2015 sea ice area and extent data

[Lord M Vader]

What I find most surprising with Slaters pic is the very high probability for ice in the ESS by the beginning of August as well as the rather low likelihood for ice at the North Pole.

//LMV

[jai mitchell]

The 2012 August 7th value for Charctic was 5.767 this is about 4 days ahead of the Slater chart for that same day, however, the rate of decline is more and it seems that it would catch up and surpass the 2012 minimum without too much difficulty.  It is not clear to me what would drive the rapid decrease?  Would it be a function of current ice thickness patterns?   or possibly a greater rate of ice export?  wave effects? all the above?

amazing that they have been so accurate up to this point, thanks for the poster LMV.

[seaicesailor]

What I find most surprising with Slaters pic is the very high probability for ice in the ESS by the beginning of August as well as the rather low likelihood for ice at the North Pole.

//LMV

From the discussion in the "melting season" thread, I gather that the Eurasian coast, including Laptev, has been cold and started melting late, but ice may be thin now, due to record strength of the Transpolar drift this winter. Seems very complicated to predict the outcome there.

[AySz88]

Tor Bejnar: not a too dramatic pic from Slater if you ask me. From August an until the minimum the Arctic loses roughly 2 million km². That would yield a minima about 4,5-5 million km². Of course, I would like to know earlier years minima/extent for the same time period.

Best, LMV

By my reading, the oddity being pointed out is not the forecast per se, but literally the fact that it has suddenly shifted down.  I wonder whether that rate is "real" or if it is due to some unexpected development in the sea ice concentration data that came in during the last few days. In the latter case, that would seem to suggest that the last few days have changed the game a bit, at least from the perspective of Slater's forecasting model.  (But on the other hand, that drop may have been waiting in the wings all along, say if we used the same method to get forecasts of days 51-57 from last week's data. Hard to tell....)

Edited to add...

What I find most surprising with Slaters pic is the very high probability for ice in the ESS by the beginning of August as well as the rather low likelihood for ice at the North Pole.

//LMV

I'd note that, as far as I can tell, the probability of survival is calculated solely from the current "concentration" in the grid cell (possibly melt pond contaminated) and the current date - the model is ignorant of where the grid cell is located.  Also the model doesn't seem that skillful in mid June....

[Jim Pettit]

ADS-NIPR Extent:

10,207,482 km2 (16 June)

Down 3,734,578 km2 (26.79%) from 2015 maximum of 13,942,060 km2 on 15 February.

7,030,027 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).

Down 76,315 km2 from previous day.

Down 380,736 km2 over past seven days (daily average: -54,391 km2).

Down 671,089 km2 for the month of June (daily average: -41,943 km2).

684,926 km2 below 2000s average for this date.

94,984 km2 below 2010s average for this date.

295,452 km2 below 2014 value for this date.

145,232 km2 above 2012 value for this date.

Lowest June to-date average.

3rd lowest value for the date.

64 days this year (38.32% year-to-date) have recorded the lowest daily extent.

32 days (19.16%) have recorded the second lowest.

32 days (19.16%) have recorded the third lowest.

128 days (76.65%) in total have been among the three lowest on record.

CT Area:

8,646,584 km2 (16 June [Day 0.4548])

Down 4,627,972 km2 (34.86%) from 2015 maximum of 13,274,555 km2 on 17 February [Day 0.1288].

6,412,574 km2 above record minimum area of 2,234,010 km2 (14 September 2012).

Down 339,857 km2 from previous day.

Down 753,696 km2 over past seven days (daily average: -107,671 km2).

Down 1,489,997 km2 for the month of June (daily average: -93,125 km2).

651,227 km2 below 2000s average for this date.

26,221 km2 below 2010s average for this date.

305,494 km2 below 2014 value for this date.

616,678 km2 above 2012 value for this date.

7th lowest June to-date average.

3rd lowest value for the date.

7 days this year (4.19% year-to-date) have recorded the lowest daily area.

19 days (11.38%) have recorded the second lowest.

29 days (17.37%) have recorded the third lowest.

55 days in total (32.93%) have been among the lowest three on record.

