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anonymous

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Piomas vs. CryoSat
« on: February 04, 2013, 03:58:17 PM »
I'm still digesting the latest thickness paper. It's a dense reading. Most importantly they draw a line from IceSat, several in-situ data measurement (moorings, submarine, icebridge) over CS2 to PIOMAS. Within an acceptable range it all makes sense, so PIOMAS is no longer just a modell working in a phantasy world, it's backed by real data from ground and orbit. Here a chart comparing CS2 with PIOMAS showing PIOMAS probably underestimates the seasonal amplitude:



The numbers might be a bit off to official PIOMAS data, because the paper mostly compares everything over the IceSat domain.

Artful Dodger

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Re: Piomas vs. CryoSat
« Reply #1 on: February 20, 2013, 09:48:43 PM »
There was an interesting press release from the folks at UWash regarding the Cryosat-2 paper published in Jan 2013:

http://www.washington.edu/news/2013/02/13/european-satellite-confirms-uw-numbers-arctic-ocean-is-on-thin-ice/

In particular, one of the paper's Authors, and PIOMAS investigators, has this to say:

“Other people had argued that 75 to 80 percent ice volume loss was too aggressive,” said co-author Axel Schweiger, a polar scientist in the UW Applied Physics Laboratory. “What this new paper shows is that our ice loss estimates may have been too conservative, and that the recent decline is possibly more rapid.”


Is it just me, or is this counter to the sea ice comparison chart from the paper, where Cryosat-2 data consistently shows slightly higher sea ice volume than shown by PIOMAS?

Have I got that wrong? Do the two use different domains? (coverage area) Is there a better interpretation of this statement? What have I missed?
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crandles

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Re: Piomas vs. CryoSat
« Reply #2 on: February 21, 2013, 12:01:46 AM »

Is it just me, or is this counter to the sea ice comparison chart from the paper, where Cryosat-2 data consistently shows slightly higher sea ice volume than shown by PIOMAS?

Have I got that wrong? Do the two use different domains? (coverage area) Is there a better interpretation of this statement? What have I missed?

No you are right Cryosat 2 is higher than PIOMAS in both years, though perhaps not at 2012 minimum.

However look at the change over time - PIOMAS is showing no fall but cryosat 2 is showing 2012 lower than 2011. Perhaps it might appear a bit iffy to extrapolate one years change to the change over last 33 years. But this cryosat 2 evidence isn't the only evidence - remember the PIOMAS verification indicating that PIOMAS overestimated thin ice and underestimated thick ice. Now we can see that PIOMAS is about right at 2012 minimum then it follows that PIOMAS underestimates past minimums. So decline over the last 33 years is probably more than the 75% to 80% reduction in minimum volume since 1979 (16.855 down to 3.261 K Km^3).

Artful Dodger

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Re: Piomas vs. CryoSat
« Reply #3 on: February 21, 2013, 01:43:52 AM »
So decline over the last 33 years is probably more than the 75% to 80% reduction in minimum volume since 1979 (16.855 down to 3.261 K Km^3).
Right Chris, that would be an 80.7% decline Dr. Schweiger refers to. But he goes on to say that the newly published data makes that 80% decline look too conservative. I still don't see that.
Anyone?
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TenneyNaumer

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Re: Piomas vs. CryoSat
« Reply #4 on: February 21, 2013, 03:22:22 AM »
Hi everybody!  I just got back from Carnival in Rio!  Let the party begin! 

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Re: Piomas vs. CryoSat
« Reply #5 on: February 21, 2013, 03:43:06 AM »
OK, that was a joke ::), but did you guys see this about the restrictions on publishing info related to a joint Canadian-U.S. research project to measure the ice in situ in order to verify CryoSat measurements:

http://www.cbc.ca/news/technology/quirks-quarks-blog/2013/02/loss-of-arctic-ice-loss-of-scientific-integrity.html

"...thanks to new confidentiality rules introduced into the U.S.-Canada project, both the Canadian scientists working at the Department of Fisheries and Oceans and the Americans may not be able to publish or distribute that data without [Canadian] government approval."

