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sailor

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Re: 2019 sea ice area and extent data
« Reply #2450 on: September 15, 2019, 05:54:44 PM »
Don't high pressures generally mean calm seas?
And is not insolation almost zero?
And is it not strong winds from low pressure systems over open water that will suck heat from open water most rapidly? i.e. calm seas reduce the rate of heat loss?
Meanwhile .... it seems the melting season is not dead yet.
Yeah, I oversimplify. But clear skies means rapid heat loss and is a friend of Arctic ice refreezing during Fall and Winter, no matter what is going on down there...I won’t derail the thread any further.
On the thin ice of modern life

Tom_Mazanec

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Re: 2019 sea ice area and extent data
« Reply #2451 on: September 15, 2019, 07:24:30 PM »
What would the area and/or extent have been in the early-mid 20th Century?
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS

Steven

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Re: 2019 sea ice area and extent data
« Reply #2452 on: September 15, 2019, 08:15:41 PM »
NSIDC daily area is now 2.90 million km2, which is second lowest for the date (slightly below 2016):



The year-to-date minimum for 2019 so far is 2.87 million km2 on 4 September 2019.

Paddy

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Re: 2019 sea ice area and extent data
« Reply #2453 on: September 15, 2019, 10:57:48 PM »
What would the area and/or extent have been in the early-mid 20th Century?

You may want this thread: https://forum.arctic-sea-ice.net/index.php/topic,1461.0.html

Or maybe one of a few others in the "Arctic Background" section

Juan C. García

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Re: 2019 sea ice area and extent data
« Reply #2454 on: September 16, 2019, 02:22:14 AM »
Hi everyone:

We are celebrating the Independence of México, so I will not be posting today.
Having fun with friends.  :)

If someone else makes the post. Thanks!

https://ads.nipr.ac.jp/vishop/#/extent
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.

aperson

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Re: 2019 sea ice area and extent data
« Reply #2455 on: September 16, 2019, 05:35:06 AM »
September 15th, 2019:
     4,006,036 km2, a drop of 19,682 km2.
     2019 is now 2nd lowest on record.

computer janitor by trade

Wildcatter

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Re: 2019 sea ice area and extent data
« Reply #2456 on: September 16, 2019, 05:36:08 AM »
Filling in for Mr. Juan Garcia :)

September 15, 2019:
4,006,036 = A decrease of -19,682 km2.

Passed 2016's minimum of 4,017,264 km2

slow wing

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Re: 2019 sea ice area and extent data
« Reply #2457 on: September 16, 2019, 05:38:13 AM »
September 15th, 2019:


     4,006,036 km2, a drop of -19,682 km2.
     2019 is 2nd lowest on record for this day.


P.S.: 2019 is now the second lowest year for extent on record, now 11,228 km2 below the 2016 minimum of 4,017,264 km2 and behind only 2012.

aperson

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Re: 2019 sea ice area and extent data
« Reply #2458 on: September 16, 2019, 05:39:33 AM »
On the bright side we've now triple-validated our work :)
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blumenkraft

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Re: 2019 sea ice area and extent data
« Reply #2459 on: September 16, 2019, 05:41:16 AM »
We are celebrating the Independence of México

Why do i hear Speedy Gonzales yelling "¡Arriba, Arriba! ¡Ándale, Ándale!" now?

Have a lot of fun Juan.  8)
Refugees welcome

gerontocrat

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Re: 2019 sea ice area and extent data
« Reply #2460 on: September 16, 2019, 12:59:18 PM »
JAXA ARCTIC SEA ICE EXTENT :- 4,006,036 km2(September 15, 2019)

Extent loss in the last 6 days of 164 K, compared with an average of a net 20 k gain over the 6 days, completely changed the end of season metrics from an early minimum 4th lowest to a late minimum 2nd lowest.