[Blizzard_of_Oz]

What I find most surprising with Slaters pic is the very high probability for ice in the ESS by the beginning of August as well as the rather low likelihood for ice at the North Pole.

Indeed the forecasts from the last few days are a surprising turn of events. The SPIE is a statistical forecast with zero memory, so let's see what happens in the next week or so. If it is in error now, it could 'self-correct' - it has done so in the past (e.g. 2010). In any case, it makes me think there are some interesting events ahead.

Also, for some info on prior performance, scroll down to 'Regional Contributions' and Figures 9 & 10
http://www.arcus.org/sipn/sea-ice-outlook/2014/post-season
(but I wouldn't judge relative skill of forecast systems on the basis of one year/event)

[Nightvid Cole]

June 16th CT value has fallen off the June cliff!

[Nick_Naylor]

Indeed. Very impressive launch to June Swoon

[Wipneus]

The cliff has already paused. The CT-area numbers (calculated from today's NSIDC sea ice concentration update) for the coming two days are:

Wed       8.646584
Thu -71.7  8.574850
Fri -54.4  8.520460

OK, the last drop would have been higher without the uptick in "lake" ice (+23k7). Also the CAB went up (+27k5). The declines are in ESS , Laptev, CAA, Beaufort, Baffin and Kara (all similar ~-18k).

[Jim Pettit]

The cliff has already paused. The CT-area numbers (calculated from today's NSIDC sea ice concentration update) for the coming two days are:

Wed       8.646584
Thu -71.7  8.574850
Fri -54.4  8.520460

OK, the last drop would have been higher without the uptick in "lake" ice (+23k7). Also the CAB went up (+27k5). The declines are in ESS , Laptev, CAA, Beaufort, Baffin and Kara (all similar ~-18k).

Those numbers will knock CT SIA back into 5th place, and again roughly three-quarters of a million square kilometers below 2012's same-day numbers. Then again, the steepest part of 2012's cliff ended this Friday; having dropped nearly 2 million km2 in the previous two week period (where 2015 will have lost just 1.3 million), 2012's torrid pace calmed for a bit, losing just 418k over the ensuing week. IOW: 2015 should be able to do a little catching up.

[Nightvid Cole]

The cliff has already paused. The CT-area numbers (calculated from today's NSIDC sea ice concentration update) for the coming two days are:

Wed       8.646584
Thu -71.7  8.574850
Fri -54.4  8.520460

OK, the last drop would have been higher without the uptick in "lake" ice (+23k7). Also the CAB went up (+27k5). The declines are in ESS , Laptev, CAA, Beaufort, Baffin and Kara (all similar ~-18k).

I am confused. Today's NSIDC data is for yesterday (6/16). Since CT data also extends through yesterday, how can you possibly 'foretell' CT data using NDISC data if the latter does not cover more days than the former? Please explain.

[Nick_Naylor]

The CT data plots area vs. publication date rather than data acquisition date, which is three days earlier. That's how Wipneus is able to forecast so spectacularly

[Wipneus]

I am confused. Today's NSIDC data is for yesterday (6/16). Since CT data also extends through yesterday, how can you possibly 'foretell' CT data using NDISC data if the latter does not cover more days than the former? Please explain.

CT presents data that is 2 days behind for reasons I do not know.
Attached is a graph with the real CT-values and my calculations. Only by a shift of two days they can match.

[Nightvid Cole]

Ok, makes sense now. 

[ChrisReynolds]

June 16th CT value has fallen off the June cliff!

Area 'proper' as calculated by Wipneus, the closest thing we have to regional has dropped even more.

http://dosbat.blogspot.co.uk/2015/06/looking-promising.html

[Wipneus]

From today's update of NSIDC sea ice concentration data, I calculate CT-area for tomorrow and the day after:

Thu       8.576599
Fri -54.5  8.522109
Sat -35.0  8.487070

Bad melting day, Saturday, especially as it includes a -21k drop in "lake ice". Upticks in CAB (+43k5 and Beaufort (+16k5). Kara, Baffin, CAA and Greenland Sea decline at rates ~ -18k.

