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Messages - aslan

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1
Arctic sea ice / Re: The 2020 melting season
« on: Today at 08:39:33 AM »
The low over southern CAA is forecasted to bottom to around 990 hPa (993 for the 00Z of IFS and 991 for the 00Z of ARP). This is going to be quite an event locally. Winds up to 35 kts are likely and the ice wich is already weak in the southern Beaufort could be decimated. Not an event of the scale of the whole arctic bassin, but this low is going to hit hard a region of above average but weak ice again. Also models are forecasting a new ridge building from the Pacific for after mid august. This is worth watching.

2
Arctic sea ice / Re: The 2020 melting season
« on: August 05, 2020, 12:57:08 PM »
Latest Five Day Forecast
Wind + Temp @ Surface
Large GiF!
Trouble about to arrive to the Beaufort in a few days with warm winds off the CAA from the east. We may also see M'Clure Strait clearing out.

Nothing new, but there is as always a strong funneling effect when isobars are parallels to the coast. The easterlies are forceast to reach 25 to 35kt along the Arctic coast and in the Parry channel. This is also going to be a significant surge event for the northern coast of Alaska.

3
Arctic sea ice / Re: The 2020 melting season
« on: August 05, 2020, 10:45:28 AM »
Are there any opinions on the value and accuracy of the various arctic 10 day forecast animations at weather-forecast.com?  I like the visuals and options but am wondering about the predictive value?
10 day right now can’t be trusted. 5 day barely ok

For now, confidence in the forecast can be high up to 5 -6 days. Models are in good agreement for a weak dipole, and the spread within the ensemble is low (this is especialy noticeable for Beaufort Sea). This pattern is linked to the propagation of two rossby waves packet from Western Pacific. This pattern should break around the 11 - 12th, but until this date, confidence in the forecast can be high?

Sorry I don't have the mean to fully exploit the dataset for MERRA reanalysis

A fellow Panoply user by the look of it  :)

Can you provide a link to the data behind that visualisation? And any other data sources you access regularly. This is my favourite:

http://nomads.ncep.noaa.gov/pub/data/nccf/com/wave/prod/

TIA

As this map generate some interests I have updated an old chart with data for 2020 (up to the 30th of June). Accumulated net downward shortwave flux was quite low until the 30 th of June.

P.S. : By the way hurricane Isaias is not going to have a significant impact on large scale circulation despite a strong XT transition, as can be seen on the hovmöller of meriodional wind.

4
Arctic sea ice / Re: The 2020 melting season
« on: August 03, 2020, 01:31:13 PM »
Sorry I don't have the mean to fully exploit the dataset for MERRA reanalysis

A fellow Panoply user by the look of it  :)

Can you provide a link to the data behind that visualisation? And any other data sources you access regularly. This is my favourite:

http://nomads.ncep.noaa.gov/pub/data/nccf/com/wave/prod/

TIA

I don't use a personal computer, and I don't have many option to plot and analyse data : excel and wathever can run without any installation, so there is only few options left  :D This is data from MERRA reanalysis, the most reliable reanalysis freely available for raditiative flux to my knowledge :

https://disc.gsfc.nasa.gov/datasets/M2TMNXRAD_5.12.4/summary

You need to register to download files, but it's all. There is also some delay, you have to wait the 20th for the most recent monthly data.
There is also data from the reanalysis from the NCEP/NCAR in near real time but it is a bit less reliable. And this year, I don't know the source of the problem, but it seems to me there is an inconsistency for radiative flux.

https://psl.noaa.gov/cgi-bin/db_search/SearchMenus.pl
https://psl.noaa.gov/cgi-bin/db_search/DBSearch.pl?Variable=Upward+Solar+Radiation+Flux&group=0&submit=Search

5
Arctic sea ice / Re: The 2020 melting season
« on: August 03, 2020, 12:21:34 PM »
Sorry I don't have the mean to fully exploit the dataset for MERRA reanalysis, but as an illustration. For June, net surface shortwave (~ solar) flux was high, but not as high as in 2019. Last year was quite extraordianry from this point of view. The first map is for 2020, the second is for 2019 and the third is the difference, 2020 minus 2019. We will see what did happened in July (MERRA data are available around the 20th for the preceding month).

6
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: July 30, 2020, 05:28:53 PM »
For ITP 113 and 114 there is also the question of temperature. The cold pool at the surface was definitively mixed, as temperature surged at surface.

7
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: July 30, 2020, 04:40:10 PM »
It can be noted also that there is a surge event ongoing for the northern coast of Alaska. I don't have knowledge of a station measuring waves height for Arctic coast of Alaska, but at least there is a surge of about 0.5 meters since the 27th of July at Prudhoe. Waves will pill up above, and as sea level is already high, tops of waves reach even higher level. As a side note, waters levels at Prudhoe are higher than in 2012. In 2019 waters levels were even higher than, now, but were not as long lasting.

https://tidesandcurrents.noaa.gov/waterlevels.html?id=9497645&units=metric&bdate=20200725&edate=20200801&timezone=GMT&datum=MLLW&interval=6&action=

8
Arctic sea ice / Re: The 2020 melting season
« on: July 30, 2020, 10:26:01 AM »
It is also worth underligning that IFS is trying to deepen again the low runs over runs, with a new minima developing within the front and warm air over canadian archipelago. As a consequence, IFS go down to 991 hPa at 90 hours (sunday evening UTC), and with a high above 1025 hPa for the siberian coast, this means a continuous wild ride for sea ice. GFS is not following, but probable answer is that GFS is lost in the wildnerss of fantasy land, as usual. Even more as others models also are trying something within this front, even tough they don't go as low as the euro guy. And again, follow the trend  :P IFS is loosing hPa by hPa run over run, and it is quite likely at this point that the trend will continue and the low will end in the 980 something hPa. And again, the difference with 2012 is the strong high over siberian coast. Even if we only bottom out to 985 hPa Sunday evening (UTC), gradient will be ~ 50 hPa beetwen Beaufort Sea and siberian coast. At the height of the GAC 2012, it was only ~ 55 hPa over about the same distance...

