Home brew AMSR2 extent & area calculation

[Wipneus]

The nice guys at the University of Hamburg have provided the results of their unfinished sea ice concentration calculation based on L1(R) AMSR2 data from JAXA  online in some very handy NetCDF files.

Citation of source data:
Data:
Beitsch, A., L. Kaleschke and S. Kern (2013), "AMSR2 ASI 3.125 km Sea Ice Concentration Data, V0.1", Institute of Oceanography, University of Hamburg, Germany, digital media
(ftp-projects.zmaw.de/seaice/), [BEGIN Jan 2013- present];
Articles:
Spreen, G., L. Kaleschke, G. Heygster (2008), "Sea Ice Remote Sensing Using AMSR-E 89
GHz Channels", J. Geophys. Res., 113, C02S03, doi:10.1029/2005JC003384.

Kaleschke, L., C. Lüpkes, T. Vihma, J. Haarpaintner, A. Bochert, J. Hartmann, G. Heygster,
"SSM/I Sea Ice Remote Sensing for Mesoscale Ocean-Atmosphere Interaction Analysis",
Can. J. Rem. Sens., 27(5), 526-537, 2001.

see also:
http://neven1.typepad.com/blog/2013/06/new-map-on-the-block.html
data:
ftp://ftp-projects.zmaw.de/seaice/AMSR2/
[EDIT 2017-03-30: source adress change]
ftp://ftp-projects.cen.uni-hamburg.de/seaice/AMSR2/

The data is provided at a 3.125x3.125 km grid.

Summing the area of the grid cells that have an ice concentration of 15% (or some other value) should give a measure of the extent that can be compared with the well known Jaxa/Ice, NSIDC and others that do similar calculations.

Here I present the first results.

The calculations have the following features:

1) uses the actual area of the grid cells, which may deviate a few perecent from the nominal 3.125^2 km²;
2) Ice concentration of the "North Pole hole" is calculated to be the same as a small ring (width 25% of the radius of the hole itself) around the hole;
3) Spurious ice is removed from coastlines where there is open water within a "few" grid cells;
3a) pixels labeled as sea, separated from the world oceans are considered "lake" and discarded;
4) "phantom" ice fleets that appear and disappear randomly, especially at lower latitudes are detected and removed;
5) an ice mask is used to split the area into regions as closely as possible similar to those of the Cryosphere Today.

 
Of course it may be regarded as a foolish undertaking:

1) the 3.125 km grid cannot be compared with anything else available;
2) the 3.125 km ice concentration values are influenced by clouds and water vapor (as a consequence of using the hi-res 89 GHz microwave band);
3) The ice concentration data is unofficial and work-in-progress;
4) The data is only available for 2013, we cannot compare with any other year directly.

Well, it is fun to try and I was supprised when I saw the first result:


 
My calculations have been tracking Jaxa's quite close.
I expected a lot of noise as there is no filter (Jaxa filters 2 days), the unfiltered data looks quite usable.
Since end of May, the two have been diverging. This is to be expected, when hole fall in the ice cover the smaller grid will more likely pick them up than the wider grid.

Considering now:
1) extent per region;
2) area calculation;
3) compactness calculation (like CAPIE but from the same source)

[update put the area graph in the top post:]


[update put the compactness graph in the top post]


[update: add regional graphs]

[ChrisReynolds]

Good stuff Wipneus,

One small point, you lost me here

Since end of May, the two have been diverging. This is to be expected, when hole fall in the ice cover the smaller grid will more likely pick them up than the wider grid.

[crandles]

Excellent.    

Chris, I would expect a fine grid to measure more area of holes because 15% of a large grid is more than 15% of a small grid. So if a cell has a single hole and that hole is between 15% of small and 15% of large cell size then it will be counted as a hole on the small grid but counted as fully ice covered if you use the large grid.

[anonymous]

If I look at the area along the Siberian coast it seems the algo picks up melting ponds as open water. The difference between MODIS and AMSR2 is quite substantial. On the other hand this tells me same area no longer qualifies as ice pack, ice swamp is a better designation.

