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Wipneus

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Re: 2018 sea ice area and extent data
« Reply #1250 on: July 31, 2018, 04:56:08 PM »

Hullo Wipneus,

Qu1. You reckon these losses are real?


I have no indication for sensor failure if that is what you mean.

But it is still extent measured on a relatively coarse (25x25km) grid: the 15% rule can cause rather big jumps in extent with comparatively small differences in concentration. Here area is only down -47k, so that is probably the case. Some "un-flashing" can happen in the next few days.

Quote
Qu2 - off-topic. I (and others) have looked for a definitive map of NSDC's 14 Arctic Seas with boundaries, and failed. Is there such a map, there must be, and could you post it on the Arctic Maps thread - https://forum.arctic-sea-ice.net/index.php/topic,417.0.html

It really helps when looking at the data sea by sea to have a map.

Cheers,

gerontocrat

ps: The best I found was this (attached) which is not much use

I am using the "Cryosphere Today" (with very minor modifications) map. A very similar map is used somewhere on NSIDC. The map is attached.

Also on NSIDC is the MASIE regional map:
https://nsidc.org/data/masie/browse_regions
A Jaxa site has yet another map:
http://kuroshio.eorc.jaxa.jp/JASMES/climate/images/NHM_9999.png

My feeling is that the "Cryosphere Today" map is mostly OK,  if something could be changed it is the Central Arctic Basin that feels to be too large.

Phil.

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Re: 2018 sea ice area and extent data
« Reply #1251 on: July 31, 2018, 05:45:03 PM »
Wipneus, looking at the detailed results things like the Okhotsk seem bogus as satellite images show no ice there!  17.6 k corresponds to a few pixels (~30) even at 25x25 resolution, I interpreted this as a land/sea boundary error.  What do you think and if this is the case what do you think the total overcoat is?

magnamentis

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Re: 2018 sea ice area and extent data
« Reply #1252 on: July 31, 2018, 06:34:15 PM »
Wipneus, looking at the detailed results things like the Okhotsk seem bogus as satellite images show no ice there!  17.6 k corresponds to a few pixels (~30) even at 25x25 resolution, I interpreted this as a land/sea boundary error.  What do you think and if this is the case what do you think the total overcoat is?

that's an old topic and has been mentioned and explained many times over many years.

yes it's false ice that depending on conditions can show along coasts.

it comes and goes but does not significantly contribute to the numbers on one hand and
part of it is considered in the algorithms hence even less significant impacts on results as a whole.

oren

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Re: 2018 sea ice area and extent data
« Reply #1253 on: July 31, 2018, 07:23:52 PM »
Quote
Qu2 - off-topic. I (and others) have looked for a definitive map of NSDC's 14 Arctic Seas with boundaries, and failed. Is there such a map, there must be, and could you post it on the Arctic Maps thread - https://forum.arctic-sea-ice.net/index.php/topic,417.0.html
I am using the "Cryosphere Today" (with very minor modifications) map. A very similar map is used somewhere on NSIDC. The map is attached.

Also on NSIDC is the MASIE regional map:
https://nsidc.org/data/masie/browse_regions
A Jaxa site has yet another map:
http://kuroshio.eorc.jaxa.jp/JASMES/climate/images/NHM_9999.png

My feeling is that the "Cryosphere Today" map is mostly OK,  if something could be changed it is the Central Arctic Basin that feels to be too large.
CT regions map is used in Wipneus' regional data and graphs.
NSIDC regions (MASIE) map is used for NSIDC regional area and extent data.
The major differences are the sizes of the Beaufort and Chukchi, which are much larger in NSIDC data. The ESS is also quite different, and the CAB is naturally much smaller.

gerontocrat

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Re: 2018 sea ice area and extent data
« Reply #1254 on: July 31, 2018, 08:23:07 PM »
Thanks for the replies.

Only glitch is MAISIE lumps Baffin & St. Lawrence as one sea. But not a big deal. So it is Maisie for me as it is NSIDC data that this amateur uses.

Question is, can I get one of the feeble microsoft packages to make a watermark of the maisie map to plonk on top of the NSIDC sea ice concentration image. Probably not.

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oren

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Re: 2018 sea ice area and extent data
« Reply #1255 on: July 31, 2018, 08:55:53 PM »
Here's an approximate comparison of the total area of the inner basin regions - those that reach maximum extent every winter - between the CT map that Wipneus uses, and the MAISIE NSIDC map.

Wipneus AMSR2 (Cryosphere Today map)  NSIDC Regions (MASIE map)
CAB         4.48     3.22
Beaufort   0.53     0.94
Chukchi    0.61     0.83
ESS         0.95     1.3
Laptev     0.73     0.87
Kara        0.9       0.92
CAA        0.78      0.76

Note: I personally much prefer the CT map, with its smaller and more geographically homogeneous seas, but I would like to see the huge CAB split up to 4 sub-regions (horribly crude drawing attached), which will enable better discerning of new alarming trends:
Pacific CAB - which will show the incursion on the pacific front and its development over the years
Siberian CAB - which will show the Laptev bite
Atlantic CAB - which will show the changes occurring off-Svalbard
Inner CAB - which will hopefully not show significant incursions until we get closer to a BOE.

