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Messages - JayW

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1
Arctic sea ice / Re: The 2020/2021 freezing season
« on: January 03, 2021, 06:16:41 PM »
A possible candidate is upwelling.
http://oceanmotion.org/html/background/upwelling-and-downwelling.htm

Meanwhile in the Beaufort the warm layer is even thicker below whoi itp120

2
Arctic sea ice / Re: The Rammb Slider Thread
« on: November 29, 2020, 11:47:43 AM »
tidal movement in the nares Band I4  https://col.st/x9U76

3
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.

4
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 20, 2020, 07:06:46 PM »
Here's the chart showing the variations in the distance from ice edge/open water to the N. Pole for all the daily extent minima from 1979 to 2020 (measured every 5 degrees).
The trends largely resembles that of other measures:
2012 had the shortest average distance, at 944 km, followed by 2020 (991 km) and 2016 (1,060 km).
The 81-10 average is 1,328 km, and the maximum occurred in 1980 at 1,452 km.

There are some major limitations to this, especially looking at the minima for a single day when the ice edge may have reached closer to the N. Pole on days other than the minimum - but it's a start.

Anyway, I'll post some more regional data up tomorrow when I have more time.

5
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

6
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 17, 2020, 04:18:34 PM »
Here's an animation comparing the first 16 days of October with 2012
A slightly large file, ~7mb. Click to play.
(larger/better quality version is up on twitter: https://twitter.com/Icy_Samuel/status/1317469236709777416).

7
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 16, 2020, 09:28:12 AM »
You ask about "the Arctic" and then concentrate solely on the surface of the ocean. Which is a fallacy. When heat escapes the sufarce on the ocean it raises air temperatures, but the heat is still in the Arctic. And since the ocean will only freeze if air temperatures are low enough, any process that raises air temperatures is going to delay refreeze.

The cup comparison repeats the same fallacy - the air that flows over the surface of the cup is a lot hotter than the surrounding air, and if we take the cup to be the open waters of the Arctic, then the surroundings of the cup are the rest of the Arctic. And blowing across the surface of the cup is going to warm up the surroundings faster than not blowing across the surface of the cup.

8
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 15, 2020, 11:17:00 PM »
But wouldn't stronger winds vent more heat out of the Arctic and therefore speed up refreeze? I mean, with stronger winds, heat exchange should be faster, the water should cool down faster and ice should appear faster as well. So isn't it a positive feedback, meaning that big open seas lead to faster refreeze due to stronger winds?

How times change. I don't think anyone in the recent past would have imagined such a statement for the Arctic in October. An Arctic where there is heat to be vented out from. An Arctic where more wind and air transported from warmer regions is supposed to make it "cool down faster". An Arctic where big open seas are going to make things colder rather than warmer. I find these statements quite remarkable.

This time of year, due to lack of solar heating the Arctic is cooling as it loses heat outer space. Any winds/mixing from other regions will tend to warm it.

Just for the record, the Arctic is currently about +5C warmer than average, and that, folks is NOT a feedback that is somehow going to make things cool down and freeze "faster".


9
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.

10
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

11
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

12
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 14, 2020, 06:10:39 AM »
October 9-13.

2019.

13
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 13, 2020, 11:31:10 PM »
It's time to go to night vision using worldview terra modis viirs brightness temperature band 15 (night or day) https://go.nasa.gov/2FpoLVd
Today's image showing the effect of wind driven drift on the Atlantic front (awi amsr2 v103 from yesterday inset)

Quote
The VIIRS Brightness Temperature, Band I5 Night layer is the brightness temperature, measured in Kelvin (K), calculated from the top-of-the-atmosphere radiances. 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 over clear land. It can be used to distinguish land, sea ice, and open water over the polar regions during winter (in cloudless areas).

The VIIRS Brightness Temperature layer is calculated from VIIRS Calibrated Radiances (VNP02) and is available from the joint NASA/NOAA Suomi National Polar orbiting Partnership (Suomi NPP) satellite. The sensor resolution is 375m, the imagery resolution is 250m, and the temporal resolution is daily.

Only one Polarview S1B of the area today.

