Support the Arctic Sea Ice Forum and Blog

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - aslan

Pages: [1] 2 3 4
1
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 26, 2020, 04:52:35 PM »
Last sounding

2
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...)

3
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 : https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/grl.50190. And during a storm in October 2015, it was about the same idea : https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2018JC013764
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 :https://reader.elsevier.com/reader/sd/pii/S1463500316300622?token=DFCB8444FB3423422C3C831531FD0FB4704E87BCAFBCCEF5681DA1C00B8EDCDAE777B94E618EBCD0F4333143CEB831D5

(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)

4
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.

5
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 :

http://ogimet.com/cgi-bin/gsynres?ind=21432&decoded=yes&ndays=20&ano=2020&mes=10&day=26&hora=12

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.

6
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).

7
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?

https://www.ccin.ca/index.php/ccw/snow/current

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 :

https://www.ospo.noaa.gov/data/sst/contour/global_small.fc.gif

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

Top level directory of the files are here :

ftp://ftp.star.nesdis.noaa.gov/pub/socd2/coastwatch/sst_blended/sst5km/

And the direct link for this year :

ftp://ftp.star.nesdis.noaa.gov/pub/socd2/coastwatch/sst_blended/sst5km/night/ghrsst_ospo/2020/

8
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.

9
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.

10
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).

11
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

12
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.

13
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,

http://ogimet.com/cgi-bin/gsynres?ind=20069&decoded=yes&ndays=50&ano=2020&mes=10&day=15&hora=12

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 :

http://ogimet.com/cgi-bin/gsynres?ind=20069&decoded=yes&ndays=50&ano=2012&mes=1&day=15&hora=12

14
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.
https://journals.ametsoc.org/jcli/article/33/18/8107/353233 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.

15
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 :

http://www.pogodaiklimat.ru/monitor.php?id=20069

http://www.pogodaiklimat.ru/monitor.php?id=21432

16
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.

17
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.

18
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.

19
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".

20
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: October 08, 2020, 01:33:38 PM »
NSIDC Data

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)

21
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.

22
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

23
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.

24
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.

25
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.

26
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  http://www.pogodaiklimat.ru/monitor.php?id=20069
For Ostrov Golomjanjy, every day of September has been a record, and the old monthly record of 2016 has been broken eleven times. http://www.pogodaiklimat.ru/monitor.php?id=20087

27
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.

28
Arctic sea ice / Re: The 2020 melting season
« on: September 11, 2020, 06:29:47 AM »

29
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.

http://www.pogodaiklimat.ru/monitor.php?id=20069&month=9&year=2020
http://www.pogodaiklimat.ru/monitor.php?id=20069&month=8&year=2020

30
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.

31
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?

https://GreatWhiteCon.info/2015/07/is-time-running-out-for-arctic-sea-ice/

Quote
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  ;)

32
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...

33
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...

http://www.pogodaiklimat.ru/monitor.php?id=20069

http://www.pogodaiklimat.ru/monitor.php?id=20069&month=8&year=2020

34
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...

35
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 :

http://ogimet.com/cgi-bin/gsynres?ind=71948&decoded=yes&ndays=20&ano=2020&mes=09&day=01&hora=15

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".

36
I'm not sure where to post this information, but the QBO is again disrupted with an anomalous interruption of the easterly phase like in 2015 - 2016 :

https://acp.copernicus.org/preprints/acp-2020-791/acp-2020-791.pdf

https://acd-ext.gsfc.nasa.gov/Data_services/met/qbo/qbo_plot.pdf

https://www.essoar.org/doi/10.1002/essoar.10503358.1#.XvEZFtQSp8M.twitter

37
Arctic sea ice / Re: Updating the ASIG
« on: August 25, 2020, 10:57:52 AM »
You probably need to update adobe on your computer, or to allow adobe to run within your browser  ;)

http://arctic.som.ou.edu/scavallo/images/real_time/conc_trth_slp/

38
Arctic sea ice / Re: The 2020 melting season
« on: August 25, 2020, 09:48:48 AM »
And, also, there are few surface observations, which makes model initialization harder. For example, the 24th of August, Polarstern ship measured a pressure of 991.4 hPa : https://www.sailwx.info/shiptrack/shipposition.phtml?call=DBLK
This is slightly off the initialization and the first forecasted hours of the weather models by one or two hPa. It is likely that the minimum pressure of this low was in the upper 980s hPa actually, as the center missed the Polarstern. But this is not unexpected. With a gap of ~500 km between Kvitoya and Polargmo Im., and a gap of ~1000 km between this two and DBLK, it is hard to know what is going on.