[SATire]

Thank you Wipneus, that you make this possible - you can check Extent and SIA with better resolution and faster than anybody else and you can perform a lot of new statistics, trends and what you want.

I hope this place is appropriate for this, otherwise feel free to move it (e.g. in Wipneus' future home-brew-SIA thread?).
For us noobs, who can not programm such nice tools I would like to summarize here an easy way to measure SIA on your own by using a paint programm of your choice. I explain it for gimp, which you can get for free (http://www.gimp.org/):

To compute SIA from that concentration maps from Wipneus (https://sites.google.com/site/apamsr2/home/pngcby32/) is totally easy with gimp:

1. Select the area of interest
2. use the histogramm function (Menue: Colors -> information -> histogramm)
3. look up the "mean" value and devide it by 255 (=100% ice) to get the ice fraction
4. multiply by selected area (e.g. number of pixel from histogramm function times 3.125 km times 3.125 again (pixel area)   

If you have the black hole in your selection, choose lower level of histogramm >38 to avoid a wrong mean since the black hole has pixel value of 37.

If you have land in your selection - use a mask or change it's color to black. If there are lakes or artifacts in the area: just paint that black, too 

All warnings Wipneus mentioned above are valid here of course, too.

This is not as flexible and cool as the thing Wipneus is doing, but it is a nice and easy thing to compare SIA in areas of your personal interest from day to day. Just note the position and the size of your selection for comparisons over time and as reference for other poeple interested.

(copy from a comment at http://neven1.typepad.com/blog/2013/06/new-map-on-the-block.html)

In attached picture I put in the SIA concentration in % and the selected area for example.

Since Wipneus also gave a map of the CT-region at ASIB - you may compute the CT-SIA with larger resulution on your own in future. One should learn to paint somehow selectively over that "weather smear" features (see redish area in attached picture), which allways disturb also U-Bremens maps for the same reason.

[ChrisReynolds]

Thanks Crandles, obvious really.

[Wipneus]

Good stuff Wipneus,

One small point, you lost me here

Since end of May, the two have been diverging. This is to be expected, when hole fall in the ice cover the smaller grid will more likely pick them up than the wider grid.

I see on the hi-res pngs lots of isolated grid cell's with less than 15% concentration, more and more within the CAB. These will lower the 3.125 extent, but not Jaxa's. Remember 16 of the 3.125 grid cells fit in one of Jaxa, 3 of them 100% concentration and Jaxa will include all of them to the extent.

[Neven]

Awesome!

[Wipneus]

Extent down 79k7 to 10.403255

Continuing extent losses in the Arctic Basin (asp. between the pole and Barentsz)

[Wipneus]

Region break down (in 1000 km²):

Code: [Select]

           Arctic Basin       East Siberian Sea              Laptev Sea
                   -2.2                    11.8                     0.2
               Kara Sea             Barents Sea           Greenland Sea
                  -27.9                     1.1                     0.0
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -34.0                     0.0                   -17.0
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                    2.0                     1.8                   -13.5
             Bering Sea          Sea of Okhotsk                   Total
                   -1.6                    -0.3                   -79.7



[Wipneus]

Here is the same for area

Code: [Select]

AREAAREAAREAAREAAREAAREAAREAAREAAREAAREAAREAAREAAREAAREAAREA
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -15.7                     5.5                    15.4
               Kara Sea             Barents Sea           Greenland Sea
                  -39.8                     0.1                    -5.0
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -34.3                     0.0                   -22.6
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -0.6                   -18.4                    -5.4
             Bering Sea          Sea of Okhotsk                   Total
                   -1.3                    -0.1                  -122.5


[SATire]

Cool Wipneus - you made it! Now all values out there are also at your fingers
And thank you very much for sharing that!

Do you think it could be possible to detect the artifacts in the AMSR2-maps one day? As Lars did explain in ASIB there are two features: Melt ponds and water vapour effects - both should be treated differently of course. I have the feeling that both effects are visible in the maps - so there should be some way to detect them automatically, too. But that is not an easy thing.