It's also worth looking at relatively cloud free sea ice north of the CAA today. High winds are forecast for this area too over the next couple of days.      https://go.nasa.gov/3dAMzSN

14
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 12, 2020, 01:00:31 AM »
Cold air is blowing off the continent, its just colder closer to shore

15
The politics / Re: The Alt Right
« on: October 11, 2020, 12:02:43 PM »
‘Umbrella Man,’ seen on video smashing windows of Minneapolis store at protests, was white supremacist trying to incite rioting, according to police affidavit

https://www.chicagotribune.com/nation-world/ct-nw-george-floyd-unrest-umbrella-man-20200728-j5dwkcthcfg7djdsctcvr7thcq-story.html


George Floyd protests in Pa. being hijacked by white supremacists, state official says

https://www.timesonline.com/story/news/local/2020/06/02/george-floyd-protests-in-pa-being-hijacked-by-white-supremacists-state-official-says/112781346/

A white supremacist channel on Telegram encouraged followers to incite violence during police brutality protests by 'shooting in a crowd,' according to internal DHS memo

https://www.businessinsider.com/white-supremacist-telegram-channel-encourages-violence-george-floyd-protests-2020-6

Trump frequently accuses the far-left of inciting violence, yet right-wing extremists have killed 329 victims in the last 25 years, while antifa members haven't killed any [up to that date]

https://www.businessinsider.com/right-wing-extremists-kill-329-since-1994-antifa-killed-none-2020-7

and on and on and on...

16
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 09, 2020, 06:34:06 PM »
... It seems to me that many of A-Team's partial BOE posts argue strongly for the accumulated, summer, albedo-driven energy gain caused by ever earlier open water as a massive positive feedback and cause/example of arctic amplification. ...

I'd be the first to admit to having misunderstood the whole thing! But here is a simple version of my naive understanding of the insolation / LWR / negative vs. positive feedback thing.

To begin with, we are talking about Arctic amplification, or the fact that the Arctic warms up faster than the rest of the globe. This is valid during our current antrophogenic warming, and was also something that happened during the last interglacial.

The standard explanation, as also repeatedly expounded by A-Team, is that less sea ice means lower albedo during peak insolation which again means that a lot more heat is absorbed by the ice-free parts of the Arctic ocean. And of course, that is exactly the correct explanation for the Arctic amplification.

But the addendum missing from the explanation is that getting extra energy into open waters during the short period of peak insolation every summer is not enough to explain the Arctic amplification which is a year-round phenomenon, raised air temperatures rather than increased ocean heat content. Lower albedo is only playing the leading role, the second and equally necessary part is played by open ocean going into the polar night, the side-kick that I and probably a lot of other people have not realised was there.

The open waters radiate the extra heat out as long-wave radiation, while at the same time contributing strongly to an isolating blanket of clouds and water vapor. The heat does of course eventually escape into space, but not before causing that good old Arctic amplification and enabling it to linger well into winter.

Which is totally opposite the claim that sees having more open water going into the polar night as some sort of negative feedback working against the Arctic amplification caused by lower albedo during peak insolation. Which was what started the whole discussion.

17
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 07, 2020, 06:20:03 PM »
Some great new forecast data made free by the ECMWF.
Includes sea ice, snow, waves, cloud and all the usual meteorological stuff.
A few sample below.
https://apps.ecmwf.int/webapps/opencharts/


18
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 07, 2020, 03:02:15 PM »
The current forecast is for quite a strong dipole to continue, with winds compressing the sea ice along the Chukchi and Russian facing edges, and spreading it out towards the Atlantic (animation below).
This shows up very nicely in the CMEMS sea ice forecasts to the 13th (2nd attachment) which predicts, amazingly, further significant losses along the Chukchi, ESS and (to a lesser extent) the Laptev ice edge. Gains in the other regions barely enough to produce growth overall.

I'd expect area and extent to be below 2012 next week, with truly exceptional regional record low ice values and further record smashing air temperatures as a result.

19
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.

20
Arctic sea ice / Re: The 2020/2021 freezing season
« on: September 23, 2020, 04:50:50 PM »
10 days of refreezing (Sep 13th to 22nd). Nearly 6mb, click to play

21
Arctic sea ice / Re: MOSAiC news
« on: September 19, 2020, 03:35:13 PM »
drift update from P176.
2 submarine landslides a day seems unlikely. I think I'll stick with tides.