On this day,
- Extent is 2nd lowest in the satellite record,
- Extent is 828 k greater than 2012, 247 k less than 2016. but 2016 extent is now increasing quickly, and 63 k less than 2007,
- Extent loss on this day 20 k, 32 k different from the average gain on this day of 12 k.
- Extent loss from maximum 10,265 k, 473 k (4.8%) greater than the average of 9,792 k loss from maximum by this day,
- On average 100% % of the melting season done, with minus 2 days to average date of minimum (13 September).

The Perils of Projections.
Average remaining melt (0.02 million km) would give a minimum of 3.98 million km2, 2nd lowest (now guaranteed), 0.80 million km2 above the 2012 low of 3.18 million km2, 0.04 million km2 less than 2016, 0.09 million km2 less than 2007.

____________________________________________________________
Ice Melt Outlook ??

From today on average there are daily extent gains . However, in the the last 10 years there were 2 years (2010 & 2018) with further extent loss greater than 6k, which give a minimum of less than 4 million km2. 
____________________________________________________________

Gets below 4 million km2? Stays above 4 million km2 ? Some of those who take their poll forecasts seriously will end up shrieking with joy, others will weep and think about taking themselves and their shotgun out to the barn.

"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)

gerontocrat

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Re: 2019 sea ice area and extent data
« Reply #2461 on: September 16, 2019, 02:01:39 PM »
JAXA ARCTIC SEA ICE EXTENT :- 4,006,036 km2(September 15, 2019)

Some other bits

Plume of projections & September average - First 2 images attached


Love the graph, so pretty. What it does show is that from now to September 30th, extent might increase by only 200k (2018) or as much as 800k (2016). The average is 500k. If that happens, the 2019 September Average will be about 200k less than the 2016 September average.

I think I will be looking at monthly averages a lot more in the future.

Current Minimum Compared with previous years

The actual minimum might be a little bit different, but the main conclusions will remain the same.
The forum, and elsewhere too often compare the current situation with 2012. But 2012 is an outlier** (see below). Although the 2012 minimum is about 0.82 million km2 below 2019, the trend shown by 2019 is clear.

The 2019 minimum is currently below the 2010's average by 388k km2, 8.8%. Taking the 2010's average as the midpoint, this implies a rate of change of somewhat more than that.

The 2019 minimum is currently below the 1980's average by 3.2 million km2, 45%.

365 Day Average
This year's melting season has seen a reduction in the 365 day average by over 150,000 km2, with a good chance of a new record low minimum 365 day average sometime in 2020.

2019 has seen a continuation of long-term reducing sea ice extent.
_______________________________________________________________________
**Outlier
In statistics, an outlier is a data point that differs significantly from other observations.  An outlier can cause serious problems in statistical analyses.
« Last Edit: September 16, 2019, 04:01:57 PM by gerontocrat »
"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)

Alphabet Hotel

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Re: 2019 sea ice area and extent data
« Reply #2462 on: September 16, 2019, 02:57:48 PM »
NSIDC daily extent

gerontocrat

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Re: 2019 sea ice area and extent data
« Reply #2463 on: September 16, 2019, 03:40:45 PM »
NSIDC Total Area as at 15 September 2019 (5 day trailing average)  2,932,327 km2


The 2019 Minimum Has Passed?- the data won't say no, it won't say yes.

On this day the 5 day trailing average AREA decreased by another 10 k,
One-day NSIDC EXTENT LOSS 10k (and again a new minimum, 77k below the previous on 4th Sep), JAXA extent LOSS 20 k (again a new minimum)

                        
Total Area         
 2,932,327    km2      
-225,901    km2   <   2010's average.
-359,209    km2   <   2018
-1,156,549    km2   <   2000's average.
         