The weather "smear" features (red stuff in above picture) show less contrast, give a SIA between 60% and 90% and move from day to day by large distances - but there may be overlapp from one day to the next day of course. Maybe a low contrast in a quite big connected area with SIA of 60-80% could be a first warning signal.
A work-around could be to check clusters of 100-200 pixels if SIA reductions with quite low contrast occure suddenly and disappear some days later and after some days to ignore SIA/Extent-losses in such areas. Maybe IJIS is doing something like that?
A perfect way would be to include information from other sensors to detect that - I think it is related to the thick orange clouds visible in MODIS 3-6-7. But unfortunately that pictures are taken at different time and the clouds move fast. Also on channel in JAXA is used to detect that. So maybe a human eye is necessary as reference...

The melt-ponds are visible by a quite rapid reduction of SIA to dark shades of grey, which then stay quite a long time without dropping close to zero. Those things do not move or only very slowly like the pack. If I understood Chris Reynolds right, that is some kind of "cliff-detector" and we could take the values seriously due to albedo things. However - it would be nice to know the amount of SIA reduction related to those melt-ponds.

Do you think those things make sense at all?

[Wipneus]

SATire,

We are not the first people that have been thinking about this stuff. If it where easy, the Uni Hamburg team would have fixed it already. Having an advantage with all microwave bands and polarizations available.

I will think about it myself, perhaps the ideas you give can be automated somehow.

On the other hand, how bad is it? Melt ponds tend to form on First Year Ice, so they will mostly be gone at minimum anyway. The clouds/vapor issue does not seem to cause strange swings compared to the Jaxa/IJS curve.

[SATire]

Wipneus,

I think you are right with all your arguments. Probably any algorithm which could solve the vapour-issue would incorporate new software specific artifacts, which could make any results questionable. It would be better for amateurs like us to work with plain data and to discuss any artifacts separatly after viewing the map. Further I believe that you allready have a lot of more fruitfull ideas, since you also have all the PIOMAS data in grids in your hands, too. To repeat it: Great work you did!

[Wipneus]

Area compared with CT area:



I am not sure why the divergence goes now the other way. The double cliff is even more pronounced.

[dree12]

Area compared with CT area:



I am not sure why the divergence goes now the other way. The double cliff is even more pronounced.

With more holes in the ice, this is to be expected. CT area will consider anything below 15% as 0, whereas AMSR2 would find isolated pieces of concentration.

[Wipneus]

Extent down: -39k9 mostly Baffin, also CAA, Beaufort and Chucki
Area up :83k4 almost all CAB

Details (upper is extent, lower half area):

Code: [Select]

           Arctic Basin       East Siberian Sea              Laptev Sea
                   -1.9                     8.8                     6.4
               Kara Sea             Barents Sea           Greenland Sea
                    1.0                     0.7                     0.1
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -20.5                     0.0                    -8.4
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -4.1                    -4.9                   -13.4
             Bering Sea          Sea of Okhotsk            Total Extent
                   -2.0                    -1.7                   -39.9

           Arctic Basin       East Siberian Sea              Laptev Sea
                   88.4                    14.3                     7.0
               Kara Sea             Barents Sea           Greenland Sea
                    4.0                     3.3                     3.4
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -20.5                     0.1                    -6.5
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   12.4                    11.2                   -29.5
             Bering Sea          Sea of Okhotsk              Total Area
                   -1.7                    -2.5                    83.4


[SATire]

Area up :83k4 almost all CAB

BTW - how do you treat the "value=37-NP-hole"? Do you ignore it or do you give that area some mean SIA from the surrounding like CT?

[Wipneus]

Area up :83k4 almost all CAB

BTW - how do you treat the "value=37-NP-hole"? Do you ignore it or do you give that area some mean SIA from the surrounding like CT?

It is in the top post. I take the average concentration of a small ring (width 25% of the hole radius) and assume that for the hole.

[Richard Rathbone]

Is there actually refreeze, or is it something like the same ice being counted twice as it moves from one pixel to another between satellite passes?

[Wipneus]

Wouldn't "pixels" with open sea in that case get counted multiple times as well?

Anyway there is an update of 20130618 tomorrow. Mostly those updates don't change anything but perhaps now is different.