22
Arctic sea ice / Re: MOSAiC news
« on: September 16, 2020, 10:05:08 PM »
A lot of good videos on https://twitter.com/seaice_de

Quote
The Polarstern is represented by the gray ball; it is moored with its starboard bow against the ice
Quote
Lars Kaleschke@seaice_de
12 Sep  Too much tension? Be careful with the anchor line. A very dangerous environment. @MOSAiCArctic  - April 28



23
Arctic sea ice / Re: MOSAiC news
« on: September 08, 2020, 07:24:38 PM »
A squadron of new Pbuoys in tight formation
click for movement and lat/lon

added tbuoys

24
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: August 29, 2020, 12:01:48 PM »
Intriguing description of motion in the fram strait here

Quote
By Matthew Shupe

7/25/20 Round and Round
We are just spinning in circles around here. Around and around. Our floe just keeps on turning. Over the many days that we’ve been here the orientation of our floe didn’t change much, the ship having a robust SW heading. But in the last two days we have spun in two full circles, including about 410 degrees in just the last day! This is really remarkable, and I have no idea how it happens. Is it somehow drag on the floe due to the ship, or just dynamics in the ocean? There have not really been many winds to speak of. No one else understands this either. But it has a fascinating effect on our perspective. Standing out on the short of the floe, you look out and so many other floes go drifting by, seemingly moving quickly. While some of these floes are likely moving in reality, our spinning floe gives the impression that everything else is moving very fast. We are not used to that, as typically our floe just drifts along with everything else. Another one of those Arctic mysteries.

On jul25 they were just crossing 80N, a little east of the large rotating eddy. (weather was only clear on jul22)

  79.9   -1.0 20-07-25 15:00    6   30     -0.1  7  1  97  4042 89/9/ 1017.8
  79.9   -0.9 20-07-25 14:00    6   30      0.0  /  /  //  //// ///// 1018.2
  80.0   -0.7 20-07-25 11:00    6   10      0.0  /  /  //  //// ///// 1018.2
  80.0   -0.7 20-07-25 10:00    5   10      0.3  /  /  //  //// ///// 1018.4



A rather messy buoys eye view of the movement. It didn't occur to me before that the floes might be spinning independently of each other. Different keels, smaller eddies...

25
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 25, 2020, 07:20:37 PM »
Quote
Having downloaded 4.11.6 I can now see the data.
It's not good enough just to 'see the data'. If it is not geo-referenced geo2D, it won't make the maps we want. I just downloaded 4.11.6 of 13 Aug 2020 and it is still showing 2D, not geo2D.

Ok, thanks, I have included the latitude and longitude. Now you can do whatever projection you like.  ;)

26
Arctic sea ice / Re: The 2020 melting season
« on: August 23, 2020, 04:07:16 AM »
Most contributors choose to remain anonymous.  There's nothing wrong with that, and it may be prudent, in many cases.

Announcing to the whole Forum that you want to know the identity of another participant is inappropriate.  in my view, it's grounds for banishment.  But I'm not in charge here. 

<Removed all personal references. O>

27
Arctic sea ice / Re: The 2020 melting season
« on: August 16, 2020, 07:50:17 PM »
As everyone can see, the majority of the ice pack is now transitioning to below freezing temperatures for the remainder of the 2020 northern hemisphere sea ice melting season.

A grand part of the blue area is 0 °C, that is still above freezing if there is on water with salt. But yes, the transition is starting...

Still one month to end the melting season.

28
Arctic sea ice / Re: Freeform season chatter and light commentary
« on: August 12, 2020, 09:00:48 PM »
Wdmn, the phase change itself needs energy.
Link >> http://hydrogen.physik.uni-wuppertal.de/hyperphysics/hyperphysics/hbase/thermo/phase.html

     Sorry, no facts to add to the question, but here some perspectives for those of us who don't work with ice physics every day. 

      It always shocks me when reminded that the heat exchange between frozen vs. melted ice is 80% of the heat energy change required to change water temperature from 0C to 100C.

      That huge energy budget to melt ice has been a defense mechanism for preserving the Arctic sea ice.  Consider the 75+% ice volume losses since 1979, the amount of heat input that required is huge.  As the Arctic loses that defensive wall (the ice phase transition energy requirement), the continued energy input into a decreasing portion of ice and an increasing portion of open water means that things will soon be getting even stranger even faster.

