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Messages - grixm

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1
Arctic sea ice / Re: The 2020 melting season
« on: September 15, 2020, 03:09:27 PM »
New yearly minimum for daily area, it looks like.


2
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: September 14, 2020, 04:36:33 PM »
PS: The only difference is that I have the impression that there is also a system of fractures a little further upstream.

This one?

3
Arctic sea ice / Re: The 2020 melting season
« on: September 12, 2020, 08:15:23 AM »
The important thing to remember is that 2019, and 2016 are not "very strong melt years".  If you run a trendline through monthly September extent, these years are barely below trend.  If you take into account the context of northern hemisphere June snow and ice area (per Dekker), these years had higher extents than expected.  2020 is also a typical melt year.


2016 certainly was a strong melting year. Extent doesn't show the whole story since the ice was very dispersed that year. But 2016 was very bad in terms of area, and later in the fall and winter it had by far the slowest re-freeze of any year.

4
Arctic sea ice / Re: The 2020 melting season
« on: September 12, 2020, 08:09:14 AM »
Reminder that if 2012 wasn't a thing we'd all be blown away by this melting year. We are so far ahead of #3 in terms of extent.

5
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: September 08, 2020, 01:09:54 PM »
Bremen extent data.

01.09 3.60
02.09 3.56
03.09 3.50
04.09 3.39
05.09 3.39
06.09 3.39
07.09 3.41

6
Arctic sea ice / Re: The 2020 melting season
« on: September 04, 2020, 04:17:02 PM »
NSIDC Daily extent below 4 000 000 km^2! Yay!

8
Antarctica / Re: Antarctic Icebergs
« on: September 02, 2020, 10:35:10 PM »
A68-A twirling around in the same spot for the last month and a half.

9
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: September 01, 2020, 08:36:09 AM »
Semimonthly BOE evaluation
[..]

I have a question regarding the "required average" numbers. It looks like these are just remaining melt divided by average remaining melt days?
If so, I think it would be very beneficial to add a column with "weighed" numbers too, i.e the current number multiplied by the average melt for this date divided by the average melt for every date during the melting season. So that the required average is higher during peak melting season, but lower during early and late season. I think this would more accurately reflect whether we are actually on pace or not.

For example, during the peak of the melting season, we saw many days where we were "on pace" because the daily melt was higher than the required average. But just looking at the chart it was pretty obvious that we were not actually on pace, that's because a BOE would require keeping the same melt rate even in April, May, September etc, as in June, July, August, which is unrealistic.

10
Arctic sea ice / Re: The 2020 melting season
« on: August 31, 2020, 01:52:31 PM »
I think something very bad has happened to the halocline. The 00z EURO's ice forecast shows almost total failure on the European side of Lomonosov Ridge by D10. There is almost open water to the North Pole.

Can you post a link to this forecast?

11
Arctic sea ice / Re: The 2020 melting season
« on: August 30, 2020, 09:47:58 AM »
August 25-29.

2019.

Huge increase in concentration in the Greenland sea in the last frame. A sudden cold spell that froze a bunch of melt pools?

12
Greenland and Arctic Circle / Re: Greenland 2020 Melting Season
« on: August 29, 2020, 09:23:03 AM »
A short cool intermezzo during the melting season or the first sign of the coming freezing season?

Certainly looks like the former.

On second look, maybe not. Significant portions of the glacier is still covered in white over two weeks after the snowfall, despite there being sunny weather and above-freezing temperatures. No clear melt ponds visible any more. During peak insolation season the glacier would have cleared of the snow and looked awful after just a few days.

13
Arctic sea ice / Re: The 2020 melting season
« on: August 24, 2020, 02:02:27 PM »
Looks like daily NSIDC area is back below 2012 to a record for this date

14
Arctic sea ice / Re: The 2020 melting season
« on: August 22, 2020, 10:28:54 PM »
Thoughts on this as a new colour scheme?

