Cryosphere Today 2013 Arctic SIA maximum

[Artful Dodger]

I'm bumping this because I do think ( over the years since 06') that the two moons approaching equinox can play merry heck with the ice.

Indeed, Gray-Wolf. It will be interesting with tomorrow's New Moon. Here's a table for Moon phases for Alert, Canada - Nunavut.

In Alert local time, the next New Moon is Mar 11 @ 2:51 PM (19:51 UTC). The next Full Moon is Mar 27 @ 4:28 AM (09:28 UTC)
Note: local time in UTC is 5 hours ahead of Alert.

[Neven]

IJIS SIE has reached a new max.

[TerryM]

I'm bumping this because I do think ( over the years since 06') that the two moons approaching equinox can play merry heck with the ice.

Indeed, Gray-Wolf. It will be interesting with tomorrow's New Moon. Here's a table for Moon phases for Alert, Canada - Nunavut.

In Alert local time, the next New Moon is Mar 11 @ 2:51 PM (19:51 UTC). The next Full Moon is Mar 27 @ 4:28 AM (09:28 UTC)
Note: local time in UTC is 5 hours ahead of Alert.

Spring Tide is ~2 days after new moon & full moon. In past years I've noticed fast ice breakup is  often associated with Spring Tide. It will be interesting to see what effects this has on the fractures we're following this year.

Terry

[Neven]

IJIS SIE has reached a new max.

And yet again, another 24K added. I would think that CT SIA will reach a new max either today or tomorrow, although still about 100K are needed.

[Neven]

IJIS SIE has reached a new max.

And yet again, another 24K added. I would think that CT SIA will reach a new max either today or tomorrow, although still about 100K are needed.

It almost happened today with an uptick of 91K. Just 3K needed tomorrow to break the max. It will then also probably be over 13.8 million km² and will probably not go over 13.9 million km², which is what most people voted for on the poll.

And who of those is still in the running for guessing date of max right?

.......

Hmmm, I looked through all the comments, but it seems that I'm the only one still left in the running with a prediction of max reached on March 18th! Hurray! Yeah me!   

To be fair, my fellow Croatian Ivica has March 19th, but he predicts between 13.6 and 13.7 million km², which of course has already been surpassed.

Cheer for me, my Arctic friends. I might be regaining some of my max predicting credibility! 

[crandles]

My chance looks very slim. I said 17th March but with 14-14.1. So to beat Neven I need at least a 154k rise and reach the peak by 17th at latest.   

[Neven]

Just 3K needed tomorrow to break the max. It will then also probably be over 13.8 million km² and will probably not go over 13.9 million km², which is what most people voted for on the poll.

And of course I cheered too early, as CT SIA had a drop yesterday and IJIS SIE looks like it has peaked...

[Neven]

Darn it, wrong after all! Looks like the max has been reached, or am I too early again?

[Jim Pettit]

Now I will place money that this year's Arctic sea ice maximum was indeed reached on Day 59, with 13,799,198 square kilometers. My thinking:

• On Day 81 (yesterday), sea ice area decreased around another 100k km2. That's the sixth drop in the last seven days, for a single week decrease of 341k km2.
• To surpass the maximum to-date, area would have to grow by nearly 344k, and that much post-Day 81 growth has never happened only happened once, in 2011, though it should be noted that area was far below the average for most of march that year, so the freeze-up merely brought 2011 back in line  (Thanks, crandles) (see image below). Even last year's unusual late growth spurt added just 108k km2 after this date.
• Only four years in the SIA record had maximums occurring after Day 81: '85, '99, '03, and '12.
• Area is currently 145k less than on this same day last year.
• By this day in 2007, area had already fallen below 13 million km2 on its way to a new record minimum.
• Various forecasts hold out little hop for a late freeze.

So, while my word doesn't mean much, I'm 99% certain that this year's area maximum has been reached, and we're on the way to a new record low minimum roughly 6 months from now.