      All of us on ASIF are interested in seeing the volume minimum this year.  We don't get daily updates and images for volume like we do for extent and area, so volume gets a lot less discussion.  But it really is the key number (with a respectful nod to Area as the factor that directly affects albedo).   The 2020 minimum volume will almost certainly be closer to the 2012 record low than either extent or area.

       Thickness is also difficult to measure and visualize.  But it also deserves more respect.  Lots of discussion recently about slow down in extent and area trends, with simultaneous comments about how terrible the ice looks.  It is too bad we don't have regular reports and images about qualitative measures of ice condition like thickness, mechanical strength, continuity etc. Concentration is a qualitative measure of ice pack condition, but it is highly variable and apparently is difficult to accurately measure because of sensor errors caused by water on the ice surface and water vapor in the air.

       One of the key things I've learned this year is to mentally blur the dark areas on the much appreciated and repeatedly viewed AMSR2, U. Bremen, U. Hamburg, and Hycom animations posted by ArticMelt, Blumenkraft, Born from the Void, and others.  I think it was a great idea somebody had on the 2020 Melt Season thread to create  5-day average values for such images as a way to smudge some of the spurious readings and highlight what are the more likely true indications of low-concentration and softening ice

       The 2020 story seems to continue the narrative from 2019  -- continued decline but no replacement of the 2012 record-low quantitative measurements, with progressive rot in the qualitative impressions of ice condition.  Continuation of that trend leads to a point where ice thickness and qualitative melt resistance, exacerbated by increased forces of albedo, ice mobility, fracturing (and thus surface area and lateral melt by contact with ocean water as noted by JD Allen) reach a tipping point at which the right conditions create a major "Poof Event" where huge number of extent and area km2 disappear in a short time period. 

       The math backs up this theoretical scenario.  At some point the flatter Extent decline curve has to catchup to the steeper Volume decline curve.  The closer to the end point at which that occurs, the more radically steep the change in Extnet curve has to be.  I thought that Exent would begin that catch up process by now, but I've been wrong about that so far.  Thickness going below 1 meter could be a key tipping point for that Extent decline acceleration to occur.  We are very close to reaching that tipping point. 
       
       Of course, it isn't a smooth incremental process.  What happens in the real world depends on the chaotic vagaries of the weather.  And the early 2020 melt season seems to have been a doozy among those vagaries.  The rot evident in the former MYI bastion of the Ellesmere - Greenland - North Pole triangle is notable as both a qualitative and quantitative highlight of 2020 so far.   

       In earlier years, for a total melt season to reach "Poof Event" intensity would have required prolonged, extreme and unusual conditions.  But with each year of progressive qualitative decline (i.e. ice pack rot), the conditions required for a severe melting event to occur become less extreme and less far beyond the normal range, and thus more likely to occur.  That is exacerbated by the fact that as the Arctic continues to warm, the "normal range" for the amount of energy in melting events increases, thus making the required intensity for a catastrophic "Poof Event" even more likely to occur.

      As for 2020, it ain't over til the fat lady sings.  The amount of low-resistance ice hovering just over the 15% concentration threshold to be counted as a 100% extent pixel could still result in some dramatic drop days.  IMHO, those values, while interesting to watch, are the daily news that is more noise than signal.  The signal is the qualitative decline in ASI overall and the increasingly dire setup for a knockout punch. 

      I didn't mean for this reply to get so long.  Oren, if this is the wrong thread for a sermon, please relocate as needed.  Here is some more positive news - Tesla Inc.'s Battery Day, scheduled for Sept. 22, could bring big news to help us dig out of this mess.  Getting back to doom and gloom, it will be interesting to see what adjectives Friv has saved up for the first big Poof Event.

29
Arctic sea ice / Re: MOSAiC news
« on: August 10, 2020, 04:23:00 PM »
drift update, mosaic Pbuoys, jul1-aug10.

30
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 07, 2020, 07:56:46 PM »
Please check this out:  8)

http://seaice.de/Arc_AWI_AMSR2_latest.png 
http://seaice.de/Arc_AWI_AMSR2_latest.tiff

http://seaice.de/Ant_AWI_AMSR2_latest.png 
http://seaice.de/Ant_AWI_AMSR2_latest.tiff

Should be based on latest 24 hour AMSR2 swath data if the automated processing works.