Total Area Change   -10    k   loss
Peripheral Seas   -8    k   loss
Central Seas__   -2    k   loss
Other Seas___    0    k   gain
         
Peripheral Seas         
Bering _______    -    k   loss
Baffin  Bay____   -1    k   loss
Greenland____   -6    k   loss
Barents ______   -1    k   loss
         
CAB Seas         
Beaufort_____   -2    k   loss
CAA_________    5    k   gain
East Siberian__   -2    k   loss
Central Arctic_    2    k   gain
         
Kara_________   -1    k   loss
Laptev_______   -3    k   loss
Chukchi______   -1    k   loss
         
Other Seas         
Okhotsk______    0    k   gain
St Lawrence___    -    k   loss
Hudson Bay___    0    k   gain
- Area loss 10 k, 39 k different from the 2010's average area gain of 29 k on this day,
- Total area 3rd Lowest, 139 k MORE than 2016 (but 2016 is past its minimum), and 684 k MORE than 2012 (15 September was the 2012 minimum) ,
- Area is 22 k more than the current minimum on the 5th September.
________________________________________________________________________
Outlook
Not a clue

We are now, on average, beyond the end of the season of area & extent losses.

But the book on JAXA & NSIDC Extent is still open, both at new minimums.
"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)

Stephan

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Re: 2019 sea ice area and extent data
« Reply #2464 on: September 16, 2019, 07:32:03 PM »

Gets below 4 million km2? Stays above 4 million km2 ? Some of those who take their poll forecasts seriously will end up shrieking with joy, others will weep and think about taking themselves and their shotgun out to the barn.


Or lay happily around, because they have chosen the 3.75-4.25 M km² bin, which will 100% be the bin this year's minimum will stay in.
It is too late just to be concerned about Climate Change

gerontocrat

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Re: 2019 sea ice area and extent data
« Reply #2465 on: September 16, 2019, 07:46:09 PM »

Gets below 4 million km2? Stays above 4 million km2 ? Some of those who take their poll forecasts seriously will end up shrieking with joy, others will weep and think about taking themselves and their shotgun out to the barn.


Or lay happily around, because they have chosen the 3.75-4.25 M km² bin, which will 100% be the bin this year's minimum will stay in.
unless....... (theme tune from Jaws commences to play)
"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)

jplotinus

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Re: 2019 sea ice area and extent data
« Reply #2466 on: September 16, 2019, 07:56:12 PM »
I well remember September, 2016 and being virtually certain the minimum would have a “3” handle, thus joining 2012 as the only years with a lead number of “3”something. But 2016 had an early minimum and stayed above 4m km2.
Here we are, yet again, poised at the 4.0-3.9 border. I’m guessing a lot of us will be checking JAXA at 11:30pm (gmt -4)

😨

binntho

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Re: 2019 sea ice area and extent data
« Reply #2467 on: September 17, 2019, 05:30:37 AM »
3,991,187
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

Juan C. García

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Re: 2019 sea ice area and extent data
« Reply #2468 on: September 17, 2019, 05:43:09 AM »
September 16th, 2019:
     3,991,187 km2, a drop of -14,849 km2.
     2019 is 2nd lowest on record.
     (2007, 2012 & 2016 highlighted).

P.S.: 2019 has broken the less than 4M km2 marker.
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.

gerontocrat

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Re: 2019 sea ice area and extent data
« Reply #2469 on: September 17, 2019, 06:09:15 AM »
JAXA ARCTIC SEA ICE EXTENT :- 3,991,187 km2(September 16, 2019)

Less than 4 million. No commentary today, just the graphs & tables.
"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)

Lord M Vader

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Re: 2019 sea ice area and extent data
« Reply #2470 on: September 17, 2019, 06:46:23 AM »
An amazingly surprising end of the 2019 melting season! Let's see if NSIDC manages to go second lowest too.

gregcharles

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Re: 2019 sea ice area and extent data
« Reply #2471 on: September 17, 2019, 08:43:03 AM »
Wow, 2019 really toyed with us! "Of course it will" became "No it won't" became "Yes it did". (Go below 4 million in the JAXA extent record, I mean.)

In just a month, we'll have the first big test of the refreeze season. For October 16th through 19th, the record low is currently held by 2007, and those are the only four days where the record isn't held by a 2010s year. There's just this one last chance for the 2010s to run the deck.