9
Arctic sea ice / Re: The 2020 melting season
« on: July 30, 2020, 07:42:05 AM »
About wave activity, it can be noted that Indian Ocean was a strong source until lately. Pacific convection was a bit muted, but a dipole dominated over Indian Ocean, and a stationary MJO stucked in phase 2- 3 in June and July, with propagation of a wave train over Pacific and a reinforced subtropical jet here. But what is really curious is the strong source of wave activity from Arctic. I mean, I really don't remember seeing such a source independently from the mid latitudes and tropics.

10
Arctic sea ice / Re: The 2020 melting season
« on: July 28, 2020, 11:17:08 PM »
For wave activity flux, anomalies are really showing up over arctic independently from a tropical forcing. The strong arctic anticyclone was a source of an anomalous wave activity, which was not the case in others years with an arctic anticyclone. This patterns breaks into a succesion of waves. This is noteworthy, to my knowldge arctic was never such a strong source of wave activity comapred to the tropics.
For thunderstorms, I must said that it is also quite likely that strikes happenned northward of 80°N but I don't know if the data from the vaisala monitoring network is accesible. Without data, who knows. But data from Alaska network is not meant to register strikes near the pole for sure, it was more an illustration of the convective instability in the warm sector of the cyclone.

11
Arctic sea ice / Re: The 2020 melting season
« on: July 28, 2020, 08:44:30 PM »
Also the ligthning map from alaska weather service is impressive, with many strikes other Chukchi sea. Since 2016 we have seen strikes more to the North than this, but still having ground strikes at 71°N over sea is no small acheviement...

There was a tropopause folding along the poleward flank of the cold front, with a strong PV anomaly along the frontal slope. Classical for this kind of front. But on the equatorward side, warmth and moisture was extraordinary. It is hard to find CAPE value as it is usually calculated from surface. Here cumulonimbus started from above the boundary layer, around 900 hPa - 800 hPa. But playing the game to make sounding on the model everywhere possible, CAPE value up to 1000 J/kg appeared on the Monday (between 06Z and 15Z). The warm sector was extraordinary for the Arctic and strong isentropic lift occured in consequence.

12
Arctic sea ice / Re: The 2020 melting season
« on: July 28, 2020, 06:21:01 PM »
I am not sure it was said, but Ostrov Vrangel and Mys Vankarem reported thunderstorm, and with gusts up to 18 m/s (about 37 knots) for Ostrov Vrangel when the front crossed the island. As others as said, it is no surprise that the low is stronger than forecasted.

http://ogimet.com/cgi-bin/gsynres?ind=21982&decoded=yes&ndays=2&ano=2020&mes=07&day=27&hora=12
http://ogimet.com/cgi-bin/gsynres?ind=25282&decoded=yes&ndays=2&ano=2020&mes=07&day=28&hora=12

13
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 09:06:58 AM »
Ok correction, 978 hPa at 144 hours... Come on Brive ! XD Forecaster widsdom, when the IFS is stable and going stronger step by step and hPa by hPa, follow the trend. Again it is not a GAC but the cyclone is going to destroy the last stronghold of this year, the Beaufort sea. We are really going to go trough the floor.

Lol wow... yeah, tonight’s Euro would be disasterous for the Beaufort. I don’t think the previous run with  the 980mb was too terrible. Pretty transient with some rain and warmth briefly pumped in, but not persistent enough to make a huge huge impact in the Beaufort via wind and waves imo. Most of the relentless warmth would’ve been over the CAA. Certainly wasn’t trying to argue it was good though, just worth watching. And now even more so for sure!

Tonight’s run would be bad bad bad news.  Relentless wind and waves pulverizing the sea ice and rubble for days. Some are overestimating the Beaufort ice, considering it a stronghold this year. But it looks terrible on satellite and the concentration maps.  A storm like this would absolutely wreck it.

Yes ;) I agree with you, to be precise I said stronghold, but it was more exactly to say that it is where there is still lot of ice, and so huge losses possible. But yeah, Beaufort sea ice is weakening and is not looking especially "strong".

14
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 08:34:36 AM »

4. Will a strong cyclone develop on the Pacific side? Right now both the GFS/Euro are forecasting a 980mb LP on day 5. The storm doesn’t look too terrible, but if a bigger/stronger/persistent cyclone does develop in this area that would be trouble for the vast amount of vulnerable ice/rubble in the Beaufort.

I kindly disagree, the forecast is looking incredibly bad for Beaufort sea over the end of the week-end. The cyclone which was forecasted to try to bomb out from the Laptev sea fizzle out, but now the machine is running full steam ahead. Each minima is pumping warm, moist air from the continent, and in the front a new low developps and push air pressure lower and lower. We are going for a persistence of cyclones rotating over Beaufort sea. IFS 12Z is reaching 980 hPa at H+120, we will see the 00Z but this is definitively a bad setup. It is not THE big one, but action will take place over Beaufort sea and act to disper sea ice here. On top of that, we still have convective instability above the boundary layer with high rain rate, locally up to 15 - 20mm in 6 hours. The washing machine is on.

P.S. : I didn't see answer from Friv' but I agree with him. And the 00Z of the IFS is still going down to 983 hPa...

Ok correction, 978 hPa at 144 hours... Come on Brive ! XD Forecaster widsdom, when the IFS is stable and going stronger step by step and hPa by hPa, follow the trend. Again it is not a GAC but the cyclone is going to destroy the last stronghold of this year, the Beaufort sea. We are really going to go trough the floor.

