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Neven

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2015 sea ice area and extent data
« on: January 10, 2015, 12:21:28 AM »
This thread replaces the 2014 version.

Both CT SIA and IJIS SIE are going relatively low at the moment:





Last post from the previous thread by Jim Pettit:

Quote

CT Area:
11,727,834 km2 (08 January [Day 0.0192])
9,493,824 km2 above record minimum area of 2,234,010 km2 (14 September 2012).
Up 30,917 km2 from previous day.
Up 236,345 km2 over past seven days (daily average: 33,764 km2).
Up 265,118 km2 for the month of January (daily average: 33,140 km2).
355,392 km2 below 2000s average for this date.
57,213 km2 below 2010s average for this date.
138,311 km2 below 2014 value for this date.
461,320 km2 below 2012 value for this date.
4th lowest January to-date average.
3rd lowest value for the date.
0 days this year (0% year-to-date) have recorded the lowest daily area.
0 days (0%) have recorded the second lowest.
2 days (25%) have recorded the third lowest.
2 days in total (25%) have been among the lowest three on record.

IJIS Extent:
12,582,981 km2 (08 January)
9,405,526 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).
Down 9,953 km2 from previous day.
Up 68,212 km2 over past seven days (daily average: 9,745 km2).
Up 101,619 km2 for the month of January (daily average: 12,702 km2).
634,021 km2 below 2000s average for this date.
140,998 km2 below 2010s average for this date.
10,214 km2 below 2014 value for this date.
437,247 km2 below 2012 value for this date.
4th lowest January to-date average.
2nd lowest value for the date.
0 days this year (0% year-to-date) have recorded the lowest daily extent.
2 days (25%) have recorded the second lowest.
3 days (37.5%) have recorded the third lowest.
5 days (62.5%) in total have been among the three lowest on record.

Have at it.
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Wipneus

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Re: 2015 sea ice area and extent data
« Reply #1 on: January 10, 2015, 09:08:39 AM »
In addition to the total Arctic figures I keep calculating daily sea ice area and extent for the regions. Source of the calculations are gridded sea ice concentration data as calculated by several institutions.

For NSIDC data my results can be found here:
https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/data

(data here should follow official NSIDC and Crysosphere Today figures closely)

For Jaxa-AMSR2:
https://sites.google.com/site/arctischepinguin/home/amsr2/data/Jaxa_AMSR2_L3_10km_Area_Extent-v0.0.txt

(data here are close but not an exact match for the Jaxa/IJIS numbers)

For Uni Hamburg AMSR2 ASI/3.125km data:
https://sites.google.com/site/arctischepinguin/home/amsr2/data/UH_AMSR2_3.125km_Area_Extent-v0.0.txt

(more datails can be found in the Home Brew thread)

Here are daily updated regional graphs based on the NSIDC sea ice concentration product:


LINK


LINK

Lord M Vader

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Re: 2015 sea ice area and extent data
« Reply #2 on: January 10, 2015, 10:46:52 AM »
Neven: just a note, the extent value of 12,582,981 km2 is incorrect. The value refers to the date for January 2014! The correct value is 12 572 767 km2.

//LMV

Jim Hunt

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Re: 2015 sea ice area and extent data
« Reply #3 on: January 10, 2015, 12:06:12 PM »
And the IJIS number for January 9th 2015 is the lowest on record for the date - 12,585,887 km2
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Lord M Vader

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Re: 2015 sea ice area and extent data
« Reply #4 on: January 10, 2015, 02:05:24 PM »
Well, Jim Hunt, I'm not surprised given that the Pacific waters have been anomalously warm for a long time now. The North Atlantic waters are chewing up the sea ice in Barents Sea. Meaning that it will take more time for sea ice to form. This trend will continue with no light in the future..

It should be interesting to see whether we will have an all time low maximum in March..

Jim Pettit

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Re: 2015 sea ice area and extent data
« Reply #5 on: January 10, 2015, 03:10:25 PM »
IJIS extent is in first place for the first time since the second week of March, 2014:

IJIS Extent:
12,585,887 km2 (09 January) [corrected]
9,459,899 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).
Up 13,120 km2 from previous day.
Up 116,847 km2 over past seven days (daily average: 16,692 km2).
Up 114,739 km2 for the month of January (daily average: 12,749 km2).
668,148 km2 below 2000s average for this date.
174,240 km2 below 2010s average for this date.
51,467 km2 below 2014 value for this date.
534,542 km2 below 2012 value for this date.
4th lowest January to-date average.
Lowest value for the date.
1 day this year (11.11% year-to-date) has recorded the lowest daily extent.
2 days (22.22%) have recorded the second lowest.
3 days (33.33%) have recorded the third lowest.
6 days (66.67%) in total have been among the three lowest on record.
« Last Edit: January 10, 2015, 03:56:56 PM by Jim Pettit »

crandles

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Re: 2015 sea ice area and extent data
« Reply #6 on: January 10, 2015, 03:42:23 PM »
Neven: just a note, the extent value of 12,582,981 km2 is incorrect. The value refers to the date for January 2014! The correct value is 12 572 767 km2.