Alison

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Re: 2019 sea ice area and extent data
« Reply #2472 on: September 17, 2019, 01:21:20 PM »
Under 4m eventually ... 2019 will not be forgotten in a hurry!

gerontocrat

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Re: 2019 sea ice area and extent data
« Reply #2473 on: September 17, 2019, 03:29:47 PM »
NSIDC Total Area as at 16 September 2019 (5 day trailing average)  2,952,068 km2


The 2019 Minimum Has Passed?- I think the NSIDC area data says yes.

On this day the 5 day trailing average AREA increased by 20 k,
One-day NSIDC EXTENT GAIN 50k , JAXA extent LOSS 15 k (again a new minimum)

                        
Total Area         
 2,952,068    km2      
-236,659    km2   <   2010's average.
-348,347    km2   <   2018
-1,144,535    km2   <   2000's average.
         
Total Area Change    20    k   gain
Peripheral Seas   -3    k   loss
Central Seas__    23    k   gain
Other Seas___    0    k   gain
         
Peripheral Seas         
Bering _______   -0    k   loss
Baffin  Bay____   -1    k   loss
Greenland____   -2    k   loss
Barents ______   -1    k   loss
         
CAB Seas         
Beaufort_____   -0    k   loss
CAA_________    7    k   gain
East Siberian__   -0    k   loss
Central Arctic_    19    k   gain
         
Kara_________    0    k   gain
Laptev_______   -2    k   loss
Chukchi______   -1    k   loss
         
Other Seas         
Okhotsk______   -0    k   loss
St Lawrence___    -    k   loss
Hudson Bay___    0    k   gain
- Area gain 20 k, 13 k less than the 2010's average area gain of 33 k on this day,
- Area is 42 k more than the current minimum on the 5th September.
________________________________________________________________________
Outlook
Not a clue.....
There are reports on the melting season thread of new ice here and there.
We are now, on average, beyond the end of the season of area & extent losses.
But the book on JAXA & NSIDC Extent might still be open.
"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)

Alphabet Hotel

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Re: 2019 sea ice area and extent data
« Reply #2474 on: September 17, 2019, 05:56:24 PM »
NSIDC daily extent

mmghosh

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Re: 2019 sea ice area and extent data
« Reply #2475 on: September 18, 2019, 05:10:17 AM »
So we now enter the "3"'s decade ...

binntho

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Re: 2019 sea ice area and extent data
« Reply #2476 on: September 18, 2019, 05:35:01 AM »
Jaxa still dropping - another 30k or thereabouts.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

slow wing

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Re: 2019 sea ice area and extent data
« Reply #2477 on: September 18, 2019, 05:36:30 AM »
Yes, another JAXA extent drop: to 3,964,239 km2, so down 26,948 km2 from yesterday.

Juan C. García

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Re: 2019 sea ice area and extent data
« Reply #2478 on: September 18, 2019, 05:43:33 AM »
September 17th, 2019:
     3,964,239 km2; another drop: -26,948 km2.
     2019 is 2nd lowest on record.
     (2007, 2012 & 2016 highlighted).
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.

Paddy

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Re: 2019 sea ice area and extent data
« Reply #2479 on: September 18, 2019, 05:53:14 AM »
So we now enter the "3"'s decade ...

I would generally anticipate the coming decade will average in the "3"s, but would expect it would have the odd "4" and quite possibly at least one "2".

MrGreeny

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Re: 2019 sea ice area and extent data
« Reply #2480 on: September 18, 2019, 08:14:33 AM »
To be really honest, I really thought it wouldn't go under 4 million this year but boy was I wrong.

Phil42

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Re: 2019 sea ice area and extent data
« Reply #2481 on: September 18, 2019, 09:31:24 AM »
According to the JAXA-Dataset, to date 2019 has:
  • 49 days of being lowest
  • 141 days in lowest 2
  • 162 days in lowest 3
after 260 days having passed this year.

gerontocrat

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Re: 2019 sea ice area and extent data
« Reply #2482 on: September 18, 2019, 12:36:43 PM »
JAXA ARCTIC SEA ICE EXTENT :- 3,964,239 km2(September 17, 2019)

There was I, expecting by now to be making sure my data for this year's freezing season was in order.......
As you can see from the first table, the melting season is supposed to be over.