Dromicosuchus

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Re: Piomas vs. CryoSat
« Reply #6 on: February 21, 2013, 06:33:51 AM »
As it is, I'm not sure that there's much more to be gleaned from this than that PIOMAS is working pretty durn well, and that the calibrations of it using ICESAT worked, and didn't end up just being so much curve-fitting.  One might hazard a guess that the decline has been greater than shown by PIOMAS, based on the larger difference between the 2010 and 2011 minima, but based on just two years of data...Yeah, no.  "One" might hazard a guess, but "one" isn't going to be me.  Still, it's very good (in a "Oh goodness, we really are toast, aren't we?  It's not just the silicon nightmare of some dozing supercomputer, this is really happening in the real world" sort of way, granted) to know that PIOMAS appears to be working properly.

On another note, do you happen to know where I might find a link to the paper in question, Arcticio?  Is it trapped behind a paywall, or has it managed to sneak out of its cage?

Artful Dodger

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Re: Piomas vs. CryoSat
« Reply #7 on: February 21, 2013, 07:33:44 AM »
On another note, do you happen to know where I might find a link to the paper in question, Arcticio?  Is it trapped behind a paywall, or has it managed to sneak out of its cage?


Hi D,

There's a pre-press version out (one of the Authors' server I suspect). Note that it is the accepted version of the paper, even though final formatting for the Journal is not done. Also note that all Tables and Charts are present at the end of the document. Here it is:

Laxon, S. et al. "CryoSat-2 estimates of Arctic sea ice thickness and volume." Geophysical Research Letters, 28 January 2013
http://www.personal.soton.ac.uk/pgc1g08/grl50193.pdf

Also, read the Journal's Press Release for this paper at:
http://phys.org/news/2013-02-cryosat-mission-reveals-major-arctic.html
« Last Edit: February 22, 2013, 09:49:15 AM by Artful Dodger »
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Re: Piomas vs. CryoSat
« Reply #8 on: February 21, 2013, 06:35:11 PM »
I'm not going to rehash all of what I've already said at my blog:
http://dosbat.blogspot.co.uk/2013/02/cryo-sat-2-and-piomas.html

But it's worth noting from Table 1 of the Laxon paper that start volumes are relatively close for ICESat and PIOMAS in Feb/Mar. However for the start volume in Oct/Nov PIOMAS is 9119 km^3 for 2003 to 2008, while ICESat is around 12000 km^3. Once you adjust the figures for this large disparity in start volume the % decline figures for Oct/Nov are reasonably close at around 30%, that's between the 2003-2008 avg and 2012.

Artful Dodger,

It's not the author's server, I think it's been put up by Phil Chapman who's recently started commenting at Neven's blog. Note the 'pgc' in the URL, that's his initials. I suspect he's taking a bit of a risk, let's hope that URL stays below the radar.

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Re: Piomas vs. CryoSat
« Reply #9 on: February 21, 2013, 08:46:20 PM »
OK, that was a joke ::), but did you guys see this about the restrictions on publishing info related to a joint Canadian-U.S. research project to measure the ice in situ in order to verify CryoSat measurements:

http://www.cbc.ca/news/technology/quirks-quarks-blog/2013/02/loss-of-arctic-ice-loss-of-scientific-integrity.html

"...thanks to new confidentiality rules introduced into the U.S.-Canada project, both the Canadian scientists working at the Department of Fisheries and Oceans and the Americans may not be able to publish or distribute that data without [Canadian] government approval."


This is a terribly important problem & I don't see it going away soon. If scientists in different countries can't collaborate, publish or even comment on their findings without the Canadian Government signing off at each step it's going to virtually shut down a huge amount of Arctic research - just when it's most needed.

I'd been aware of the crackdown within Canada, but now it's spread to anyone anywhere that has signed Canada on as a partner in their research.

As more information comes in this may be deserving of it's own thread.

Terry

Artful Dodger

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Re: Piomas vs. CryoSat
« Reply #10 on: February 21, 2013, 08:59:12 PM »
Artful Dodger,

I suspect [pgc]'s taking a bit of a risk, let's hope that URL stays below the radar.