I realize AMSR2 data only goes back 6 years, but I think it can still teach us a lot about new trends going forward, especially thanks to its relatively high accuracy.

Tor Bejnar

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Re: 2018 sea ice area and extent data
« Reply #1256 on: July 31, 2018, 09:17:40 PM »
I find it interesting how the Navy Beaufort thickness 30-day gif [note: certificate issues - I ignore them] auto-corrects when new data 'changes everything'.  Specifically, near the start, a bite of 2 m ice (pale to dark green) poofs, and later on, a rectangle of largely 0.5 m ice (purple) semi-poofs. [I cannot choose when my gif-maker starts, so the show starts with a flicker of the end scene.]
« Last Edit: July 31, 2018, 09:27:31 PM by Tor Bejnar »
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LDorey

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Re: 2018 sea ice area and extent data
« Reply #1257 on: July 31, 2018, 11:27:01 PM »
Isn't there some kind of manual re-calibration at the end of every month, I kind of remember that from when Wipneus did the daily posts of his home brew last year?
Liam

Massive drop in NSIDC SIE (253K, following 211K yesterday), second lowest on record now, causing massive uptick in compactness. Glitch or real?

bbr2314

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Re: 2018 sea ice area and extent data
« Reply #1258 on: July 31, 2018, 11:51:50 PM »
Isn't there some kind of manual re-calibration at the end of every month, I kind of remember that from when Wipneus did the daily posts of his home brew last year?
Liam

Massive drop in NSIDC SIE (253K, following 211K yesterday), second lowest on record now, causing massive uptick in compactness. Glitch or real?

That happens the first of the month, which means we probably get another double century break tomorrow, joy!

DavidR

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Re: 2018 sea ice area and extent data
« Reply #1259 on: August 01, 2018, 02:29:18 AM »
Isn't there some kind of manual re-calibration at the end of every month, I kind of remember that from when Wipneus did the daily posts of his home brew last year?
Liam

Massive drop in NSIDC SIE (253K, following 211K yesterday), second lowest on record now, causing massive uptick in compactness. Glitch or real?

That happens the first of the month, which means we probably get another double century break tomorrow, joy!
Not Quite. The 253K figure is for July 30th so we have July 31st to go yet.   And the average drop on Aug 1st  is 107 K.  Only 2 years have dropped 200K or above on Aug 1st with a record drop of only 202K.

Currently we have the biggest ever decline (-3.377M Km^2)  in July. Although not the biggest decline in the first 30 days of July as 2009  had an increase on July 31st to take its total July loss  (-3.375) to  less than 2018

2018  has had 6,  200+K drops this year, the previous record was 4 in 1991. 1993 and 2012 had three.  It  has 7 days with the lowest drop for that day, three days with the biggest increase for the day and the 71K increase on July 8 was the largest ever increase in July. Its been very  volatile.

A total drop of 308K over the next two days would put 2018  lowest on record.
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bbr2314

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Re: 2018 sea ice area and extent data
« Reply #1260 on: August 01, 2018, 11:40:09 AM »
Isn't there some kind of manual re-calibration at the end of every month, I kind of remember that from when Wipneus did the daily posts of his home brew last year?
Liam

Massive drop in NSIDC SIE (253K, following 211K yesterday), second lowest on record now, causing massive uptick in compactness. Glitch or real?

That happens the first of the month, which means we probably get another double century break tomorrow, joy!
Not Quite. The 253K figure is for July 30th so we have July 31st to go yet.   And the average drop on Aug 1st  is 107 K.  Only 2 years have dropped 200K or above on Aug 1st with a record drop of only 202K.

Currently we have the biggest ever decline (-3.377M Km^2)  in July. Although not the biggest decline in the first 30 days of July as 2009  had an increase on July 31st to take its total July loss  (-3.375) to  less than 2018

2018  has had 6,  200+K drops this year, the previous record was 4 in 1991. 1993 and 2012 had three.  It  has 7 days with the lowest drop for that day, three days with the biggest increase for the day and the 71K increase on July 8 was the largest ever increase in July. Its been very  volatile.

A total drop of 308K over the next two days would put 2018  lowest on record.
My mistake! And you are correct. I think we stand a decent chance of taking the record, as well. Looking at Bremen, there is an enormous amount of peripheral ice now disappearing entirely. With cloud-free days coming up, there is a bunch of false ice that will also finally register as open water.

If we don't eclipse 2012, I expect we match its pace of decline, leaving all other years in the dust.

DavidR

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Re: 2018 sea ice area and extent data
« Reply #1261 on: August 01, 2018, 01:41:43 PM »
That happens the first of the month, which means we probably get another double century break tomorrow, joy!

Currently we have the biggest ever decline (-3.377M Km^2)  in July. Although not the biggest decline in the first 30 days of July as 2009  had an increase on July 31st to take its total July loss  (-3.375) to  less than 2018
A total drop of 308K over the next two days would put 2018  lowest on record.
My mistake! And you are correct. I think we stand a decent chance of taking the record, as well.
If we don't eclipse 2012, I expect we match its pace of decline, leaving all other years in the dust.