On this day,
- Extent is 2nd lowest in the satellite record,
- Extent is 750 k greater than 2012, 330 k less than 2016, and 101 k less than 2007,
- Extent loss on this day 27 k, 35 k different from the average gain on this day of 8 k.
- Extent loss from maximum 10,307 k, 516 k (5.3%) greater than the average of 9,791 k loss from maximum on this day.

The Perils of Projections.
2018 remaining melt (0.03 million km & the only year left) would give a minimum of 3.93 million km2, 2nd lowest (now guaranteed), 0.75 million km2 above the 2012 low of 3.18 million km2, 0.09 million km2 less than 2016, 0.14 million km2 less than 2007.

____________________________________________________________
Ice Melt Outlook ??

It is supposed to be the beginning of extent gains.
The melting season thread reports new ice in several locations.

But......
____________________________________________________________
So far the minimum is 4 days later than average. 2018 kept on reducing extent for another 4 days. Vague memory of some science papers talking about further sea ice reduction being concentrated in autumn and early winter. The shape of things to come ?
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
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Lord M Vader

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Re: 2019 sea ice area and extent data
« Reply #2483 on: September 18, 2019, 03:01:24 PM »
WOW, just WOW!!! NSIDC just came in with a big fat century break(!) Yes, a CENTURY BREAK(!!) How many times Have THAT happened at this time at year, or at least in September?😵 Anyone who knows?

Pavel

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Re: 2019 sea ice area and extent data
« Reply #2484 on: September 18, 2019, 03:15:08 PM »
NSIDC had an uptick of 50k yesterday because of noise and it did not show 2019 at the 2nd lowest minimum. So the century break mostly because of clearing noise. But it's of course unusual for this date despite the new ice is appearing in some places we're not sure the extent minimum is reached.

gerontocrat

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Re: 2019 sea ice area and extent data
« Reply #2485 on: September 18, 2019, 03:46:57 PM »
NSIDC Total Area as at 17 September 2019 (5 day trailing average)  2,981,528 km2


The 2019 Minimum Has Passed?- I think the NSIDC area data says yes.

On this day the 5 day trailing average AREA increased by 29 k,
One-day NSIDC EXTENT LOSS 111k ,
JAXA extent LOSS 27 k (again a new minimum)

Since 5 September 5-day area has increased by 72k, while 5-day extent has reduced by 155k. The length and scale of this divergence especially at this time of year is, I think, unusual

                        
Total Area         
 2,981,528    km2      
-236,601    km2   <   2010's average.
-337,745    km2   <   2018
-1,120,043    km2   <   2000's average.
         
Total Area Change    29    k   gain
Peripheral Seas   -6    k   loss
Central Seas__    35    k   gain
Other Seas___   -0    k   loss
         
Peripheral Seas         
Bering _______   -0    k   loss
Baffin  Bay____    0    k   gain
Greenland____   -5    k   loss
Barents ______   -1    k   loss
         
CAB Seas         
Beaufort_____    3    k   gain
CAA_________   -1    k   loss
East Siberian__    0    k   gain
Central Arctic_    34    k   gain
         
Kara_________    0    k   gain
Laptev_______    0    k   gain
Chukchi______   -1    k   loss
         
Other Seas         
Okhotsk______   -0    k   loss
St Lawrence___    -    k   loss
Hudson Bay___    0    k   gain
- Area gain 29 k, 1 k less than the 2010's average area gain of 30 k on this day,
- Area is 72 k more than the current minimum on the 5th September.
________________________________________________________________________
Outlook
Not a clue morphed into totally clueless.....