[Peter Ellis]

Is there actually refreeze, or is it something like the same ice being counted twice as it moves from one pixel to another between satellite passes?

Most likely melt ponds showing up (or not) depending on multiple factors like the angle of the satellite relative to the Sun, the amount of water vapour in the atmosphere, cloudiness, temperature, etc.  That's why it affects area much more than extent.

[Wipneus]

Update for 20130618 did not change anything.

Extent: down -68k4, fastest runner is Laptev also Baffin, Hudson, Chucki and Greenland sea.

Area: down -40.1 Very mixed on regional scale. Note that Greenland Area increases where extent declined.

Details (upper extent, lower area):

Code: [Select]

          Arctic Basin       East Siberian Sea              Laptev Sea
                   -0.1                     5.7                   -31.1
               Kara Sea             Barents Sea           Greenland Sea
                   12.1                    -4.8                   -10.1
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -16.5                    -0.2                    -8.1
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -0.7                    -0.4                   -10.7
             Bering Sea          Sea of Okhotsk            Total Extent
                   -2.8                    -0.8                   -68.4


           Arctic Basin       East Siberian Sea              Laptev Sea
                   12.1                    14.7                   -42.6
               Kara Sea             Barents Sea           Greenland Sea
                   34.9                    -3.6                     6.8
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -26.6                    -0.1                   -28.9
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   24.9                   -20.5                    -7.3
             Bering Sea          Sea of Okhotsk              Total Area
                   -2.6                    -1.3                   -40.1
 

[Wipneus]

Compactness (Area/extent) compared with CAPIE:

[Wipneus]

Update:

Extent: -44k5. Mostly Baffin, Kara and Greenland Sea. An increase for ESS and Hudson.

Area: -75k3. Mostly same movements as extent, but increase for CAB and noticable decrease for CAA and Beaufort.

The details:

Code: [Select]

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                    0.5                     9.6                    -0.4
               Kara Sea             Barents Sea           Greenland Sea
                  -13.8                    -6.8                   -14.0
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -18.8                    -0.3                     5.9
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -4.0                    -1.0                    -2.5
             Bering Sea          Sea of Okhotsk            Total Extent
                   -0.1                     1.0                   -44.5

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   38.4                    21.2                    14.2
               Kara Sea             Barents Sea           Greenland Sea
                  -22.5                    -5.5                   -24.8
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -48.2                    -0.3                    -3.5
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                  -29.4                    -9.3                    -2.1
             Bering Sea          Sea of Okhotsk              Total Area
                   -0.7                    -2.8                   -75.3


[Wipneus]

Looking at the graph, it is now getting clear to me that the CT area is lagging two days compared with this calculation and the Jaxa/IJIS data.

First the date tag included with the CT data is already the day before yesterday.
Second when computing the cross correlations between changes in my data and those in CT area we get a peak at -1 (indicating my calculation leads):



Total makes two days.

[Wipneus]

Midsomer update:

extent: -88k1  Mostly Hudson, declines for Barentsz, Kara,Laptev. Also Greenland sea and CAA. Increase for Baffin.

area:-53k7 Also here it is Hudson, but CAB is good second together with CAA and Greenland sea. Baffin has the big increase, with ESS.

The details:

Code: [Select]

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   -5.2                     3.3                    -3.8
               Kara Sea             Barents Sea           Greenland Sea
                  -11.5                    -4.6                    -8.0
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                   11.0                     0.1                   -67.7
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -4.6                    -0.3                     4.4
             Bering Sea          Sea of Okhotsk            Total Extent
                    0.1                    -1.2                   -88.1

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -49.8                    31.5                     0.2
               Kara Sea             Barents Sea           Greenland Sea
                   -5.4                    -0.6                   -13.1
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                   44.5                     0.0                   -73.2
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                  -19.7                    14.9                    17.4
             Bering Sea          Sea of Okhotsk              Total Area
                    1.4                    -1.8                   -53.7


[jdallen]

Baffin *Increase*!?

How?

[Wipneus]

Baffin *Increase*!?

How?

divergence (negative)?