[Jim Pettit]

From today's update of NSIDC sea ice concentration data, I calculate CT-area for tomorrow and the day after:

Thu       8.576599
Fri -54.5  8.522109
Sat -35.0  8.487070

Bad melting day, Saturday, especially as it includes a -21k drop in "lake ice". Upticks in CAB (+43k5 and Beaufort (+16k5). Kara, Baffin, CAA and Greenland Sea decline at rates ~ -18k.

That will knock 2015 back down to 7th place (behind 2012, 2011, 2007, 2006, 2008, and 2010), and nearly three-quarters of a million square kilometers behind 2012.

With the singular exception of the 340k drop the other day, this has been a very mild few weeks melt-wise. Will it continue this way? Or is there any mechanism by which the melt season might get even close to what was hinted at back just a month or two ago? Eight weeks ago, 2015 was 840k ahead of 2012; 2012 is now 629k ahead of 2015, a swing of nearly a million-and-a-half square kilometers. What happened?

[DavidR]

From today's update of NSIDC sea ice concentration data, I calculate CT-area for tomorrow and the day after:

Thu       8.576599
Fri -54.5  8.522109
Sat -35.0  8.487070

Bad melting day, Saturday, especially as it includes a -21k drop in "lake ice". Upticks in CAB (+43k5 and Beaufort (+16k5). Kara, Baffin, CAA and Greenland Sea decline at rates ~ -18k.

That will knock 2015 back down to 7th place (behind 2012, 2011, 2007, 2006, 2008, and 2010), and nearly three-quarters of a million square kilometers behind 2012.

With the singular exception of the 340k drop the other day, this has been a very mild few weeks melt-wise. Will it continue this way? Or is there any mechanism by which the melt season might get even close to what was hinted at back just a month or two ago? Eight weeks ago, 2015 was 840k ahead of 2012; 2012 is now 629k ahead of 2015, a swing of nearly a million-and-a-half square kilometers. What happened?

Eight weeks ago, in 2012, there was an extra 6-700 K km^2 in the north Pacific plus a much larger area of ice that was between 0.6 and 1 m  in 2012 compared to 2015. This ice has now melted out.  2012 was also much  warmer in May and June. Given the fact that early  May this year was comparatively cold the fact that  we have lost as much ice as we have this year is surprising.     

[Wipneus]

Today's NSIDC sea ice concentrate update gives these expected CT-area updates:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337985

So on Sunday again a big drop in sea ice area, while the extent is hardly changed. That is a sign of surface melting. Regions are  ESS, Laptev and CAB where this is happening (-71k, -31k and -15k).

[Jim Pettit]

Today's NSIDC sea ice concentrate update gives these expected CT-area updates:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337985

So on Sunday again a big drop in sea ice area, while the extent is hardly changed. That is a sign of surface melting. Regions are  ESS, Laptev and CAB where this is happening (-71k, -31k and -15k).

And that will drop SIA from its current 5th spot to 6th, behind 2012, 2011, 2010, 2006, and 2007.

[Wipneus]

Based on today's NSIDC sea ice concentrate update I expect on Monday another large drop in CT-area:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.6  8.168340

With the corresponding extent drop very limited (-28k2 for NSIDC extent), we can assume this is mostly a surface melting effect. The drop is very large in the ESS (-71k1) and CAB (-43k3). "Lake ice" jumped +17k2.

[Lord M Vader]

Wipneus: what were the corresponding CTA numbers for the years ahead 2015? If possible, do you have an opportunity to put in the leaders number when you're doing those great updates?

Looking at ESS today is very interesting! Wipneus 3,125 km resolution of the Arctic basin shows that the ESS is breaking up at the shoreline, something I think didn't occurred until sometime in July both 2014 and 2013? Correct or?!

If current trend in the ESS continues and some more melting will be seen in the Laptev Sea, the Northern Sea Route should maybe, just maybe, open up in a narrow channel by July 15...

Best, LMV

[seaicesailor]

Wipneus: what were the corresponding CTA numbers for the years ahead 2015? If possible, do you have an opportunity to put in the leaders number when you're doing those great updates?

Looking at ESS today is very interesting! Wipneus 3,125 km resolution of the Arctic basin shows that the ESS is breaking up at the shoreline, something I think didn't occurred until sometime in July both 2014 and 2013? Correct or?!