//LMV

Maybe this should have been addressed to Jim Pettit whose automated procedure still picks up 2014 data

9 Jan 2014 12637354
9 Jan 2015 12585887

Jim Pettit

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Re: 2015 sea ice area and extent data
« Reply #7 on: January 10, 2015, 03:55:20 PM »
Neven: just a note, the extent value of 12,582,981 km2 is incorrect. The value refers to the date for January 2014! The correct value is 12 572 767 km2.

//LMV

Maybe this should have been addressed to Jim Pettit whose automated procedure still picks up 2014 data

9 Jan 2014 12637354
9 Jan 2015 12585887

There was a single reference in my algorithms still pointing to the 2014 data, which has been fixed. However, I should note that all the other calculations in my updates--daily, weekly, and monthly changes, along with ranks, etc.--were and still are being performed properly, and based on the correct reference.

Ah, January. I do love you so... :\

crandles

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Re: 2015 sea ice area and extent data
« Reply #8 on: January 10, 2015, 03:56:57 PM »
Very good, thank you Jim.  :)

Lord M Vader

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Re: 2015 sea ice area and extent data
« Reply #9 on: January 10, 2015, 04:09:11 PM »
January is a really good month, right!! :)

Jim Pettit

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Re: 2015 sea ice area and extent data
« Reply #10 on: January 11, 2015, 02:39:52 PM »

CT Area:
11,717,905 km2 (10 January [Day 0.0247])
9,483,896 km2 above record minimum area of 2,234,010 km2 (14 September 2012).
Up 46,864 km2 from previous day.
Up 177,199 km2 over past seven days (daily average: 25,314 km2).
Up 255,189 km2 for the month of January (daily average: 25,519 km2).
465,750 km2 below 2000s average for this date.
101,533 km2 below 2010s average for this date.
30,814 km2 below 2014 value for this date.
613,404 km2 below 2012 value for this date.
4th lowest January to-date average.
3rd lowest value for the date.
0 days this year (0% year-to-date) have recorded the lowest daily area.
0 days (0%) have recorded the second lowest.
4 days (40%) have recorded the third lowest.
4 days in total (40%) have been among the lowest three on record.

IJIS Extent:
12,614,229 km2 (10 January)
9,436,774 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).
Up 28,342 km2 from previous day.
Up 122,256 km2 over past seven days (daily average: 17,465 km2).
Up 143,081 km2 for the month of January (daily average: 14,308 km2).
674,887 km2 below 2000s average for this date.
204,854 km2 below 2010s average for this date.
132,676 km2 below 2014 value for this date.
563,542 km2 below 2012 value for this date.
3rd lowest January to-date average.
2nd lowest value for the date.
1 days this year (10% year-to-date) has recorded the lowest daily extent.
3 days (30%) have recorded the second lowest.
3 days (30%) have recorded the third lowest.
7 days (70%) in total have been among the three lowest on record.


BornFromTheVoid

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Re: 2015 sea ice area and extent data
« Reply #11 on: January 11, 2015, 05:03:51 PM »
Update for the week to January 10th

The current 5 day mean is on 13,171,300km2 while the 1 day extent is at 13,231,900km2.

The daily anomaly (compared to 81-10) is at -923,350km2, an increase from -710,630km2 last week. The anomaly compared to the 07, 11 and 12 average is at -159,920km2, an increase from -6,010km2 last week. We're currently 2nd lowest on record, compared to 4th last week.



The average daily change over the last 7 days was +19.1k/day, compared to the long term average of +49.5k/day, and the 07, 11 and 12 average of +41.1k/day.

The average long term change over the next week is +38.2k/day, with the 07, 11, and 12 average being +27.8k/day.



The increase so far this January is the smallest on record. To achieve the largest recorded monthly increase, a daily gain of over 74.1k/day is required, while the smallest requires a gain of less than 27.7k/day and an average requires +42.6k/day.


Jim Pettit

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Re: 2015 sea ice area and extent data
« Reply #12 on: January 13, 2015, 02:18:58 PM »

CT Area:
11,738,707 km2 (12 January [Day 0.0302])
9,504,697 km2 above record minimum area of 2,234,010 km2 (14 September 2012).
Up 28,053 km2 from previous day.
Up 80,944 km2 over past seven days (daily average: 11,563 km2).
Up 275,991 km2 for the month of January (daily average: 22,999 km2).
482,712 km2 below 2000s average for this date.
120,867 km2 below 2010s average for this date.
121,422 km2 below 2014 value for this date.
581,909 km2 below 2012 value for this date.
3rd lowest January to-date average.
3rd lowest value for the date.
0 days this year (0% year-to-date) have recorded the lowest daily area.
1 day (8.33%) has recorded the second lowest.
5 days (41.67%) have recorded the third lowest.
6 days in total (50%) have been among the lowest three on record.