And we got a 14K rise on  the last day taking the monthly drop to  just (-3.363) and second place.
Toto, I've a feeling we're not in Kansas anymore

Tetra

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Re: 2018 sea ice area and extent data
« Reply #1262 on: August 01, 2018, 01:49:04 PM »
That happens the first of the month, which means we probably get another double century break tomorrow, joy!

Currently we have the biggest ever decline (-3.377M Km^2)  in July. Although not the biggest decline in the first 30 days of July as 2009  had an increase on July 31st to take its total July loss  (-3.375) to  less than 2018
A total drop of 308K over the next two days would put 2018  lowest on record.
My mistake! And you are correct. I think we stand a decent chance of taking the record, as well.
If we don't eclipse 2012, I expect we match its pace of decline, leaving all other years in the dust.

And we got a 14K rise on  the last day taking the monthly drop to  just (-3.363) and second place.

Woah. That’s a huge variation. So the sensors are just glitching out all over the place? Thanks to cloud cover etc?

I’m not saying the ice isn’t slush or anything, but it’s obvious that there must be some left where open water is being reported. Like the Beaufort.

gerontocrat

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Re: 2018 sea ice area and extent data
« Reply #1263 on: August 01, 2018, 02:37:14 PM »
NSIDC Total Area as at 31 July (5 day trailing average) =  4,717,046     km2
This is 120 155 k above the 2010-2017 average area


Total Area loss 34 K, Central Seas loss 20k, Periphery loss 12 k, Other Seas loss 2 k  
Analysis of individual seas.

Pacific Side
- The Bering Sea - finished,
- Chukchi Sea loss 7 k, area is now well below the 2010's average,
Atlantic Side
- Baffin Sea loss 5 k,
- Greenland Sea loss 6 k,
- Barents Sea - finished,
- The Kara Sea area loss 1 k, Area now just 52 k, less than 5% of 1980's maximum,
- The Laptev Sea area loss 5 k.
CAB
- Beaufort Sea loss 14 k,
- The Central Arctic Sea gain 18 k,
- The Canadian Archipelago loss 2 k,
- East Siberian Sea loss 10 k .
Other seas
- St Lawrence -finished,
- Hudson Bay area loss 2 k, Area now 70 k and just about at average.
- The Okhotsk Sea - finished.

On average, this is when daily area loss declines sharply - on this day to 50+k. This low area loss of 34 k is 20+k below average. The  5 day trailing average extent loss in contrast wasover 100k per day for the last three days (5 day average eliminates most of the ups and downs of daily extent measures and the monthly adjustments). Extent losses are still catching up with area losses again.

Qu1. The question is - will above average area losses follow the big NSIDC daily extent losses ? Not on July 31, that's for sure. GRAPH attached (extent vs area)

Qu2. How low will Greenland Sea Ice Area go ? If export of ice down the FRAM strait is finished for this season and that warmth keeps drifting up from the Atlantic (that blocking high from Western Europe across the Atlantic is liable to stay there for some time) then....

Qu 3. Commenters have suggested the massive ice loss in Beaufort etc may be a mirage. Illusion or reality or a bit of both?

ps:- A dose of reality to counter the hyperbole of recent posts on this thread ?
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Phil.

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Re: 2018 sea ice area and extent data
« Reply #1264 on: August 01, 2018, 02:50:45 PM »
Wipneus, looking at the detailed results things like the Okhotsk seem bogus as satellite images show no ice there!  17.6 k corresponds to a few pixels (~30) even at 25x25 resolution, I interpreted this as a land/sea boundary error.  What do you think and if this is the case what do you think the total overcoat is?

that's an old topic and has been mentioned and explained many times over many years.

yes it's false ice that depending on conditions can show along coasts.

it comes and goes but does not significantly contribute to the numbers on one hand and
part of it is considered in the algorithms hence even less significant impacts on results as a whole.

Yes I know that, but most years Okhotsk has gone to zero, whereas this year it has not.  I was wondering if Wipneus had an explanation for that (new algorithm etc.)

gerontocrat

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Re: 2018 sea ice area and extent data
« Reply #1265 on: August 01, 2018, 03:16:54 PM »
Area vs Extent where it matter most - the Central Arctic.

Two graphs attached - Central Arctic Sea Extent, and Central Arctic Sea Area.
On which one are you going to base your opinion as to the state of the ice ?

Me?  I say area as, in theory, should show changes earlier than extent, and is a better measure than extent of how much ice there is (volume would be the best).

Also the area being so much above the 2010's average suggests to me that this year's extent minimum will be nothing special.
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Tor Bejnar

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Re: 2018 sea ice area and extent data
« Reply #1266 on: August 01, 2018, 05:32:46 PM »
Attached two sets of graphs show 2018-07-31 JAXA data (from the ASIG), with extent on the left and area on the right.  The area graphs have had the vertical scale changed and the graphs position shifted so that the June (2016 or 2017) peak and September (2016 or 2017) minimum are juxtaposed.  In both cases, the 2018 area is proportionally 'ahead' (closer to eventual minimum) of the 2018 extent.  As the current extent is in record early territory and the current area is mealy very close to the earliest, this ahead-ness is less pronounced than in 2012 and 2016. 