Honestly it's not so good on the eyes, I think. The contrast between cyan and green is unpleasant. And also dark gray ocean is not intuitive either, I associate gray with invalid or irrelevant data such as land in the case of ice, not the value 0.

15
Arctic sea ice / Re: The 2020 melting season
« on: August 19, 2020, 07:33:43 PM »
August 4-18 (fast).

Was busy. Normal gif will be tomorrow.

Looks like Beaufort is primed for the chopping block, but I wonder if there is enough melt days left to see the same thing as we did in Chukchi and ESS.

16
Arctic sea ice / Re: The 2020 melting season
« on: August 18, 2020, 07:35:36 PM »
While the DMI 80 temperature has usually dipped below freezing at this point, we're still chugging away above that, this year.

17
Arctic sea ice / Re: The 2020 melting season
« on: August 16, 2020, 01:59:21 PM »
Looks like large extent losses today too.

18
Greenland and Arctic Circle / Re: Greenland 2020 Melting Season
« on: August 15, 2020, 08:16:27 PM »
A short cool intermezzo during the melting season or the first sign of the coming freezing season?

Certainly looks like the former.

19
Greenland and Arctic Circle / Re: Greenland 2020 Melting Season
« on: August 15, 2020, 07:50:00 PM »
Both GFS and ECMWF predicts a heatwave over Greenland starting in around Wednesday.

20
Arctic sea ice / Re: The 2020 melting season
« on: August 15, 2020, 11:43:55 AM »
The extent hole in the Beaufort grows, looks like we'll see big drops the next few days at it fills out through to the edge. Click gif

21
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: August 15, 2020, 10:50:07 AM »
I think it's pretty clear grixm. Extent would be shown as fully ice-covered, but ice concentration data would show less than 100% because of surface wetness and a bit of open water in parts of the pixel. The signal would be different and the algorithm used for concentration data will be able to judge lower concentration and thus lower area in that pixel.
Basically, what you said.

Thanks, that's what I thought

22
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: August 15, 2020, 08:19:20 AM »
Help settle a debate on how concentration data is produced and whether or not we can measure concentration based on features smaller than the concentration data resolution. Here is their argument for why we can't:

Quote
As my second reply pointed out, my understanding is that concentration maps - like the DMI (Or was it NOAA - I believe they actually use the same data source but are slightly different models...) one I believe you posted - are derived from plugging in satellite telemetry to a model and based on that, assigning a concentration value based on the signal return strength in that data.  That is resolved to a binary "On (covered with ice)/Off (no ice)" toggle.

The resolution of that data is pretty coarse. In the case of the NOAA data, the grid cell used is 25km by 25km - basically the size of a large city.

By necessity that means the sensitivity of the measurement is regional rather than local - like seen in the image I posted from Polarstern.  My core argument is,that  if you took the ice quality you see around Polarstern in that image, and covered a 25x25km2 block with it, the return *and* the model output would show that section of sea surface as covered with ice.  It would not see the 10-15% of that surface which is actually open water between the mish-mash of small floes that caused the model to return a positive signal.

And my argument for why we can is that the sensors used for concentration data do not resolve individual pixels to a binary on/off. The microwave imagining sensors functionally work much like normal camera imaging sensors work in that each pixel gets a value on a scale based on the strength of the signal it receives, and this value can be processed into a percentage of ice concentration. Just like how a normal camera gets a value on a scale for each color channel based on the brightness, not just a binary on/off.

And what happens if you have features smaller than the resolution? Well if you for example draw a white and black checkerboard where each square is 1 mm wide, and take a picture from such a distance so that the resolution of one pixel is 10mm, how does the checkerboard pattern look? It doesn't look black, or white, but gray, in other words a 50% brightness value. That's because the sensor naturally averages out the signal from all the colors found inside the pixel. And if we have more black than white squares, the pixel turns into a darker shade of gray. Meaning that we have successfully measured the concentration of black vs white even though the patterns of black and white is smaller than our pixel resolution.

