 PM »
Mercator's take on SST's.
amsr2, awi dev v103 overlaid onto mercator 0m ocean temperature, sep4-oct22  (7MB)
Ok, from your animation is it correct to say all the regions susceptible to warming from Atlantic Waters are already covered by ice or about to be covered? (exception Barents and Kara but we know those two seas are already lost to climate change)
It seems to me the anomalously warm Laptev and ESS areas are basically over the shallow shelf, which will have a record heat release (consistent with the record heat income from GAAC and the season in general). So no Atlantic warmth here to speak about.

The Laptev sea extent beyond the shelf (and so the heat anomaly, by the way). Intrusion of Atlantic waters are discernible on the salinity maps of the mercator. (P.S. : And acknoledging that the heat and salinity extent beyond the Laptev into the central bassin, even under the sea ice).

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 23, 2020, 03:15:23 PM »

Have you seen the snow extent growth over Siberia and Western Canada? Anything to comment or you only rejoice on the bad feedbacks?

Apart from this, the weather is about to become propitious for a quick rebound of sea ice next week.

Speaking of a great peril does not sound too much like being merry and joyfull... And for the snow extent, it is no news that late Autumn snow extent is not showing a significant decrease lately. It is even more the case this year. But this fact has not prevented ongoing anomalous warmth up to now. Which is still this case this year, as temperatures are still above normal overall in Siberia, no matter the snow extent. And for the quick rebound in ice extent we will see.

Can that be set for a narrower palette gamut (called squeeze at WorldView vs outlier clamp at CMEMS)? The bins are too large to resolve temperatures in the -2 to 0 and 0 to 2 ranges on the last frame of Nov 7th. The shoreline color seems off, not clear what temperature it is. Overall it does not seem that unreasonable: very little advance in the ice pack but with the stage still not set for rapid closure with so much open water between 0 to 2ºC.

There is also the SSTs from the coral watch of the NESDIS :

Same picture, Laptev and even more Chukchi sea are not going to freeze tomorow...

Top level directory of the files are here :

And the direct link for this year :

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 23, 2020, 08:41:20 AM »
What I am trying to bring up is that extent by itself is only an indication of when ice thickening can possibly begin, and with the current extreme delay in the Asian sea ice extent, the ice growth in thickness is being delayed. While historically some areas of the Asian seas have had slow growth in extent, 2020 is the first year on record (as far as I know) that will likely still have an ice free NE passage on Nov 1. (And not just dodging ice, but wide a open sea lane.) The fear is that if this continues much longer even with eventual universal 100% extent on the Asian side, that first year ice will not have a chance for a 'normal' gain in thickness. Instead of >1M ice, much of the Asian sea ice could end the freezing season in a very fragile state leading to much earlier breakup and melt in 2021. Already basically the whole of the Asian side has lost a month of thickness growth, where in previous years a fairly large percentage of those seas had already started that growth.

It is a rough estimate, but if you use the correlation of Freezing Degrees Day (FDD) with ice thickness, you need ~5500 FDD to go to 2m first year ice, and ~3500 FDD to go to 1.5 meters. October is usually worth ~300 to ~400 FDD in the Arctic, so it can make a significant dent into the ice growth.
To give some more numbers, for Ostrov kotel'nyj for example. Mean temperature from 1st of October to 30th of April over the last 10 years (2010-2019) was -20.8°C, which is about 4400 - 4500 FDD. If you count from the 1st of November, this leads to 4100 - 4200 FDD. And if you ignore November and start the ice thickening the 1st of December, it makes only 3800 - 3900 FDD. This is ignoring the risk that oceanic heat flux could be strong enough this winter to weaken this correlation. If ice growth does not start in a hurry on the Siberian side, the winter would probably not be able to fully erase the memory of this melting season. Which is a great peril, as up to the last years, winter was always cold and long enough to at least bring Arctic back to some kind of a "2m FYI" state, helping to stabilize the system.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 21, 2020, 06:39:45 PM »
After the storm of this mid October I was also wondering myself what are the consequences of the open water on synoptic forcings for ascent. As a remainder, vertical velocity are stronger for a same forcing with lower static stability. I don't know if there is studies about this subject, or if it is a significant effect, but it is an open question for me. This is probably linked to the displacement of the eddy driven jet, but I am not aware of any study really looking specifically at the consequences of this reduced static stability. This is also leading to higher wind speed at surface, as seen with the last storm. On top of that, strong inversion over ice pack, and now over the continent, is on juxtaposition of this low static stability, leading to increased baroclinic instability. But what is the magnitude of this effect ? I am really clueless. To illustrate, I have compute a crude static stability parameter, by subtracting potential temperature at 700 hPa and at 950 hPa, normalized by the thickness 700 - 950 hPa. All of this multiplied by 10 to better seen what is going on. Below 0, the atmosphere is superadiabatic, and everything above is subadiabatic. Over mountains (like, said, the Rockies...), results are of course useless, as the model interpolate trough the terrain. Maps are for, in order, the 21st to the 24th at 00Z. Didn't try to average trough time, the computer would probably have hoist the white flag before the end... We can see a persistent area of low stability over the Siberian seas.

Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: October 21, 2020, 06:47:10 AM »

Almost half a million km2 less than 2019 and more than a million km2 less versus 2012, 2016 and 2007!  :o

This said, in 2007 at this time of the year, we were about 1.0 to 1.5 millions km² below the previous daily record, 2005 (something like 6 to 6.5 millions km² in 2007 versus 7.5 to 8 millions km² in 2005).

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 19, 2020, 03:59:11 PM »
For what is worth (not much, admittedly), but the surface analysis of GFS (the GDAS) did not show a significant drop for SST during the week-end. The image is the difference of surface temperature (sea or land) between the 19 at 00Z and the 15 at 00Z. Over land, there is definitively nothing to analysis. However, for SST, even though not too much weight has to be given, it is still showing something. Surface analysis even show some patches of more than 1°C rise in SST. But what all this show is that the storm did not lead to a massive drop in SST.

P.S. : Better image this way

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 15, 2020, 05:41:55 PM »
I think it is worth remembering we are living on Earth not Mars... We have a layer of gas above ours heads which is not transparent to IR. Even in the old, dark, dry Arctic of the past it was impossible to radiate an infinite amount of heat to space. There is always an upper limit. A temperature inversion in the low layer, even in Siberia in the 1880s could not have been greater to ~ -25°C. At some point, even in an absolutely dark and dry Arctic a point of equilibrium will be reached. And on top of that amount of heat lost to space is not primarily a function of the temperature at surface, it is not the case, definitively. The temperature at surface is not totally decorrelated from the heat lost to space of course. But there is an atmosphere above surface, in the end. It is Earth here, not Mars... Heat has to go trough the atmosphere before, and there is on the road CO2, CH4, H2O in every states possible, etc... And now that Arctic is providing a lot of heat and moisture, we are seeing a new state where there is a layer of clouds and moisture in the low layers which is isolating the surface, with temperature between 0 and -5°C at 2 meters versus -20°C to -30°C at 2 meters in the case there is no clouds.
Holy mother of Einstein, it is Earth here, not Mars !
The picture which follows is the forecast for Saturday for a given model. It is the minimum for the temperature of brilliance in infrared (10.8 microns) for the all day. Scale is from blue for the warmest (~0°C) to white (~ -40°C) going trough the brown / beige / I don't know which color (-10°C to -20°C). There is also the isolign for the surface temperature of -2°C to roughly approximate the edge of sea ice (more or less, we all see what the shape of sea ice currently). Over Beaufort, yes we are radiating at 0°C (blue color) and we are losing heat to space. But over Chukchi, ESS, Laptev, Kara, Barents, we have a layer of clouds as thick as the troposphere. And the temperature of brilliance is -20°C to -40°C. The temperature of brilliance is more directly correlated to heat lost to space than surface temperature. This really means, this really means, that during the storm, we are not going to radiate heat toward space at ~0°C from the ocean. We are going to radiate heat at -20°C or -30°C or -40°C. And there is a factor 1.5 to 2 between the radiation from a black body at 0°C and a black body at -30°C or something. The heat stirred by the storm is heat at ~0°C, the heat lost to space is heat at -30°C, and there is a ratio of 1.5 to 2 between the two... I made the same map but with the mean of the IR temperature from Friday to Thurday. The ice sheet is high and dry, radiating at -30°C and isolating the ocean at 0°C below. The Beaufort is, yes, a good heat sink fully radiating toward space. But for the siberian side, the clouds are here as the ice sheet, isolating the surface below. Even with a mean over 5 days, almost all the siberian side is forecasted to be isolated.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 15, 2020, 03:41:17 PM »
There's always been enough incoming heat to melt all the ice, the issue has been meager re-distribution by double diffusion staircases prior to export back out the Fram. However the downward trend in sea ice has brought a change-over from atmospheric to marine dominance of the energy balance.