What I conclude from this analysis is that (generally) extent drops proportionately more than area after July 31 than it does before July 31.  Whatever path CAB area loss takes (whether a high melt 2016 path or a low melt 2017 path), the extent will drop somewhat more than the corresponding year, but not significantly more.  If 2018 CAB area loss 'duplicates' the 2016 losses from here on out (nearly duplicating 2012's loss), I would expect the CAB extent to remain above the 2012 minimum.
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Michael Hauber

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Re: 2018 sea ice area and extent data
« Reply #1267 on: August 02, 2018, 01:33:09 AM »
Massive drop in NSIDC SIE (253K, following 211K yesterday), second lowest on record now, causing massive uptick in compactness. Glitch or real?

I don't think the conditions in the Arctic were suddenly so much worse than the previous few days so at to more than double the rate of melt. 

If sensor variations can cause ice to be measured at 50k more or less on the day, then the sensors are working well, and measuring ice to about 1% accuracy (when area/extent is near 5m).  But then if daily losses are near 100k, and sensors switch from an overestimate of 50k to an underestimate of 50k, then sensors are reporting twice as much ice lost for the day as actually occurred.
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Rod

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Re: 2018 sea ice area and extent data
« Reply #1268 on: August 02, 2018, 05:23:27 AM »
Massive drop in NSIDC SIE (253K, following 211K yesterday), second lowest on record now, causing massive uptick in compactness. Glitch or real?

I don't think the conditions in the Arctic were suddenly so much worse than the previous few days so at to more than double the rate of melt. 

If sensor variations can cause ice to be measured at 50k more or less on the day, then the sensors are working well, and measuring ice to about 1% accuracy (when area/extent is near 5m).  But then if daily losses are near 100k, and sensors switch from an overestimate of 50k to an underestimate of 50k, then sensors are reporting twice as much ice lost for the day as actually occurred.

It is important to remember that extent and melt are two totally different things. Extent tells you where the ice is, but it does not tell you how much ice is there.  It is an all or nothing number and each cell in the grid is worth 625 km2.  Those numbers can go from 0 to 625 depending on how the wind blows. 

I only bring this up because of all the talk lately about sensor malfunctions. If the numbers seem odd just look at worldview and you can see for yourself where the ice is and how much is there. 

With that said, in answer to Neven's question, Zack Labe posted a really nice demonstrative on his twitter account on 7/31 showing the loss of the ice in the Beaufort caused by the recent cyclone.  It appears to be real and not a glitch.  I'm on my phone and can't figure out how to link it. 

However, I highly recommend checking out Zack's twitter post from 7/31/18.  Maybe someone more tech savvy than me can link it here?




miki

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Re: 2018 sea ice area and extent data
« Reply #1269 on: August 02, 2018, 05:38:33 AM »

With that said, in answer to Neven's question, Zack Labe posted a really nice demonstrative on his twitter account on 7/31 showing the loss of the ice in the Beaufort caused by the recent cyclone.  It appears to be real and not a glitch.  I'm on my phone and can't figure out how to link it. 

However, I highly recommend checking out Zack's twitter post from 7/31/18.  Maybe someone more tech savvy than me can link it here?

Here's a link to Zack's twit:

https://twitter.com/ZLabe/status/1024315118530658304

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Re: 2018 sea ice area and extent data
« Reply #1270 on: August 02, 2018, 07:05:07 AM »
Jaxa needs a smack in the face. It’s 2018 people.
"When the ice goes..... F***

oren

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Re: 2018 sea ice area and extent data
« Reply #1271 on: August 02, 2018, 07:22:44 AM »
Jaxa needs a smack in the face. It’s 2018 people.
On the one hand you are right that the downtime this year is very annoying, but on the other hand please remember the satellite is already past its planned life, and maybe the supporting ground infrastructure has been extended as well and therefore needs frequent maintenance. In a year or three when we might be left with no sea ice data at all, we may look with longing on the times when we got the data mostly every day.
Quote
GCOM-W1 (Global Change Observation Mission – Water "Shizuku") is the first in the GCOM-W series. Its mission is to observe the water cycle. The satellite carries the AMSR2 (Advanced Microwave Scanning Radiometer 2) instrument, the successor to the AMSR-E carried by Aqua. This microwave radiometer will observe precipitation, water vapor, wind velocity above the ocean, sea water temperature, water levels on land areas, and snow depths. GCOM-W1 was approved in 2006, and development of the satellite started in 2007 with a mission budget of 20 billion Yen (200 Million USD). Mass of the satellite is 1990 kg. Planned lifespan is 5 years. Polar orbit (altitude 700 km) with equator crossing local time on the ascending orbit is 13:30PM +/- 00:15.
GCOM-W1 was launched on May 17, 2012 via a H-IIA rocket, and it flies in a sun-synchronous orbit as part of the "A-train" satellite constellation. It successfully began collecting data on July 4, 2012. Its planned lifespan of 5 years means that the satellite is set to operate until 2017, although JAXA hopes that it will last longer.
https://en.wikipedia.org/wiki/Global_Change_Observation_Mission
« Last Edit: August 02, 2018, 07:30:37 AM by oren »