This is still under development. Feedback about the data format is appreciated.

Landmask=101
Missing=102

Is the colorscale fine?
Do you need NetCDF?
Does the GeoTiff projection work with your GIS as it should? I tried QGIS only.

New land mask: Danmark and Hagen Fjord north of Greenland are now visible. This is a bug in most other data products!

After some testing I will provide the reprocessed data and updates through AWI ftp site. UHH product will cease.

31
Arctic sea ice / Re: The 2020 melting season
« on: August 06, 2020, 11:05:36 AM »
Animation of the Beaufort sea over the last 12 days.

32
Arctic sea ice / Re: Tides
« on: August 03, 2020, 01:57:49 PM »
<>The tides are always there doing their bits with eddies and some fast ice breakup (e.g. in the CAA) but the ice north of Greenland does not melt and retreat north every summer.
I expect that shelf break melt will become a more accepted part of the melting season as the arctic moves to a higher percentage FYI. Without a constant supply of MYI, north of Greenland could start to look more like north of FJL/Svalbard, dependent on wind direction.
Unfortunately there is only a buoy swarm in the Fram at the moment. Most viewers will be able to detect non negligible tidal movement. For me this disproves the theory that tides just go up and down with a negligible tidal current that has no effect on ice. There is, to me, clearly a more circular motion involved, suggesting eddies and mixing that would affect ice melt, particularly at shelf breaks, where the underlying slope of the ocean floor likely amplifies the turbulence.
These buoys are over 250km from nearest land

shelf break image from http://mseas.mit.edu/Research/MOPE/index.html  (not arctic but shows some of the processes)

added gif from http://rob-hetland.blogspot.com/2005/04/shelf-break-front-simulation.html
Quote
Shelf break front simulation
Here is a sample cross-section from an idealized shelf break front simulation. The contours are salinity, the colorfill velocity.
This is exactly the kind of movement seen in the FJL/Svalbard gap.  click
rammb example here

33
Arctic sea ice / Re: The 2020 melting season
« on: July 26, 2020, 03:23:45 AM »
      After looking at the GFS July 25 18Z forecast, two things jump out that no one has commented on that may be significant. 
 
1.  It looks like the low pressure on the Pacific side and the moderate but not trivial high pressure on the Atlantic side is creating a sustained reversed-Arctic transport wind field moving already fractured ice toward the Laptev Sea where the high surface temperature is an ice killing zone.  The wind speeds are not that high, mostly below 15 knots, but they are persistent.  I don't know how much ice and how far the ice will actually move, but it could be one more negative influence to bleed out CAB ice.   If signficant, the Laptev bite may not have to reach the North Pole ice, that ice may come out to meet the Laptev bite halfway.




2.  Some of the surface heat in the CAA - Greenland - North Pole triangle is from a 2.5 day period of clear sky extending right up to the pole.  Looking at the surface insolation chart, even late July is still close enough to solstice for that to be another significant dagger into the heart of the CAB.  Thus, energy that does not even show up as changing the temperature will be going into melting ice. The triangle used to be home to some of the thickest toughest multiyear ice.  The ice that remains there this September could be a remnant Extent with none of those other qualitative characteristics.   


Pale, light blue = clear sky over ice.  Dark blue = clear sky over water. 
Green - rain, "Aqua-blue" = snow.

    With only 6 years as an Arctic voyeur, I don't know enough to be apocalyptic, but FWIW in addition to what we are hearing from the old hands on deck, add one more "Holy Cow, I've never seen anything like 2020".  After all the melt season conditioning this year, if these forecasts verify the cumulative effect of the different Arctic regional weather events looks to be in the same league as the GAC2012. 

    No, the low pressure system is not as intense or as long lasting as GAC2012, but this Arctic-wide scenario has someting going on just about everywhere: cyclone in the already fractured Beaufort, unprecedented subsurface heat in the Beaufort, roasting top down heat in the CAA, clear sky and heat in the heart of the CAB triangle, extensive and intensive heat across the entire Atlantic front.  All this happening to ice that has been softened up by May melt pond set up, and extended periods of heat and clear sky in June and July.  So the widespread melt pressure is going onto ice with far below normal resistance.