Thanks, Chris. I think the bird is out of the cage on that one. I found it with a search of the title on Google Scholar.  ::)
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ChrisReynolds

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Re: Piomas vs. CryoSat
« Reply #11 on: February 21, 2013, 09:18:05 PM »
Pesky Google Search Bots!

PhilGChapman

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Re: Piomas vs. CryoSat
« Reply #12 on: February 21, 2013, 10:56:54 PM »
Consider it my #pdftribute  :)

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Re: Piomas vs. CryoSat
« Reply #13 on: February 22, 2013, 07:52:06 AM »
Thanks Phil,  ::)

Dromicosuchus

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Re: Piomas vs. CryoSat
« Reply #14 on: February 22, 2013, 08:00:30 AM »
Many thanks for the link!  And yeesh, Arcticio, you were right; that is dense.  Very nice to have so much info on the methods used, though.  It'll be interesting to work my way through it.

Artful Dodger

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Re: Piomas vs. CryoSat
« Reply #15 on: February 23, 2013, 02:45:47 AM »
In my continuing attempt to understand the Feb 13 Press Release from UWash/APL (and in the keenly felt absence of the rapier intellect and steady hand of blog commenter Peter Ellis ;) ), I have attached an annotated Figure 3 (see original up-thread) from the CryoSat2 paper to show the monthly decline in sea ice volume as estimated by CryoSat2 for each of 7 months.

As you can see, the line segments connecting the tops of each CS2 'triangle' in the chart show a decline for each month measured. Further, the slope of the monthly decline is steepest in the early Fall, and less severe for each successive month until peak volume is reached near the end of Winter.

So if I am interpreting the APL statement correctly, their reasoning goes to this argument: Given that CS2 measured GREATER volume loss from October 2010 to October 2011 than PIOMAS estimated as the volume loss, therefore PIOMAS is likely to be underestimating the volume loss.

Does that sound plausible? Your opinions? Peter sightings? Axel?
« Last Edit: February 23, 2013, 05:04:22 AM by Artful Dodger »
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Peter Ellis

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Re: Piomas vs. CryoSat
« Reply #16 on: February 23, 2013, 11:58:17 AM »
Eh, it's pretty obvious what the press release is saying.  The rate of decline of autumn (edit: presumably October) ice as measured by satellite is even faster than the rate of decline modelled by PIOMAS. Moreover, they're not relying on just two years to make that conclusion.

From the abstract of the paper:

"Between the ICESat and CryoSat-2 periods the autumn volume declined by 4291 km3 and the winter volume by 1479 km3. This exceeds the decline in ice volume in the central Arctic from the PIOMAS model of 2644 km3 in the autumn, but is less than the 2091 km3 in winter, between the two time periods."

This is no more than was already said some months ago and discussed extensively by us and others back then.  I really don't know why everyone's acting surprised this time round.

In general, the satellite data seem to be reading slightly higher than the PIOMAS model, and also showing a somewhat wider seasonal cycle across the board.  This is not necessarily surprising because it's already known that PIOMAS tends to overstate thin ice and understate thick ice.  However, the satellite also has (potential) errors that work the same way.  Just as PIOMAS overstates thin ice, the satellite may understate it - PIOMAS models ice right down to ~25 cm thickness or even lower.  With a freeboard of only a couple of cm, that ice might not be seen at all by the satellite.  Conversely, just as PIOMAS understates thick ice, the satellite may overstate it: remember how it was showing thicknesses of up to 3m for the first year ice in Baffin Bay?  The suggestion at the time was that the satellite may have been confused by the overlying snow, or by thin icy layers within the snow.  Not having read the paper yet, I don't know if they fixed this issue.
« Last Edit: February 23, 2013, 12:07:16 PM by Peter Ellis »

anonymous

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Re: Piomas vs. CryoSat
« Reply #17 on: February 24, 2013, 01:55:55 PM »
I think CS2's accuracy mostly depends on proper estimation of snow load. 10cm of snow wrongly taken for ice adds apprx. 1m of ice thickness. From what I understand (please correct me, if needed) there are two approaches: 1) assuming the radar goes right through the snow and got reflected by the snow ice interface. The paper indicates this is not settled science:

Our assumption that the radar penetrates to the snow-ice interface is still the subject of investigation and may also introduce errors into bias our thickness estimates [Willatt et al., 2011, pdf]

And 2) using data from weather models, like PIOMAS probably does to calculate heat flux. The CS2 QA site http://cryosat.mssl.ucl.ac.uk/qa/snowdepth.php?phase=Operational&baseline=B gives some insight, but I doubt it's actually used. See the image below from last August.