If current trend in the ESS continues and some more melting will be seen in the Laptev Sea, the Northern Sea Route should maybe, just maybe, open up in a narrow channel by July 15...

Best, LMV

From MODIS today,

https://forum.arctic-sea-ice.net/index.php/topic,1149.msg54504.html#msg54504

Count Laptev Sea as well for the July crash

[Lord M Vader]

Seaicesailor: aaah, yes, I saw that nice picture Will be interesting to see if the July crash materializes! 

[Wipneus]

Based on today's NSIDC sea ice concentrate update I expect Tuesday to be a slow melt day:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.5  8.119998

That includes a -21k drop in "lake ice". Conditions in the ESS (+69k7) and Laptev (+23k8) seem to have gone from melting to freezing somehow. Hudson (-29k4) and Baffin (-22k1) drop most (and those lakes of course).

[BornFromTheVoid]

Update for the week to June 20th

The current 5 day mean is on 10,780,600km2 while the 1 day extent is at 10,693,000km2.
The daily anomaly (compared to 81-10) is at -887,150km2, an increase from -859,890km2 last week. The anomaly compared to the 07, 11 and 12 average is at +98,467km2, an increase from -73,930km2 last week. We're currently 4th lowest on record, the same as last week.



The average daily change over the last 7 days was -56.5k/day, compared to the long term average of -52.6k/day, and the 07, 11 and 12 average of -81.2k/day.
The average long term change over the next week is -60.5k/day, with the 07, 11, and 12 average being -81.1k/day.



The loss so far this June is the 18th largest on record. To achieve the largest monthly drop, a daily loss of at least 187.9k/day is required, while the smallest drop requires a loss of less than 5.1k/day and an average drop requires a loss of 65.4k/day.

[Buddy]

...and an average drop requires a loss of 65.4k/day

An average drop covering what time span?

Thanks...

[DavidR]

...and an average drop requires a loss of 65.4k/day

An average drop covering what time span?

Thanks...

All rates are quoted until the end of the month ie to acheive an average drop  for the month of June. 
Recently average drop  for the remainder of the month is over 100k / day so 65.4 would remain remarkably  low.

[Wipneus]

No losses on Wednesday, expected CT-area updates from today's update of NSIDC sea ice concentration data:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.9  8.119646
Wed +0.3  8.119995

Area in ESS and CAA went up (+22k5 and 13k7), Hudson and Baffin down (-18k and -16k4).

[jdallen]

No losses on Wednesday, expected CT-area updates from today's update of NSIDC sea ice concentration data:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.9  8.119646
Wed +0.3  8.119995

Area in ESS and CAA went up (+22k5 and 13k7), Hudson and Baffin down (-18k and -16k4).

...

Got to be melt ponds draining.

[Wipneus]

For a better understanding where the area increase and decreases are coming from, I have added a color shade tot the NSIDC delta map. Pinkish is where concentration dropped more than some threshold, light bluish is where the concentration increased. For now I have set the threshold at 7%.

As before bright red and blue indicate crossing the 15% line, meaning extent increase/decrease.

[ChrisReynolds]

No losses on Wednesday, expected CT-area updates from today's update of NSIDC sea ice concentration data:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.9  8.119646
Wed +0.3  8.119995

Area in ESS and CAA went up (+22k5 and 13k7), Hudson and Baffin down (-18k and -16k4).

That takes me up to 23 June with CT Area data, albeit 'provisional'.

So my CT Area prediction for 2015 September minimum (daily value) is:

3.0 to 3.8M km^2, central value 3.4M km^2

The hindcasts for the model are 80% successful. In the post 2007 period there were two failures, 2009 and 2012 (0.18 and 0.17 respectively below the lower bound).

This prediction encompasses 2009, 2010, 2013 and 2014. This suggests a relatively normal post 2015 minimum.

Method described here:
http://dosbat.blogspot.co.uk/2015/05/predicting-ct-area-minimum.html

[AySz88]

...and an average drop requires a loss of 65.4k/day

An average drop covering what time span?

Thanks...

