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Messages - uniquorn

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1
Arctic sea ice / Re: Latest PIOMAS update (January, mid-monthly update)
« on: January 20, 2021, 12:09:54 PM »
Some people have good use for the updated regional data files.

daily:
https://sites.google.com/site/arctischepinguin/home/piomas/data/PIOMAS-regional.txt.gz

2
Arctic sea ice / Re: Latest PIOMAS update (January, mid-monthly update)
« on: January 20, 2021, 12:07:37 PM »
The updated Fram volume export graph.

3
Arctic sea ice / Re: Latest PIOMAS update (January, mid-monthly update)
« on: January 20, 2021, 11:18:48 AM »
Updated volume and volume-anomaly graphs.

4
Arctic sea ice / Re: Latest PIOMAS update (January, mid-monthly update)
« on: January 20, 2021, 09:32:42 AM »
PIOMAS gridded thickness data was updated to day 15 (15th January). Volume calculated from thickness was 15.56 [1000km3], second lowest for that day of year.

Here is the animation for January so far.

5
Arctic sea ice / Re: Latest PIOMAS update (January)
« on: January 05, 2021, 09:58:48 AM »
Thickness map of day 365, a comparison with previous years and their diff's.

7
Arctic sea ice / Re: Latest PIOMAS update (January)
« on: January 05, 2021, 09:54:38 AM »
Here are the update volume and volume-anomaly graphs.

8
Arctic sea ice / Re: Latest PIOMAS update (January)
« on: January 05, 2021, 09:50:44 AM »
Here is the updated Fram volume export graph.

9
Arctic sea ice / Re: Latest PIOMAS update (January)
« on: January 05, 2021, 09:49:12 AM »
PIOMAS gridded data was updated. Last day is 2020, day 365 which is indeed in the PIOMAS data the last day of the year but in some graphs may be displayed as 30th of December.
Volume calculated from this thickness was 13.90 [1000km3], which is second lowest for day 365 (well behind 2016, but close to 2012).

Here is the animation of December.

10
Arctic sea ice / Re: Latest PIOMAS update (December, mid-monthly update)
« on: December 20, 2020, 05:43:51 PM »
Some people have good use for the updated regional data files.

daily:
https://sites.google.com/site/arctischepinguin/home/piomas/data/PIOMAS-regional.txt.gz

11
Arctic sea ice / Re: Latest PIOMAS update (December, mid-monthly update)
« on: December 20, 2020, 05:42:17 PM »
Updated Fram volume export graph.

12
Arctic sea ice / Re: Latest PIOMAS update (December, mid-monthly update)
« on: December 20, 2020, 05:41:23 PM »
Updated volume and volume anomaly graphs.

13
Arctic sea ice / Re: Latest PIOMAS update (December, mid-monthly update)
« on: December 20, 2020, 05:39:50 PM »
PIOMAS gridded thickness data was updated up to day 350 (15th or 16th December). Volume calculated from this thickness was 11.8 [1000km3], second lowest for day 350.

The animation for December sofar is attached.

14
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: November 21, 2020, 02:51:42 AM »
Yermak plateau area.  36 hour loop
Band I4 inverted colors


15
Arctic sea ice / Re: Latest PIOMAS update (November mid-monthly update)
« on: November 18, 2020, 09:47:11 AM »
Some people have good use for the updated regional data files.

daily:
https://sites.google.com/site/arctischepinguin/home/piomas/data/PIOMAS-regional.txt.gz

16
Arctic sea ice / Re: Latest PIOMAS update (November mid-monthly update)
« on: November 18, 2020, 09:45:19 AM »
Updated Fram volume export graph.

17
Arctic sea ice / Re: Latest PIOMAS update (November mid-monthly update)
« on: November 18, 2020, 09:41:20 AM »
Updated volume and volume-anomaly graphs.

18
Arctic sea ice / Re: Latest PIOMAS update (November mid-monthly update)
« on: November 18, 2020, 09:33:25 AM »
PIOMAS has updated the gridded thickness data to day 320 (16th or 15th of November). Calculated volume on day 320 was 8.07 [1000km3], second lowest, slightly over the 8.00[1000km3] in 2016 .