[crandles]

• To surpass the maximum to-date, area would have to grow by nearly 344k, and that much post-Day 81 growth has never happened (see image below). Even last year's unusual late growth spurt added just 108k km2 after this date.

Sorry
2011.2219  -1.2557037  12.7125549
2011.2548  -0.6518973  13.0952930

An increase of 382k after this time of year.

Not that that is likely to happen after a 100k drop.

[Neven]

Crandles, are you challenging Jim to a bet? 

Jim, that's a very nice graph. I'm going to update the ASIG page real soon now and will be sure to visit your shop.

[crandles]

Crandles, are you challenging Jim to a bet? 

His 99% looks about right for this year's maximum. But if Jim is offering 99 to 1 on the 2013 minimum not being a record low, then I might bet on it not being a record low. Somehow I think that is a misinterpretation of what he wrote though. 

[Shared Humanity]

I think that's a great graph! It provides a visual which suggests confidence intervals going out into the future for the year.

[Jim Pettit]

Neven: thanks. My Google site has versions of that same "plume" projection graph for volume and extent, as well.

Crandles: you are correct; 2011 is the lone exception, and I'll make note of it in my comment.

Tally in haste, correct in leisure ;-)

But my initial point stands: based on history and the current polar forecasts, this year's maximum was reached three weeks ago. And that was my awkwardly-worded bet. As to whether this year's area minimum will be lower than 2012's, ask me in a few months... ;-)

[DungeonMaster]

Ouch, I was too pessimistic by 100k km^2 - let's hope my pessimism will be defeated again in September.

Nice graph, Jim - crandles, I wondered if you would have data, tools and time to apply a similar approach to Volume and Piomas map ?  I mean, reapplying previous losses of volume to current ice as we can know it ?

[Jim Williams]

Jim, that's a very nice graph. I'm going to update the ASIG page real soon now and will be sure to visit your shop.

I really like the "where they went from here" plots too.  When guesstimating the future these plots help clear the mind without having the noise of past trends.  You can see the range pretty clearly.

[Jim Pettit]

I wondered if you would have data, tools and time to apply a similar approach to Volume and Piomas map ?  I mean, reapplying previous losses of volume to current ice as we can know it ?

If I read you correctly, I've already created similar projection maps for both PIOMAS volume (https://sites.google.com/site/pettitclimategraphs/sea-ice-volume#asivpts) and IJIS extent (https://sites.google.com/site/pettitclimategraphs/sea-ice-extent#asiepts).

[DungeonMaster]

Hi Jim,

I hadn't seen your graphs yet - clear and nice !

No, I mean : applying previous ice losses (march to september) on each point of the Arctic Ice Map used by Piomas, and get some September maps - and compute some total volume?

I think that Chris has these data and know-how... But time ?

[crandles]

If I read you correctly, I've already created similar projection maps for both PIOMAS volume (https://sites.google.com/site/pettitclimategraphs/sea-ice-volume#asivpts) and IJIS extent (https://sites.google.com/site/pettitclimategraphs/sea-ice-extent#asiepts).

Very Nice. I was briefly a little puzzled. Last data has 2013 above 2012 so following 2012 movements the minimum should stay above the 2012 minimum. The explanation is that it is the 2010 movements that goes below the 2012 minimum not the 2012 line.


Only a 1 in 34 chance of a new record this year doesn't look right, therefore:

Another potential approach would be to say that melt volume approximates 22.78-0.213* max volume. Therefore an appropriate adjustment to make to previous years' melt volume would be 0.213*(max volume in year concerned-max volume this year) and scale movements from maximum to minimum in that manner.

Would that make more sense?

[crandles]

No, I mean : applying previous ice losses (march to september) on each point of the Arctic Ice Map used by Piomas, and get some September maps - and compute some total volume?

Well I could but....

Which year do you want to follow? If some average I don't think that is appropriate because the lower the max volume the higher the melt.