IIRC, I've also read somewhere a paragraph referring to kind of climatology with Arctic snow load, which might render useless if more open water leads to more humidity and more snow.

So, 1cm of snow can explain a lot of the ups and downs of CS2. So far I also assume wet snow and melting ponds totally mess up approach #1 and this is why there is no summer data.





dlen

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Re: Piomas vs. CryoSat - Error margins?
« Reply #18 on: March 01, 2013, 03:16:06 AM »
I did not read Laxon's paper thoroughly yet - what are the error margins, are they mentioned? This is not unimportant.

Schweiger et al gave +-1,35 1000 km³ for October PIOMAS values in their 2011 paper. This seems to have been too small.

Concerning all the calibration work with snow cover concerns, cracks, inhomogenities and the small tracked area per overflight, calculation of total volume is still a very indirect, intricate way of volume determination (though much better then mere simulation). Consequently, we remember the first publications in 2012 having been way off the mark and the work has taken an awful lot of time.
« Last Edit: March 02, 2013, 01:59:13 PM by dlen »

Artful Dodger

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Re: Piomas vs. CryoSat - Error margins?
« Reply #19 on: March 01, 2013, 08:45:50 AM »
Schweiger et al gave +-1,35 Mio km³ for October PIOMAS values in their 2011 paper. This seems to have been too small.

Hi dlen,

I estimate the difference CS2-PIOMAS for Jan 2012 to be <1300 km3. That month seems representative, except for Oct 2011 which has a much smaller difference.

That's well within the stated uncertainty for PIOMAS.
« Last Edit: March 02, 2013, 05:27:27 AM by Artful Dodger »
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dlen

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Re: Piomas vs. CryoSat
« Reply #20 on: March 01, 2013, 04:01:47 PM »
Hmm, You may be right.

In this graph, where is the actual datum point in the triangles: in the center of gravity or in the center of the smallest containing rectangle? That would be    (y_max + y_min) / 2    ?  I think the latter, but I am not sure.

I want to digitize the graph and add it to the plot in commons.wikipedia.org.

Or is there somewhere a table of the values printed out?


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Re: Piomas vs. CryoSat
« Reply #21 on: March 01, 2013, 06:00:23 PM »
I'm not aware of any of the values in figure 3 being available tabulated.

But the PIOMAS values should tally with monthly averages which can be calculated from PIOMAS main series, this is dependent on whether they've used a subset area, not the full PIOMAS domain.

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Re: Piomas vs. CryoSat
« Reply #22 on: March 01, 2013, 07:01:10 PM »
And if they are using the "official" piomas figures.
Eg Massonnet et al use a corrected series:

We also use the Pan-Arctic Ice Ocean Modeling and Assimilation
System (PIOMAS, Schweiger et al., 2011) output for
sea ice volume estimates. This Arctic sea ice reanalysis is
obtained by assimilation of sea ice concentration and sea surface
temperature data into an ocean–sea ice model.We use an
adjusted time series of sea ice volume partly accounting for
the possible thickness biases in the reanalysis (A. Schweiger,
personal communication, 2012)

Vergent

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Re: Piomas vs. CryoSat
« Reply #23 on: March 01, 2013, 07:29:01 PM »
I hate to be a technocrat, but the arctic sea ice volume is in the kilo km^3 range, not the mega.

dlen

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Re: Piomas vs. CryoSat
« Reply #24 on: March 02, 2013, 02:56:17 AM »
Yeah, that was tiredness or something alike. Corrected.
« Last Edit: March 02, 2013, 01:59:55 PM by dlen »

Artful Dodger

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Re: Piomas vs. CryoSat
« Reply #25 on: March 02, 2013, 05:32:27 AM »
...the arctic sea ice volume is in the kilo km^3 range, not the mega.