IJIS Extent:
12,797,534 km2 (12 January)
9,620,079 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).
Up 105,824 km2 from previous day.
Up 213,606 km2 over past seven days (daily average: 30,515 km2).
Up 326,386 km2 for the month of January (daily average: 27,199 km2).
560,042 km2 below 2000s average for this date.
163,896 km2 below 2010s average for this date.
99,748 km2 below 2014 value for this date.
518,942 km2 below 2012 value for this date.
2nd lowest January to-date average.
3rd lowest value for the date.
1 days this year (8.33% year-to-date) has recorded the lowest daily extent.
4 days (33.33%) have recorded the second lowest.
4 days (33.33%) have recorded the third lowest.
9 days (75%) in total have been among the three lowest on record.

Jim Pettit

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Re: 2015 sea ice area and extent data
« Reply #13 on: January 19, 2015, 01:01:35 PM »
IJIS Extent:
13,210,842 km2 (18 January)
10,033,387 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).
Up 51,857 km2 from previous day.
Up 519,132 km2 over past seven days (daily average: 74,162 km2).
Up 739,694 km2 for the month of January (daily average: 41,094 km2).
415,841 km2 below 2000s average for this date.
42,370 km2 above 2010s average for this date.
50,961 km2 above 2014 value for this date.
115,299 km2 above 2012 value for this date.
2nd lowest January to-date average.
5th lowest value for the date.
1 day this year (5.56% year-to-date) has recorded the lowest daily extent.
4 days (22.22%) have recorded the second lowest.
5 days (27.78%) have recorded the third lowest.
10 days (55.56%) in total have been among the three lowest on record.

BornFromTheVoid

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Re: 2015 sea ice area and extent data
« Reply #14 on: January 19, 2015, 02:03:25 PM »
Update for the week to January 17th

The current 5 day mean is on 13,594,000km2 while the 1 day extent is at 13,713,800km2.

The daily anomaly (compared to 81-10) is at -767,750km2, a decrease from -923,350km2 last week. The anomaly compared to the 07, 11 and 12 average is at +68,160km2, a decrease from -159,920km2 last week. We're currently 5th lowest on record, compared to 2nd last week.




The average daily change over the last 7 days was +60.4k/day, compared to the long term average of +38.2k/day, and the 07, 11 and 12 average of +27.8k/day.

The average long term change over the next week is +38.9k/day, with the 07, 11, and 12 average being +39.4k/day.




The increase so far this January is the 8th smallest on record. To achieve the largest recorded monthly increase, a daily gain of over 80.9k/day is required, while the smallest requires a gain of less than 11.3k/day and an average requires +39.8k/day.


Jim Pettit

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Re: 2015 sea ice area and extent data
« Reply #15 on: January 24, 2015, 02:27:31 PM »

CT Area:
12,486,433 km2 (23 January [Day 0.0603])
10,252,424 km2 above record minimum area of 2,234,010 km2 (14 September 2012).
Up 32,208 km2 from previous day.
Up 305,633 km2 over past seven days (daily average: 43,662 km2).
Up 1,023,717 km2 for the month of January (daily average: 44,509 km2).
248,969 km2 below 2000s average for this date.
213,815 km2 above 2010s average for this date.
99,296 km2 above 2014 value for this date.
202,494 km2 above 2012 value for this date.
5th lowest January to-date average.
9th lowest value for the date.
0 days this year (0% year-to-date) have recorded the lowest daily area.
1 day (4.35%) has recorded the second lowest.
5 days (21.74%) have recorded the third lowest.
6 days in total (26.09%) have been among the lowest three on record.

IJIS Extent:
13,387,581 km2 (23 January)
10,210,126 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).
Up 58,324 km2 from previous day.
Up 248,162 km2 over past seven days (daily average: 35,452 km2).
Up 916,433 km2 for the month of January (daily average: 39,845 km2).
409,098 km2 below 2000s average for this date.
42,120 km2 above 2010s average for this date.
32,657 km2 below 2014 value for this date.
16,227 km2 below 2012 value for this date.
3rd lowest January to-date average.
5th lowest value for the date.
1 days this year (4.35% year-to-date) has recorded the lowest daily extent.
4 days (17.39%) have recorded the second lowest.
5 days (21.74%) have recorded the third lowest.
10 days (43.48%) in total have been among the three lowest on record.

Jim Pettit

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Re: 2015 sea ice area and extent data
« Reply #16 on: January 28, 2015, 12:58:36 PM »

CT Area:
12,700,735 km2 (27 January [Day 0.0713])
10,466,726 km2 above record minimum area of 2,234,010 km2 (14 September 2012).
Up 74,357 km2 from previous day.
Up 266,775 km2 over past seven days (daily average: 38,111 km2).
Up 1,238,019 km2 for the month of January (daily average: 45,853 km2).
122,505 km2 below 2000s average for this date.
303,928 km2 above 2010s average for this date.
182,716 km2 above 2014 value for this date.
304,209 km2 above 2012 value for this date.
Sixth lowest January to-date average.
9th lowest value for the date.
0 days this year (0% year-to-date) have recorded the lowest daily area.
1 day (3.7%) has recorded the second lowest.
5 days (18.52%) have recorded the third lowest.
6 days in total (22.22%) have been among the lowest three on record.