I could try using 2012 but...

Note we have only got thicknesses up to Dec 2012 in monthly averages so it would be Dec 2012 thicknesses plus changes from Dec 2011 to Sept 2012.

At Dec 2012 volume was lower than previous year but we know it has caught up in Jan and Feb so it wouldn't really be fair not to adjust for that but I wouldn't know the distribution.

Also the distribution of thicknesses will be different. this mean some cell will melt out earlier but what happens to that heat? If nothing then you surely end at a higher total volume than you really expect.

With such issues is it worth the attempt?

[Ice Cool Kim]

I do think that, over the coming years, the thin ice will respond to the spring tide moons each year and that , as we will see this spring/early summer, such a mangled pack helps with the rapid melt of young ice.

I noticed looking at last year vs this year there is a offset in the short term bumps. By eye it looks like roughly biweekly patterns and an offset of about 10 days.

Not had time to look into it but my impression on seeing that is that it could be tide related.

What was the phase difference (in days) between lunar declination 2012/2013 ?

[ChrisReynolds]

Dungeon Master,

I'm not sure what you're asking for. Do you mean like this?
http://dosbat.blogspot.co.uk/2013/01/cumulative-volume-and-area-2012.html
Basically I've aligned each melt season to start from the maximum after offsetting the max to start at zero for each year.

[Ice Cool Kim]

Then calculate the difference between each day and calculate a running series by summing those daily differences. The result being a running total of daily differences in volume or area.

That seems like rather an elaborate way to subtract the starting value (annual max) from the rest of the series.

The daily sum of the daily differences is exactly what you stared with. Am I missing something?

[crandles]

The daily sum of the daily differences is exactly what you stared with. Am I missing something?

That you use it for all years from current point to get lots of possible futures and so an indication of the range that is possible.

https://sites.google.com/site/pettitclimategraphs/sea-ice-volume#asivpts
PIOMAS is a bad example because volume melt seems to be increasing as volume goes down so some adjustment like I suggested above is needed.

[Jim Pettit]

Very Nice. I was briefly a little puzzled. Last data has 2013 above 2012 so following 2012 movements the minimum should stay above the 2012 minimum. The explanation is that it is the 2010 movements that goes below the 2012 minimum not the 2012 line.

Only a 1 in 34 chance of a new record this year doesn't look right, therefore:

Another potential approach would be to say that melt volume approximates 22.78-0.213* max volume. Therefore an appropriate adjustment to make to previous years' melt volume would be 0.213*(max volume in year concerned-max volume this year) and scale movements from maximum to minimum in that manner.

Would that make more sense?

Well, my original intention had been to present a simple "if what happened in Year XXXX from today onward were to happen this year from today onward, here's where the ice would end up" scenario, just for purposes of making quick and dirty comparisons. I realize the obvious limitations with such a method--mainly, that echoes of the previous season's minimum are carried over and accumulated into subsequent seasons, so direct apples-to-apples comparison between any two seasons aren't as valuable as they might otherwise be. But, still, I think the graphs as-is do provide another piece of the puzzle, and are thus useful in their own right.

Having said all that, I agree with you that a similar graph making the adjustment you suggested might be valuable, too. So, I'll work on it and let you guys know...

P.S. -- Area dropped another 23k km2 yesterday. SIA is now 366k km2 lower than the 0.1589 maximum--and that much post 0.2219 area has never been seen. Not even in 2011.  So, again--and with even more confidence: this year's SIA maximum was reached more than three weeks ago.

[Shared Humanity]

Isn't this early for a SIA max?

[Neven]

It's one day later than in 2007, but it doesn't say all that much, because in this period SIA and SIE are on a plateau of sorts, and just one small excursion can lead to a slightly higher and later peak. If that doesn't happen, you get an early max.

[Jim Pettit]

Isn't this early for a SIA max?