There are reports on the melting season thread of new ice here and there.
We are now, on average, beyond the end of the season of area & extent losses.
But the book on JAXA & NSIDC Extent might still be open.
« Last Edit: September 18, 2019, 04:23:46 PM by gerontocrat »
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Alphabet Hotel

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Re: 2019 sea ice area and extent data
« Reply #2486 on: September 18, 2019, 04:37:15 PM »
NSIDC daily extent


Aleph_Null

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Re: 2019 sea ice area and extent data
« Reply #2487 on: September 18, 2019, 05:46:05 PM »
I'd like to hear if any of you has a thought about relative volatility of these metrics. Has anyone measured whether one is more jagged than the other? Would that mean anything? Thanks.

blumenkraft

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Re: 2019 sea ice area and extent data
« Reply #2488 on: September 18, 2019, 05:54:20 PM »
I actually expected high volatility although earlier. The ice is very thin and it's dispersing before it melts short after. Perfect behavior to get high volatility, no?
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Re: 2019 sea ice area and extent data
« Reply #2489 on: September 18, 2019, 06:11:14 PM »
Sorry, my verbiage was imprecise. I don't mean a comparison of the volatility of the ice itself (which is why I ask the question here) but of the JAXA vs. NSIDC instrumentation/assimilation/etc. Just a simple statistical reckoning of the relative smoothness of their daily curves for area and extent. Does one data-source tend to be smoother than the other? On the other hand, if that comparison is probably meaningless, that's also interesting to hear.
« Last Edit: September 18, 2019, 06:21:53 PM by Aleph_Null »

charles_oil

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Re: 2019 sea ice area and extent data
« Reply #2490 on: September 18, 2019, 07:09:12 PM »
Isn't that exactly why there is the NSIDC 5 day trailing average - to avoid the daily swings ??  I imagine there will have been a lot of thought into how many days makes the best curve i.e 3/4/5/6 days etc - to give sensible, but without either losing the irregularities or smoothing the data too much.

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Re: 2019 sea ice area and extent data
« Reply #2491 on: September 18, 2019, 08:26:30 PM »
NSIDC Extent & Area

Attached is a table showing recent extent losses and area gains.
A lot of it is about the Central Arctic Sea. Mind you, both area and extent are currently well above the 2010's average. See graph.
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gerontocrat

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Re: 2019 sea ice area and extent data
« Reply #2492 on: September 18, 2019, 08:42:35 PM »
I'd like to hear if any of you has a thought about relative volatility of these metrics. Has anyone measured whether one is more jagged than the other? Would that mean anything? Thanks.

The **average daily change of one-day extent in 2019 is 17.45 k per day
The **average daily change of five-day extent in 2019 is 16.31 k per day

So the 5 day average is merely 7% less than the one day. That was a surprise.

** N.B. -ve daily changes concerted to absolute (+ve) values.

So why do I use 5-day values? Because that is what NSIDC provides for regional seas - where perhaps volatility is more significant. Also 5-day average helps to reduce impact of artifacts as extensively examined in the melting thread.
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Re: 2019 sea ice area and extent data
« Reply #2493 on: September 18, 2019, 10:58:10 PM »
Sorry if I'm misunderstanding "volatility". As I take it, Aleph_Null means the variations between each two consecutive values of the underlying data series, i.e. for each day2 vs. day1 the variation is ABS(day2 - day1).

The sum of the variations in the latest NSIDC extent table (18 days, i.e. 17 daily changes) is:
1-day avg: 916 (average per day 53.9)
5-day avg: 238 (average per day 14.0)

I did not check the whole year, but I find it hard to believe that the difference between the two should be only 1k per day? As to JAXA, it uses a 2-day average as has been pointed out here recently. I'm too tired to check its volatility now, though  ;)

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Re: 2019 sea ice area and extent data
« Reply #2494 on: September 18, 2019, 11:20:08 PM »
Sorry if I'm misunderstanding "volatility". As I take it, Aleph_Null means the variations between each two consecutive values of the underlying data series, i.e. for each day2 vs. day1 the variation is ABS(day2 - day1).