In the same way, if you have tiny cracks or melt ponds on the ice, they affect the total signal brightness that the microwave sensor picks up even if those features are smaller than the pixel size, and thus it can successfully measure the concentration anyway.

NB: Remember that we are talking about concentration/area data here, not extent. I know that extent maps do have a binary ice/no ice value for each pixel. (But this is still derived from the same analog sensor tech though)

We've gone back and forth with the same reworded arguments and are making no headway so I ask you guys which of us are correct. The other guy can chime in as well if he wants, I didn't post his username just in case he wants to stay private.

23
Arctic sea ice / Re: The 2020 melting season
« on: August 14, 2020, 08:40:03 AM »
To amplify my thoughts here, consider this image from the Mosaic thread.  This is Polarstern at the end of June in what would certainly show up as 100% concentration.

It would certainly not show up as 100% concentration. <SNIP>

Not sure if or not you are actually making my argument for me or just quibbling over a detail.

I presume you are looking at DMI?

Am I correct in thinking that's using smoothed data that is 25x25km2?

https://nsidc.org/data/NSIDC-0508/versions/1

How is refuting the entire statement in your post making your argument for you, or quibbling over a detail? I used NSIDC concentration data, I am not sure what the exact resolution it is but the point is that it doesn't matter, because like I said regardless of resolution the ice in your image would not show up as 100% concentration. You asked "How much melt is missed because it's below resolution?" The answer is that practically no melt has been missed because it's below resolution, on area data.

24
Arctic sea ice / Re: The 2020 melting season
« on: August 13, 2020, 10:27:00 PM »
To amplify my thoughts here, consider this image from the Mosaic thread.  This is Polarstern at the end of June in what would certainly show up as 100% concentration.

It would certainly not show up as 100% concentration. The concentration measurement is perfectly able to pick up small cracks between shattered ice, as well as melt ponds on top. That's because the the signal intensity the satellite sees for a certain area at its minimum resolution, will be naturally averaged out for that whole area, because it's an inherently resolution-less analog sensor. If a pixel only has 50% ice in it, the signal the sensors pick up for that pixel will be 50% strong, regardless of how the ice in the pixel is distributed. One wide crack or many tiny cracks, it doesn't matter.

And attached is the actual concentration data for that date with the Polarstern location highlighted. It shows up as around 85-90% concentration, which looks about right to me based on the photo.

25
Arctic sea ice / Re: The 2020 melting season
« on: August 12, 2020, 09:34:15 PM »
North of Greenland today. The deterioration spreads  :o

26
Looks like Greenland had close to its first day since spring of SMB gain

27
Glaciers / Re: Milne Glacier / ice Shelf
« on: August 07, 2020, 08:03:30 AM »
https://ca.reuters.com/article/idCAKCN2523JH

Quote
(Reuters) - The last fully intact ice shelf in the Canadian Arctic has collapsed, losing more than 40% of its area in just two days at the end of July, researchers said on Thursday.

28
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: August 05, 2020, 04:48:33 PM »
In the mean time, while I don't know how to find exact area numbers, Nico's graph for the last two days suggest an averaged drop not much different from the past week, in other words around -60k km^2 per day.

29
Arctic sea ice / Re: The 2020 melting season
« on: August 04, 2020, 10:22:06 AM »
July 30 - August 3.


Looks like the entire pack is slowly being pulled apart down the middle. You can see it on the drift chart too.

30
Greenland and Arctic Circle / Re: Greenland 2020 Melting Season
« on: August 01, 2020, 07:44:12 PM »
What is the large black splotches on the webcam ice? Rock/dirt on the bottom of the glacier? In that case I didn't realize the valley was so shallow. Or is it just a dirty ice layer of the glacier?