15
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 08:05:06 AM »

4. Will a strong cyclone develop on the Pacific side? Right now both the GFS/Euro are forecasting a 980mb LP on day 5. The storm doesn’t look too terrible, but if a bigger/stronger/persistent cyclone does develop in this area that would be trouble for the vast amount of vulnerable ice/rubble in the Beaufort.

I kindly disagree, the forecast is looking incredibly bad for Beaufort sea over the end of the week-end. The cyclone which was forecasted to try to bomb out from the Laptev sea fizzle out, but now the machine is running full steam ahead. Each minima is pumping warm, moist air from the continent, and in the front a new low developps and push air pressure lower and lower. We are going for a persistence of cyclones rotating over Beaufort sea. IFS 12Z is reaching 980 hPa at H+120, we will see the 00Z but this is definitively a bad setup. It is not THE big one, but action will take place over Beaufort sea and act to disper sea ice here. On top of that, we still have convective instability above the boundary layer with high rain rate, locally up to 15 - 20mm in 6 hours. The washing machine is on.

P.S. : I didn't see answer from Friv' but I agree with him. And the 00Z of the IFS is still going down to 983 hPa...

16
Arctic sea ice / Re: The 2020 melting season
« on: July 17, 2020, 09:08:29 PM »
WTF

The IFS did remember what a thunderstorm of the free atmosphere means. No surprise here. Fasten your seat belt we are going for a wild ride for weather forecast -& probably for sea ice also-. Anticyclone are so anoying, now it is time for real weather forecast and putting balls on the desk :D

17
Arctic sea ice / Re: The 2020 melting season
« on: July 17, 2020, 01:56:44 PM »
As Friv pointed out, there is lifting occuring from the warm air coming from the siberian coast above the boundary layer. It is becoming a new normal, but still on the scale of weather craziness this easily reached the batshit crazy level... Soundings are the ones forecasted from IFS 12Z (cf. the picture from wetterzentrale) over ESS and Laptev, in the ridge of warm Theta'w. If the forecast verifies as it is, this means thunderstorms. This is also probably adding instability to the forecast.

Sorry for quoting myself, but this is really going to be an important point. There is a first low east of Taymyr and Severna Zemlya, from now to H+120, going down to ~995 hPa at 72h - 96h. This first low is going to bring a massive surge of heat from Siberia, and rough sea over Laptev bite tanks to the fetch of the now open Lapev sea. But, in this massive surge of heat, isentropic lift and thunderstorms are likely, wich is going to bring cyclogenesis. This secondary low starting from the front of the first low is the one to look. Like last year and one or other years before, isentropic lift and buoyancy is going to be an important factor, thanks to the reccord warmth ongoing. And like others years, it is way more likely that models are underestimating the deepening of this low than the other way round. This can be seen comparing precipitations from the 00Z and the 06Z of GFS. The GFS 06Z is way waty worst for sea ice than the 00Z, and one reason is probably due to stronger thunderstorms and higher max rain rate forecasted in the 96H - 120H range in the front of the first low. The 00Z is reaching "only" 10 - 15mm in 06 hours -this already qualify as bath crazy for Arctic...-, the 06Z is reaching more than 30 (30 !!!) mm in 06h under the strongest cells. Don't ask why the 06Z is total mayhem for sea ice....

18
Arctic sea ice / Re: The 2020 melting season
« on: July 17, 2020, 08:25:53 AM »
As Friv pointed out, there is lifting occuring from the warm air coming from the siberian coast above the boundary layer. It is becoming a new normal, but still on the scale of weather craziness this easily reached the batshit crazy level... Soundings are the ones forecasted from IFS 12Z (cf. the picture from wetterzentrale) over ESS and Laptev, in the ridge of warm Theta'w. If the forecast verifies as it is, this means thunderstorms. This is also probably adding instability to the forecast.

19
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: November 02, 2019, 08:00:40 PM »
Daily gain 170 k, 46 k MORE than the 2010's average of 124 k.

Still very high, and just three seas (ESS, Laptev & Kara) gained 164 k of that total.

_______________________________________________


I think this is an important point. The biggest difference with 2016 is the Kara Sea and to a lower extent the ESS. Kara Sea has seen quite unexpectedly high sea ice gain and is ahead of the most recent years (2016 and after I mean). Big gain in ESS and Laptev is a fatality, nothing can make for shallow waters and fresh water. But now that the sea ice has hit the hard land, ESS and Laptev can't see any more gain, this two seas are already near the 100% mark. If Kara sea is not able to sustain the surge in gain, it is likely that a stall in Arctic sea ice extent will happen. As for now, the great battle of this winter for Chuckchi and Barents sea is starting, and easy ice gain are likely over. I am quite ready to bet that Kara Sea will not be able to sustain the pace, and that we are going to see stall shocking the extent growth like in 2016. The biggest hope for now I think is the Beaufort Sea, the only sea which can keep things up for now I think.

20
Arctic sea ice / Re: The 2019/2020 freezing season
« on: October 19, 2019, 12:17:23 PM »
Even for the Arctic Ocean, we will be hard press to end the winter with at least a 2m first year ice, putting the risk of a memory of this summer. The islands on the russian side are nearing or breaking record which are only a few years old, like Ostrov Vrangel :

http://www.pogodaiklimat.ru/monitor.php?id=21982&month=10&year=2019

versus 2016 :

http://www.pogodaiklimat.ru/monitor.php?id=21982&month=10&year=2016

Or Ostrov Kotelnyj :

http://www.pogodaiklimat.ru/monitor.php?id=21432&month=10&year=2019

versus 2018

http://www.pogodaiklimat.ru/monitor.php?id=21432&month=10&year=2018

Or Ostrov Vize :

http://www.pogodaiklimat.ru/monitor.php?id=20069&month=10&year=2019

versus 2016 :

http://www.pogodaiklimat.ru/monitor.php?id=20069&month=10&year=2016

And again, a layer of low level clouds is keeping in check the refreze, as shown for example with Ostrov Vrangel between 300 and 600 meters since the end of the Summer :

http://ogimet.com/cgi-bin/gsynres?ind=21982&decoded=yes&ndays=50&ano=2019&mes=10&day=19&hora=06