As Neven just explained, at this time of year, both ice area and extent spend several weeks bumping along the ceiling like a helium balloon, so it doesn't take much to put either one over the top. But even so, as the following quick-and-dirty normal distribution graph shows, even if this year's maximum did indeed occur on Day 59, it's still within one standard deviation of the mean:

[Ice Cool Kim]

The daily sum of the daily differences is exactly what you stared with. Am I missing something?

That you use it for all years from current point to get lots of possible futures and so an indication of the range that is possible.

https://sites.google.com/site/pettitclimategraphs/sea-ice-volume#asivpts
PIOMAS is a bad example because volume melt seems to be increasing as volume goes down so some adjustment like I suggested above is needed.

I was not saying taking the max as a starting point was a good or bad idea. It just seemed that sum of diffs trick was a total waste of time and was mathematically identical to simply  subtracting the max from the whole year.

I may have misunderstood but it sure looks that way.

[crandles]

Sorry Ice Cool Kim, I misunderstood you.

[DungeonMaster]

Dungeon Master,

I'm not sure what you're asking for. Do you mean like this?
http://dosbat.blogspot.co.uk/2013/01/cumulative-volume-and-area-2012.html
Basically I've aligned each melt season to start from the maximum after offsetting the max to start at zero for each year.

Hi Chris,

Not really, I've not been clear enough. I meant, is there a way to re-apply precedent losses (March to September for years 2012, 2011, 2010...) to the incredible thickness maps you produce from PIOMAS gridded data, dot per dot? And so, to simulate where ice would be lost, how much would be lost, and where we'd have new holes?

(btw, apologies to both you and crandles for mixing your names)

[crandles]

Not really, I've not been clear enough.
(btw, apologies to both you and crandles for mixing your names)

No problem and I would be happy to do such an exercise to save Chris Reynolds the time. However as I tried to explain:

1. It would have to start from Dec 2012 thicknesses as 2012 is the last data available by cell.
2. That doesn't account for more volume added in Jan and Feb 2013 than in 2012. If you want to account for that you would have to tell me how to distribute it.
3. If a cell has less thickness than at Dec 2011 and it melted out in 2012, presumably it will also melt out in 2013. You would need to tell me what if anything to do with the surplus heat. Is that used to increase melt in nearby cells?

If you don't do anything with such surplus heat, the consequence of a different distribution of thicknesses is to end up with more volume than the previous year.

If you want to explain more precisely what you want doing with especially with regards to above issues then I will see if I can do it.

[ChrisReynolds]

DM,

Sorry, but I'm not very convinced about this. Sea ice motion and weather are major reasons why such a detailed approach isn't likely to be very informative, it's a very poor step down from having the actual model and applying different year's weather from a baseline. As Crandles points out, this baseline would have to be December. The major problem is that I see the progression of ice melt as very sensitive to initial conditions, so unless you start from initial conditions similar to conditions on the ground the 'projection' will have no validity.

As an example. In my most recent blog post I discussed the influx of a lot of MYI into the Siberian sector during 2010, and showed how ice recession in that area was retarded, I suspect because of that MYI.

The spur of MYI passing through the Chukchi Sea in 2010:
http://farm9.staticflickr.com/8387/8569938970_f47c226c78_o.gif
The lack of recession of the ice in that very region.
http://www.iup.uni-bremen.de/seaice/amsredata/asi_daygrid_swath/l1a/n6250/2010/aug/asi-n6250-20100801-v5_visual.png

[Jim]

Hmm...
I notice today that both NSIDC Extent and CT Area both show levels below 2011-2012 up to the 1st week in April - we are about 10-12 days ahead of last year.

Of course, the levels are bound to wiggle a bit, being very weather dependent at the moment, but I did rather expect the levels of both extent and area to at least match last year.
That it has failed (so far) to do so, as well as seeming to be over a week ahead of last year is a bit worrying :-(

Edited 19:02 CET

[Sigmetnow]

I see the Navy ice thickness forecast for the next week (run 3/22) suggests thinning of the pack -- less black, and the red is changing to yellow, even north of 80N.