Here is the animation for November so far.

19
Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 10, 2020, 10:21:34 PM »
It would be better to see also the 18GHZ and 37GHz but I don't know if there is an easy way to vizualise this data.<>
JAXA RGB uses 36H, 36V and 18V, nov1-9 shown split into the 3 component greyscale images.

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

I have taken the 8th of November because it is a cloud free day and the IR channel allow use to spike at the surface:

https://worldview.earthdata.nasa.gov/?v=182321.86694795976,358462.0295864898,905260.1729350943,702610.7856657819&p=arctic&t=2020-11-08-T02%3A00%3A00Z&l=Coastlines,AMSRU2_Sea_Ice_Concentration_12km(max=30),VIIRS_SNPP_Brightness_Temp_BandI5_Night(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_SNPP_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_NOAA20_Brightness_Temp_BandI5_Night(palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_NOAA20_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),AMSRU2_Sea_Ice_Brightness_Temp_89V(hidden),AMSRU2_Sea_Ice_Brightness_Temp_89H(hidden),Reference_Labels(hidden),Reference_Features(hidden),VIIRS_NOAA20_CorrectedReflectance_TrueColor(hidden),VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor

What I find curious is that this high PR is in connection with high IR temperatures. For the 1st and 2nd of November for example, where we can also see a highly fractured ice and open leads, IR temperatures are lower :

https://worldview.earthdata.nasa.gov/?v=245158.89853261935,130120.98769930608,1046101.2498590265,511402.9195286478&p=arctic&t=2020-11-01-T10%3A00%3A00Z&l=Coastlines,AMSRU2_Sea_Ice_Concentration_12km(max=30),VIIRS_SNPP_Brightness_Temp_BandI5_Night(palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_SNPP_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_NOAA20_Brightness_Temp_BandI5_Night(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_NOAA20_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),AMSRU2_Sea_Ice_Brightness_Temp_89V(hidden),AMSRU2_Sea_Ice_Brightness_Temp_89H(hidden),Reference_Labels(hidden),Reference_Features(hidden),VIIRS_NOAA20_CorrectedReflectance_TrueColor(hidden),VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor

https://worldview.earthdata.nasa.gov/?v=249857.53638176603,-49112.767427918385,1270724.6748952155,436862.52663525497&p=arctic&t=2020-11-02-T10%3A00%3A00Z&l=Coastlines,AMSRU2_Sea_Ice_Concentration_12km(max=30),VIIRS_SNPP_Brightness_Temp_BandI5_Night(palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_SNPP_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_NOAA20_Brightness_Temp_BandI5_Night(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),VIIRS_NOAA20_Brightness_Temp_BandI5_Day(hidden,palette=rainbow_2,min=239.6,max=266.5,squash=true),AMSRU2_Sea_Ice_Brightness_Temp_89V(hidden),AMSRU2_Sea_Ice_Brightness_Temp_89H(hidden),Reference_Labels(hidden),Reference_Features(hidden),VIIRS_NOAA20_CorrectedReflectance_TrueColor(hidden),VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor

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

21
Arctic sea ice / Re: Latest PIOMAS update (November)
« on: November 04, 2020, 12:23:49 PM »
The Fram volume export graph.

22
Arctic sea ice / Re: Latest PIOMAS update (November)
« on: November 04, 2020, 12:13:58 PM »
The volume and volume-anomaly graphs.

23
Arctic sea ice / Re: Latest PIOMAS update (November)
« on: November 04, 2020, 12:11:38 PM »
PIOMAS gridded thickness data was updated. Last day was day 315, 31st of October or first of November as you like. Calculated volume on that day was 6.19 [1000km3], which the lowest value for day 315 (by a "firm" margin).

Here is the animation of October.

24
Permafrost / Re: Northern Hemisphere Winter 2020-2021 Snowcover / Misc Obs
« on: November 03, 2020, 02:31:19 AM »
Also, if the EURO is correct it looks like Foxe Basin will be totally iced over by D10 and much of Hudson will be following suit at a rapid pace. There is a chance most of Hudson Bay will ice by 11/15-20, which would be very early. 11/25 is more reasonable which is still 1980s ish.