In case you're asking about years and not days, I think it's the average of 1981-2010 assuming its the same time period as the middle graph.

[Buddy]

In case you're asking about years and not days, I think it's the average of 1981-2010 assuming its the same time period as the middle graph.

Yes....thanks.  I asked a "sloppy" question, and was just about to clarify.

Thanks again....

[seaicesailor]

No losses on Wednesday, expected CT-area updates from today's update of NSIDC sea ice concentration data:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.9  8.119646
Wed +0.3  8.119995

Area in ESS and CAA went up (+22k5 and 13k7), Hudson and Baffin down (-18k and -16k4).

...

Got to be melt ponds draining.

All at the same time... like somebody flushed them down?
Just teasing 

[Stephen]

Looks like CT is having a little break, they haven't updated their area graph since the 18th

[Wipneus]

From today's NSIDC sea ice concentration update I calculate the following future CT-area updates:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.9  8.119646
Wed +0.3  8.119965
Thu -92.9  8.027085

Biggest declines for Thursday are CAA (-23k), Baffin (-21k), CAB (-16k2) and Beaufort (-12k1).
In the attached delta map, pixels with larger concentration changes than 7% or colored pinkish (down) or light blue (up)

[seaicesailor]

No losses on Wednesday, expected CT-area updates from today's update of NSIDC sea ice concentration data:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.9  8.119646
Wed +0.3  8.119995

Area in ESS and CAA went up (+22k5 and 13k7), Hudson and Baffin down (-18k and -16k4).

That takes me up to 23 June with CT Area data, albeit 'provisional'.

So my CT Area prediction for 2015 September minimum (daily value) is:

3.0 to 3.8M km^2, central value 3.4M km^2

The hindcasts for the model are 80% successful. In the post 2007 period there were two failures, 2009 and 2012 (0.18 and 0.17 respectively below the lower bound).

This prediction encompasses 2009, 2010, 2013 and 2014. This suggests a relatively normal post 2015 minimum.

Method described here:
http://dosbat.blogspot.co.uk/2015/05/predicting-ct-area-minimum.html

You recently wrote in your blog (post about possible crash this year) about the possibility of area going down in June (unremarkably) while June extent stalling. Compaction dropping, but still not meaning much in either direction.

So your method is purely quantitative, but still, don't you think your result has much to do with recent weather (and by recent I mean past 7 days).

A sensitivity test would consist on doing same math analysis for 15 June, or for July 1st when it comes. Just to see how your semi-statistical method converges...

Just a thought.

[Jim Pettit]

ADS-NIPR Extent:

9,991,615 km2 (22 June)

Down 3,950,445 km2 (28.33%) from 2015 maximum of 13,942,060 km2 on 15 February.

6,814,160 km2 above record minimum extent of 3,177,455 km2 (16 September 2012).

Down 40,059 km2 from previous day.

Down 292,182 km2 over past seven days (daily average: -41,740 km2).

Down 886,956 km2 for the month of June (daily average: -40,316 km2).

491,449 km2 below 2000s average for this date.

79,923 km2 above 2010s average for this date.

29,009 km2 above 2014 value for this date.

302,133 km2 above 2012 value for this date.

Lowest June to-date average.

5th lowest value for the date.

64 days this year (36.99% year-to-date) have recorded the lowest daily extent.

32 days (18.5%) have recorded the second lowest.

32 days (18.5%) have recorded the third lowest.

128 days (73.99%) in total have been among the three lowest on record.

CT Area:

NOTE: due to the prolonged absence of official CT sea ice area data, I've instead used Wipneus' calculated area numbers for the period from 18 June through 22 June. The official numbers will be inserted if/when available. In the meantime, thanks, Wipneus!

8,119,646 km2 (22 June [Day 0.4712])

Down 5,154,909 km2 (38.83%) from 2015 maximum of 13,274,555 km2 on 17 February [Day 0.1288].

5,885,637 km2 above record minimum area of 2,234,010 km2 (14 September 2012).

Down 48,898 km2 from previous day.

Down 866,795 km2 over past seven days (daily average: -123,828 km2).

Down 2,016,935 km2 for the month of June (daily average: -91,679 km2).

542,932 km2 below 2000s average for this date.