[DungeonMaster]

Crandles and Chris,

Thanks for your feedback - I had thought we'd have february or march data soon, but I forgot that they're not pseudo-real time.

The idea was 'just' to re-apply previous years to current situation and see what comes out. After all, most projections we play with don't take many parameters... It's not about having a realistic model, just a simplistic substraction to see what may happen. Of course extra heat, clouds, highs, winds will all play their part and we cannot forecast them.

My questions are:
- what would happen if we apply the extreme 2007 conditions, april to september, to march 2013 ice - say, the "replay" scenario?
- what happens if we apply, for each day, the worst past figure - some "worst case" scenario?
- same, with "best" previous figure - a "best case scenario"
- and finally, the average of previous years for that day and cell

I've not seen the data and don't know if it makes any sense. But it might be an approach for the SEARCH study, using volume rather than extent or area evolution. Perhaps this can be tested on 2012 data to see if if produces anything interesting?

I mean, if we loose 50% of the area of a big, thick piece of ice of 8 million km^2, it's still 4 million, and it not in danger if the thickness remains the same. But if we loose 2 meters of thickness on thin ice, it can remain at 1 meter, or go down to nil - I mean, it can take no time to loose huge areas once the ice approaches the limit thickness. I wonder we enter times when area or extent won't tell anything about chances of ice survival.

Anyway if there's no way nor data to try this experiment, we'll just watch curves go down! Please don't try if you feel it would be a waste of time...

[Jim]

Hi Sigmetnow,
I wouldn't be surprised - the high pressure north of Greenland seems to be pulling the pack away from the CAA coast and pushing the old ice into the open ocean, as well as sweeping more ice into the Fram Strait to oblivion.

[crandles]

- what would happen if we apply the extreme 2007 conditions, april to september, to march 2013 ice - say, the "replay" scenario?
- what happens if we apply, for each day, the worst past figure - some "worst case" scenario?
- same, with "best" previous figure - a "best case scenario"
- and finally, the average of previous years for that day and cell

I've not seen the data and don't know if it makes any sense.

2007
max daily volume 23.865
min daily volume 6.458 so a fall of 17.407

2013 max look like it is heading for .133 more than last years 21.923 so 22.056

Using 2007: 22.056 - 17.407 = 4.649
using worst year 2010: 22.056 - 18.974 = 3.080
using second worst year, 2012: 22.056 - 18.662 = 3.394

2012 minimum was 3.261. So only one year of 34 years' patterns gives a record low volume. Does that make you think that there is only a 1 in 34 chance of there being a record low volume?

I hope not because volume lost during melt season has been rising as the maximum volume has declined. I think some sort of adjustment has to be made for that.

More important for assessing chance of a record low might be considerations like record lows do not seem to follow each other and the negative one year auto-correlation. That makes a record low seem unlikely. That volume is higher than last year also makes it seem less than a 50% chance. Cracking, snow cover, exponential trend getting steeper and possibly other factors may make it more likely than above indicates.

Would an invalid application of previous years distribution of thinning inform our assessment of the chance of a record low? Failure to deal with the problem 3 in previous post seems likely to create a bias towards more volume, so that seems more likely to mislead than help. Figuring out how best to deal with that problem might be interesting but also difficult. That difficulty may well amount to 'create a sea ice model'.

[Pmt111500]

Dungeon Master asked "- what happens if we apply, for each day, the worst past figure - some "worst case" scenario?
- same, with "best" previous figure - a "best case scenario""

I did just this with Ijis-extent numbers a while back and concluded one shoud take at least a week - preferably two week averages to get a plausible scenario. I didn't do that though. If one takes biggest drops of past figures for each day the numbers go to zero in July, and with smallest drops or increases the number gets higher than historical maximum by february next winter... so it's not very useful measure. Since then I've had two computer crashes so I'm not sure if I have the file intact anymore.

