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DMI (And e.g. ROOS) includes the coastal areas in their measurements, which are excluded in most other SIE measurements This is incorrect, all SIE calculations that I know of (with one exception) include most of the coastal ice. That includes NSIDC (multiple extent calculations), ADS Jaxa (formerly known as IJIS), Bremen, Hamburg, ROOS and Cryosphere Today (it is sea area, just added to be complete). The one exception is the DMI graph based on OSISAF sea ice concentration that has the coasts masked out. DMI calls this graph "old": In the coastal region ice may be falsely detected due to the "land spillover" effect. All these calculations include measures to deal with that (with variable success). Cryosphere Today only shows ice, where the concentration is 30-35%, even if their legend includes colors for lower concentrations. For the record: the Cryosphere Today Area is calculated using a threshold of 0%. The DMI graph discussed here "thinks" it uses 15%.
Toggle Commented Sep 9, 2015 on PIOMAS September 2015 at Arctic Sea Ice
Is there a known reason for such a difference between DMI Extent and the others? Billy, I answered a very similar question on the forum recently: Why is the DMi arctic sea ice extent so much higher than everyone else's? My answer is here:,143.msg60794.html#msg60794 Basically they are using OSISAF input data, not being sea ice concentration data, that is not meant to be used for the purpose of calculating extent. Just by eyeballing the graph you can see something suspect. Looking at the grey (mean) line, notice the steps at some of the first of the months? Those are tell-tale indications of application of monthly ocean filters, designed to filter "false ice". Other extent sources use the same filters (originating from ice experts from NSIDC) but nowhere it is so visible in the graphs! This is a clear indication that the OSISAF data (on which the DMI graphs is based) contains a lot of this "false ice", probably the reason why they end up with such large extent numbers.
Toggle Commented Sep 9, 2015 on PIOMAS September 2015 at Arctic Sea Ice
the 'course' (25 km^2) NSIDC concentration dropped very quickly to normal levels, but the high resolution (3.125 km^2) concentration is still anomalously high. Yes and it is a bit of a puzzle. Compactness is depending on resolution, but melt ponds are small (I think) compared even with the 3km resolution. So in this case resolution should not matter. At the very least some response should be seen. The SIC product differ in more aspects than resolution, the microwave bands and calculations (known as "algorithms") are all different. The NSIDC uses the NT (NASA Team) algorithm, that is known to underestimate concentration especially during melting conditions. More than other algorithms. Melt ponds that deserve the name "pond" should affect all algorithms equally, the microwave bands used cannot distinguish ponds from open water. Therefore I think that the melt effect we are seeing is not melt ponding yet but rather the change from dry ice to wet ice, dry snow to wet snow, ice covered with snow to bare ice. So will this melting effect continue? Will ponds form and affect the other ice algorithm as well? FYI, I posted this on the forum today: From today's NSIDC sea ice concentration data update, I calculate the CT-area updates of the coming few day's: Mon 9.106157 Tue -119.6 8.986600 Wed -340.2 8.646372 Thu -71.6 8.574772 After Wednesday the drop on Thursday will be much smaller. Regarding the small extent uptick of (NSIDC calculation +4k6), the melting effect is still very much active.
Toggle Commented Jun 16, 2015 on Melt Pond May 2015 at Arctic Sea Ice
NSIDC sea ice concentration has dropped substantially today. That will not be reflected in Cryosphere Today Area numbers until Wednesday when it will drop by a massive 340k. The first sign of this was an explosion of melt area in today's ADS-NIPR Jaxa thickness/melting maps ( A sequence was posted at the forum (,1112.msg54089.html#msg54089). This is also the place to look at tomorrows and the day after tomorrows CT numbers. Since extent did "only" drop by about 75k, the compactness calculated from NSIDC concentration has taken a plunge as well and is now at similar levels as 2013 and 2014. To stay there (at 2103/14 levels), let alone get into record territory area will have to keep falling in the next few days. Today has shown it is possible.