80,808 km2 above 2010s average for this date.

141,966 km2 below 2014 value for this date.

532,248 km2 above 2012 value for this date.

7th lowest June to-date average.

6th lowest value for the date.

7 days this year (4.05% year-to-date) have recorded the lowest daily area.

19 days (10.98%) have recorded the second lowest.

29 days (16.76%) have recorded the third lowest.

55 days in total (31.79%) have been among the lowest three on record.

[jdallen]

No losses on Wednesday, expected CT-area updates from today's update of NSIDC sea ice concentration data:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.9  8.119646
Wed +0.3  8.119995

Area in ESS and CAA went up (+22k5 and 13k7), Hudson and Baffin down (-18k and -16k4).

...

Got to be melt ponds draining.

All at the same time... like somebody flushed them down?
Just teasing 

Taken in good spirit

[wanderer]

CT Area:

8,119,646 km2 (22 June [Day 0.4712])

Down 5,154,909 km2 (38.83%) from 2015 maximum of 13,274,555 km2 on 17 February [Day 0.1288].

532,248 km2 above 2012 value for this date.

2015 is 532k above 2012.

Baffin: ~ 200k behind 2012 -> will melt
Kara: ~ 100k behind 2012 -> will melt
Barents: ~ 100-150k behind 2012 -> will melt

2012 is just a little bit ahead in Laptev and Beaufort, other regions are almost the same.

So... I expect more losses soon, nothing is decided yet.

[Neven]

From today's NSIDC sea ice concentration update I calculate the following future CT-area updates:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.9  8.119646
Wed +0.3  8.119965

Wipneus, did you perhaps count a day double (maybe the one that has +0.3)? CT SIA is now one day ahead of IJIS SIE in my CAPIE spreadsheet (it used to be one day behind, with your calculations everything was going synchronously).  But maybe/probably I'm doing something wrong.

[ChrisReynolds]

No losses on Wednesday, expected CT-area updates from today's update of NSIDC sea ice concentration data:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.9  8.119646
Wed +0.3  8.119995

Area in ESS and CAA went up (+22k5 and 13k7), Hudson and Baffin down (-18k and -16k4).

That takes me up to 23 June with CT Area data, albeit 'provisional'.

So my CT Area prediction for 2015 September minimum (daily value) is:

3.0 to 3.8M km^2, central value 3.4M km^2

The hindcasts for the model are 80% successful. In the post 2007 period there were two failures, 2009 and 2012 (0.18 and 0.17 respectively below the lower bound).

This prediction encompasses 2009, 2010, 2013 and 2014. This suggests a relatively normal post 2015 minimum.

Method described here:
http://dosbat.blogspot.co.uk/2015/05/predicting-ct-area-minimum.html

You recently wrote in your blog (post about possible crash this year) about the possibility of area going down in June (unremarkably) while June extent stalling. Compaction dropping, but still not meaning much in either direction.

So your method is purely quantitative, but still, don't you think your result has much to do with recent weather (and by recent I mean past 7 days).

A sensitivity test would consist on doing same math analysis for 15 June, or for July 1st when it comes. Just to see how your semi-statistical method converges...

Just a thought.

It was pointed out back in 2013 that this method is going to be overly sensitive to short term weather. Yes I could adapt it by filtering or averaging data around a date. Maybe that would decrease the sigma, and narrow the range?

Likewise the sensitivity test. You can see the tests I have done to select the date in the graph on my blog post. But running multiple predictions from multiple dates with multiple constants for the standard deviation of error, not to mention running hindcasts/forecasts for different past periods of data... It all sounds like a lot of programming (too complex for a speadsheet) and I hate programming.

In the end, CT Area isn't a dataset I use anymore since Wipneus figured out how they calculate it (and I wasn't impressed). So I can't be bothered. The method stands as it is, late summer losses in CT Area show virtually no trend which is a useful feature. As for trying to improve it, I can't be bothered.    Sorry.

My main method remains April volume and NSIDC extent, that's simple too.