[wanderer]

Extent is now below 14.000 000 km2:

http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

[wanderer]

PS: I don't think that 2013 max volume will be higher than 2012!

[Ice Cool Kim]

Pmt: I did just this with Ijis-extent numbers a while back and concluded one shoud take at least a week - preferably two week averages to get a plausible scenario.

Very good point , but don't use averages, that's equivalent to doing a running mean (crap filter) and subsampling.

I would suggest at least a 15 day gaussian or similar filter. There seems to be some circa 14 day small scale cyclical variation in ice (probably lunar tidal)  that pushes annual extrema back and forth and is disruptive to seeing multi-year patterns.

This sort of filter also removes most of the "weather" variations and give a nice smooth annual cycle.

If you're not equipt for applying a proper filter, a triple running mean is pretty good.  Apply 3 running means in succession which shortens by a factor or 1.3371 each time (fixes distortions due to negative lobe of simple RM), round to nearest integer.

eg.  30 / 22 / 17 or 14 / 10 / 8    those filters have a zero at 30 days and 14 days respectively and a good, clean frequency response.

If you have a precise, stable frequency that you want to remove it's actually a bit better than a gaussian.



"I did just this with Ijis-extent numbers a while back"
Do you have a link ? I signed up for access to the whole data set but it was more than I need or care about . If you have a link to regional time series or similar, could you post it? Thanks.

[Pmt111500]

Thanks Kim, will remember your suggestion if I ever get in doing time series analysis again (last time was in 2009, assistant in a larger project in the local university). AFAIK, there are plenty more qualified people than me in this site, engineers and other technically (and scientifically) well-versed persons, so I'm mainly following their analysis, and trying to put their sometimes truly horrific results in larger context in my mind.

[ChrisReynolds]

DM,

As you know one of my obsessions is the 2010 event. I'm now interested in what it is about the PIOMAS model that causes ice under 2.5m in April to have a greater spread of thickness loss from April to September. From April to June (the period of the spring melt) the thicker ice barely loses any thickness, while once again the thinner shows a wider spread of thickness loss. I will blog on this over the coming weekend, but here's my point:

Having noticed this, I wondered what would happen if I replace thick ice with thinner ice and allow that thinner ice to proceed with its seasonal thickness loss. This would be done by grid box, so some of the thicker grid boxes would no longer follow the melt profile that the PIOMAS gridded data contains, but would follow the seasonal melt profile of a randomly chosen thin ice grid box. I haven't decided whether this will be of any more use than the data I already have showing that thinner ice thins more, so I've not programmed it. At present I'm tending to think that it's a messy and not very convincing approach when I can already show that thin ice thins more and draw inference from that. But while pondering this issue I came across a significant problem.

If I take a proportion of grid cells over 2.5 or 3m thick in April, and replace them with randomly selected melt profiles from cells under 2.5m thick, some of those cells will melt out, which will leave me with the physically implausible situation of an ice pack full of small holes (not seen in the PIOMAS model). So how do I deal with this? I don't know.

It wasn't really an issue for me because all I was thinking of doing was using the procedure to calculate a total thickness for each month and see if the spring melt appeared when the procedure was done on years from the 1980s, before most of the thinning occurred.

[ChrisReynolds]

To continue...

(Anyone else find long posts exhibit a very slow response time to typing?)

I think Crandles' approach of using periods of change in volume/area is more useful in giving answers to the question: "What if year X happened from now?" Although it's still a poor cousin to having a model like PIOMAS and running forward, because it still doesn't fully account for initial conditions. However I think that for volume one can only use years 2010 2011 and 2012, whereas for area/extent one can use 2007 and after, a longer period.