39
Arctic sea ice / Re: Updating the ASIG
« on: August 25, 2020, 09:10:27 AM »
I've updated the Forecasts page, as none of the images were working. Unfortunately, there aren't any good SLP forecast maps out there, either GFS or ECMWF. Tropical Tidbits has a good one, but it's for the Northern Hemisphere, so you can't see much detail when it's in the size I'm using for the Forecasts page. So, I was forced to use to the Climate Reanalyzer MSLP/Precipitation map which lacks the geopotential height colours for a quick glance.

Oh, well...

I'm a bit late, but have you consider this site ?

http://arctic.som.ou.edu/scavallo/images/real_time/conc_trth_slp/looper.html

http://arctic.som.ou.edu/scavallo/real_time_plots.html

40
Arctic sea ice / Re: The 2020 melting season
« on: August 25, 2020, 08:54:26 AM »
Latest Five Day Forecast
Wind @ Surface + Total Precipitable Water
Large GiF!
It’s funny how the big storm over Greenland Gap never gets to fully realize
It's been like that for over a month now, where big apocalyptic storms get announced on the long term forecast, but never materialize.

GFS really needs to find a way to improve their long term forecast. Or just stop making them, because this is useless...

Models don't work this way.

For Franz Josef Land, record high temperature for the last decade of August, record high daily rainfall and near record gust speed for August :
http://ogimet.com/cgi-bin/gsynres?ind=20046&decoded=yes&ndays=2&ano=2020&mes=08&day=25&hora=00

Old value : 16 mm in 24h (August 89), 5.5°C (August 2019 and August 1978)

P.S. : And there is a ~500 km gap between WMO station 01011 (Kvitoya) and WMO station 20046 (Polargmo Im. on Heis Island - Ostrov Kheysa). The worst of the storm on Sunday and Monday was in this gap.

41
Arctic sea ice / Re: The 2020 melting season
« on: August 22, 2020, 12:15:57 AM »
And, as an illustration, 63.4 millimeters of rain in 1 hour at Sandefjord Gjekstad, highest hourly rainfall rate for Norway. Old record was 54.9 mm in 1 hour at Asker. The thermal wave, consequence of Kyle and Ellen, is by no mean a joke. No matter the exact to the nearest decimal of the min pressure for the North Pole, this is going to be bad for the atlantic front.

42
Arctic sea ice / Re: The 2020 melting season
« on: August 21, 2020, 01:54:42 PM »
The storm is still in the forecast for Monday. A little weaker, but within the model run to run fluctuations we might expect.

Yep. But, not wanting to sound hysterical, but the subttle changes are not good at all. Baroclinical energy is more dilute along the thermal wave. This means that the pressure at North Pole is now forecasted to be a bit higher, but the string of low pressures is still here and there. And so the winds are still forecasted at 25 - 35 kts, and rain (and really, rain, liquid water at ~5°C) amount are still forecasted to reached 20 - 30 mm.
Also, the Arctic low in this wave is forecasted to move a bit more toward the Beaufort sea, with some waves action, which was not the case in the forecast last days. And, mantra of this year, but there is still a lot of easy ice to loss in this corner of the Arctic.