The sum of the variations in the latest NSIDC extent table (18 days, i.e. 17 daily changes) is:
1-day avg: 916 (average per day 53.9)
5-day avg: 238 (average per day 14.0)

I did not check the whole year, but I find it hard to believe that the difference between the two should be only 1k per day? As to JAXA, it uses a 2-day average as has been pointed out here recently. I'm too tired to check its volatility now, though  ;)
End of season wobbles ? i.e. not typical of the year as a whole.
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Re: 2019 sea ice area and extent data
« Reply #2495 on: September 18, 2019, 11:20:22 PM »
I'd like to hear if any of you has a thought about relative volatility of these metrics. Has anyone measured whether one is more jagged than the other? Would that mean anything? Thanks.

The **average daily change of one-day extent in 2019 is 17.45 k per day
The **average daily change of five-day extent in 2019 is 16.31 k per day

So the 5 day average is merely 7% less than the one day. That was a surprise.

** N.B. -ve daily changes concerted to absolute (+ve) values.

So why do I use 5-day values? Because that is what NSIDC provides for regional seas - where perhaps volatility is more significant. Also 5-day average helps to reduce impact of artifacts as extensively examined in the melting thread.
I think a good way to quantify this is the mean square error taken over a substantial period of time, one to ten years, taking the mean of squares of each daily extent value minus the average extent for each date  (for average use the last ten years average). See formula below. Then the square root of the final result is a meaningful noise quantification
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gerontocrat

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Re: 2019 sea ice area and extent data
« Reply #2496 on: September 18, 2019, 11:23:40 PM »
I'd like to hear if any of you has a thought about relative volatility of these metrics. Has anyone measured whether one is more jagged than the other? Would that mean anything? Thanks.

The **average daily change of one-day extent in 2019 is 17.45 k per day
The **average daily change of five-day extent in 2019 is 16.31 k per day

So the 5 day average is merely 7% less than the one day. That was a surprise.

** N.B. -ve daily changes concerted to absolute (+ve) values.

So why do I use 5-day values? Because that is what NSIDC provides for regional seas - where perhaps volatility is more significant. Also 5-day average helps to reduce impact of artifacts as extensively examined in the melting thread.
I think a good way to quantify this is the mean square error taken over a substantial period of time, one to ten years, taking the mean of squares of each daily extent value minus the average extent for each date  (for average use the last ten years average). See formula below. Then the square root of the final result is a meaningful noise quantification
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philopek

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Re: 2019 sea ice area and extent data
« Reply #2497 on: September 18, 2019, 11:51:53 PM »
So we now enter the "3"'s decade ...

I would generally anticipate the coming decade will average in the "3"s, but would expect it would have the odd "4" and quite possibly at least one "2".

I'm seconding that ;)

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Re: 2019 sea ice area and extent data
« Reply #2498 on: September 19, 2019, 03:07:04 AM »
I'd like to hear if any of you has a thought about relative volatility of these metrics. Has anyone measured whether one is more jagged than the other? Would that mean anything? Thanks.

The **average daily change of one-day extent in 2019 is 17.45 k per day
The **average daily change of five-day extent in 2019 is 16.31 k per day

So the 5 day average is merely 7% less than the one day. That was a surprise.

** N.B. -ve daily changes concerted to absolute (+ve) values.

So why do I use 5-day values? Because that is what NSIDC provides for regional seas - where perhaps volatility is more significant. Also 5-day average helps to reduce impact of artifacts as extensively examined in the melting thread.

Thats not a measure of jaggedness, unless you take the seasonal cycle out of the data first. Its telling you something about the seasonal cycle instead, so you get pretty much the same result from both datasets.

Juan C. García

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Re: 2019 sea ice area and extent data
« Reply #2499 on: September 19, 2019, 05:40:58 AM »
September 18th, 2019:
     3,978,839 km2, an increase of 14,600 km2.
     2019 is 2nd lowest on record.
     (2007, 2012 & 2016 highlighted).
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.