This would probably anchor a -500MB area in North America accompanied by associated negative temp anomalies, I think this would also advect a major amount of heat into both PAC and ATL fronts but esp the ATL fronts as Baffin is also icing over very quickly while Laptev, Kara, and Barentz are not. They will probably bear the brunt of poleward heat transport derivative of the continental and sea ice anomalies impending in aforementioned regions (IMO) as these anomalies are upwind of an Atlantic Ocean that has a LOT of heat to send poleward.

25
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 25, 2020, 03:03:07 PM »
Building on uniquorns nice code. (current date only)

26
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 25, 2020, 01:56:51 PM »
Quote
Winter is finally here, Kotolny Island is really cold!
No it isn't. The quite moderate 10 day forecast is attached below. The icons indicate extent of cloud cover which affect radiative balance. The weather station reports 2m temperatures but those are relative to its elevation of 8m above sea level.

http://www.aps-polar.org/mv_html/j00001/2015-02/20150206_APS.htm congelation land-fast ice

While ECMWF and GFS assimilate this station in their regional forecasts (and CR in turn), it's not at all clear which hPa over the Laptev (925? boundary layer?) is most relevant to the cold experienced by open water (near-surface air is somewhat clamped to surface water temperature).

GFS is currently reporting air temperatures of -4.5, -4.7, -15.9 at the surface, 1000 hPa, 850 hPa respectively at UTC noon today. These bear no immediate relationship to highs or lows at Kotolny (-12. -7).
Quote
Can buoys in Laptev validate or improve on SST measurement
That 204672 buoy is in a good location but it does not currently appear in IADP's table!
https://iabp.apl.uw.edu/TABLES/ArcticTable.php

However 204761 and 204762 do: these are global drifters of type SVP-B, placed by AARI-USIABP (Russian Arctic and Antarctic Research Institute joint US Interagency Arctic Buoy Program). The former is at 75.23 114.88 on 10/25/2020 measuring water temperature at the bottom of the buoy at 0.96ºC. The latter is at 76.78 118.34 showing 1.68ºC.

It seems like 204763 and 204764 are also worthy of consideration. These are at 76.70 111.48 showing -1.68ºC and 79.90 121.38 seeing -0.80ºC. Uniq has picked these up in #538 below.

"These SVP (surface velocity drifters) were standardized in 1991 with small spherical hull, floats and large Holey-Sock drogues 15m below the surface. In 1993, drifters with barometer ports, called SVPB drifters measure sea surface currents, sea surface temperature baryometric pressure and lat/lon."

The hourly data is in .dat format which opens as tab-ready row & column in any text editor. It uses day number instead of dates: 299 is today Oct 25th. The most recent 557 readings from 204761 average 1.36ºC with a range of 0.58 to 4.08 ºC and stdev of 0.97, that is, the buoy has not seen any temperatures below zero and has mostly been around 1.4±1.0 ºC during its drift.
Quote
Do direct buoy measurements provide an independent check on the daily SST product from GHRSST?
More likely, the buoy data is assimilated into the product but that's unconfirmed.
Quote
Can radiative heat loss be determined from Worldview?
No. Clear weather allows that dramatic definition of heat loss leads via band 15 of Suomi VIIRS along the upper CAA. Note this is calculated from top-of-atmosphere in kelvin and is not suitable for determining overall blackbody heat loss:

"It does not provide an accurate temperature of either clouds nor the land surface, but it does show relative temperature differences which can be used to distinguish features both in clouds and in sea ice and open water over the polar regions during winter (in cloudless areas).... The sensor resolution is 375m, the imagery resolution is 250m, and the temporal resolution is daily."
Quote
How unusual is the current pattern of open water?
The image below calculates the frequency of open water at each position on Nov 1st for the seven years 2013-19 (this date in 2012 is not available from AMSR2_UHH). This gives the lightest gray for open water in all seven years, a slightly darker gray for open water in six of seven years and so on. The progression is fairly orderly Chukchi; the Laptev has mostly been frozen over. The pink shows areas that have never before been open on Nov 1st.