Thanks, Vergent. Fixed in my comment above.  8)
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Re: Piomas vs. CryoSat
« Reply #26 on: March 02, 2013, 09:28:26 AM »
Here is the digitized plot data:
:

[[1]]
          x line_piomas
1  2010.539    8.511989
2  2010.622    5.195339
3  2010.708    4.200344
4  2010.790    5.365653
5  2010.881    7.633525
6  2010.962    9.587660
7  2011.041   11.308732
8  2011.124   12.868454
9  2011.211   14.006872
10 2011.292   14.643311
11 2011.380   14.437141
12 2011.460   12.285800
13 2011.541    7.794876
14 2011.621    4.729215
15 2011.711    3.904534
16 2011.792    4.890565
17 2011.881    7.346680
18 2011.960    9.524912
19 2012.041   11.237021
20 2012.122   12.733996
21 2012.210   13.863450
22 2012.292   14.732950
23 2012.381   14.670202
24 2012.457   11.927243

[[2]]
          x line_cryosat2
1  2010.790      6.844700
2  2010.881      9.892433
3  2010.960     11.165310
4  2011.038     12.483006
5  2011.122     13.962053
6  2011.210     15.692089
7  2011.288     16.274744
8  2011.787      5.249122
9  2011.879      8.996041
10 2011.957     10.788825
11 2012.040     12.249944
12 2012.119     13.648316
13 2012.208     14.723986
14 2012.288     15.907223


(in 1000 km3 of course)

Wipneus

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Re: Piomas vs. CryoSat
« Reply #27 on: March 02, 2013, 09:36:00 AM »
And attached the plot. Red line is "official" piomas.

« Last Edit: March 02, 2013, 09:40:35 AM by Wipneus »

dlen

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Re: Piomas vs. CryoSat
« Reply #28 on: March 02, 2013, 02:02:10 PM »
So I understand: the "inofficial" PIOMAS volume (used for the publication) relates to a considerably reduced base area.? As the "official" value is so much bigger?
« Last Edit: March 02, 2013, 02:05:28 PM by dlen »

Wipneus

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Re: Piomas vs. CryoSat
« Reply #29 on: March 02, 2013, 03:02:22 PM »
It is all in the paper:

"The data are restricted to the “ICESat” domain"
"Arctic sea ice volume (km3) for the ICESat domain"

As far as I can see figure 1 is the clearest definition of that domain.

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Re: Piomas vs. CryoSat
« Reply #30 on: March 02, 2013, 03:46:34 PM »
Thanks Wipneus.

dlen

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Re: Piomas vs. CryoSat
« Reply #31 on: March 02, 2013, 08:36:23 PM »
Yes thanks from the lazybones.  :)

The authors give actually a coarse error assessment, when they write:

"Our present understanding of both the
satellite and in-situ data is insufficient to resolve any inter-satellite bias to a higher
degree of certainty, but we note that an inter-satellite bias of 10cm would result in an
error in volume of ~700 km³, much lessthan the change in volume between the two
time periods."

Taking into account the mean errors against "in-situ-measurments", namely:
  • airborne electromagnetic - (7 cm),
  • upward looking sonar - (-8 cm) and
  • airborne laser measurement (-5 cm)
leads to a thickness error estimate around 7 cm against those comparison data.

Remains to add the errors of those data sources themselves, which are given as +-10 cm (airborne EM, ULS), while for the airborne laser data, no error margin is given in the Laxon paper. As lazybones I take its error as the same +-10 cm.

AFAIK error margins add like (sigma_1² + sigma_2²)1/2, that would be then 12,2 cm. If we are more cautious and take +-10 cm as uncertainty for the in-situ-measurement-Cryosat-relation, we arrive at +-14,4 cm.

Under the assumption of homogeneity this yields together with the base area of 7.2 Mio km² a Cryosat volume error margin of +- 880 km³ or, more cautiously, 1040 km³.