[Wipneus]

From today's NSIDC sea ice concentration update I calculate the following future CT-area updates:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.9  8.119646
Wed +0.3  8.119965

Wipneus, did you perhaps count a day double (maybe the one that has +0.3)? CT SIA is now one day ahead of IJIS SIE in my CAPIE spreadsheet (it used to be one day behind, with your calculations everything was going synchronously).  But maybe/probably I'm doing something wrong.

Neven,

I have not changed anything to the script that produces this list, nor do I see anything strange about the sequence.
It may mean nothing but you did not include the last line in your quote:

Thu -92.9  8.027085

Also note that the days in the list are the dates of the expected CT update, and starts with the last day that CT updated (last Friday at this moment).

[Neven]

From today's NSIDC sea ice concentration update I calculate the following future CT-area updates:

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.9  8.119646
Wed +0.3  8.119965

Wipneus, did you perhaps count a day double (maybe the one that has +0.3)? CT SIA is now one day ahead of IJIS SIE in my CAPIE spreadsheet (it used to be one day behind, with your calculations everything was going synchronously).  But maybe/probably I'm doing something wrong.

Neven,

I have not changed anything to the script that produces this list, nor do I see anything strange about the sequence.
It may mean nothing but you did not include the last line in your quote:

Thu -92.9  8.027085

Also note that the days in the list are the dates of the expected CT update, and starts with the last day that CT updated (last Friday at this moment).

Okay. I just fill in your calculated data in as preliminary data, in my CT spreadsheet and in my CAPIE spreadsheet. In the latter I noticed that CT SIA data was now 1 day ahead of IJIS SIE data. For instance, when IJIS SIE data was reported yesterday June the 23rd, the data was running up to June 22nd. But your preliminary CT SIA data was running up to June 23rd, on June 23rd. That's a combination of ultra-fast and a time zone difference thing.

But I've probably made a mistake somewhere. Thanks for checking.

[Wipneus]

Let us have a look where we (dis)agree.

The last line in CT's data file is:

2015.4603  -1.2570381   8.5203056   9.7773438

The file date shows that the update was on:

Last-Modified: Fri, 19 Jun 2015 10:13:15 GMT

What date is meant by 2015.4603, and what date is it actually from?

And of course how was it entered in your spread sheet?

Here is my interpretation:

2015.4603 is 0.4603 years into 2015. That is 0.4603*365=168 days. Day 168 is the 17th of June.
(I base myself on something Dr. Chapman said a long time ago on ASIB, implying 2015.0000 in the file was actually 2014-12-31).

So CT says it reports data from the 17th in their update on the 19th.

My research has shown that this update is actually calculated from NSIDC sea ice concentration data that was published on the 17th of June and labeled as the 16th of June.

If you are still with me, this means there is actually a two day gap in NSIDC's data and CT-area data if you compare their day-to-day updates.

The data previously known as IJIS, is probably more like that from NSIDC. There should theoretically be a delay of 0.5 day due to the two day filtering but it is not obvious from their data (correlation).

[Neven]

Aha, so what CT reports as data for June 17th (like I have it in my spreadsheet, ie 8.5203056 for June 17th ), NSIDC reports as data for June 16th? That explains it then.

[Wipneus]

Aha, so what CT reports as data for June 17th (like I have it in my spreadsheet, ie 8.5203056 for June 17th ), NSIDC reports as data for June 16th? That explains it then.

That is correct.

[Wipneus]

From today's NSIDC sea ice concentration update I calculate the following future CT-area updates:
(starts with the last actual CT update on Friday, 19 June 2015)

Fri       8.520306
Sat -35.0  8.485257
Sun -147.3  8.337926
Mon -169.4  8.168544
Tue -48.9  8.119646
Wed +0.3  8.119965
Thu -92.5  8.027503
Fri -70.6  7.956866


Regions where area declined: CAB (-65k5), Baffin (-25k7), Hudson (-16k2) and Laptev (-12k2). Area increased in the Beaufort (+31k4) and "lakes" (+13k9).
In the attached delta map, pixels with larger concentration changes than 7% or colored pinkish (down) or light blue (up)

[jdallen]

The Wed. Number (0.3) still looks like a glitch.  Given the current heat exchange, at the peak of insolation, I'm hard pressed to come up with an explanation for it.