As the buoyancy gradient (thermohalocline) begins dissipating from more shear and turbulence attributable to more open water resulting from sea ice decline, the heat brought nearer to the surface just leads to more sea ice decline, a runaway positive feedback that the authors see as immune to climate change mitigation efforts.

Not sure how that works.

Let's take this weekend as example. Strong winds are going to pull some (or a lot) of heat excess to the open ocean surface, which is continuously going to be released to the atmosphere (much colder than the ocean surface) and to the space. It is not going to lead to more sea ice decline, since in the following days darkness is an almost infinite sink of heat excess until next Spring. So this weekend is going to lead to less heat stored beneath.

Where in the preceding paragraph am I wrong?

The Arctic in winter is not an infinite heat sink. Definitively NOT. There is a thing names moisture and another names cloud which is in play,

and there is also the fact that heat builds up in summmer in Arctic, and the heat transported from the tropics - a region where the bilan is strongly positive - etc. Arctic in winter is not an infinite heat sink. And never was one by the way. It is not a proof, but just look at the correlation between Nh and T at Ostrov Vize here for example :

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 15, 2020, 10:50:59 AM »
This is the second mentioning of "shoaling" in recent days, see also A-Teams post above:

Weakening of Cold Halocline Layer Exposes Sea Ice to Oceanic Heat in the Eastern Arctic Ocean
IV Polyakov, T Rippeth et al
J. Climate (2020) 33 (18): 8107–8123. free full

"The upward release of AW heat is regulated by the stability of the overlying halocline, which we show has weakened substantially in recent years. Shoaling of the AW has also contributed ...

I understand shoaling to mean what happens to waves as the approach shallower water (shoals) . According to Wikipedia shoaling happens when depth is less than half the wavelength.

Other meanings are "becoming shallower" and also when aquatic organisms group together (e.g. a shoal of herring).

So how does that fint into the bigger picture of an open ocean as Aslan seems to talk about, and what is meant by a phrase like "shoaling of the Atlantic Waters" as in the paper quoted by A-Team?

Err I am not really good at speaking english. AW are below the halocline. With waves, mixing weakens the halocline and allow heat transfer from the AW. For me shoaling means that AW are "less deep" and nearer to surface, with increased heat flux.

For the baroclinicity, I have added the vorticity (blue, positive, and red negative) and T'w in black. We can see that near the surface, the strong inversion is associated with the gradient in wind speed. This also creates shear and then vorticity. We have, as usual, shear zone and vorticity to the left and right to the LLJ, but near the surface there is also vorticity associated with the shear zone at the interface between sea ice and open ocean. But the max of vorticity over sea ice in the lowest 500 meters is really linked to the interface between sea ice and open ocean, it is not linked to the shear due to the deceleration of wind speed.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 15, 2020, 09:57:15 AM »
This means a stronger broclinic zone, with more clouds and moisture keeping the Arctic warm, and it means a weaker halocline with more mixing and shoaling of the Atlantic waters. By the way, even though the anomalies of temperatures are less extreme, the islands of the russian arctic are still running for the hottest month of October in record from the Barents to the East Siberian sea :

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 15, 2020, 09:09:55 AM »
On top of all the retroaction already described, there is also the fact that an open ocean generate less friction, and the lack of an inversion increase even more the wind speed at surface. This is visible for the storm of Friday and Saturday. The low level jet brings stronger winds at surface over open ocean than sea ice. The cross section is from south to north, trough the low level jet for Saturday at 12Z. Higher wind speed reached the surface open ocean.