31
Greenland and Arctic Circle / Re: Greenland 2020 Melting Season
« on: August 01, 2020, 05:08:43 PM »
I have a question regarding how this mass gain/loss is calculated. Is this a model based upon precipitation? Or is this using date from GRACE data?

How much of this precipitation is falling as rain? If you look a lot of the mass gain is right on the edge of the ice sheet. Isn’t it possible that a lot of moisture in the summer months is rain and that it may not actually add to the mass of the ice sheet long term? Is this taken into account when the calculate the yearly gain/loss?

Also is it possible that some of the mass gain on the outside of the ice sheet is due to the glacier slumping slightly? For example if the glacier sped up slightly and caused the area nearest the sea to rise by say 5 meters would that not show up on GRACE?

Maybe these are separate topics but I’ve been wondering about them for a few years.

TIA

It is a model based on lots of input, including precipitation. You can read all about it in this paper: https://www.frontiersin.org/articles/10.3389/feart.2016.00110/full

But GRACE data is not used. It does not update fast enough and is probably not good enough resolution for a near-real-time product.

32
Arctic sea ice / Re: The 2020 melting season
« on: July 28, 2020, 02:17:58 PM »
Another quite large daily drop in area. We are now below 4 million km^2.

33
Arctic sea ice / Re: The 2020 melting season
« on: July 28, 2020, 07:55:48 AM »
Both 0z GFS and ECMWF initialized with the storm at 968 hPa

34
Consequences / Re: Heatwaves
« on: July 27, 2020, 07:03:28 PM »
Extremely hot weather is forecast in the middle east over the next few days. Over 53 C several places in Iraq and near Kuwait and Iran.

For reference the all-time record for Iraq is 53.8 C. Iran 54 C and Kuwait 53.9 C.

35
Arctic sea ice / Re: The 2020 melting season
« on: July 26, 2020, 08:17:03 AM »
The anomalously thick ice that we had earlier this season along the Atlantic front has been destroyed.


1. The Atlantic  side where it says had ice 1-1.5M above normal(the recent normal,  not the 1970s-90s) has melted out.

It must be mentioned that this ice has been pushed away from land by the compacting winds. I don't how thick it still is and it certainly has melted some, but your posts make it seem like just because there were ice touching the island shores a month ago and now there isn't, means that it all has vanished. No, much of the same ice is still there, just a few hundred km further to the north. So it is possible that the high thickness anomaly from before was reasonably accurate.

36
Arctic sea ice / Re: The 2020 melting season
« on: July 25, 2020, 01:50:47 PM »
How is this ice here being so robust? It's very warm in the water and air, there's little other ice around to buffer the heat, and last PIOMAS update the 15th said that the ice was quite thin at that time. Yet it is still there in significant amounts, it almost doesn't look like it has melted much at all in the past week or two.

37
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 02:33:47 PM »
Daily NSIDC area value went back to record low today.

38
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 11:15:10 AM »
Just wondering, when will the ice in CAA start to give in. It seems like for much of CAA islands temperatures will remain nicely near +10C until the end of July.

It has already started to give in. The southernmost channel is already at least halfway open water, and the innermost large channel is cracking and disintegrating more day by day. This will just slowly spread more and more inwards over the next couple of months. It won't happen all at once though, the CAA ice is resilient.

39
Arctic sea ice / Re: The 2020 melting season
« on: July 23, 2020, 08:06:29 AM »
The ice is compact, I don't understand how that's a controversial statement at all. Like it has been said before, compactness is just area divided by extent. And that figure is very high, as is to be expected after the central basins have experienced compacting winds for weeks on end.

40
Following a discussion from another thread, here is the promised chart of PIOMAS volume divided by UH area, a measure of average thickness.
Please note that due to the wide distribution of ice thicknesses, and by the definition of the measure, average thickness will often rise (or slow down its drop) in times of accelerated area loss, and will drop sharply during initial ice regrowth.
Click each chart to enlarge and zoom.