Althoug this is the error margin of one value, the errors are probably not uncorrelated. This means, that I wouldn't expect the values jumping wildly over the whole error interval from one point to the next. It is more like a smaller value of point-to-point jumping added to some longer term shift of the curve.
« Last Edit: March 03, 2013, 01:25:14 AM by dlen »

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Re: Piomas vs. CryoSat
« Reply #32 on: March 03, 2013, 02:19:22 AM »
I'd like to add one comparison plot from Tamino, for the sake of completeness
 ( http://tamino.wordpress.com/2013/02/20/cryosat-2-confirms-stunning-arctic-ice-loss/ )

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Re: Piomas vs. CryoSat
« Reply #33 on: March 03, 2013, 05:27:06 AM »
I'd like to add one comparison plot from Tamino, for the sake of completeness
Yeah, probably not too helpful, since CS-2 has not released any data for Oct/Nov 2012 yet.

The last CS-2 data point, from the Laxon paper that Tamino refers to, is for April 2012. Yet the line graph above show data for Oct/Nov 2012.

Probably needs to be redone.  ;)
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Re: Piomas vs. CryoSat
« Reply #34 on: March 03, 2013, 05:59:47 AM »
I used Wipneus' digitized data to extrapolate on the bigger PIOMAS domain by this method

vcryobig = vpiobig * ( vcryosmall / vpiosmall )

..big are data on the bigger PIOMAS domain
..small are data on the ICESat domain
pio.. are PIOMAS data
cryo.. are CryoSat2 data

and worked it into

http://commons.wikimedia.org/wiki/File:Plot_arctic_sea_ice_volume.svg

This is somewhat courageous, but I hope the error introduced is kind of second order.

Artful Dodger

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Re: Piomas vs. CryoSat
« Reply #35 on: March 03, 2013, 02:50:04 PM »
In this graph, where is the actual datum point in the triangles: in the center of gravity or in the center of the smallest containing rectangle?
Hi dlen,

I don't think it matters, since the circles and triangles are exactly the same height. Therefore the centers must also be the same.

That is why all I've done in my annotated graph is connect the tops of each figure. It should be as valid a comparison for rate-of-change as if you computed the center and connected those dots.  8)
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Re: Piomas vs. CryoSat
« Reply #36 on: March 03, 2013, 02:54:55 PM »
I tried to reproduce the "PIOMAS on IceSat domain" values from the piomas gridded data.

First the PIOMAS grid with my best guess for the IceSat domain. Area is 7.17 Mm2, Laxon et al. give 7.2 Mm2.


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Re: Piomas vs. CryoSat
« Reply #37 on: March 03, 2013, 03:01:49 PM »
And here is the result (attached):

Still a bit bigger, but the remaining difference can be explained by the uncertainty of the "IceSat domain", I think.

dlen

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Re: Piomas vs. CryoSat
« Reply #38 on: March 05, 2013, 04:45:21 PM »
@Artful Dodger: You are right, for the connection lines, one can take anything, but when You want absolute values to get the ratio, You need to know where Your datum point is.

@Wipneus: What do Ye think, how come Laxon et al published smaller PIOMAS volumes? Did they do a different run with a smaller base area? No, I don't think so.

Artful Dodger

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Re: Piomas vs. CryoSat
« Reply #39 on: March 05, 2013, 05:33:50 PM »
@Artful Dodger: You are right, for the connection lines, one can take anything, but when You want absolute values to get the ratio, You need to know where Your datum point is.
Hi dlen,

APL makes no guarantee about the absolute value of their data. Their strong claim is that they've captured the volume loss trend correctly. The recent CS-2 data supports the position that PIOMAS loss rates are probably too conservative.

Wipneus has extracted numerical data for you for both. What else is it that you are looking for?
Cheers!
Lodger

dlen

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Re: Piomas vs. CryoSat
« Reply #40 on: March 09, 2013, 06:43:24 PM »
This is a misunderstanding - I am o.k. with the data I got.


Artful Dodger

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Re: Piomas vs. CryoSat
« Reply #41 on: March 10, 2013, 12:15:41 AM »
This is a misunderstanding - I am o.k. with the data I got.
Okay, cool.  8) Let us know if you find anything interesting!
Cheers!
Lodger

Ice Cool Kim

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Re: Piomas vs. CryoSat
« Reply #42 on: March 23, 2013, 09:36:37 PM »
A***: So, 1cm of snow can explain a lot of the ups and downs of CS2. So far I also assume wet snow and melting ponds totally mess up approach #1 and this is why there is no summer data.