The base image is Smos-Smap ice thinness for Oct 23rd. It has an interesting green fringe of presumably nascent ice in the 2-3 cm thinness range. The interior ice thicker than 0.5m has been replaced with OsiSaf ice motion for the same date; the exterior open water has been removed to reveal the historical open water probabilities.

27
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 25, 2020, 12:52:51 AM »
Here is the Oct 23rd situation. Panoply makes a quite decent no-click map out of GHRSST data with a little help from AMSR2_AWI, OsiSaf and Gimp. Click to see at full resolution of the data source. Note this is SSTfnd, not skin or subskin temperatures. The contour lines correspond to tick mark bins in the palette.

What this is saying is the open water is far too warm from the surface down to 10m depth to even be talking about ice forming without really cold air. Right now, the 2m air temperature at 85º on the 140th meridian connecting the NSI to the North Pole is -2ºC. Please remind me to make a new map when it is has been -35ºC for a couple weeks!

Late fall temperatures seen by the Polarstern:
https://www.awi.de/fileadmin/user_upload/MET/PolarsternCoursePlot/psobsedat.html


20201023000000-OSPO-L4_GHRSST-SSTfnd-Geo_Polar_Blended_Night-GLOB-v02.0-fv01.0.nc

28
The rest / Re: SpaceX
« on: October 23, 2020, 02:46:56 PM »
—- Lunar Starship mockup?
Quote
Austin Barnard (@austinbarnard45)10/22/20, 12:41 PM
NASA Artemis Moon lander anyone?
https://twitter.com/austinbarnard45/status/1319318065872556035
Austin Barnard: Yes this is real,
Austin Barnard: No this is not for flight, my best guess is this will be a mock up lunar variant for the starship presentation.
#Artemis

More photos:
https://twitter.com/austinbarnard45/status/1319387277748019201

https://twitter.com/superclusterhq/status/1319387578026676224

29
Find me another single month that is split at 500mb in the NH as I have shown repeatedly and I would reconsider this stat as a measure of anything.  feel free to adjust the scale, it may be not what I am imagining.

pointing at a massive average of the geopotential heights is not yet useful, and when it becomes apparent that annual or even seasonal averages are split at 500mb, I'm not confident we will retain the capacity to observe it.

The Earth is still round.. Is that the test?

Is splitting at 500mb a useful test?  It's a valid question.

30
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 20, 2020, 12:17:58 AM »
Quote
Effect of storms and high winds on freeze open water?
Whatever the actual effects, we are quite limited by available observables in terms of validation. As with the 2012 GAAC controversy, there is no control on what would have happened without the GAAC.

Consequently even if we had seen SST change here, attribution to the storm is problematic. Here the highest winds and swells did not hit the ice pack head on which has been required for major damage in the past. OsiSaf is showing a distinct anti-cyclonic rotation but has no motion coverage of open water (but see CMEMS).

The first image below maps out where it is currently cold enough to bring surface sea water to -1.8ºC. This would have to persist a very long time without wind to actually freeze anything. Here GFS nullschool doesn't offer SST contouring so it has to be done from a screenshot with wind turned off in Gimp GMIC, then labelled multiple times with green circle site data. A lot of the 'upper half' of the Arctic Ocean is just not cold enough yet.

The slide show looks at entrained Pacific Ocean moisture intrusion via total cloud water (TCW) which is determinable from satellite. The height of the cloud deck above the water surface is not available but presumably low; this property had to be measured during the Mosaic expedition.

This event brought in a gale force jet, matching the maximum the Polarstern encountered during its year. Moist low clouds can completely offset blackbody cooling of the surface but not evaporative, convective, conductive or mixing effects which potentially could be much larger.

Following moist intrusions into the Arctic using SHEBA observations in a Lagrangian perspective
S. Mubashshir Ali  Felix Pithan  19 June 2020
https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/qj.3859 free full

"Warm and moist air masses are transported into the Arctic from lower latitudes throughout the year. Especially in winter, such moist intrusions (MIs) can trigger cloud formation and surface warming. While a typical cloudy state of the Arctic winter boundary layer has been linked to the advection of moist air masses, direct observations of the transformation from moist midlatitude to dry Arctic air are lacking.