Using volume of 2010 and later from 1st March applied to this year:

Losses from 1st March to minimum are:
16.765,   15.839,   16.41

Apply these to the current volume level and we get 'projected' minima for 2013:
2.981,   3.907,   3.336

Where only 2010, a massive volume loss year is below 3.261k km^3, the minimum for 2012. But this doesn't make me think we won't see a new record this year.

Over at my blog Neven has just commented confirming my impression that in 2010 area/extent didn't drop so fast in the Chukchi/East Siberian region, I have suggested that this was because of a large influx of MYI that delayed the melt. Such an event won't happen this year because there is so much FYI in the seas that will melt out in the summer. Once again - initial conditions impacting. And the above calculation doesn't take into account the exceptional extent of FYI in the pack at present.
http://dosbat.blogspot.co.uk/2013/02/ascat-piomas-and-dam.html

Such an approach is more likely to be of use later in the season. I found reasonable results using post 2007 years and average losses for periods after day 150 last year. As is to be expected the predictions got better the later in the season one went because later in the season the dominant factor in initial conditions is the melt in that season. In terms of volume the greatest monthly loss is in July, after that events are already set in motion.

[Ice Cool Kim]

Chris, I'm new here, can you bring me up to speed?

It appears that you have access to PIOMAS source and are modifying it. Are you an insider on the modelling team, or is this publicly available?

" However I think that for volume one can only use years 2010 2011 and 2012, whereas for area/extent one can use 2007 and after, a longer period."

Am I correct in inferring form this comment that PIOMAS works reasonably well for area if primed with initial conditions of 2007 but only works for volume over a couple of years?

If I've misread what you meant, could you clarify?

Thx

[ChrisReynolds]

No I'm not an insider. I'm an engineer and this is my hobby.

Crandles found that PIOMAS gridded data is available.
http://psc.apl.washington.edu/zhang/IDAO/data_piomas.html

He got together a group of us to start using it. I've used VBA in Excel to produce some stuff based on the gridded data, mainly plots of thickness and derived variables.
http://www.arctic-charts.net/volume-charts/
Hosted courtesy of Dungeon Master, but not updated for 2012 data* - the PIOMAS data updates annually. Wipneus has worked out area for the gird points. *I must confess that a fault of mine is that I go where I'm interested, interest hasn't dragged me back to update that stuff, this is compounded by the fact that few people have used it.

Since then I've broken down the gridded volume (thickness field * Wipneus' areas, grid point by grid point) into regional data and am busy analysing that.
http://dosbat.blogspot.co.uk/2013/02/piomas-volume-thickness-breakdowns.html

My most recent blog post using this data is here:
http://dosbat.blogspot.co.uk/2013/03/what-caused-volume-loss-in-2010-part-2.html

If I had a big enough computer(s) I'd love a copy of PIOMAS to run for myself. If my maths and programming skills were good enough I'd knock one together myself from the published literature.

[ChrisReynolds]

To explain the 2007 / 2010 issue.

There has been a change in the seasonal cycle of area (and presumably extent) post 2007, which makes those years unique in the satellite record. So using characteristics of pre 2007-years isn't really a good idea. In terms of volume there has been a change in the seasonal cycle - PIOMAS data, seen in the anomalies for both daily series and gridded (monthly) data.

If there's a change in the seasonal cycle it's useless to use data from before that change to try to establish behaviours that could be used predictively.

[Ice Cool Kim]

Thanks for the explanation. I did not quite realise the context. Makes sense.

I just had a look at the post you linked and you have a fairly important error:

" average absolute temperature was around -25degC for February to April 2010, this being some 4 degrees warmer than average, that's a factor of 1.16. As the heat flux through the ice is inversely proportional to the difference in temperature between the ocean at the base of the ice and the air at the surface, this 4 degC warm anomaly corresponds to a heat flux of 86%"

That should be 1.016 and thus 98.4% 

[ChrisReynolds]

Sorry but I'm right.

-29 / -25 = 1.16.

-29 deg C being 4 degC colder than -25degc, or a +4deg C warm anomaly.