See attached, red pixels have concentration going below 15%, blue pixels passing the 15% the other direction.

[Wipneus]

Update 20130622:

extent: -67k9
area: -26k0

Baffin and Hudson are declining fast. Kara and Barentsz a bit less.
Gainers are Greenland sea, ESS, Beaufort and Chukchi.

the details:

Code: [Select]

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                    1.8                     2.5                    -2.3
               Kara Sea             Barents Sea           Greenland Sea
                   -9.7                    -8.1                    18.7
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -32.6                     0.2                   -37.3
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                    3.4                     1.0                    -2.9
             Bering Sea          Sea of Okhotsk            Total Extent
                   -1.7                    -0.8                   -67.9

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -15.2                    35.3                    -0.9
               Kara Sea             Barents Sea           Greenland Sea
                   -5.9                    -4.8                    43.3
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -69.9                     0.1                   -21.8
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -3.1                    13.0                     5.0
             Bering Sea          Sea of Okhotsk              Total Area
                   -1.2                    -0.1                   -26.0


[Wipneus]

Extent: -50k1
Area: +28k4

Decline mostly Hudson and Barentsz
Increases for Laptev and ESS.
CAB has large increase in area but small decrease in extent

The details:

Code: [Select]

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   -3.6                     3.1                     7.2
               Kara Sea             Barents Sea           Greenland Sea
                   -4.9                   -11.5                    10.6
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                   -1.3                     0.0                   -42.9
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -2.2                    -0.4                    -4.8
             Bering Sea          Sea of Okhotsk            Total Extent
                   -0.2                     0.7                   -50.1

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   59.1                    11.9                    16.1
               Kara Sea             Barents Sea           Greenland Sea
                   -3.5                    -9.1                    -4.2
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -12.6                     0.0                   -50.1
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   16.8                     9.3                    -5.6
             Bering Sea          Sea of Okhotsk              Total Area
                   -0.5                     0.7                    28.4


[Wipneus]

Extent: -144k3
Area: -112k4

Biggest declines in Hudson, Baffin and Greenland sea. Further Barents (what is left of it), Kara and Laptev.

Still little movement or even increases in CAB, ESS and Beaufort.

The details:

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                    1.3                    -0.1                   -11.2
               Kara Sea             Barents Sea           Greenland Sea
                  -20.8                    -5.8                   -38.7
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -38.3                     0.3                   -29.6
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                    5.5                     1.4                    -4.0
             Bering Sea          Sea of Okhotsk            Total Extent
                   -2.2                    -2.0                  -144.3

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   66.8                     9.5                    -2.4
               Kara Sea             Barents Sea           Greenland Sea
                  -24.7                    -7.3                   -48.8
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -38.5                     0.3                   -47.9
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                  -11.0                     3.7                    -8.5
             Bering Sea          Sea of Okhotsk              Total Area
                   -1.7                    -1.9                  -112.4

[Wipneus]

Extent: -122k3
Area: -181k6

Declines almost in all regions. This day, also declines in Chucki and Beaufort. ESS is the most stubborn  with a very small increase in extent and a decline in area.

The details:

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   -1.4                     0.2                   -17.0
               Kara Sea             Barents Sea           Greenland Sea
                  -22.6                    -7.7                    -0.3
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -30.7                     0.0                   -26.0
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                    3.4                    -1.8                   -14.3
             Bering Sea          Sea of Okhotsk            Total Extent
                   -0.4                    -3.7                  -122.3

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -28.9                    -3.2                   -14.7
               Kara Sea             Barents Sea           Greenland Sea
                  -48.8                    -4.7                    11.5
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -32.7                     0.1                   -25.4
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -1.9                   -11.3                   -15.4
             Bering Sea          Sea of Okhotsk              Total Area
                   -0.6                    -5.6                  -181.6

[jdallen]

Extent: -122k3
Area: -181k6

Declines almost in all regions. This day, also declines in Chucki and Beaufort. ESS is the most stubborn  with a very small increase in extent and a decline in area.

No surprises here at all, as far as I'm concerned.