P.S. ; One important point... For the map, it is wind speed at 500m, not surface. There is two LLJs, one over sea ice and one over open ocean, but strong winds at 10m are only found over open ocean.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 09, 2020, 08:16:46 PM »
It’s not that it is good. It is that there are physical reasons (Stefan-Boltzmann Law) to expect that the more energy you make available now, the more energy will radiate out to space during the NH night.

It's you who are confusing the whole thing. Plank feedback (function of T^4) is well known but others feedback also: lapse rate, water vapor, clouds, etc. Overall, climate sensitivity is 3 degres to doubling co2. Nothing new. With your reasoning, more co2 would mean a cooling earth. Open arctic in winter is stable state. Point in case: barents and bering sea, kara sea in 2012 and 2016, likely laptev sea winter 2021. You are pushing this topic off road with unbased statement. Open arctic in winter is definitively not a giant radiator cooling down the earth. It is a stable system from an energy POV.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 08, 2020, 02:41:55 PM »
Yes, Arctic was ice free many times in the geological time. It is true that loosing ice cover in winter would in theory implies a massive heat loss by longwave radiation to space, but things are not as simple as "If I pull out your blanket, you are going to freeze to death.". And there is over factors at play. This discussion will lead us off topic if we continue, but an ice free Arctic means also a complete reorganization of the atmospheric and oceanic circulation.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 08, 2020, 02:25:37 PM »
This article pretty much ignore clouds or overall atmospheric circulation, or anything else, and is just saying that if you remove sea ice, a lot, lot, lot of energy will be radiated to space in winter. Yes of course, nothing new. But it is likely that things will not proceed as linearly. Studies and measures are showing that it seems likely that open water during fall and winter is going to destabilize the PBL. Implying more clouds and moisture, which is going to limit the amount of heat lost to space. And atmospheric circulation, and oceanic circulation, and etc... are also going to respond to an ice free Arctic and establish a new equilibrium which is definitively not going to be the same that "all else equal excepted for sea ice".

Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: October 08, 2020, 01:33:38 PM »

Both the ESS and the Laptev sea ice extent are at record lows. Perhaps of the greatest interest, given the high heat content of the sea, will be how long before the Laptev re-freeze happens, and how quickly.

Small quibble, but in 2007 ESS area and extent was even lower. And this metric bottoms out lately, the 3rd of October. But we are not far away (25 000 km² for area, not zero but almost) and still loosing ice. But overall, the Russian side (ESS + Laptev + Kara + Barents) is at a record low, and still loosing ice, which is pretty impressive.

P.S. : Graphs made in a hurry... (and, it is the same idea with extent by the way)

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 06, 2020, 06:15:49 PM »
aslan you're right these are truly amazing spikes. There is no denying that the Arctic is changing much faster than we expected.

It could also be noted that mean wind speed was a bit above average for this corner of Arctic in September. Excepted for Ostrov Heiss, which was near average with mean wind speed of 5.8 m/s, normal 6.0 m/s. For Ostrov Vize, 7 m/s versus 6.5 m/s, for Ostrov Golomyanyj it was 7.25 m/s for a normal of 5.7 m/s, for cape Chelyuskin 6.4 m/s versus 5.8 m/s, etc. It is not particulary noteworthy. But given the magnitude of the anomlies for latent and sensible heat, this is not helping at all. The amount of heat mixed during this month of Septemebr is crazy.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 06, 2020, 12:41:40 PM »
To illustrate, a set of graph for the period August - Septemeber. Record for Gmo Im. E. K. Federova, breaking its record by 2.2°C (cap Tcheliouskine),or 3.5 sigma above the most recent 30 years mean... And there is ~ 1500 km between Heiss (Polargmo or wmo 20046) and Hatanga (20891), which squared is ~ 2 millions km²

Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 06, 2020, 11:59:06 AM »
Not sure if this is autocorrelated with the current low extent but the temperature anomaly forecast in the arctic and especially siberian seas is extreme, hovering around +15C.
Keep in mind the image below is the forecasted 10-day average. Usually you'd see quite low anomalies on such a map because such long term forecasts tend to go up and down and thus even out the average. But now the forecast just stays red hot in the ESS and Laptev for the entire 10-day period without pause.
Laptev-ESS seas venting out their energy excess?

I would expect an acceleration of refreezing around the pack this week in view of Freegrass animations, but it is difficult to say.

I doubt it. There is still a massive amount of oceanic heat and it is still looking like the halocline has taken a hit. And massive heat wave is still ongoing, no matter the temperature at 850 hPa. And this is not only a matter of absolute magnitude of the anomaly. October is probably going to be less extreme than September from a certain point of view. I mean, in term of deviation to the norm, the month of September was probably the most extreme month ever recorded anywhere on earth, no exaggeration. Ostrov Golomyanyj (data since the 30s...) has broken its monthly mean temperature by 3.3°C ! Ostrov Vize by 1.6°C after breaking the monthly record of august by 2.3. Same idea for Kotel'nyj, Izvestij Tsik, Dikson, Heiss (Polargmo), Hatanga etc... As an illustration, September mean temperature for Ostrov Kotel'nyj (WMO 21432). I have never heard of a heat wave so extreme over a two month period, and this is over an area of 2 millions of km² or something like that. Even though October will be extremely warm, such deviation is not likely in October (hopefully…). But in any case, there is really something ongoing on the Atlantic side. It will take more than a week of seasonal cooling for resorbing these anomalies.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: September 25, 2020, 09:26:00 AM »
Well. With Mosaic basically proving that the best piece of ice in the best position on the Atlantic side of the Lomonosov ridge LOST thickness on its entire transit from October to may, from 7m to 5m, through constant bottom melt, and never froze it's soggy core. And now that they can cruise at open water efficiency, from laptev to Fram north of 86 latitude, and never register any fresh freezable layer...
 There appears to be no such thing as a Arctic sea ice freezing season anymore in this half of the Arctic basin.
Therefore I suggest a poll to rename this forum the SiAlCa sea ice forum. Hopefully there will be a few years while those elements hydrated minerals can still stay cold enough to remain solid on those sectors polar seas. Unlike Venus.
Wry and somewhat twisted that this bad half joke may sound.

On the Atlantic side, it is looking like that the halocline has taken a serious hit. And the weather is totaly nuts on the russian islands. As of the 24th, the record of the most crazy anomaly is probably for Ostrov Golomnjannyj. The current mean temperature, 4.7°C, is 4° (!) above the old record of 2012, and even 2°C above the warmest month ever recorded, August 1932. Every day have broken their daily record, 15 days had a Tx above the old monthly record, and even one Tn was above the monthly record of Tx... And all of this with 71 mm of rain (and I mean, really rain, liquid water at 5°C), wich is more than three time the normal monthly precipitation amount. From Ostrov Heiss to Ostrov Kotel'Nyj, crossing Khatanga and Ostrov Vize, mean monthly temperature are going to be 2 to 4°C above previous record, and going to be more than 3 sigma above normal. Seing such and anomaly over such an area (we are speaking of something like more than 2 millions of km² or 0.5% of Earth surface) for a monthly mean is unprecedent.

Arctic sea ice / Re: The 2020 melting season
« on: September 17, 2020, 09:42:24 PM »
It's not just a SST thing in the Barents, Kara and Laptev seas. The heat goes town to 30m or more. Compare the 30 m Arctic temperatures of this year with 2019 on Mercator ocean and you will see that there's much more ocean heat on the Atlantic side this year than last. On the other hand, there's less heat on the Pacific side. Over both sides, there's much more heat this year, but there is almost always a see saw effect in the Arctic between the Atlantic and Pacific.