IJIS Extent:
13,329,480 km2 (27 January)
10,152,025 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).
Down 1,341 km2 from previous day.
Up 106,457 km2 over past seven days (daily average: 15,208 km2).
Up 858,332 km2 for the month of January (daily average: 31,790 km2).
609,960 km2 below 2000s average for this date.
138,294 km2 below 2010s average for this date.
213,019 km2 below 2014 value for this date.
125,579 km2 below 2012 value for this date.
3rd lowest January to-date average.
2nd lowest value for the date.
1 day this year (3.7% year-to-date) have recorded the lowest daily extent.
5 days (18.52%) has recorded the second lowest.
7 days (25.93%) have recorded the third lowest.
13 days (48.15%) in total have been among the three lowest on record.

BornFromTheVoid

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Re: 2015 sea ice area and extent data
« Reply #17 on: February 01, 2015, 05:32:58 PM »
Apologies for the delay. A broken finger and a lack of time means this will be a double update, for last weekend and this.

Update for the week to January 24th


The current 5 day mean is on 13,812,600km2 while the 1 day extent is at 13,890,700km2.

The daily anomaly (compared to 81-10) is at -821,270km2, an increase from -767,750km2 last week. The anomaly compared to the 07, 11 and 12 average is at +10,650km2, a decrease from +68,160km2 last week. We're currently 5th lowest on record, the same as last week.




The average daily change over the last 7 days was +31.2k/day, compared to the long term average of +38.9k/day, and the 07, 11 and 12 average of +39.4k/day.

The average long term change over the next week is +34.0k/day, with the 07, 11, and 12 average being +32.9k/day.



The increase so far this January is the 9th smallest on record. To achieve the largest recorded monthly increase, a daily gain of over 130.6k/day is required, while the smallest requires a loss of at least 8.6k/day and an average requires an increase of +60.8k/day.


BornFromTheVoid

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Re: 2015 sea ice area and extent data
« Reply #18 on: February 01, 2015, 06:19:13 PM »
Update for the week to January 31st


The current 5 day mean is on 13,991,700km2 while the 1 day extent is at 14,124,860km2.


The daily anomaly (compared to 81-10) is at -880,120km2, an increase from -821,270km2 last week. The anomaly compared to the 07, 11 and 12 average is at -40,490km2, a decrease from +10,650km2 last week. We're currently 4th lowest on record, down from 5th last week.




The average daily change over the last 7 days was +25.6k/day, compared to the long term average of +34.0k/day, and the 07, 11 and 12 average of +32.9k/day.

The average long term change over the next week is +28.0k/day, with the 07, 11, and 12 average being +18.3k/day.




The increase in January was the 10th smallest on record.




BornFromTheVoid

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Re: 2015 sea ice area and extent data
« Reply #19 on: February 08, 2015, 05:25:53 PM »
Update for the week to February 7th

The current 5 day mean is on 14,226,500km2 while the 1 day extent is at 14,222,990km2.

The daily anomaly (compared to 81-10) is at -841,310km2, a decrease from -880,120km2 last week. The anomaly compared to the 07, 11 and 12 average is at +66,220km2, an increase from -40,490km2 last week. We're currently 6th lowest on record, up from 4th last week.



The average daily change over the last 7 days was +33.5k/day, compared to the long term average of +28.0k/day, and the 07, 11 and 12 average of +18.3k/day.
The average long term change over the next week is +18.9k/day, with the 07, 11, and 12 average being +32.8k/day.



The increase so far this February is the 12th largest on record. To achieve the largest recorded monthly increase, a daily gain of over 30.2k/day is required, while the smallest requires a loss of at least 6.1k/day and an average requires an increase of +15.6k/day.


BornFromTheVoid

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Re: 2015 sea ice area and extent data
« Reply #20 on: February 16, 2015, 11:53:05 AM »
Update for the week to February 14th

The current 5 day mean is on 14,392,900km2 while the 1 day extent is at 14,426,260km2.

The daily anomaly (compared to 81-10) is at -807,680km2, a decrease from -841,310km2 last week. The anomaly compared to the 07, 11 and 12 average is at +3,280km2, an decrease from +66,220km2 last week. We're currently 5th lowest on record, up from 6th last week.



The average daily change over the last 7 days was +23.8k/day, compared to the long term average of +18.9k/day, and the 07, 11 and 12 average of +32.8k/day.
The average long term change over the next week is +20.9k/day, with the 07, 11, and 12 average being +22.8k/day.



The increase so far this February is the 14th largest on record. To achieve the largest recorded monthly increase, a daily gain of over 33.1k/day is required, while the smallest requires a loss of at least 20.1k/day and an average requires an increase of +11.7k/day.