Moist intrusions are usually triggered by an anticyclonic blocking‐like feature to the east and a low‐pressure system to the west and also linked to Rossby wave‐breaking events (Liu and Barnes, 2015). MIs cause strong downward long‐wave radiation due to a high localised concentration of water vapor which can lead to anomalous surface warming over land or sea ice."

31
Arctic sea ice / Re: Latest PIOMAS update (Oktober, mid-monthly update)
« on: October 18, 2020, 07:14:14 PM »
Some people have good use for the updated regional data files.

daily:
https://sites.google.com/site/arctischepinguin/home/piomas/data/PIOMAS-regional.txt.gz

32
Arctic sea ice / Re: Latest PIOMAS update (Oktober, mid-monthly update)
« on: October 18, 2020, 07:11:44 PM »
The Fram volume export graph. Looks are a bit different this time  after upgrading the plotting software (matplotlib), probably needs a bit of tweaking.

33
Arctic sea ice / Re: Latest PIOMAS update (Oktober, mid-monthly update)
« on: October 18, 2020, 07:02:21 PM »
Here are the volume and volume-anomaly graphs.

34
Arctic sea ice / Re: Latest PIOMAS update (Oktober, mid-monthly update)
« on: October 18, 2020, 06:59:10 PM »
PIOMAS has updated the gridded thickness data upto day 289 (15th or 16th of Oktober). Volume calculated from thickness on that day was 4.91 [1000 km3]. That is the second lowest value for day 289. The difference with the lowest (2012) is very small though.

Here is the animation for Oktober 2020 sofar.

35
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.

36
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

37
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.

38
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.

39
Developers Corner / Re: Test space
« on: October 03, 2020, 12:29:23 PM »
VISHOP file

41
Arctic sea ice / Re: Latest PIOMAS update (September 2020)
« on: September 03, 2020, 06:47:42 PM »
Latest thickness map compared with recent years and their differences.

42
Arctic sea ice / Re: Latest PIOMAS update (September 2020)
« on: September 03, 2020, 06:42:48 PM »
Fram volume export graph.

43
Arctic sea ice / Re: Latest PIOMAS update (September 2020)
« on: September 03, 2020, 06:41:47 PM »
Volume and volume-anomaly graphs.

44
Arctic sea ice / Re: Latest PIOMAS update (September 2020)
« on: September 03, 2020, 06:39:21 PM »
PIOMAS has updated the gridded thickness data to day 244 (31 August or first of September). Volume calculated from thickness was 4.31 [1000 km3] which is third lowest for that day (behind 2012 and 2019).

Here is the August animation.

45
Some people have good use for the updated regional data files.

daily:
https://sites.google.com/site/arctischepinguin/home/piomas/data/PIOMAS-regional.txt.gz

46
Updated Fram volume export graph.

47
Updated volume and volume-anomaly graphs.

48
PIOMAS gridded thickness data was updated to day 228 (15/16 August). Calculated volume on that day is 5.14 [1000km3], which means a third lowest place before 2012 and 2019.

Here is the animation for August thus far.

49
Developers Corner / Re: Sentinel-Hub custom rendering settings
« on: August 18, 2020, 10:49:49 AM »
Im working on a large project at the moment (Scottish snow, not Arctic stuff), but heres the mask im using;

easy distinction between clouds and ice/snow

https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=81.2492016395353&lng=-70.00167832709849&zoom=11&preset=CUSTOM&layers=B01,B02,B03&maxcc=100&gain=1.0&gamma=1.0&time=2020-01-01%7C2020-07-01&atmFilter=&showDates=false&evalscript=cmV0dXJuIFtCMDEqMi41LEIwNCoyLjUsQjExKjIuNV0%3D


You can separate ice (yellow) from clouds (white) in python with;

img = cv2.imread(directory + filename)
hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)
lower_range = np.array([22, 93, 0])
upper_range = np.array([45, 255, 255])
mask = cv2.inRange(hsv, lower_range, upper_range)

'mask' then becomes cloud-corrected ice, with caveats


50
Arctic sea ice / Re: The caa-greenland mega crack
« on: August 16, 2020, 07:41:41 PM »
A brief peek through the clouds of the eddies north of Ellesmere Island.
Click to run

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