Wherestheice

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Re: 2018 sea ice area and extent data
« Reply #1272 on: August 02, 2018, 07:40:10 AM »
Jaxa needs a smack in the face. It’s 2018 people.
On the one hand you are right that the downtime this year is very annoying, but on the other hand please remember the satellite is already past its planned life, and maybe the supporting ground infrastructure has been extended as well and therefore needs frequent maintenance. In a year or three when we might be left with no sea ice data at all, we may look with longing on the times when we got the data mostly every day.
Quote
GCOM-W1 (Global Change Observation Mission – Water "Shizuku") is the first in the GCOM-W series. Its mission is to observe the water cycle. The satellite carries the AMSR2 (Advanced Microwave Scanning Radiometer 2) instrument, the successor to the AMSR-E carried by Aqua. This microwave radiometer will observe precipitation, water vapor, wind velocity above the ocean, sea water temperature, water levels on land areas, and snow depths. GCOM-W1 was approved in 2006, and development of the satellite started in 2007 with a mission budget of 20 billion Yen (200 Million USD). Mass of the satellite is 1990 kg. Planned lifespan is 5 years. Polar orbit (altitude 700 km) with equator crossing local time on the ascending orbit is 13:30PM +/- 00:15.
GCOM-W1 was launched on May 17, 2012 via a H-IIA rocket, and it flies in a sun-synchronous orbit as part of the "A-train" satellite constellation. It successfully began collecting data on July 4, 2012. Its planned lifespan of 5 years means that the satellite is set to operate until 2017, although JAXA hopes that it will last longer.
https://en.wikipedia.org/wiki/Global_Change_Observation_Mission

It just sucks because this topic is very important. I mean if we want to actually do something about climate change we need to know about what’s going on with the ice. This just shouldn’t be happening, but then again when we have trumpo in office, he wouldn’t support having satellites up there being replaced or fixed.
"When the ice goes..... F***

Alexander555

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Re: 2018 sea ice area and extent data
« Reply #1273 on: August 02, 2018, 11:58:48 AM »
Who needs a sattelite to observe the ice if we have a Tesla cruising trough space.

Tor Bejnar

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Re: 2018 sea ice area and extent data
« Reply #1274 on: August 02, 2018, 04:43:25 PM »
We do, Alexander, we do.  :'(
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magnamentis

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Re: 2018 sea ice area and extent data
« Reply #1275 on: August 02, 2018, 08:06:29 PM »
Massive drop in NSIDC SIE (253K, following 211K yesterday), second lowest on record now, causing massive uptick in compactness. Glitch or real?

I don't think the conditions in the Arctic were suddenly so much worse than the previous few days so at to more than double the rate of melt. 

If sensor variations can cause ice to be measured at 50k more or less on the day, then the sensors are working well, and measuring ice to about 1% accuracy (when area/extent is near 5m).  But then if daily losses are near 100k, and sensors switch from an overestimate of 50k to an underestimate of 50k, then sensors are reporting twice as much ice lost for the day as actually occurred.

this topic has been subject to controversial discussions for several years and in one or another form most users sooner or later came to the conclusion that due to the way extent is measured and due to the ever thinner, more mobile and more fragmented ice that we could be in for a few "sudden death" events during the future melting seasons which is more or less what happens now IMO and it will happen sooner or later arctic wide if ice conditions continue to get worse which is something i did not see many doubts around here.

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Re: 2018 sea ice area and extent data
« Reply #1276 on: August 02, 2018, 08:46:17 PM »
NSIDC Total Area as at 1 August (5 day trailing average) =  4,691,850     km2
This is 155   201 k above the 2010-2017 average area

     
Area loss (5 day average)       25k,
Extent loss (5 day average)   119k,

Total Area loss 25 K, Central Seas loss 11, Periphery loss 12 k, Other Seas loss 2 k  
Analysis of individual seas.

Pacific Side
- The Bering Sea - finished,
- Chukchi Sea loss 7 k, area is now well below the 2010's average,
Atlantic Side
- Baffin Sea loss 3 k, area 55k less than 5% of 1980's average maximum,
- Greenland Sea loss 8 k,
- Barents Sea - finished,
- The Kara Sea area loss 0 k,
- The Laptev Sea area loss 5 k.
CAB
- Beaufort Sea loss 10 k,
- The Central Arctic Sea gain 30 k,
- The Canadian Archipelago loss 3 k,
- East Siberian Sea loss 15 k .
Other seas
- St Lawrence -finished,
- Hudson Bay area loss 2 k, Area now 67 k and just about at average.
- The Okhotsk Sea - finished.

On average, this is when daily area loss declines sharply  This low area loss of 25 k is 45k below average this days 2010's average. The  5 day trailing average extent loss in contrast was over 119k per day for the last three days (5 day average eliminates most of the ups and downs of daily extent measures and the monthly adjustments). Extent losses are still catching up with area losses again.