And SSTs are still extrememly warm, locally up to 7 or 8 (!) °C. And with the clouds in place, cooling is going to be slow. It is a sure bet that southern Chukchi would not freeze before December or January, and it is increasingly likely that this sea could not fully refreeze before the end of the winter.
For now, the downward IR flux at surface is a bit less averaged over Arctic comapred to record holder 2018 and 2016, meaning a bit more heat is escaping the furnace of the Arctic. But we are starting with an ocean wich is way warmer than in 2016 or 2018 and to cool down this thing this small diff is not enough...

21
Consequences / Re: Forests: An Endangered Resource
« on: September 27, 2019, 05:48:20 PM »
Yes, it is already some years that horse chestnut is screaming its sorrow and pain. It is often question of Amazon or Indonesia or California... but here in northeastern France trees are dying everywhere, it is crazy. Bark beetle are eating away forest, and relentless heatwaves are drying trees. You can't walk 5 meters in any forest without spotting dead trees after dead trees, of any species, old one or young one. Leaves are already falling here, which is really early -and while temperatures are still high and there is no frost still-.

https://www.foretpriveefrancaise.com/data/fe248_p54_60_1.pdf

In the mean, around 10% to 20% trees are dying now. With an annual harvest of 12 millions m3 it is at least 2 millions m3 of damaged wood for this year for France. But locally up to 80% to 90% (!) of trees are dry and dead. Hornbeam, beech, spruce, ash, douglas, you name it.

http://www.fncofor.fr/docs/library/secheressequestions-reponsesonf-fncoforseptembre-2019.pdf

Here it is named a "sanitary crisis", but it is no longer a crisis as it is only worst years after years. It was already very, very bad in 2018, and "only" very bad years before. It is just that mass mortality is growing more massive years after years. And in Deutshland or in Switzerland it is no better.

22
Arctic sea ice / Re: The 2019 melting season
« on: September 06, 2019, 11:44:13 AM »
Sum of forces is definitively not the same. Ice and water does not respond in the same way to winds. And there is also hydrostatic equilibrium, 100 hPa is worth one meter of sea level, but zero point zero meter of ice level. And of course in the end gravity would even out the sea level if the winds stop blowing.

23
Arctic sea ice / Re: The caa-greenland mega crack
« on: September 03, 2019, 09:47:01 PM »
Yes thanks longwalks ;) If there is specfic interest for the Nare Strait, the work of A. Münchow is worth citing :

"The established flow of seawater from Pacific to Atlantic Oceans through the Arctic has been attributed to higher sea level in the Pacific (Wijffels et al. 1992), associated with the lower salinity of Pacific waters. Sea level in the Atlantic may be more than 0.5 m lower than in the Pacific and 0.1–0.3 m lower than in the Arctic (Muench 1971). More accurate estimates of steric forcing have yet to be determined, but it is probably safe to conclude that much of the drop in sea level between Arctic and Atlantic Ocean occurs along the 530-km length of Nares Strait, thereby providing the impetus for the fluxes that we have measured.'

https://journals.ametsoc.org/doi/full/10.1175/JPO2962.1

https://www.researchgate.net/publication/233704692_Ocean_current_observations_from_Nares_Strait_to_the_west_of_Greenland_Interannual_to_tidal_variability_and_forcing

24
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 03, 2019, 09:22:10 PM »
Ok, I might be stubborn,  ;D but I will rephrase more abruptly. What if the change in sea ice extent does not reflect a change from an energy point of view?

25
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 03, 2019, 04:22:09 PM »
Without wanting to look harsh, but I think the discussion is taking a bad way. I am not a specialist of this question, but a big missing piece of data is the problem of land versus ocean distribution in Northern Hemisphere.

I think it is useful to go in several different directions. Extract what we can from trends but also consider physical reasoning.

I am not sure I agree on the importance of land restricting ice extent. It certainly does in winter but it is constrained at same places each year. So I am not convinced it has much effect on trends.


If I may insist. Considering for example an uniform retreat of 1° northward per decade, Summer as Winter.
If the ice edge is 1 000 km long, the 1° will lead to 100 time 1 000 km², i.e. 100 000 km² ice loss over a decade. Or, said otherwise, peanuts.
If the ice edge is 10 000 km long, this will lead to 10 000 time 100 km², i.e. 1 000 000 km² ice loss over a decade.
This is really what is ongoing. In winter, the "free" ice edge is not really wide, so even if the ice is marching toward the North at the same speed as in Summer, ice loss will be small. And as said, in the Pacific we are now in the bottleneck of the strait, and in the Atlantic it is not really better. So even a retreat of 2 or 3° over a few years will lead to almost no sea ice extent loss in Winter, while in Summer a retreat of 2° or 3° will be almost the end of the sea ice. This is simple but important math’s. Of course, it makes the evaluation of trends in ice extent more complex. But I really do think brain storming over breaks of the linear slope without acknowledging this fact will lead to a sterile discussion. The changes in slope are way more better explained by changing ice edge conditions than by "hard" physics.

https://tamino.wordpress.com/2010/08/22/on-ice-with-a-twist/

26
Arctic sea ice / Re: The caa-greenland mega crack
« on: September 03, 2019, 03:05:44 PM »
Yes, the conditions are more suitable for ice export in Winter, mostly due to variation in sea surface elevation :