It is too bad we don't have buoy. With melt still ongoing noth of 85°N it is looking like that the halocline has taken a hit and Atlantic layer is pushing upward. Salinity at surface is higher than in 2019 also, implying a reduced stability. The high salinity is also to be compared to the high freshwater input this year.

Arctic sea ice / Re: The 2020 melting season
« on: September 15, 2020, 08:39:22 AM »
As a testimony of the disruption ongoing on the Atlantic front, the extraordinary heatwave is still ongoing for the Russian islands of the Barents and Kara. For weather stations with such a long record, this is crazy. Up to the 15th of Septembrer, the mean of temperature (the mean...) is above the old monthly record of September. And it is raining, raining, raining.
For Ostrov Vize, with the exception of the 10th, every day since the 14th of August is a record, and the old monthly record of 2015 has been broken twelve days as of now... The month of September is for the moment the warmest month ever recorded, ahead of August 2020
For Ostrov Golomjanjy, every day of September has been a record, and the old monthly record of 2016 has been broken eleven times.

Arctic sea ice / Re: Rain-On-Snow Events (ROS)
« on: September 11, 2020, 10:30:21 AM »
Rainfall is already on the increase by the way (and this summer can testify, with record amount of rain here and there). One point that is not discussed to my knowledge is the study of warm rain in the Arctic. This study only cover the question of snow melting before reaching surface, which obviously is the biggest factor. But given the ongoing trend toward stronger shallow convection, and soundings like this one during the rain event of the 23rd and 24th of August, the question of warm rain microphysic could be asked.

Arctic sea ice / Re: The 2020 melting season
« on: September 11, 2020, 06:29:47 AM »

Arctic sea ice / Re: The 2020 melting season
« on: September 09, 2020, 07:24:37 AM »
Final answer is 983 hPa according to environnement Canada. For Ostrov Vize, the string of records is still going on. It has been since the 14th of August that every day break its record ! Almost a month of absolutely continous record. But, on top of that, every day since the 2nd of September has registered a temperature higher than the old monthly record (5.4°C in 2015) ! Probably including the 9th of Septemeber, this day, as Tx was at least 5.3°C. For now, the mean of Tx is higher than the old monthly record of Septemebr by 0.3°C.

Arctic sea ice / Re: The 2020 melting season
« on: September 07, 2020, 01:34:22 PM »
In the Arctic basin, even a 8 to 10 seconds wave period is significant.

Unusual certainly, but not necessarily "significant". See just above.

For one part, forecast is worsening. Now, waves are forecasted to reach an height of up to 3 - 4 meters and a period of up to 08 - 09 seconds. Which is no surprise.

But anyway these waves are going to occur at the edge of an already weakened ice pack, and be orthogonal to the ice edge in Beaufort sea. And up to now such strong waves had consequences, so I do not see why this will not be the case today and tomorrow. And if we really want to argue over details, it is not swell but wind waves. Perhaps it is difficult to fully appreciate the consequences of this low. I do not want to forecast exact consequences of this cyclone in terms of the size of the floes break up or of upwelling, or etc... But for one part a low level jet at 30 – 35 knots with a sea state in consequence (Beaufort 6 – 7 in a word) is unusual at this time of year. It is the Arctic, not Hawaii. And on top of that, I really don’t see how this is going to just be unusual and not be significant. The arm of sea ice in Beaufort is probably going to loss ice again.

Arctic sea ice / Re: The 2020 melting season
« on: September 03, 2020, 11:36:38 PM »
I think I have never seen a wave period greater than 10 seconds in the Arctic basin proper, even in 2012 or in 2016 (not counting the Kara sea were some long swells from Atlantic can be worst, of course).

In which case you might well be interested in reading about a fairly well documented 13.5 second swell in the Beaufort Sea in 2009?

On 09 September 2009, we conducted a longitudinal helicopter EMI survey at 72.5 N, and determined the limit of the swell penetration into the pack ice at 72.526 N 134.51 W, a penetration of 350 km.