Qu1. The question is - will above average area losses follow the big NSIDC daily extent losses ? Not on July 31 or August 1, that's for sure. GRAPH attached (extent minus area)

Qu2. How low will Greenland Sea Ice Area go ? If export of ice down the FRAM strait is finished for this season and that warmth keeps drifting up from the Atlantic (that blocking high from Western Europe across the Atlantic is liable to stay there for some time) then....

ps:- Another dose of reality to counter the hyperbole of recent posts ?
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gerontocrat

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Re: 2018 sea ice area and extent data
« Reply #1277 on: August 03, 2018, 12:59:04 AM »
NSIDC's July analysis is out - http://nsidc.org/arcticseaicenews/
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Juan C. García

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Re: 2018 sea ice area and extent data
« Reply #1278 on: August 03, 2018, 01:26:08 AM »
[ADS-NIPR-JAXA] ASI Extent.

The data is starting to appear:

July 30th, 2018: 6,526,249 km2, a century drop of -140,688 km2.
2018 is the fifth lowest on record.

« Last Edit: August 03, 2018, 01:36:49 AM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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Re: 2018 sea ice area and extent data
« Reply #1279 on: August 03, 2018, 05:57:24 AM »
[ADS-NIPR-JAXA] ASI Extent.

August 2nd, 2018: 6,272,893 km2, a drop of -74,900 km2.
2018 is the fifth lowest on record.

« Last Edit: August 03, 2018, 06:04:12 AM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

oren

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Re: 2018 sea ice area and extent data
« Reply #1280 on: August 03, 2018, 08:43:30 AM »
The relative cliff continues... JAXA extent lost 1.863 M km2 in 17 days, quite extreme for the period.

I'll take this opportunity to thank again Juan C. Garcia and gerontocrat for your updates on this most important matter. I am sure I am not the only addict.

Edit reason: adding the total loss.

Wherestheice

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Re: 2018 sea ice area and extent data
« Reply #1281 on: August 03, 2018, 08:44:43 AM »
The relative cliff continues...

I'll take this opportunity to thank again Juan C. Garcia and gerontocrat for your updates on this most important matter. I am sure I am not the only addict.

I second that!
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Stephan

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Re: 2018 sea ice area and extent data
« Reply #1282 on: August 03, 2018, 09:00:40 AM »
[ADS-NIPR-JAXA] ASI Extent.

August 2nd, 2018: 6,272,893 km2, a drop of -74,900 km2.
2018 is the fifth lowest on record.
It is time to thank you, Juan, for posting the ice extent data and the ranking list every day (except when JAXA is on holidays or on calibration).
From the table the first three years are also the "Top Three" minimum years. Therefore I make the assumption that this year will be finally ranking in the #4 to #6. Let's revisit that in September.
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Stephan

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Re: 2018 sea ice area and extent data
« Reply #1283 on: August 03, 2018, 09:15:48 AM »
The three most southern seas with significant ice are Baffin, Hudson, and Kara. I just compared their area (from Gerontocrat's actual post → THANK YOU FOR THIS VERY VALUABLE CONTRIBUTION!!) with their extent (from MASIE). All these seas show a very low compactness which makes them likely to melt out the next week(s):
Baffin area 0.23 extent 0.55 (compactness ~ 40%)
Hudson area 0.28 extent 0.70 (compactness ~ 25%)
Kara area 0.28 extent 0.50 (compactness ~ 55%)
The extents sum up to 1.75 mio. km² which should lead to further "century meltdowns" in the next days...
This post is just to revisit older predictions.
From July 11 to Aug 01 following losses are reported:
Baffin extent loss 0.30 mio. km² (55% loss compared to July 11)
Hudson extent loss 0.425 mio. km² (65% loss compared to July 11)
Kara extent loss 0.425 mio. km² (85% loss compared to July 11).
So the sum of extent loss of these three seas is 1.15 mio. km². And there is more to melt, although now slower because we are heading towards the end of the melting season.

The number of century meltdowns was impressive and probably one of the highest ever recorded for the second half of July (see for details Juan's postings).
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gerontocrat

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Re: 2018 sea ice area and extent data
« Reply #1284 on: August 03, 2018, 10:15:40 AM »
JAXA ARCTIC EXTENT 6,272,893 km2(August 2, 2018)

So I got a few days off - these things happen and the sun was shining.

Just to add to Juan's post....
- Extent loss in the last 2 days was about the average for this date,
- Extent is now 100k km2  (1.6%) below the 2010's average extent on this date, first time in ages,
- and just 14 k (0.2%) above 2017,
- Extent loss to date is now 420k 293 km2 (3.7 %) below the 2008-2017 average, with 79.4 % of the average melting season done.

Resulting minimum from average remaining melt is down to 4.22 million km2, (excluding 2012 from the average gives 4.31 million km2). Range of results from last ten years remaining melt is 3.42 to 4.61 million km2.

That 2017 feeling fades yet but still lingers on - extent losses are not still yet enough to catch up on the slow melt to date and NSIDC Area losses have slowed significantly. There is, on average, just 20.6 % (41 days) of further extent loss to go. Could the melting season last a bit longer than that - Yes.  On the other hand, could extent loss sharply reduce? Yes.