Our model results based on 26-years of simulation with monthly output demonstrate that SSH gradients (calculated between two points north and south of each passage, which are denoted with asterisks shown in Figure 12) do explain the annual peak volume fluxes (around March) through both Nares Strait (Figure 14a) and Lancaster Sound (Figure 14b). The volume flux anomalies and SSH gradient anomalies are also highly correlated. Volume flux anomalies through Nares Strait (Figure 15a) and anomalies of the SSH gradient (measured from the Lincoln Sea to Smith Sound) (Figure 15b) were highly correlated (R = 0.89). Volume flux anomalies through the mouth of Lancaster Sound (Figure 15c) and anomalies of the SSH gradient (measured between the Queen Elizabeth Islands and western Baffin Bay) (Figure 15d) were also highly correlated (correlation R = 0.85).

https://pdfs.semanticscholar.org/870a/ad3242a2f319c69031342c9cedfa291df51e.pdf

27
Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: September 03, 2019, 02:40:21 PM »
Without wanting to look harsh, but I think the discussion is taking a bad way. I am not a specialist of this question, but a big missing piece of data is the problem of land versus ocean distribution in Northern Hemisphere. I mean, in winter, ice edge is constrained more by geography (coast of Russia and Canada) than by physics (warming / cooling atmosphere, ocean currents, and so on). Which is no longer the case in Summer, where ice edge is, but for Greenland, in open Ocean and can retreat as the thermodynamics warrants. This is probably why seasonal cycle changed dramatically after 2005. Until 2005, ice was still mostly bounded by the coast, even in Summer. Now, ice has all the possibility to expand and retreat without being imped by the coasts. One possibility is to look instead at sea ice edge latitude. Doing this, difference between Summer and Winter is lessened and the downward trend is more even.
On top of that, captain obvious helping, it should be noted that sea ice area can't go negative. But this has the implication also that the downward trend should go to zero sooner rather than later, as there is no more ice to melt in summer. Losing 2 million squared km when you have like 20 million at hand is almost nothing, losing 2 million squared km when you have like 1 million at hand is impossible... This is probably the first big answer to the question "why trend is so irregular and the seasonal cycle has gone mad ?".

It should be noted also that from this point of view, the situation is “worsening” on the Pacific side. When the edge was in the Bering Sea, there was still some width to “yielded” big loses. Now that the edge is in the bottleneck of the strait, even a retreat of 1° North –which is quite significant– would amount to almost zero ice area loss. Zero time a thousand km is still zero :p We will have to wait for ice edge in winter to reached Beaufort / Chukchi / ESS for seeing anew some significant ice loss for the Pacific side. Same on the Atlantic side, as Barents and Kara Sea are zeroing, going further North will become complicated in the short term. It will happened in the decades to come of course, but over the course of the coming years, variability of winter sea ice as seen from the metric of extent will probably still be dampened, even if the warming speed up bigly.

https://www.tandfonline.com/doi/full/10.3402/polar.v33.21249

P.S. And on top of that "simple" geographical explanation, geaography also lead to "energy yield" vastly different from Winter to Summer. Land and Ocean distribution are also responsible for bigly different thermal answer in Summer and in Winter under the same forcing. We will also probably have to wait that the Ocean becomes an "heat accumulator" in winter for seing warming speeding up in Arctic.

28
Arctic sea ice / Re: The caa-greenland mega crack
« on: September 03, 2019, 07:17:06 AM »
Yes, it was bad wording on my part, not reflecting what I was actually thinking. It was more like, there was a strong preconditioning earlier with the lack of blocking in Nares strait, and now winds have an easier job.

29
Arctic sea ice / Re: The caa-greenland mega crack
« on: September 03, 2019, 06:42:42 AM »
This topic has drowned into the abyss of this forum, but the mega crack is still here and alive. And there is still sign of melt going on. To justify, Kap Moris Jesup hit 10.3°C the last day of August, a record for this time of year. And to the the North of Ellesmere, the Nares strait export has lead to a big, big hole. Fortunately the season is ending.

30
An unspoken consequence, here in northeastern part of France, is the sanitary situation of forests. Some plants are dying like never. Spruce, european spruce, beech, ash, bilberry etc... Many plants and trees are dying. And some are still alive but are on the brink of disaster like apple trees or more generally fruits trees which are not enough vernalized in winter. In my valley, there are big brown patches everywhere, like pictures in this article : https://www.lemonde.fr/planete/article/2019/07/24/la-secheresse-et-la-canicule-deciment-les-forets-francaises_5492869_3244.html And in the forest, we can't walk an hundred meters without seeing a tract of land which is dead. In Swiss, there is even a declaration of emergency ... https://www.letemps.ch/suisse/jura-situation-catastrophe-forestiere Consequences will be long lasting but big : flooding of the wood market with lower quality tree, increase risk of accidents, increase risk of forest fire, loss of biodiversity etc... The financial burden for some villages could be unbearable in years to come, as many rural towns have big incomes from the trade of wood. I don't know what a valley here could look like without beech, spruce, apples and cherries...

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The rest / Re: Are you hoping for a global civilisational collapse?
« on: August 27, 2019, 02:01:34 PM »
It is ongoing, but I am not hoping for it, just preparing and praying the Lord. And reading ancient books from the late Roman Empire. But I am not a big fan of the world "collapse". Collapse will not happens instantly nor globally, but is an already ongoing step downward trend with some periods of temporary improvements, being better or worst here and there, and it is not going to be a global catastrophe over a day or so. https://books.google.fr/books?id=M4H-02d9oE0C&redir_esc=y Humans are often fascinated by big catastrophes, but the collapse of a civilization never followed this path.