Notes: Thanks to Wipneus for both sets of data. Some missing UH values were interpolated manually.

Hmm, I thought the PIOMAS raw output was a thickness map, and this had to be masked with an area map to produce a volume figure. And this mask is normally NSIDC area, so I wanted to see what the volume would be if the thickness was masked with the AMSR2 area instead, that's what I meant in the other thread.
In your charts however, it goes the other way: The PIOMAS volume from Wipneus is used as is, and divided by the AMSR2 area, to give a different thickness than PIOMAS originally produced. But this means that the PIOMAS volume input for your equation is already masked with the NSIDC area, no? Or am I misunderstanding something?

41
Has anyone combined the PIMOAS thickness data with AMSR2 area to create a better volume measurement then?

42
Arctic sea ice / Re: HYCOM
« on: July 19, 2020, 10:43:53 PM »
Piomas also shows ice that isn’t really there.  I noticed in particular around the islands east of Svalbard.  Attaching a mostly cloud free pic from 2 days before.  Hycom seems to match better what can be seen in worldview.



PIOMAS does not try to accurately model the ice edges, only the average thickness of an area *if* there is ice there. To calculate the volume it uses external data for area and thus it doesn't count ice in locations that the area data says there is no ice in, even if PIOMAS has modeled a thickness above 0 there.

43
Consequences / Re: Global Surface Air Temperatures
« on: July 19, 2020, 08:02:58 PM »
NASA GISS For June 2020

June: 0.92C above 1951-1980 average (1.18C above preindustrial; 1.38C above 1750)

First 6 months 2020: 1.11C: degrees above 1951-1980 average (1.37 above preindustrial; 1.57C above 1750)

https://data.giss.nasa.gov/gistemp/maps/index_v4.html

As far as I can tell, this is tied with 2019 for hottest month for June ever recorded. Again.

44
Arctic sea ice / Re: The 2020 melting season
« on: July 19, 2020, 07:43:10 AM »
The animation below is from the laptev and near ESS.

The last 4 days.

We can see major melt out in PLACE...

Now that is pretty interesting. With the constant compacting winds one would expect such gaps to be quickly filled by the ice around it, rather than expand because they melt even faster than new ice can fill them.

45
The forum / Re: Forum Decorum
« on: July 18, 2020, 10:30:26 PM »
I must ask why in the world blumenkraft's comment accusing GSY of making a racial slur was left in the melting thread. It is 1) completely off-topic and derailing, and 2) an unfounded and outrageous attack on his character, at least it looks that way from the outside. It deserved to be deleted as much as any of GSY's posts as it was the root cause of the entire drama. Fellow moderators cannot be given special treatment.

46
Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: July 18, 2020, 06:02:08 PM »
I don't think NSIDC area will ever reach zero unless they apply a mask in the Gulf of Ob and the Yenisey Gulf. The NSIDC algorithm thinks ice is present there year-round.

Of course it will if things continue as they are, just maybe not in your lifetime.

He means that it is literally impossible for the NSIDC area to reach zero because the model erroneously but consistently reports ice in areas where there is none, such as the gulf of Ob.

47
Arctic sea ice / Re: The 2020 melting season
« on: July 17, 2020, 03:37:08 PM »
The rate of area loss in the respective seas suggests that Hudson, Baffin, Laptev and Kara all will be empty of ice within 10 days.

48
Arctic sea ice / Re: The 2020 melting season
« on: July 16, 2020, 07:42:27 PM »
The evolution of some dark stains 86N in the CAB. Big gif.

49
Arctic sea ice / Re: The 2020 melting season
« on: July 15, 2020, 08:03:23 PM »
2.  The conclusion that the ice is currently compact is utter rubbish.

There is open water all over the ice pack and huge melt lakes and ponds.


Melt ponds, sure. But open water? I don't really see it. The resolution on sat pics is not great, but still..

50
The fast ice in the fjord is cracking and also draining fast. This is today vs yesterday.

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