Toggle Commented Jun 15, 2015 on Melt Pond May 2015 at Arctic Sea Ice
Rob, I was tired glad you could figure it out. Make sure that you did see my compactness graph at Three different sea ice concentration datasets, computed by very different methods (not to mention the two different satellite sensors) all agree that the compactness in May (and currently) is unusually high. Daily data for NSIDC is here: Data for the Jaxa L3 SIC is here: Data for the Uni Hamburg 3.125km AMSR2 SIC is here:
Rob Dekker, That data file does not give you what you think it does. Instead of average {extent|area} computed from daily sea ice concentration, it is {extent|area} calculated from average monthly sea ice concentration. Think of it: even if area equals extent every day of the month - 100% concentration within the ice extent, never any melt ponds or leads- grid cells that are only covered with ice during part of the month lead to an average concentration less than 100%. Thus monthly area < monthly extent. I think, the monthly E-A may be at least biased by the change in extent in that month, explaining at least some correlation in an obvious way.
Gerg, the numbers are from the Cryosat Team. Latest description is Laxon at al., 2013. Of course with "lots of useful improvements".
Toggle Commented Apr 20, 2015 on CryoSat-2 sea ice thickness maps at Arctic Sea Ice
Unless I missed something, it is all quit about the Antarctic Sea Ice. Have they given up getting meaningful numbers from there?
Toggle Commented Apr 18, 2015 on CryoSat-2 sea ice thickness maps at Arctic Sea Ice
Re: volume 201110 5285.7710 201111 10393.6171 201112 14260.6350 201201 19034.4468 201202 21914.0118 201203 25264.4449 201204 25277.3580 201210 5419.6971 201211 10169.5799 201212 14236.0916 201301 18041.6983 201302 20869.0761 201303 24601.5179 201304 24265.1174 201310 8879.8820 201311 13095.3897 201312 17235.3437 201401 21020.1913 201402 23995.5547 201403 26838.7185 201404 26420.0175 201410 7632.6782 201411 13032.8434 201412 16795.5443 201501 20503.3015
Toggle Commented Apr 18, 2015 on CryoSat-2 sea ice thickness maps at Arctic Sea Ice
Werther, The resolutions of the Sentinel 1 products vary, with 10, 25 and 40 meters/pixels the most common. Far better than MODIS, usable day and night, clouded or clear skies. They tend to be a bit less clear due to the "speckle noise" common to SAR imaging. A Landsat 8 image taken under the best conditions will be better, but those conditions are rare. One problem is the size: 1, 4 and 8GB single slice data products are an indication. ESA seems to have problems at the moment with populating the public archive (that Jim pointed to). For Greenland most products after Jan 27 have yet to appear. DMI appears to get their data via a better route.
Toggle Commented Feb 8, 2015 on PIOMAS February 2015 at Arctic Sea Ice
This brings the larger question whether 2014 ice was overall thicker than 2012 at this time of year. Wayne, I post with some regularity ice thickness maps derived from the SMOS instrument on the forum. Perhaps they are interesting in regard to the questions you ask.,587.msg40407/topicseen.html#msg40407
Landsat 8 orbits are repeated exactly every 16 days. So if you have a successful image look for image 16 (32,...) days later. Places in the polar regions appear in multiple paths, also the ascending (night) half of each orbit can be used in summer. So there may be more image series to be found. Because the position of the satellite differs, there will be distortions with the elevation of the surface. I don't know if you have already found this. The acquisition schedule (for June) is here: Last time I looked the usefulness was very limited: many images on the list are don't become available but also the reveres is true.
Data - the one problem I have is with netcdf format. Panoply handles it, but doing math on the data can't be done in Panoply. Flat binary and csv are fine in Excel (flat binary can be handled easily in Excel VBA - I'm a programming dunce and I manage it). ncdump gives a csv representation of the contents of netcdf files.
Toggle Commented May 15, 2014 on SIPN presentation at Arctic Sea Ice
Lodger: yes Neven notified me of dr Schweigers post. I am glad we are able do something useful in return for (and with) all the data we get every month.