Quote
I had problems voting here because I think the concept of collapse as given here is a bit of a straw man. I don't think it likely that it will be Armageddon, with hardly any survivors... but I'm sure there will, at some point, be a major reduction in population, and a reversion to a largely agrarian society in places that aren't used to such lifestyles. Many indigenous cultures will carry on, under trying conditions. What I expect to be the main symptom of collapse is the loss of the framework that allows intensive industrial civilisation. First there will be food shortages, then public unrest and lawlessness, then a new equilibrum will emerge later. The skills and knowledge to survive as sustainable communities still exist, although yes, life would be less comfortable. And yes, I expect this to happen (at least in part) within a few decades.

I fully agree. I am trying to build a sustainable community in my neighborhood, reviving ancient practices from the past.

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Arctic sea ice / Re: The 2019 melting season
« on: August 24, 2019, 02:53:12 PM »
Thanks, no worries  ;)

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Arctic sea ice / Re: The 2019 melting season
« on: August 24, 2019, 01:18:49 PM »
But, Aslan, before you said the low goes poof, not the ice. ;)

I am not sure to understand ? For me there were always arguments for saying that models are under estimating this beast. Not yet a true GAC but still quite deep and durable with migthy impacts for an already weakened ice pack.

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Arctic sea ice / Re: The 2019 melting season
« on: August 24, 2019, 09:27:12 AM »
Models are trending deeper and deeper. Below 970 hpa will as forecasted now make this complex looking like a GAC. Brace yourself for ice armagedon.....

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Arctic sea ice / Re: The 2019 melting season
« on: August 22, 2019, 09:04:49 AM »
This is the same low, or the same complex if one prefers. And IFS has output only every 24h. I don't have the exact evolution of SLP at end but this model is forecasting SLP lower than 980 hPa over central Arctic (GFS is at 978 hPa at 75h, a forecast time not available over internet for IFS to my knowledge). And it is not only about the minimum SLP but also about gradient, with a strong ridge on the Atlantic side, and multiple low centres interacting together. And it is also about Beaufort, as it is likely that the vertical stability of the Ocean column is weaker than in 2012. By the way, GFS, after a good fight up to this morning, has surender, so again it is way more likely that the models are under estimating this thing. Attached is the forecast 980hPa cyclone in 2019, and the 2012 GAC at 980hPa. We are not yet to the point where we can compare this low to the 2012 GAC, but this is going to be really, really bad for Beaufort sea and more generally for Arctic. Hope the best, but be ready. At 72h-96h lead time there is still time for loosing hPa.

But you can't possibly compare this low to the one in 2012 though as its a totally different set up.

First things first, the low in 2012 originated from Siberia so on its Western flank, there was warm air heading northwards towards the pole, this low is coming from Alaska/CAA and on its Eastern flank is cold air heading southwards. The warm air mixing in the circulation probably what caused the rapid development in 2012. Also the low in 2012 crossed over thin ice just at the right time and area which split the ice pack and what resulted in the dramatic extent losses, this low is crossing a ice pack which is not as thin as that was and nor is this low is as deep so its affects on the ice in theory should be minimal. It will be interesting too see how the ice reacts on the CAA and Greenland coasts with such strong winds.

I suppose never rule anything out these days but in the past, this set up should mean a rapid slow down in ice extent and some freezing of any diffuse ice in the CAB.

There is also a warm belt from Siberia, from the ridge over the coast. This also explains why the low is not as strong as in 2012 or 2016 from the point of min SLP. But min SLP is not the whole story, two 980 hPa lows playing together is not necessarily better than a big one at 965 hPa. Here, there is really multiple thermal waves with different sets of warm / cold fronts, with multiple warm belt feeding into the lows.

P.S. I have tried hard without success, but I will still show a sounding from GFS over ESS for Friday. I am showing this sounding, because at the same time IFS is showing an even steeper profile, with some weak mid level instability between 850 and 500 hPa. Here, GFS is a bit marginal. But nonetheless this is showing that there is a true warm belt feeding into the low from the siberian side (by the way, and again, this is also why the forecasted low from IFS is still bigger and stronger than the low from GFS).

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Arctic sea ice / Re: The 2019 melting season
« on: August 22, 2019, 08:55:24 AM »
Models are concerning. The american and the euro boy are showing the possibility of a new thermal wave building day 7 - day 10 for a third round. IFS has probably gone made with a 980 hPa low over Beaufort at D 7. But GFS has the same idea. Even though, overall, the cyclogenesis fail, this boy is still trying something with a new stream coming from the american continent again. Energy will perhaps not been exhausted after a two punches low. For the moment, the low is still forecasted to weaken and spin down, but who knows? This said, this does not preclude a new ridge coming from the Siberia.

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Arctic sea ice / Re: The 2019 melting season
« on: August 21, 2019, 10:44:55 PM »
a forecast time not available over internet for IFS to my knowledge

ECMWF forecasts every 3 hours can be found here:
https://kachelmannwetter.com/de/modellkarten/euro/nordpol/luftdruck/20190825-1200z.html

Thanks, not aware of this site. Crazy that they even have it every hour. Like what everything is available over internet...

IFS has output only every 24h.
Nullschool every 3 hours...

I wish there would be a Euro Nullschool, because we're way better with our weather predictions in Europe than the Americans are...



Nothing like bashing Americannots on your century post!  ;D ;D ;D 8)

Yes good job ^^ joke aside, GFS has been really behind the curve lately.

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Arctic sea ice / Re: The 2019 melting season
« on: August 21, 2019, 09:48:53 PM »
This is the same low, or the same complex if one prefers. And IFS has output only every 24h. I don't have the exact evolution of SLP at end but this model is forecasting SLP lower than 980 hPa over central Arctic (GFS is at 978 hPa at 75h, a forecast time not available over internet for IFS to my knowledge). And it is not only about the minimum SLP but also about gradient, with a strong ridge on the Atlantic side, and multiple low centres interacting together. And it is also about Beaufort, as it is likely that the vertical stability of the Ocean column is weaker than in 2012. By the way, GFS, after a good fight up to this morning, has surender, so again it is way more likely that the models are under estimating this thing. Attached is the forecast 980hPa cyclone in 2019, and the 2012 GAC at 980hPa. We are not yet to the point where we can compare this low to the 2012 GAC, but this is going to be really, really bad for Beaufort sea and more generally for Arctic. Hope the best, but be ready. At 72h-96h lead time there is still time for loosing hPa.