Jim Pettit

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Re: 2015 sea ice area and extent data
« Reply #21 on: February 17, 2015, 02:58:55 PM »
IJIS Extent:
13,883,835 km2 (16 February)
10,706,380 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).
Down 58,225 km2 from previous day.
Up 100,003 km2 over past seven days (daily average: 14,286 km2).
Up 337,383 km2 for the month of February (daily average: 21,086 km2).
558,544 km2 below 2000s average for this date.
127,469 km2 below 2010s average for this date.
88,528 km2 above 2014 value for this date.
178,655 km2 below 2012 value for this date.
Sixth lowest February to-date average.
Third lowest value for the date.
1 day this year (2.13% year-to-date) has recorded the lowest daily extent.
7 days (14.89%) have recorded the second lowest.
13 days (27.66%) have recorded the third lowest.
21 days (44.68%) in total have been among the three lowest on record.


CT Area:
13,233,112 km2 (16 February [Day 0.126])
10,999,103 km2 above record minimum area of 2,234,010 km2 (14 September 2012).
Up 82,176 km2 from previous day.
Up 490,897 km2 over past seven days (daily average: 70,128 km2).
Up 520,046 km2 for the month of February (daily average: 32,503 km2).
196,879 km2 below 2000s average for this date.
194,175 km2 above 2010s average for this date.
459,896 km2 above 2014 value for this date.
320,777 km2 above 2012 value for this date.
8th lowest February to-date average.
8th lowest value for the date.
0 days this year (0% year-to-date) have recorded the lowest daily area.
1 day (2.13%) has recorded the second lowest.
5 days (10.64%) have recorded the third lowest.
6 days in total (12.77%) have been among the lowest three on record.
« Last Edit: February 17, 2015, 07:17:36 PM by Jim Pettit »

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Re: 2015 sea ice area and extent data
« Reply #22 on: February 17, 2015, 08:26:38 PM »
Up 337,383 km2 for the month of February (daily average: 21,086 km2).
This makes us 4th lowest so far in February.

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Re: 2015 sea ice area and extent data
« Reply #23 on: February 18, 2015, 05:26:11 PM »
Since Jim P doesn't seem to have popped in yet, it seems both IJIS and NSIDC show February 17th as their lowest ever values for the date in the respective recorded histories:

http://GreatWhiteCon.info/2015/02/shock-news-ijis-arctic-sea-ice-extent-lowest-ever/#comment-196444

Whether CT area follows suit we won't find out for another couple of days, but it has a long way to fall in order to do so.
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Re: 2015 sea ice area and extent data
« Reply #24 on: February 18, 2015, 05:52:07 PM »
Whether CT area follows suit we won't find out for another couple of days, but it has a long way to fall in order to do so.

From area calculated from NSIDC sea ice concentration I expect the following changes of  CT-area:

Thu: -114k
Fri: -154k

Will that do?

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Re: 2015 sea ice area and extent data
« Reply #25 on: February 18, 2015, 08:57:34 PM »
Will that do?

Thanks Wipneus, but not quite (if my spreadsheet is to be believed). That would take us down to 12.965 versus an all time minimum of 12.835?

However if this continues for another day or two?
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Re: 2015 sea ice area and extent data
« Reply #26 on: February 18, 2015, 10:23:17 PM »
Will that do?

Thanks Wipneus, but not quite (if my spreadsheet is to be believed). That would take us down to 12.965 versus an all time minimum of 12.835?

However if this continues for another day or two?
Based on Jim Pettits' last figures we are missing Wednesdays' figures from this calculation.  If the Wednesday CT drop was significant we might get a lot closer to that 12.835 figure.
These massive fluctuations have to be more to  do with wind than melt  though.   

As an afterthought, I  wonder what  effect having all this ice rushing about has on ice formation. I  suspect that the ice is not thickening or consolidating while it is being thrown about in the recent storms.
« Last Edit: February 19, 2015, 03:38:09 AM by DavidR »
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Re: 2015 sea ice area and extent data
« Reply #27 on: February 19, 2015, 04:19:10 AM »
Will that do?

Thanks Wipneus, but not quite (if my spreadsheet is to be believed). That would take us down to 12.965 versus an all time minimum of 12.835?

However if this continues for another day or two?
Based on Jim Pettits' last figures we are missing Wednesdays' figures from this calculation.  If the Wednesday CT drop was significant we might get a lot closer to that 12.835 figure.
These massive fluctuations have to be more to  do with wind than melt  though.   

As an afterthought, I  wonder what  effect having all this ice rushing about has on ice formation. I  suspect that the ice is not thickening or consolidating while it is being thrown about in the recent storms.

Wind can mean melt (or at least, no thickening), even in winter, via Ekman pumping drawing heat to the surface from deeper water.

It has seemed pretty clear to me that there is a lot of melt happening at the margins of the pack as it gets shoved into the Barents and the upwelling near Svalbard.  That water is 2-3C at minimum, and would make short work of very thick ice, unless that ice was supported by very low  SST's.