     Thus the cumulative effect looks equally as significant as the GAC2012.  If I'm wrong, let me know.  That's how I learn.   

34
Arctic sea ice / Re: The Rammb Slider Thread
« on: July 25, 2020, 06:55:21 PM »
Just another GIF of the Nares tides. I know, i've posted them a lot already, but i can't help but being fascinated by them.

A tiny bit of export happened!

Stills not skipped, BIG FILE, click to play.

35
Arctic sea ice / Re: The science of ice ridging and rafting
« on: July 24, 2020, 11:33:42 AM »
Good thread. Although I'd like to point out to Michael that if he thinks anticyclonic ridging during summer can be seen in satellite imagery, he has some maasssssssive explaining to do.

And to gandul and others - I dislike phrasing like "Ice piling up must have happened in substantial degree". Totally groundless without a shred of evidenced, not only making a "must have happened" claim but adding "substantial" to it as well!

Why "must" it? And where is the evidence for "substantial"? Please give reasoning and evidence for any claims, and don't just repeat them at nauseam.

36
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 03:38:02 PM »
Oren, compaction is well known to lead to ridging (I would not call it stacking) in 1D meshes (seen fron above) as the ice is rigid and fragile and it is the only way to alleviate pressure.
I don't find no reason to think this summer compaction has led to this in several places. I don't buy the 'as it compacts the exact amount of holes appear by meltout'. Many holes have indeed been seen but not in the central pack.
The burden of proof falls on those who claim there has not been ridging at all, not in those who claim the opposite. Thickening by pressure is a very well known feature of Arctic landscape.

But anyway, stormy August may destroy much of this, and this discussion may be forgotten.
I'm with Oren on this. I'd be extremely surprised to see any ridging resulting from mild winds at the height of the melting season. And I haven't seen any good arguments claiming otherwise.

The recent fall in concentration is not that massive anyway, and is probably not caused by any significant "compacting" by the slight winds as much as by fast melting of very dispersed ice on the Siberian side as can be seen very clearly in Aluminium's animation.

<Removed personal character claim. O>

37
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 08:23:42 AM »
Isn’t the so called compaction simply masking in situ melt in the CAB? That explains the rapid retraction of ice edge towards north with unprecedented extent losses.

38
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...

39
I think we all agree, as Glen points out, that the decline in extent must at some point catch up with the decline in volume. Hence the decline in extent cannot continue at its current linear rate. But will the rate of change be incremental or sudden? I.e. will the curve bend or break?

And is it somehow linked to the thickness of the ice, i.e. does the rate of melt increase with falling average thickness? The physics are not reversible, but still, the following holds true:

      It is well documented and accepted that the chemical and structural characteristics of Arctic sea ice varies with thickness.  Those qualitative differences have to make some difference to the melt rate. 

One of the important differences is to do with the core temperature of the ice. The sooner the core warms up, the faster the ice melts. And thinner ice warms up faster than thicker ice. Other differences between various thicknesses are based more on the age of the ice than the thickness per se. Brine channels, brittleness, structural strength etc. change with age rather than thickness, but then thickness also increases with age so again there is a link albeit not a direct causal link.

All in all I agree with Glen that ice melt should accelerate with decreasing thickness, but how large is this effect, and more importantly, could it be used as an explanation for the current rapid decline in ice extent?

     Is there a fallacy in this line of thinking?  What alternative mechanism accounts for the  required unification of Extent and Volume as they approach zero.  Binntho I'm talking to you!  This is right up your alley and I haven't seen you post for a while.

The Internet for the entire country was blocked for over 2 weeks, and then only activated in the capital. So I took the first plane and here I am in a hotel room, hoping to catch up on some work and instead indulging in my preferred pastime of writing on the ASI forum!

Coming back after 3 weeks and seeing the incredibly rapid melting that has taken place in July has been fairly stunning. As of today the difference between the current year and the second lowest is almost 630.000 km2 - an incredible difference.

My own view as developed over the seasons is that it is rather the amount of open water along the perifery of the ice that will be the largest contributor to accelerated fall in extent, rather than the average thickness of the ice.