[Wipneus]

Extent: -171k5
Area: -124k

Extent is lost in all regions with ice cover. Biggest decline Baffin and Greenland sea.
Area is gained in Hudson and Kara, a big loss in the CAB.

The details:

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   "-7"                  "-5.8"                 "-10.3"
               Kara Sea             Barents Sea           Greenland Sea
                "-13.2"                   "0.5"                 "-48.6"
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                "-38.3"                   "0.1"                  "-2.7"
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                 "-7.1"                   "-15"                 "-18.5"
             Bering Sea          Sea of Okhotsk            Total Extent
                 "-0.6"                    "-5"                "-171.5"

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                "-33.5"                  "-9.2"                    "-3"
               Kara Sea             Barents Sea           Greenland Sea
                 "16.4"                  "-2.9"                 "-46.8"
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                "-24.1"                  "-0.1"                  "30.2"
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                "-15.2"                 "-13.5"                 "-18.3"
             Bering Sea          Sea of Okhotsk              Total Area
                 "-0.4"                  "-3.8"                  "-124"

[Wipneus]

Studying the images I find that to days source data contains rather a lot of what I call "ghost" ice: fileds of ice appearing for single days in area's that are crealy ice free.

For today this affects mostly the Barentsz region, the extent increase in not real and more something like -5k. The real total extent decrease is about -185k. Other regions and SIA are less affected.

I will set the parameters controlling the "ghost ice removal" procedure a bit tighter.  Tomorrows data will be based on those: having to recompute the whole time series takes several hours.

[Tor Bejnar]

Thanks, Wipneus, for doing this work. Although I'm not doing anything with your data, I've been checking in almost daily.  At some point I hope to find time to graph this data and compare to CT.
Mostly, I want you to know how appreciative I am (and I'm sure others are).

[Wipneus]

 At some point I hope to find time to graph this data and compare to CT.

Thank you for your kind words.

In the top post you will find the updated extent and area (including the current CT area) graphs.

Do not go to https://sites.google.com/site/arctischepinguin/home/amsr2 just yet. This is where I hope give these things a more permanent place.

[Tor Bejnar]

Thanks,
I hadn't noticed that the graphs are kept up-to-date.  My (hopeful) future graphs, I was thinking when I wrote just above, would be the Central Arctic or Barentsz or Greenland Sea data.

_{Arctic ice is healthy for children and other living things.}

[Wipneus]

Well about the regional area. Here are two attachments (need to be logged in to see them).
The first one compares regional CT with this calculation. As you can see there is positive differences for the CAB and (lesser) the other regions within the Arctic Ocean. Differences in the outer, lower latitudes tend to be negative.

In the second attachment, I dit use nominal grid cell areas (3.125*3.125 km2) instead of adjusted for the sterographic projection. The differences are much smaller (except st Lawrence and CAA).

So it is my hypothesis that CT does not use the real grid cell area's. I have send an email last week, but did no get an answer yet.

[Wipneus]

To days update:

Extent -99k2
Area: -111k2


CAB, Beaufort and ESS still slow. Other regions continue the decline, including today the CAA.

The details:

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   -7.8                     0.0                    -7.4
               Kara Sea             Barents Sea           Greenland Sea
                   -4.4                    -6.7                    -4.2
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -21.6                     0.4                   -34.5
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -5.7                    -1.1                    -2.7
             Bering Sea          Sea of Okhotsk            Total Extent
                    0.9                    -4.3                   -99.2

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                    3.5                    -3.6                    -6.2
               Kara Sea             Barents Sea           Greenland Sea
                  -19.7                    -3.4                     0.9
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                   12.5                     0.4                   -78.5
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                  -17.4                     2.8                    -0.9
             Bering Sea          Sea of Okhotsk              Total Area
                    0.9                    -3.6                  -112.2

[Wipneus]

To days update:

Extent: -105k1
Area: -118k4

Big declines in Kara, Baffin and Greenland sea. Increase in CAA. ESS is starting to decline. Other regions keeping it easy, including the Hudson that was such a big runner the last week.