The perturbation from wind I think will become increasingly important in how well the ice survives.  More wind, more surf, less ice, with almost certainty.

While the new low doesn't strike me as significant in and of itself, I think the scale of the drop is very telling.  For the ice to be in such poor condition that we could see that large a multi-day *drop* is unsettling.
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Re: 2015 sea ice area and extent data
« Reply #28 on: February 19, 2015, 07:13:44 AM »

Based on Jim Pettits' last figures we are missing Wednesdays' figures from this calculation. 

Yes I did not realize CT was late. It still has not updated. These are the figures:

Wed: +43k
Thu: -114k
Fri: -154k

Attached the actual CT figures compared to my calculations


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Re: 2015 sea ice area and extent data
« Reply #29 on: February 19, 2015, 08:32:18 AM »
IJIS extent for February 18th shows a slight increase at 13,774,725 km², but remains the lowest reading for the date.
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Re: 2015 sea ice area and extent data
« Reply #30 on: February 20, 2015, 07:19:41 AM »
From area calculated from NSIDC sea ice concentration I expect the following changes of  CT-area:

Fri: -154k
Sat: -19k

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Re: 2015 sea ice area and extent data
« Reply #31 on: February 20, 2015, 01:52:49 PM »
IJIS Extent:
13,789,853 km2 (19 February)
10,612,398 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).
Up 15,128 km2 from previous day.
Down 99,460 km2 over past seven days (daily average: -14,209 km2).
Up 243,401 km2 for the month of February (daily average: 12,811 km2).
707,712 km2 below 2000s average for this date.
231,145 km2 below 2010s average for this date.
145,229 km2 below 2014 value for this date.
343,682 km2 below 2012 value for this date.
5th lowest February to-date average.
2nd lowest value for the date.
3 days this year (6% year-to-date) have recorded the lowest daily extent.
8 days (16%) have recorded the second lowest.
13 days (26%) have recorded the third lowest.
24 days (48%) in total have been among the three lowest on record.


CT Area:
13,011,439 km2 (19 February [Day 0.1343])
10,777,430 km2 above record minimum area of 2,234,010 km2 (14 September 2012).
Down 149,235 km2 from previous day. (NOTE: third largest one-day February SIA decrease on record; largest two-day February SIA decrease on record)
Up 122,015 km2 over past seven days (daily average: 17,431 km2).
Up 298,373 km2 for the month of February (daily average: 15,704 km2).
527,528 km2 below 2000s average for this date.
95,805 km2 below 2010s average for this date.
178,301 km2 above 2014 value for this date.
25,034 km2 above 2012 value for this date.
8th lowest February to-date average.
5th lowest value for the date.
0 days this year (0% year-to-date) have recorded the lowest daily area.
1 day (2%) has recorded the second lowest.
5 days (10%) have recorded the third lowest.
6 days in total (12%) have been among the lowest three on record.


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Re: 2015 sea ice area and extent data
« Reply #32 on: February 20, 2015, 06:33:07 PM »
From area calculated from NSIDC sea ice concentration I expect the following changes of  CT-area:

Sat: -19k
Sun: +29k

That was all for the moment.

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Re: 2015 sea ice area and extent data
« Reply #33 on: February 21, 2015, 06:04:29 PM »
From area calculated from NSIDC sea ice concentration I expect the following changes of  CT-area:

Fri: -154k
Sat: -19k

That means CT SIA will probably go lowest as well.
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Re: 2015 sea ice area and extent data
« Reply #34 on: February 21, 2015, 08:06:31 PM »
That means CT SIA will probably go lowest as well.

Not according to my trusty spreadsheet? I get 13.02 versus a minimum of 12.86
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Re: 2015 sea ice area and extent data
« Reply #35 on: February 21, 2015, 09:35:54 PM »
We have dropped by 264k compared with 2 data days ago.

12 of 36 years show gains from last data day to max of less than 264k, so possibly a 1 in 3 chance we have passed the max.

OTOH recent years have shown late maximums and large late rises:
only 2 of last 10 years have shown rises of less than 264k, so maybe only 1 in 5 chance ... or if this trend is continuing even less chance than that.

or maybe such differences arise by chance. Difference is fairly small: projected max using 36 years = 13.41 versus 13.44 using last 10 years so just 30k difference. As the maximum further increase for 1988 is 835k a difference of 30k seems likely to arise by chance.


Projected maximum of 13.41 or 13.44 would make 2015 4th lowest maximum area on record.

2nd lowest to 6th lowest maximum area on record seems a likely range (only 2 of 36 years take us to higher than 6th lowest)

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Re: 2015 sea ice area and extent data
« Reply #36 on: February 22, 2015, 11:49:14 AM »
That means CT SIA will probably go lowest as well.

Not according to my trusty spreadsheet? I get 13.02 versus a minimum of 12.86

Indeed, I subtracted twice.
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Re: 2015 sea ice area and extent data
« Reply #37 on: February 22, 2015, 04:27:52 PM »
Update for the week to February 21st

The current 5 day mean is on 14,367,470km2 while the 1 day extent is at 14,483,980km2.