That is the main thing I don't get with this CS2 data. March is hardly "summer" and ice pools tend to refreeze in August.  They don't even manage to capture the one point either side of the extrema.

Also they should be able to distinguish melt pools from leads since most will be nearly the same height as the ice surface.

May be it's early days yet and they still have some issues to sort out but it's over 2y years since they've had actual data coming in to work on.  Seven dots per year is a bit disappointing.

Not having September data really limits how much use this is, even just for calibrating the range of the annual oscillation in PIOMAS.

Maybe I missed something but they don't even seem to comment on or explain the glaring hole in the coverage.


Ice Cool Kim

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Re: Piomas vs. CryoSat
« Reply #43 on: March 24, 2013, 12:40:21 PM »
 Dodger: The recent CS-2 data supports the position that PIOMAS loss rates are probably too conservative.


I don't think that one monthly dot in each of two years shows anything at all except rough agreement.

The very small drop in max CS2 is way smaller than the discrepancy between CS2 and PIOMAS , well below the uncertainly of the CS2 data and can not be deemed to "support" anything.

Don't try to read too much (ie anything) into something that is well below the significance of the data.


anonymous

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Re: Piomas vs. CryoSat
« Reply #44 on: May 04, 2013, 02:10:56 AM »
I'd like to point a post by Martin Doble at the French forum called 'Chantier Arctique'. He describes measurements needed to get a higher accuracy from CS2 results. As he explains the draft/freeboard ratio is highly variable, especially if acquired from deformed ice. Although deformed ice might be soon a specialty from the past the post is interesting:

Estimating sea ice thickness from its freeboard

So far we can question the accuracy of detecting the ice-snow-interface and the correct draft/freeboard ratio of deformed ice. I see negative freeboard looming at the horizon, too. Do we need more buoys instead of satellites to get answers in time?

pdjakow

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Re: Piomas vs. CryoSat
« Reply #45 on: May 04, 2013, 01:16:27 PM »
I wonder if there are PIOMAS data in gridded dataset i.e. netCDF files...

Wipneus

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Re: Piomas vs. CryoSat
« Reply #46 on: May 04, 2013, 02:50:50 PM »
I wonder if there are PIOMAS data in gridded dataset i.e. netCDF files...


Even better, they are available as flat FORTRAN data files. ;)

The but's are: only monthly files and not regularly updated every month.

Have a look at http://psc.apl.washington.edu/zhang/IDAO/data_piomas.html


anonymous

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Re: Piomas vs. CryoSat
« Reply #47 on: May 06, 2013, 05:54:14 PM »
ESA just released GBs of data from the CryoSat Cal/Val campaign and lowered access restrictions, here the list: https://earth.esa.int/web/guest/campaigns

anonymous

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Re: Piomas vs. CryoSat
« Reply #48 on: June 17, 2013, 05:08:47 PM »
ESA recently launched a CryoSat Wiki and Forum at https://wiki.services.eoportal.org/tiki-index.php?page=CryoSat%20Wiki

Registration starts top right, prepare to find a strong password :)

The Wiki is organized in five areas:

Documentation that provides a one shop stop for the most relavant CryoSat official Documents,  Technical Notes, Proceedings and News related to the mission

Publications that provides the links to a number of Publications and ESA Study Reports related to the mission

Thematic forums that provides an online discussion board where CryoSat users can post and follow threads over specific topics organized by System, Sea ice, Land ice, Ocean and Coastal zones

Resources that provides a repository of a number of useful links and software tools and readers related to the mission

Events, workshops and important meetings, providing links, minutes, presentations and reports when available

anonymous

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Re: Piomas vs. CryoSat
« Reply #49 on: September 11, 2013, 02:33:16 PM »
BBC's Jonathan Amos covers the presentation of Cyosat 2 thickness data at Esa's Living Planet Symposium in Edinburgh and cites Prof Alan O'Neill: "What Cryosat has done in the past three years is to confirm the volume decline predicted by the modelling from the atmospheric record"