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Arctic sea ice / Re: The 2019 melting season
« on: August 20, 2019, 09:02:24 PM »
If it was 500 or 1000 km toward Beaufort, it would be a party of ice destruction.
In that location it smells season brake of an already braking season.

Again, this is definitively not the opinion of the Euro guy. I am ready to bet that this boy will be closer to the reality than GFS. The IFS at 120h - 144h is extraordinarily bad and the IFS at 96-192h is "only" really, really bad. There is a lot of energy to dissipate and the GFS, sitting like a big fat guy in his chair and waiting God knows what's sighing "Energy, which energy?" is really not a credible option in my opinion. Also, IFS (00Z or 12Z of this day) is able to go to a warm seclusion. This point is also not in favor of GFS. From the season, we have learned that the Arctic is under steroids and a cold, dreary frontolysis is not looking likely. Perhaps I am badly mistaken and fooling myself, but for me this is not looking like anything serious.
The point is really not about the deepening low above the archipelago. Now, every one is ok for a deep low over this region. But after, some models like IFS are able to let the low spinning, with a new feeding of energy from Atlantic and Eurasia, while GFS is letting this thing dying.
Perhaps it is the hour where Denethor is whispering the antithesis of your one signature to the lasts floes of sea ice still standing : "Why do the fools fly? Better to die sooner than later. For die we must."

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Arctic sea ice / Re: The 2019 melting season
« on: August 20, 2019, 08:42:59 AM »
Yes GAC power !!!!  ;D
As it is in the range 96h - 120h, it is almost lokked in. Not as big as in 2016 or 2012 but still significant, sub 980 hPa at least, sub 970 hPa possible. But the radius of gale force is limited and it will occur over the Canadian Archipelago also, so with less impact for sea ice (but lest keep an eye on what will happen in the Beaufort Sea -especially after 120h-). In the end, it is a compromise between IFS and GFS, big cyclone, but coming from Alaska and not from Atlantic.

P.S. : For the Beaufort, what I wanted to say actually is that with the euro guy the low is able to reorganize itself and build a new thermal wave, streaming warm air from Atlantic and then Eurasia, but for GFS this will not happen and the low will spin down quickly. Again, I am skeptical of the solution offered by GFS. It was already not able to anticipate the deepening of this low, and now it want us to believe that it will be short lived. Even though the Euro guy was not sure about the precursor (the one from the Atlantic, or the one from Alaska ?), since mid week the model is quite consistent showing that some big pressure drop is going to occur, not matter the exact details.

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Arctic sea ice / Re: The 2019 melting season
« on: August 18, 2019, 01:24:17 AM »
As CSNavywx noted a while back, ridges tend to persist and the models often underestimate the persistence. We should not ignore the latest Euro model run. We'll know that the threat to the ice is over when temperatures drop and area losses stop. The recent slowdown in extent losses was associated with a rapid drop in area, an indication that the melt season has not yet stalled out. The DMI 80N graph shows the melt season has gone into extra time.

I don't think that this means this year will catch up with 2012, but there's still time for surprises.

Yes, GFS is probably lost in the wilderness again. I have put also Arpege, a french model which is not often look but is often good and is a close friend of IFS, despite being coded quite differently. At 96-120 h, the low over north Pole must be closely monitored. It is not deep, but again it is deepening against a strong ridge. And so, a sub 995 hPa low vs a top 1025 hPa high result in a strong low level jet over CAB. I don't have all the tools for an analysis, but it also likely that the high and the low are feeding each over. Stronger high with warmer air mass is probably enhancing the baroclinic zone trough stronger temp gradient and stronger wind speed, helping the low to deepen. No GAC again, but these recurrent, nasty low battling strong highs are not helping. A solution like GFS with a broad low sipping a cold drink and waiting I don't know what would be way better but it is not really the most likely outcome.

42
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: August 17, 2019, 08:34:25 PM »
Yes it is probably the explanation, despite Copernicus showing data available since 2006. And yes it is really frustrating to be blind while the Beaufort sea is beaten like never. The beaufort gyre is quite an important thing, but who know what is really happening ?

43
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: August 17, 2019, 04:53:35 PM »
I make a quick map to compare 2019 on the 26th of August (forecast from Mercator) to mean from 2016, 2017, 2018. I don't know why, I was not able to download data for prior years, I don't know why... Excepted for the Barents sea which is cooler than over the 3 previous years (also the case for SSTs with a true base period), everywhere the warmth is showing, and even in the central basin there is streams of abnormally warm temperature.

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Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: August 16, 2019, 04:54:21 PM »
And now ITP 110 has hoisted the white flag and surrender. No news since two weeks. Too bad, as Mercator is showing extreme warmth in Beaufort. It should have been interesting to see what really happens here. The build up of heat shown at 30m and 100m is like nothing ever seen. Will this have an influence on refreeze season ? And Mercator was shown to be warming not enough compared to ITP 100. Depite this, in part of the Beaufort Sea, the big mess is going on and on, with a loosening of the stratification and a build up of energy wich is beyond superlatives and the "spot the difference" game ... Where now the Pacific layer and the halocline ? Where is the freshening and the cooling ? I don't know where we are going at this pace, but here we go.

P.S. : There is no special reason for a comparison with 2016, it was only to give a point of reference for a year wich was in its own quite bad for Arctic.

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Arctic sea ice / Re: The 2019 melting season
« on: August 14, 2019, 02:04:57 PM »
Wind is basically going bonkers at the moment.