Yeah ok :D But without trying to defend myself, the point was more about model values than measured values. And in the end, the difference is not that big. Long swell is usually said for period of more than 15 seconds, and my point was mostly that this definition can only be true for the Pacific or the Atlantic. In the Arctic basin, even a 8 to 10 seconds wave period is significant, even though it is not a lot by "usual" (Pacific or Atlantic) standard. But thanks for the reference anyway  ;)

Arctic sea ice / Re: The 2020 melting season
« on: September 03, 2020, 09:14:40 PM »
While the weather forecasts for storms entering the arctic have been incorrect or overly optimistic, what is impressive to me is the current weather history of strong winds blowing north from the laptev/kara shores over the ice (and the fact that these were present in the forecasts 5 days out for the last 10 days at least. That length of time for a consistent 20-30+km/hr wind over the very open arctic ocean and into the ice edge has built up significant wave height that must be propagating some distance into the ice.

The only source I know of that provides an actual indication of wave close to the ice edge indicates 5-6 ft with 5-6 second period - not long swell so not as destructive to the ice behind the edge.

The forecast continues this wind through the next 4 days.

It is the Arctic Ocean here, not Hawaii. Even though I understand what you mean, even a 6 second period is quite significant for the Arctic. I think I have never seen a wave period greater than 10 seconds in the Arctic basin proper, even in 2012 or in 2016 (not counting the Kara sea were some long swells from Atlantic can be worst, of course). On top of that, wave period is probably going to be higher. I am not sure where you draw your values, but for now the forecast is for a wave period of at least 6 to 8 seconds. The strongest winds are likely to be over ice, but even in this case the fetch will probably be quite enough for this kind of value.

P.S : For ones who like esoteric diagramm...

Arctic sea ice / Re: The 2020 melting season
« on: September 03, 2020, 09:22:42 AM »
Also, new daily record for Ostrov Vize this morning, at +4.6°C at least (final value at 12Z) for the third of September. Old record, +4.0°C in 2016. This is the 21th daily record in a row, almost a month of continuous daily record...

Arctic sea ice / Re: The 2020 melting season
« on: September 03, 2020, 08:38:23 AM »
August 29 - September 2.

The tail is melting quite fast!

And it is not over yet.

Again, about the GAC during the month of August 2012, the minimum pressure was quite low, but environmental pressure also. And winds are function of pressure gradient, not pressure. The IFS this morning is going down to 974 hPa. But, there is an anticyclone over the coast, with pressure up to almost 1025 hPa. In 2012, pressure along the coast were around 1010 hPa. Going from 1010 to 965 hPa is about the same (45 hPa of difference) than going from 1025 to 980 hPa (45 hPa of difference). Admittedly, total kinetic energy was greater in 2012 than what is forecasted for Monday, but overall a 980 hPa low embedded in a 1020 hPa high is able to do a lot of damages also. To illustrate, the wind in meters per second analyzed by GFS at 00Z the seventh of August 2012. Maximum winds are around 30 kts (15 m/s), which is also maximum winds forecasted by models on Monday. Again, the GAC of 2012 was probably worst with a greater total kinetic energy, but overall the absolute minimum pressure of a low is quite not the full story. This is going to be a really rough ride and it is really bad, even though we are more than 10 hPa away of the lowest pressure of the GAC 2012.

P.S. : Did not see that at first glance, but IFS 00Z is pushing above 40 kts at surface on Monday 12Z O.o ouch...

Arctic sea ice / Re: The 2020 melting season
« on: September 01, 2020, 04:05:19 PM »
Today's images and slow animation (slightly larger version on twitter)...

The drop in concentration in the Beaufort in the last 24 hours is somewhat concerning.

Easterlies and waves are probably hitting the Beaufort sea. Winds up to 30kt from the east, for the southern part of the arm of ice :

And models are showing waves of up to 3 meters with a period of up to 7 seconds. It is not the big washing, but way enough for some floes to go "poof".

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