The daily anomaly (compared to 81-10) is at -979,110km2, an increase from -807,680km2 last week. The anomaly compared to the 07, 11 and 12 average is at -181,500km2, an decrease from +3,280km2 last week. We're currently 2nd lowest on record, down from 5th last week.



The average daily change over the last 7 days was -3.7k/day, compared to the long term average of +20.9k/day, and the 07, 11 and 12 average of +22.8k/day.
The average long term change over the next week is +14.1k/day, with the 07, 11, and 12 average being +12.6k/day.



The increase so far this February is the 12th smallest on record. To achieve the largest recorded monthly increase, a daily gain of over +74.7k/day is required, while the smallest requires a loss of at least 39.4k/day and an average requires an increase of +28.8k/day.


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Re: 2015 sea ice area and extent data
« Reply #38 on: February 22, 2015, 06:49:51 PM »
We have dropped by 264k compared with 2 data days ago.

12 of 36 years show gains from last data day to max of less than 264k, so possibly a 1 in 3 chance we have passed the max.

OTOH recent years have shown late maximums and large late rises:
only 2 of last 10 years have shown rises of less than 264k, so maybe only 1 in 5 chance ... or if this trend is continuing even less chance than that.

or maybe such differences arise by chance. Difference is fairly small: projected max using 36 years = 13.41 versus 13.44 using last 10 years so just 30k difference. As the maximum further increase for 1988 is 835k a difference of 30k seems likely to arise by chance.


Projected maximum of 13.41 or 13.44 would make 2015 4th lowest maximum area on record.

2nd lowest to 6th lowest maximum area on record seems a likely range (only 2 of 36 years take us to higher than 6th lowest)
My own prediction: SIA is five to six weeks from maximum, which will end up somewhere between 13.3 and 13.6 million km2 (Keep in mind that 2012 saw nearly 700k km2 of ice form after this date). Having said that, however, I agree that there remains a not-insignificant chance that this year's maximum has indeed already been reached.

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Re: 2015 sea ice area and extent data
« Reply #39 on: February 22, 2015, 08:34:37 PM »
Surely any gains from this point in are transient 'ice factory' type ice and of no consequence through the coming melt season?

What is important are the changes to the ice types that stand a chance of surviving the melt season and where those ice types are in the run up to melt?

We saw Fram fire back up into a more normal pattern of drainage from the basin in December so we lost much of the ice that survived the past two melt seasons from in front of Fram  , and to the NE of Svalbard also.

We also saw Nares decondition the ice in Lincoln allowing rotation more freely in the Beaufort (under correct forcings)

so it is not what is happening that is most important than what we have seen happen surely?

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Re: 2015 sea ice area and extent data
« Reply #40 on: February 22, 2015, 09:28:54 PM »
What is important are the changes to the ice types that stand a chance of surviving the melt season and where those ice types are in the run up to melt?

What do you make of the current ASCAT then?



The Pole itself looks vulnerable this year?
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Re: 2015 sea ice area and extent data
« Reply #41 on: February 22, 2015, 09:36:02 PM »
What do you make of the current ASCAT then?

The ASCAT looks like something from a car. I suggest all new cars be delivered with mandatory ASCATs on their wheels that show the polar region at the time of purchase. People can then compare their 'progress' as they move to a new car, with updated ASCATs.
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Re: 2015 sea ice area and extent data
« Reply #42 on: February 23, 2015, 10:33:09 AM »
The ASCAT looks like something from a car. I suggest all new cars be delivered with mandatory ASCATs on their wheels that show the polar region at the time of purchase.

Is that your (tongue in cheek?) way of saying you don't understand what you're looking at?
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Re: 2015 sea ice area and extent data
« Reply #43 on: February 23, 2015, 11:40:18 AM »
Not at all. I'm sorry if I mix sciences and blend in some social science now and then. Seeing that driving a car is still legal in most countries, having ASCATs on the wheels as a mandatory arrangement might make drivers think twice before using their cars. In other news driving cars and flying planes is destroying this planet. Same planet as in the 'hard' sciences, BTW.
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Re: 2015 sea ice area and extent data
« Reply #44 on: February 23, 2015, 12:11:21 PM »
ASCAT images look rather like turbine blades also?
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Re: 2015 sea ice area and extent data
« Reply #45 on: February 24, 2015, 01:44:12 AM »
To try and reduce noise in day of maximum, I tried using a 31 day centred average. Cryosphere today area numbers. Still leaves noisy data, but anyway: The day of maximum looks strangely early in the period 1986 to 1998 and then no trend this century.

31centeredaveragemaximumday by crandles2011, on Flickr

Just random noise or is there likely to be an underlying cause, and if so what?

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Re: 2015 sea ice area and extent data
« Reply #46 on: February 24, 2015, 07:39:58 AM »
To try and reduce noise in day of maximum, I tried using a 31 day centred average. Cryosphere today area numbers. Still leaves noisy data, but anyway: The day of maximum looks strangely early in the period 1986 to 1998 and then no trend this century.