43
Arctic sea ice / Re: The 2020 melting season
« on: August 20, 2020, 01:49:10 PM »
It is not useful to look at exact number for weather forecast. This is why there is the feeling of coin flipping. That the models go back and forth for exact min pressure at the nearest hPa or max surface wind at the nearest km/h is normal and should not be confusing the forecast. Models are still a bit unsure about the deepening of the low, but in any way and in any case, a wave in the frontal boundary from the complex low linked to ex Kyle, now storm Ellen, is going to deepen. The details of the exact minimum pressure and of which exact wave in the front and of the exact km/h of the max wind and so on are not really relevant. We can be 100% that a low is going to deepen from a wave in this complex, and that it is going to be a wild ride for the Atlantic side. And the ranges of some physical parameters are not going to evolve in the coming days. Precipitable water is forecasted to reached 25 - 30 millimeters in the warm air advection and this is not going to change, strong winds of 30 - 35 kts are also a sure thing, I am ready to bet on thunderstorms northward of the 80°N also, etc... That the low go to the 970s or stall in the bottom of the 980s hPa or that lightning strike will be here or there is asking too much, and is not really the biggest question. The difference between a 980 hPa low with 34 kts of wind and 29 mm / 24 h of rain at max, which develops from this wave, or a 975 hPa low with 36 kt of wind and 31 mm /24 h at max which develops from that wave, is not significant. Weather forecasting is not reading model outputs and going back and forth with them. This is going to be a significant event for the Atlantic side, with the injection of tropical moisture from Kyle, and with implications for planetary rossby waves train, no matter the exact unit of this or that parameter.

44
Arctic sea ice / Re: The 2020 melting season
« on: August 20, 2020, 09:50:19 AM »
silly question .. would the weather models have any concept of how wet the ice is atm ? If they see it like piomass sees it they may be surprised by developments .  b.c.

No they don't, sea ice is parametrized in the models with fixed constants. It would be way to complex to explicitly model the sea ice for a weather model running every six hours. And yes, models can be underestimating cyclogenesis, which is no news. But this is not only a problem with sea ice. Cyclogenesis is a complex process and is hard to forecast. But in the Arctic, with all the changes ongoing, this is worst, yes. As a side note, models are again forecasting explicitly thunderstorms above the boundary layer on the Atlantic and Pacific side. I did not fully check the models from 00Z today, but IFS or ARP are going on for over 30 millimeters of rain (and rain, no sleet or snow) in 24h for Franz Joseph Land this week-end ! This is crazy. And even up to 85°N, they are going with thunderstorms and a good 20 mm per 24 hours. Sea ice on the Atlantic side is going to be wash out.

For Beaufort Sea, as already said, the warm air advection on the flank of the anticyclone is going to be bad. Even though there is no deep low, there is enough pressure gradient for some significant winds (field of 15 - 25 kts), and with the help of Coriolis, with the fetch of open waters, etc... Waves are going to be pretty significant for the Arctic, from the south east to the south (wave period up to 6  to 8 seconds). This not a big event, but again locally and given the sore state of sea ice in this corner of the Arctic, and the fact that there is a lot to loss, etc... Beaufort Sea is likely to continue its nose dive in the coming days.

45
Arctic sea ice / Re: The 2020 melting season
« on: August 10, 2020, 10:19:25 AM »
As forecasted, the low over the southern CAA and Beaufort is not an event at the scale of the whole bassin, but for Beaufort sea, it is bad. This low was accurately predicted since the end of last week, as it is for now as bad as forecasted then. I did not check all the values but the station of Aulvik reached 31 knots for example : http://ogimet.com/cgi-bin/gsynres?ind=71974&decoded=yes&ndays=2&ano=2020&mes=08&day=10&hora=06
At Sachs Harbour also it was quite an event : 992.9 hPa at minimum and 25.3 millimeters of rain in 24 hours.
http://ogimet.com/cgi-bin/gsynres?ind=71467&decoded=yes&ndays=2&ano=2020&mes=08&day=10&hora=06
One thing is sure, ice in the Beaufort sea is in the washing machine for now, while there is ~ 1 million squared kilometers of weak ice there.

And the ridge over Arctic is linked to strong convection over the western Pacific, with the MJO in phase 3 - 4. For now, there is now surprise to the trend toward higher values. This said, uncertainty increased after mid-august as a new wave packet should propagate, with higher values coming from the south by the Pacific. What will happen then is not clear. GFS is leaning toward building a new ridge, while IFS is skipping into lower values.

46
Arctic sea ice / Re: The 2020 melting season
« on: August 07, 2020, 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.

47
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.

48
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.

49
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

50
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).

Pages: [1] 2 3 4