As a result of these persistent higher than average extent loss, a September minimum down one bin in the range of 4.25 to 4.75 million km2, and perhaps even another bin lower, now looks increasingly possible or even likely. But that is still possibly 0.5 0.4 0.3 million km2 above 2nd place and 1 million km2 above the 2012 outlier.

ps: The last graph shows well the catch-up in extent losses in the second half of July.
pps: I won't be making a vote on the minimum until the last moment. Breathlessly awaiting PIOMAS volume for July.
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Jim Hunt

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Re: 2018 sea ice area and extent data
« Reply #1285 on: August 03, 2018, 01:56:56 PM »
The number of century meltdowns was impressive and probably one of the highest ever recorded for the second half of July (see for details Juan's postings).

And that's despite a "relatively cool July":

https://forum.arctic-sea-ice.net/index.php/topic,2278.msg165525.html#msg165525

Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Shared Humanity

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Re: 2018 sea ice area and extent data
« Reply #1286 on: August 03, 2018, 02:04:28 PM »
The relative cliff continues... JAXA extent lost 1.863 M km2 in 17 days, quite extreme for the period.

I'll take this opportunity to thank again Juan C. Garcia and gerontocrat for your updates on this most important matter. I am sure I am not the only addict.

Edit reason: adding the total loss.

You are not. I come here every single day. I may not post comments daily but I am reading the comments of others.

Geert

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Re: 2018 sea ice area and extent data
« Reply #1287 on: August 03, 2018, 02:51:36 PM »
Me, too with lots of greetings from the Netherlands at minus 18 feet and 30+C  :)

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Re: 2018 sea ice area and extent data
« Reply #1288 on: August 03, 2018, 03:11:57 PM »
NSIDC Total Area as at 2 August (5 day trailing average) =  4,650,127 km2
This is 208  241 k above the 2010-2017 average area


Area loss 2 Aug                               42k,
Extent loss  2 Aug (5 day average)   114k,
Extent GAIN 2 Aug (daily)                 14k

Total Area loss 42 K, Central Seas loss 31, Periphery loss 7 k, Other Seas loss 3 k  
Analysis of individual seas.

Pacific Side
- The Bering Sea - finished,
- Chukchi Sea loss 6 k, area is now well below the 2010's average,
Atlantic Side
- Baffin Sea loss 3 k, area 52k - less than 5% of 1980's average maximum,
- Greenland Sea loss 5 k,
- Barents Sea - finished,
- The Kara Sea area loss 2 k,
- The Laptev Sea area loss 3 k.
CAB
- Beaufort Sea loss 20 k,
- The Central Arctic Sea gain 14 k,
- The Canadian Archipelago loss 1 k,
- East Siberian Sea loss 12 k .
Other seas
- St Lawrence -finished,
- Hudson Bay area loss 3 k, Area now 65 k and just about at average.
- The Okhotsk Sea - finished.

On average, this is when daily area loss declines sharply  This low area loss of 42 k is 35 k below this days 2010's average. The  5 day trailing average extent loss in contrast was over 110k per day for the last four days (5 day average eliminates most of the ups and downs of daily extent measures and the monthly adjustments). But daily extent rose by 14k. Extent losses are still catching up with area losses again.

Qu1. The question is - will above average area losses follow the big NSIDC daily extent losses ? Not on July 31 or August 1 & 2, that's for sure. GRAPH attached (extent minus area) - quite a dramatic change.

Qu2. How low will Greenland Sea Ice Area go ? If export of ice down the FRAM strait is finished for this season and that warmth keeps drifting up from the Atlantic (that blocking high from Western Europe across the Atlantic is liable to stay there for some time) then....

ps:-Yet another dose of reality to counter the hyperbole of recent posts ?
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

Juan C. García

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Re: 2018 sea ice area and extent data
« Reply #1289 on: August 03, 2018, 03:13:31 PM »
The relative cliff continues... JAXA extent lost 1.863 M km2 in 17 days, quite extreme for the period.

I'll take this opportunity to thank again Juan C. Garcia and gerontocrat for your updates on this most important matter. I am sure I am not the only addict.
You are welcome everybody!

The true is that this Forum is a team work and it is impossible to make a explicit thanks to everyone. But I am sure that a lot of us enjoy the multiple posts that are making us able to follow the Cryosphere and the Antrophogenic impact that we are doing on our planet.

So Thanks everyone for the work that you are doing on this Forum!  :)
Thanks to the external groups also, like ADS-NIPR (JAXA), PIOMAS, NSIDC, OMG, etc.
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Shared Humanity

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Re: 2018 sea ice area and extent data
« Reply #1290 on: August 03, 2018, 03:17:01 PM »
Yet another dose of reality to counter the hyperbole of recent posts ?

Always nice to have actual data provide a foundation for the discussion here.

Stephan

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Re: 2018 sea ice area and extent data
« Reply #1291 on: August 03, 2018, 03:27:46 PM »
Looking at the ice areas of different seas and keeping in mind the slow-down of melt within the next five to seven weeks I expect only the
Baffin Sea
Hudson Sea
Kara Sea
to be able to fully melt out (apart from eventual fast ice somewhere at the coastline).
For the Chukchi Sea and the Grønland Sea it might be possible; the percentage of melt from 19 July to 02 August equals nearly 50%.
All other seas (especially CAB) will surely be largely ice-covered. The only bigger losses should be expected in Beaufort, Laptev and maybe the ESS and the CAA.
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Shared Humanity

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Re: 2018 sea ice area and extent data
« Reply #1292 on: August 03, 2018, 03:39:44 PM »
Looking at the ice areas of different seas and keeping in mind the slow-down of melt within the next five to seven weeks I expect only the
Baffin Sea
Hudson Sea
Kara Sea
to be able to fully melt out (apart from eventual fast ice somewhere at the coastline).
For the Chukchi Sea and the Grønland Sea it might be possible; the percentage of melt from 19 July to 02 August equals nearly 50%.
All other seas (especially CAB) will surely be largely ice-covered. The only bigger losses should be expected in Beaufort, Laptev and maybe the ESS and the CAA.