Large areas of open water during maximum insolation means that a lot of extra energy enters the system, but of course only where the ice is not. A delay to refreeze rather than an accelerated melt. The second factor needed is storminess - which has been missing for all of July as far as I can gather, but which might well be picking up now. Storms move the warm waters around, bringing them to where the ice is, storms cause waves that break up the ice (and the longer the fetch, the bigger the waves), and storms late in the season probably have a positive impact on the radiative balance.

So the current situation is exactly what I would predict would accelerate melt as soon as the storms kick in. But that does not explain why we have so much open water to begin with!

Perhaps a simplification of the current situation would be to reduce it to three or four factors that combine to cause increased melt at different times - the first of course being the steadily increasing global temperature, the second being the unusually warm spring followed by a very sunny July this year, the third being the increasingly thin and fragile ice that undoubtedly melts faster than the older and thicker ice, and the final (and to my mind, increasingly important as time goes), is the amount of open water.

But for the future, in my opininon the main factor in increasing the rate of melt will be the amount of open water in the second (post max insolation) part of the melting season. A steady linear decline overall will secure the increased amount of open water up to that point, and a non-linear effect of open water + storminess will take care of the rest.

40
     Does anybody care to disabuse me of my conjecture that there is a nonlinear relationship between ice thickness and melt resistance - with decrease in melt resistance curving down faster than the linear % decline in thickness - due to qualitative differences in thinner vs. thicker ice?

     The fact that ice accumulation is radically nonlinear with increasing thickness is accepted as established fact, e.g. the curve published by Thorndike 1975
.

     Earlier this year I pitched the idea that the reverse is true for melting, with 1 meter thick ice melting at twice the rate of 2 meter ice (0.8 cm/day vs. 0.4 in the example shown):  .

     Those who actually understand the physics of ice melt shot down that theory, explaining that the energy flows involved in summer melt are not simply the reverse of winter freeze.  Correction which I gratefully accept, .... but

     ....even if a straight reversal of the thickness-freeze rate curve to estimate thickness-melt rate curve is too simplistic to be valid, that still leaves open the possibility, and (in my mind at least) the near certainty that the melt rate vs. thickness ratio is not a stricltly linear 1:1 ratio.  I have no idea what it would be, but it I'm almost certain that the melt rate for 1 meter vs. 2 meter thick ice has to be greater than 1:1.  And that ratio has to be even greater for 0.9, 0.8, 0.7 etc. meter thick ice vs 2 meter ice. 

      It is well documented and accepted that the chemical and structural characteristics of Arctic sea ice varies with thickness.  Those qualitative differences have to make some difference to the melt rate. 

      This is not merely an academic question.  An accelerating melt rate with declining thickness would have major consequence for acceleration of Extent and Volume losses as average thickness continues to decline as shown on the chart posted by gerontocrat at https://forum.arctic-sea-ice.net/index.php/topic,119.msg275579.html#msg275579  (A chart which I nominate for the ASI Graphical Hall of Fame).

      Which leads to a vision of the near future of the ASI showing accelerated melt to the same weather conditions and energy inputs of previous years, and even more so as continued cumulative global warming, exacerbated by Arctic amplification, increases energy inputs into melt seasons and reduces winter refreeze potential (and greater potential for Arctic cyclones, and jet stream weakening to allow warm air mass incursions, etc.). 

      If so, the drop from 4 million km2 September Extent to 3 million could occur in a shorter time frame than the observed trend for the drop from 5 million to 4 million.  And with average ice thickness in late summer approaching 1 meter, a nonlinear melt response for thinner ice would  accelerate even more for the drop from 3 million to 2 million km2, and even more than that for the drop from 2 million to 1 million km2. 

    (I suspect that dropping below 1 million km2 would complicate things because that final ice has resistance due to protection within bays etc. that would compensate for a thin ice melting effect).

      By extrapolation, the linear Extent decline trend reaches zero decades later than the Volume trend.  But of course that is impossible, because when there is no Volume, there is no ice left to create Exent.  So the Extent trend has to eventually start accelerating to curve downward to catch up with Volume by the date when they both reach zero.  I think that thin ice melt acceleration will be a major contributing factor (along with mobiillty for export, fracturing, surface area and possible others), that will cause that to happen.