Just random noise or is there likely to be an underlying cause, and if so what?

What you are trying to do is find the maximum of a function in the presence of noise, when the function is essentially flat at the maximum. This is a hard problem. Still, I have some thoughts.

Since you didn't say otherwise, I assume you are using an unweighted average. This is still sensitive to the noise at the ends of the averaging window. You may get better results with a weighted average. Depending on what software you are using, you should check for kernel smoothers or binomial smoothers or Gaussian smoothers, or possibly other terms. You may be able to smooth the data better, but with a smaller effective averaging window.

These smoothers all assume the noise is uncorrelated, which is probably not the case. There are statistical tools which perform smoothing with autocorrelated noise, so if you want to go that far you could probably find an R package which will do all the work for you, for example.

Even then, the variance is likely to be large, making year to year comparisons difficult. If you're really motivated, you could do a bootstrap estimate of the variance, but it's probably a lot of effort with little point.

Looking at the graph as is, there's no visual evidence of a trend, but you could do a test for a change point in 1998. Again, depending on what software you are using, you may be able to directly do a statistical test of whether the mean maximum day for years up to 1998 is different than the mean maximum day after 1998.

On the other hand, if there has been a change in the maximum day, I would expect it to be a smooth trend rather than a jump at a change point. Even if the change point test is statistically significant, I'm not sure it would be physically meaningful.

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Re: 2015 sea ice area and extent data
« Reply #47 on: February 24, 2015, 09:59:28 AM »
My 2 lepta.

As is, the 2007 IJIS extent maximum was the earliest on record at Feb 24th. When filtered weekly the max date adjusts to Feb 23rd. The rest of the 2004–2014 field when filtered is spread out rather narrowly from Mar 4th to Mar 18th, and centered around Mar 9–10th. Could 2015 be an even earlier outlier than 2007 with a Feb 15th extent maximum? Too early to tell, of course. But if we were to max out like 2007 on Feb 23rd, we would need daily delta gains of on average 33467 km² for the next 5 days. (If we were to max out like #2, 2009, on Mar 4th, we would need daily delta gains of on average 11952 km² for the next 14 days.

Is there at all any advantage to turning early for achieving brilliant melt during melt season? Hard to tell. We have not enough data, and 2012 that went lowest turned late (March 7th or 18th filtered), but lost 11.532 M km² during melt season, while earlybird 2007 lost 'only' 10.144 M km². At this point I'd say there's no connection between starting early and melting much.

and

A good melt in the earliest 3rd of melt season, with bountiful early melt ponds, is of importance for the final melt amount. The amount of melt ponds, however, isn't directly measured by sea ice extent. I believe an early numerical max extent date is mainly a random feature, becoming a little less random using a weekly filter, but ultimately doesn't say much about whether or not there will be a good melt in the earliest 3rd of melt season, and therefore neither says much about final melt amount.

If you want to quantify this, March melt is generally lousy, with an average loss of 181 000 km². April has an average loss of 1 122 000 km², and the first 3rd of May a monthly equivalent of on average 1 529 000 km². Some of the best melt seasons have sported huge extent *increases* during March, like 2010 which put on almost half a million km². So March is generally undecided and indecisive for final melt (while a good melt in the earliest 3rd of melt season IS decisive).

PS: When talking about the earliest 3rd of the melt season, I'm in effect operating with three 70–day periods, the first of these going from Mar 1 to May 9.
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Re: 2015 sea ice area and extent data
« Reply #48 on: February 24, 2015, 12:42:27 PM »
Thanks for the replies.  :D

I agree a trend would seem more likely than a step change. Perhaps there could be a trend with 81, 84 and 85 being unusually high by chance. But if it doesn't look like a trend then correlation with something might be a better possibility than a step change?

I wondered if there might be a correlation with PDO or some other ocean oscillation. Doesn't look too promising even though PDO did change from warm phase to cool around 1998.

There could be relations with PDO for pacific side and other indices for the atlantic side. Also not impossible to imagine a changing relation with PDO depending on level of ice on the Pacific side.

I am just using google sheets and searching for smoothers terms mentioned didn't find anything. I am sure you are right that there are better ways of finding a smoothed max and I probably should be able to do better with more effort. That ought to be done before I get too carried away with looking for PDO and other correlations. Whether the effort is worth it or not does seem rather questionable.

Anyway thanks for the comments.

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Re: 2015 sea ice area and extent data
« Reply #49 on: February 24, 2015, 04:13:42 PM »
Tried what I guess would be a binomial smoothing 15 day weighted average. I suspect this is too short a period for what I want as there were several instances of double peaks often up to two weeks or more apart. Anyway the days are not as interesting looking to me:


If I can get interesting or not interesting depending on the processing then I suspect I have probably already done too much processing of the data.


« Last Edit: February 24, 2015, 04:20:42 PM by crandles »