I respectfully disagree.

https://sites.google.com/site/arcticseaicegraphs/regional

The Laptev is already largely ice free and the melt progress is aggressive. I expect the Laptev to be essentially ice free by the end of this melt season.

While Beaufort melt started slowly, recent aggressive melt has it on track with 2015 and the Beaufort was ice free at the end of the melt season in 2015.

And depending on your definition of "largely ice covered" the ESS is on track to have only 20% of of its water covered with ice.

If you look at these graphs, you could make the argument that the CAB is the only region in the Arctic that ends the melt season largely ice covered.

« Last Edit: August 03, 2018, 03:46:27 PM by Shared Humanity »

Stephan

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Re: 2018 sea ice area and extent data
« Reply #1293 on: August 03, 2018, 05:17:44 PM »
Yes, you are completely right concerning Laptev and Chukchi if you look at the graphs.
I have only taken gerontocrat's table with the ice area numbers, which are for some seas (e.g. Laptev and ESS) much higher than the graphs. This is probably due to different sizes/borders of the individual seas [has been recently discussed here in this forum].
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oren

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Re: 2018 sea ice area and extent data
« Reply #1294 on: August 03, 2018, 05:36:57 PM »
Stephan, there's another major difference - gerontocrat's numbers are NSIDC data with its coarse 25x25 km resolution, while SH's link is for UH AMSR2 with its 3.25x3.25 km resolution and improved sensors.

Csnavywx

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Re: 2018 sea ice area and extent data
« Reply #1295 on: August 03, 2018, 05:45:36 PM »
Given the current conditions and short-to-medium term weather forecast, it's arguable whether much of the ESS's ice survives at all. It's already down to about the same thickness the Beaufort had in mid-July and that lasted all of 2 weeks before caving. Early August with clear skies, strong winds and very strong warm advection is especially deleterious.

Surface wind divergence from the high will cause dispersion in the short run though, and this will probably serve to prop up extent numbers for a time (until thickness gets very low and breakup suddenly occurs).

The current airmass over the CAB is subtropical in origin (700mb temps >+5C/>-12C at 500mb), so expect some serious top-down melt losses over the next few days.

Shared Humanity

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Re: 2018 sea ice area and extent data
« Reply #1296 on: August 03, 2018, 08:24:42 PM »
I very much appreciate gerontocrat's contributions here and I am not sure there is a lot of logic with how the sea boundaries are defined but if we want to be able to compare years and trends, we need to use a standard, consistent definition.

However you draw the boundaries of seas, the method is arbitrary. If we really want to discuss what is going on in the Arctic using a truly scientific perspective, it would make far more sense to evaluate ice based on bathymetry, the location of islands and currents etc.

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Re: 2018 sea ice area and extent data
« Reply #1297 on: August 03, 2018, 09:29:00 PM »
I am not sure there is a lot of logic with how the sea boundaries are defined but if we want to be able to compare years and trends, we need to use a standard, consistent definition.

However you draw the boundaries of seas, the method is arbitrary. If we really want to discuss what is going on in the Arctic using a truly scientific perspective, it would make far more sense to evaluate ice based on bathymetry, the location of islands and currents etc.

For the data I post, I have to use what I am given on a consistent basis. So I use for area analyses the NSIDC definition of the various seas as shown in MASIE ( https://nsidc.org/data/masie/browse_regions ) which also gives instant access to maps of extent by those seas.

I don't think that anyone (but Wipneus !) is going to go back and realign the data from 1979 to date according to boundaries defined by "bathymetry, the location of islands and currents etc ", especially as some parameters, e.g.s currents, limits of seas (especially peripheral seas), have and will change as sea ice declines.

BUT, on the melting season thread, images and comments are on areas that ignore boundaries, as sea ice changes (extent, thickness et al) and weather ignore the lines cartographers put on the maps. And a good thing too.

As far as basic extent and area data is concerned, my major concern is the lack of news on any plans to ensure the data record is maintained after the last USAF satellite and the Japanese satellite croak, expire, are no longer extant.

Without data we are stuffed.
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Re: 2018 sea ice area and extent data
« Reply #1298 on: August 03, 2018, 11:32:32 PM »
This is one strong argument against a top 3 minimum, compactness very high for the time of year:
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Re: 2018 sea ice area and extent data
« Reply #1299 on: August 04, 2018, 05:48:37 AM »
[ADS-NIPR-JAXA] ASI Extent.

August 3rd, 2018: 6,204,054 km2, a drop of -68,839 km2.
2018 is the fifth lowest on record.

Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.