Toggle Commented May 14, 2014 on PIOMAS May 2014 at Arctic Sea Ice
Hi everybody, I have been absent due to a broken telephone cable. Coming back I noticed that after I wrote this about the PSC thickness graph: The PSC graph shows average grid cell thickness. That is they add up all grid cell thickness measures and divide that by the number of grid cells. So it is not a true area-averaged number: the smaller grid cells have a relative overweight. The next day PSC changed the graph! I haven't looked at it in detail, but would not be surprised if the average is now more area-weighted and perhaps more in line with Neven's graph.
Toggle Commented May 13, 2014 on PIOMAS May 2014 at Arctic Sea Ice
The Polar Science Center thickness graph looks a lot different this month, with 2014 jutting out a lot more above the other post-2010 years. It has something to do with how they calculate average thickness, but I forgot the details: The PSC graph shows average grid cell thickness. That is they add up all grid cell thickness measures and divide that by the number of grid cells. So it is not a true area-averaged number: the smaller grid cells have a relative overweight. Those small grid cells are near the grid pole: in the northern half of Greenland. This fits nicely with observations that more thick ice near Greenland and Canadian Archipelago is found this year. We will be able to check this when/if the gridded daily data from April will become available as well.
Toggle Commented May 8, 2014 on PIOMAS May 2014 at Arctic Sea Ice
PIOMAS update: Latest value: 2014-2-28 20.86 I have updated my graphics at ArctischePinguin for the latest data. Monthly Data Daily Anomalies Daily data
3. Is river water anything to do with this strange arrival of open water in ESAS? idunno, it is Laptev Sea. West, with the Severnaya Zemlya islands on the lower left. See,382.msg21111.html#msg21111 how the open water formed. It is wind, not river warmth. As it happens, there is a clear first Landsat 8 image of the area. I will post it in the Image-of-the-day thread on the forum.
I'm not sure whether the PIOMAS sea ice volume anomaly graph has also been upgraded to Version 2.1 (it says V2 in the file name), There are two files, named: BPIOMASIceVolumeAnomalyCurrentV2.1.png and: BPIOMASIceVolumeAnomalyCurrentV2.png but they appear identical in my eyes, and both say: "Version: IC-SST 2.1" Comparing with last months version, the downward spikes (I think you know what I mean) are a bit smaller now.
I have posted an animation of ASI AMSR2 ice concentration (from Uni Hamburg data) on the forum (registration required):,382.msg18817/topicseen.html#msg18817
"no update for 2014 yet from Uni Hamburg." And that is still true today. Lots of my own scripts were not 2014-ready, so I guess something similar is the case there.
Toggle Commented Jan 5, 2014 on Merry christPIOMAS at Arctic Sea Ice
My PIOMAS graphics update announcement has, as usual, landed in the spam box. They are to be found in the usual place. [released now, thanks for the heads-up; N.]
Toggle Commented Dec 4, 2013 on In memoriam: Albert A. Bartlett at Arctic Sea Ice
Does anyone know why there is such a big difference between the daily ice extent from NSIDC : Look at the differences between Svalbard and Bering Strait... That grey between Svalbard and Bering Strait means it is unavailable, caused by the data problems with the DMSP F17 satellite. Discussed on the forum in the NSIDC tread.
Here is the today's ice cover compared with last year, seen by AMSR2 and processed by Jaxa. Blue is concentration now above 15% and below last year. Red is the reverse. I am placing such images with some regularity on the forum. It is more convenient for me, and Typepad seems to particularly dislike me which is not encouraging.
Toggle Commented Sep 9, 2013 on PIOMAS September 2013 at Arctic Sea Ice
Forcings are proportional to log(concentration), so a doubling of methane from 1->2 ppm, compared with CO2 concentration of 390->391 ppm gives a forcing ratio of: (log(2)*.8)/(log(391/390)*4.5) = 48.1 close enough to 54?