Details:

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   -1.5                    -3.1                    -3.3
               Kara Sea             Barents Sea           Greenland Sea
                  -22.2                    -2.5                   -35.8
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -34.7                    -0.2                    -4.6
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                    7.5                    -0.5                    -1.4
             Bering Sea          Sea of Okhotsk            Total Extent
                   -1.0                    -1.7                  -105.1

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   -4.9                    -6.5                   -10.2
               Kara Sea             Barents Sea           Greenland Sea
                  -41.4                    -1.8                   -31.4
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -35.1                     0.0                     3.8
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   10.0                     0.8                     0.6
             Bering Sea          Sea of Okhotsk              Total Area
                   -0.6                    -1.8                  -118.4

[Wipneus]

Here is the situation around Kara. Red pixels indicate extent decreased, blue increased.

It is still very peripheral ice that is melting. Just nibbles at the central Arctic.

(picture attached, need to be logged in to see)

[ChrisReynolds]

Wipneus,

If I haven't commented, it's not because I'm not reading, it's because you're doing such a good job it leaves little for me to say. I'll keep reading as long as you keep posting.

Thanks.

[Tor Bejnar]

Thanks for the regional graphs, Wipneus.  It is curious that line sets in some regions diverge consistently.  My initial reaction was "Are the areas measured the same?" (North Pole hole? Hudson Bay/Can. Arch. boundary?? Fresh water lakes in Can.Arch.?)  I'm guessing, though, that you have quite a tighter hold on possibilities than I have!

[danp]

Wipneus,

If I haven't commented, it's not because I'm not reading, it's because you're doing such a good job it leaves little for me to say. I'll keep reading as long as you keep posting.

Thanks.

100% agree.  This has been an incredibly useful project and I've been watching this data eagerly alongside other daily measures.

-Dan

[Neven]

Same here, Wip. This is great stuff. I can stop watching day-to-day changes by comparing UB SIC maps.

[Wipneus]

Update:

Extent: -90k5
Area: -57k

Biggest decline in Greenland sea, but that is an area with the net balancing with even bigger increases and declines.  Further declines on one side Baffin and CAA and on the other side Kara and Laptev. ESS and Beaufort are quit.
Note the big decline in area for Chukchi.
CAB is making a start now: it is mostly on the border with Barentsz that is "virtually" ice free but also a few pixels within the pack near the side of Chukchi. See if that is the beginning of a "hole".

Details:

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   -8.5                     0.6                    -9.4
               Kara Sea             Barents Sea           Greenland Sea
                  -11.5                    -2.4                   -28.6
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -10.8                    -0.4                    -8.0
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -9.2                     2.4                    -3.1
             Bering Sea          Sea of Okhotsk            Total Extent
                    0.0                    -1.4                   -90.4

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   -7.2                    -4.4                    -8.4
               Kara Sea             Barents Sea           Greenland Sea
                   -0.2                    -0.9                    10.7
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -16.5                    -0.4                     4.2
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -1.2                    -2.9                   -30.7
             Bering Sea          Sea of Okhotsk              Total Area
                   -0.1                     0.9                   -57.0

[Wipneus]

Region of the day is Greenland sea. Ice creates blues where it moves to and leaves reds in its wake. The reds in the top of the image are actually counted as in the Arctic Basin.

(attached, need to be logged in to see).

 

[Wipneus]

Thanks for the regional graphs, Wipneus.  It is curious that line sets in some regions diverge consistently.  My initial reaction was "Are the areas measured the same?" (North Pole hole? Hudson Bay/Can. Arch. boundary?? Fresh water lakes in Can.Arch.?)  I'm guessing, though, that you have quite a tighter hold on possibilities than I have!

Tor,

First I am happy that most regions are doing very well: maximum areas are very close. That includes ALL regions within the Arctic basin.

About the Canadian Archipelago: the region graph:



counts 1183 pixels in "CAA grey". That is 1183*25^2= 0.74 Mm²
But the max ice in CAA is about 0.6 Mm²

Clearly not all pixels are counted in the CT regional area. Some disconnected pixels may be dropped as virtual lakes, in the high resolution maps that I use the are connected to open sea.

CT still counts positive area for st.Lawrence, I don't see how that is possible.

I will try again to contact CT in a week or so.