     Is there a fallacy in this line of thinking?  What alternative mechanism accounts for the  required unification of Extent and Volume as they approach zero.  Binntho I'm talking to you!  This is right up your alley and I haven't seen you post for a while.

    One more conjecture.  I think that as the average thickness in the High Arctic Seas, as shown in gerontocrat's graph, is approaching 1 meter in September, the accelerated thin ice melt effect, which might have been relatively inconsequential until now, will become an increasingly important influence.  As a result, there will be "Extent goes poof" events of increasing scale and frequency over the next 10 years, resulting in a BOE by the early 2030s if not before.

41
Arctic sea ice / Re: The 2020 melting season
« on: July 20, 2020, 04:16:55 PM »
Folks, this thread is for discussing the melting season itself. When the thread hits a point of scientific contention about whether something affects or not affects this specific melting season or the ice in general, that is the time to move that discussion to an existing or new thread.
Recently a thread was started discussing the effect of flights on the Arctic, though it then deteriorated a bit.  I recommend moving along to that thread or another of your choice, to discuss whether in fact clean skies made the melting season more extraordinary or not.

42
Arctic sea ice / Re: Arctic Image of the Day
« on: July 20, 2020, 08:57:55 AM »
A cute island in the ESS from the second of July to yesterday. Cloudy days skipped. Needs a click.

43
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: July 19, 2020, 03:53:08 PM »
NSIDC daily extent

7-day average: (6789-7819)/7 = -147
14-day average: (6789-8807)/14 = -144

2020-07-04  8.807
2020-07-05  8.648  -159
2020-07-06  8.455  -193
2020-07-07  8.276  -179
2020-07-08  8.133  -143
2020-07-09  8.037    -96
2020-07-10  7.861  -176
2020-07-11  7.819    -42
2020-07-12  7.747    -72
2020-07-13  7.473  -274
2020-07-14  7.308  -165
2020-07-15  7.188  -120
2020-07-16  7.078  -110
2020-07-17  6.954  -124
2020-07-18  6.789  -165

44
The forum / Re: Forum Decorum
« on: July 19, 2020, 08:33:46 AM »
Quote
“You can please some of the people all of the time, you can please all of the people some of the time, but you can’t please all of the people all of the time”.”
John Lydgate
Well. this lurker is happy with the mods, and grateful for them. Would be even happier if they were stricter with some of the stragglier elements. Dissent is never a problem; arrogance, ignorance and discourtesy are.

45
Arctic sea ice / Re: The 2020 melting season
« on: July 18, 2020, 10:42:08 PM »
Agreed. CAB compaction. A lot of talk but no analysis yet. Here looking at four identifiable points from jul10-17 north of Laptev.  https://go.nasa.gov/3fGWDd7
area jul10=64,120.16km^2
area jul18=63,738.14
ratio= 0.9903. Compaction in this area=not much
   a       nice      slow      animation 
The tools are all on worldview. An enthusiast might measure a larger area

46
Arctic sea ice / Re: The 2020 melting season
« on: July 18, 2020, 01:52:34 PM »
The ensemble probability maps (animated below for 120 to 192 hours out) are now showing a high risk of strong winds (>50km/h) around the Arctic from 5 days out. These kinds of maps can be more informative than looking at individual model runs when assessing the probability of storms and such.

47
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: July 17, 2020, 05:30:27 PM »
Not really bouncing. Two points of interest here, the large lift off and the smaller floe (marked) drifting in a different direction

added large rammb, jul13-17

48
Arctic sea ice / Re: The 2020 melting season
« on: July 17, 2020, 11:30:58 AM »
With the NSIDC data updated, we've seen a drop of 2.257 million km2 since June 30th, this is a record for that time period, with the next lowest being 2007 with 1.951 million. It's also a record in terms of the % dropped, 23.9% , much higher than the next largest, 20.2% in 2011. Incredible changes.

Will PIOMAS join in on the dramatics, I wonder?

49
Arctic sea ice / Re: The 2020 melting season
« on: July 16, 2020, 10:03:29 PM »
The ice in the Victoria Strait (SE of Victoria Island in the CAA) is starting to break up.

50
Arctic sea ice / Re: The 2020 melting season
« on: July 16, 2020, 06:23:12 AM »
July 1-15 (fast).

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