45 knots off the NE coast of Greenland into Fram. 20 knots from the Kara straight into the CAB and noticably moving the ice edge.

Same in Beaufort with 20 - 30 kts of easterly winds now. Ship NWS003 measured 51 km/h but not sure of the configuration of the anemometer and ASCAT is quite explicit. Wind speed is not extremely high but occuring over a wide swath around the high. Also models have been a notch too low for wind speed. The vertical profile is of course helping, with the lack of strong near surface inversion, but it is still interesting to see models not fully bringing winds to surface.

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Arctic sea ice / Re: The 2019 melting season
« on: August 12, 2019, 01:05:54 PM »
This said, even without GAC, weather is going to be very rough on the Pacific side. Low over Chukchi is not so hollow, but there is strong gradient, and mean winds more than 30 kts are going to occur. Sea is going to be not so friendly, with wave action. As others said, GAC 2012 pumped heat from deep ocean, but this year there is way enough heat at surface for melting sea ice edge with a good shaker mixing. Same can be said on the Atlantic side. The low over Kara is only going to a bit below 1000 hPa, but interacting with a 1030 high, this is going to be a wild ride for sea ice in coming days. Hopefully it will not last, but damages are likely in the next 2 - 3 days. It should be noted that some mid level instability is again modelized in the WAA coming from Siberia  :P

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Arctic sea ice / Re: The 2019 melting season
« on: August 12, 2019, 10:01:36 AM »
I’m really surprised that the lightning strikes 300 miles from the North Pole yesterday did not cause more discussion on the forum. 

The scientists on climate Twitter could not find any instance of lightning so far north.

It was a strange, and in my opinion important, event.  The arctic is changing!

This is from work, so no one has seen the following pictures... The IFS 0.125° for the 11th at 00Z, wet bulb potential temperature at 850 hPa, vorticity at 850 hPa (above 16, step 4), SLP, thickness 500 (Z500-Z100). There is  a front with a ribbon of vorticity to the North, stretching from the low over Barents to the Chucki sea, with low and mid level clouds, as visible from sat pictures. But associated with the low over Laptev, to the west of the head of the low, there is a maximum of vorticity. Sounding show mid level instability from ~800 hPa to ~250hPa with ~100 to ~200 J/Kg. Marginal, be with good forcings enough for TS.
As Rod said, this is significant.
For one part, this is an illustration of the evolving Arctic. Again, CBs were probably not directly linked to the crazy warm SST, but it is definitively showing that Arctic is warming. The warm air advection was extreme, and was able to carry a potentialy instable airmass up to 85°N. Mid level CBs at the head of a thermal wave are not a thing of the Arctic, up to today...
For the other part, this also means that cyclogenesis is on the move on the Arctic. This low had some characteristics of a warm seclusion with a slight max of temperature, TA and wind around 850 hPa - 900 hPa. Cold, pure baroclinic process are loosing a bit of grip and now warm core process and moist instability is starting to play a role. For the second point, it was of course more evident with the low over Beaufort at the start of the month for example. Here a lone CB will not make any meaningfull difference of course. But next year it could be 10 CBs, then etc... And on the end it will change the cyclogenesis process. It could also be noted that Laptev sea being shallow, it could quickly warm without sea ice. With Siberia snow free earlier and earlier, this could mean a quick increases of moist instability with a warming Arctic.

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Arctic sea ice / Re: The 2019 melting season
« on: August 11, 2019, 07:44:19 PM »
As an illustration of the growing importance of the convection for Arctic : https://mobile.twitter.com/Climatologist49/status/1160400333601832960

And on this GFS was not too bad (I did not look at IFS). Not yet to the point where subtropical storms Can be, but we are on the good way  :D

https://twitter.com/NWSFairbanks/status/1160456516849172480

It was probably mid level thunderstorms, starting from around 750 hPa. Strong shear and vorticity at this level probably help the convection. Sat pictures is showing top CBs down to -50° to -60°, which means a slight overshot, up to 250 hPa. In this case, surface conditions (i.e. batshit crazy SSTs) were not a direct factor. CBs starts in the warm air advection associated with a low centered around 84°N 135°E. But the WAA was extreme, with temperature above 10°C at 850 hPa in the ribbon of max temperature. CBs were probably on the western flank of thiw WAA, and not directly linked to the front to the North, stretching from the low over Barents to the aforementioned low. It is also likely the most northern strike detected.

P.S. : WAA can also - in this case - be traced with smokes. Coming from Taymyr peninsula in the morning (UTC time) of the 10th, and advected towards Laptev Sea on the 11th. Between the two pictures, on the western flank of the advection, something happened...

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Arctic sea ice / Re: The 2019 melting season
« on: August 11, 2019, 09:35:43 AM »
As an illustration of the growing importance of the convection for Arctic : https://mobile.twitter.com/Climatologist49/status/1160400333601832960

And on this GFS was not too bad (I did not look at IFS). Not yet to the point where subtropical storms Can be, but we are on the good way  :D

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Arctic sea ice / Re: The 2019 melting season
« on: August 01, 2019, 10:41:09 PM »

It was not fully intended, but by the way and by way of illustration, GFS has come closer to others global models, and is showing more deepening forced by diabatic heating.

And the follow-up... Sorry, but I like to understand how models works and to cook them, and why they are always in epic fail but are still incredible useful. The low is now forecasted to go down to 988 hPa -the attached image is showing 989 hPa but this is not the absolute minimum-, and this will probably be the last say. Don't be shy if you are sure that the models are shy :p So real world consequences, with a sea like rarely seen in Arctic, up to 4 m and 10 s, with Barrow and Prudhoe Bay going to be battered : https://tidesandcurrents.noaa.gov/waterlevels.html?id=9497645&units=standard&bdate=20190801&edate=20190802&timezone=GMT&datum=MLLW&interval=6&action=

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