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Author Topic: Home brew AMSR2 extent & area calculation  (Read 1282783 times)

seaicesailor

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Re: Home brew AMSR2 extent & area calculation
« Reply #2000 on: June 05, 2016, 11:13:52 AM »
Something I found striking from one of A-team's visialization is the along-the-tangent speed these floes get as soon as they get a bit out of the main pack. This can be ocean current driven, since there is no much wind-driven drift. Maybe the Gyre ocean current surfaces out there and still strong due to inertia , or perhaps is wild imagination.

These floes would melt much faster if pushed toward the coast just like last year, given that surface melting is picking up very slowly and the ice is so thick.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2001 on: June 05, 2016, 12:16:30 PM »
A slow day, for area and extent both.

Update 20160604.

Extent: -21.1 (-516k vs 2015, -803k vs 2014, -1206k vs 2013, -1057k vs 2012)
Area: -25.8 (-846k vs 2015, -716k vs 2014, -1251k vs 2013, -1004k vs 2012)
 
Extent went down in the Kara Sea (-17k) and the CAA (-12k, some serious darkening with SIC dropping below 15% in the south branch of the NW passage, between Victoria Isl. and the continent). CAB extent went up by +13k.

AREA the forces are very mixed. The ESS continued its dive downward (-33k) but the CAB recovered quite a bit by +30k.

For the images I show delta maps of two different regions. First is the ESS/Laptev region. Some of the very dark/low concentration places show an increase (bluish hues), others continue to decrease.
The second is the region north of Svalbard. As can be seen the ice is extending over a wide front. It is one of the reasons why extent is dropping so slow in the numbers of different agencies.
 

Paddy

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Re: Home brew AMSR2 extent & area calculation
« Reply #2002 on: June 05, 2016, 12:23:40 PM »
Looking at the sea ice concentration off about half the coast of Russia, should we expect extent there to drop soon as well?

http://www.iup.uni-bremen.de:8084/amsr2/arctic_AMSR2_nic.png

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2003 on: June 05, 2016, 12:39:17 PM »
Rob makes it easier for me to choose the region of the day to animate.

Here is one other reason why ice may disappear, not being visible in the sea ice concentration maps, and suddenly pop=up again.
The satellite that is taking the microwave radio measurements is in a (near) polar orbit. It completes about 14 orbits every day. So regions in the Arctic Ocean will be seen by the satellite multiple times.
Moving ice floats may have traveled (whole or partly) to another grid cell. Since the algorithm averages the concentration prom different passes, the resulting measured sea ice concentration will be lower. In cases where the speeds are great, grid cells are small and satellite visits are frequent the resulting sea ice concentration may be below 15% and not "seen". 
So the black apparently ice free open water in the Beaufort Gyre may contain more/brighter ice than you'd think.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2004 on: June 05, 2016, 01:07:16 PM »
Melt extent is increasing fast.

Neven

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Re: Home brew AMSR2 extent & area calculation
« Reply #2005 on: June 05, 2016, 01:18:17 PM »
Wip, how are you making that second graph? Is there a data file somewhere, or do you use the maps themselves (pixel counting)? I assume it is a numerical version of the melt extent shown on that JAXA thickness map.
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Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2006 on: June 05, 2016, 01:39:44 PM »
Wip, how are you making that second graph? Is there a data file somewhere, or do you use the maps themselves (pixel counting)? I assume it is a numerical version of the melt extent shown on that JAXA thickness map.

Look at the top: "From Sea Ice Thickness Maps", so it is indeed pixel counting. Nothing really wrong with that, because the underlying PNG files are an exact representation of a (rotated) Polar Stereo Graphic grid with 10x10 km cells, and the color coding is unambiguous.

Sourabh

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Re: Home brew AMSR2 extent & area calculation
« Reply #2007 on: June 05, 2016, 01:50:15 PM »
Wipneus,

Silly question:

What is melt extent? What does bottom graph represent?

Neven

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Re: Home brew AMSR2 extent & area calculation
« Reply #2008 on: June 05, 2016, 01:52:16 PM »
Cool, thanks for explaining. Is there some live version I can squeeze in on the ASIG somewhere?

Either way, it'll be good to use for next week's melting momentum blog post, so expect me to come begging for it.  ;)
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Richard Rathbone

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Re: Home brew AMSR2 extent & area calculation
« Reply #2009 on: June 05, 2016, 02:16:35 PM »
Wipneus,

Silly question:

What is melt extent? What does bottom graph represent?

Top line is the total extent of ice, bottom line the extent of ice with a wet surface. I assume some of it is actually freezing rather than melting, particularly in the winter.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2010 on: June 05, 2016, 02:39:48 PM »
Wipneus,

Silly question:

What is melt extent? What does bottom graph represent?

Good question of course.
Let me explain what I do.
Start with the ADS thickness/melt maps. Thickness is explained on the ADS site, but "melt ice concentration" is not. I assume that it is the same as "melt pond concentration". Algorithms for both thickness and "melt pond concentration" are given here:
http://www.iarc.uaf.edu/sites/default/files/workshops/2011/iarc-jaxa-4th-generation-kickoff/seaice/Tateyama_Wakabayashi.pdf

What I do is take these maps, detect the blue pixels, this is where "melt pond concentration" is over 20% and calculate the sum of area's of those cells. Same spirit as sea ice extent is calculated, so I call the result "melt extent".
 

Sourabh

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Re: Home brew AMSR2 extent & area calculation
« Reply #2011 on: June 05, 2016, 05:49:09 PM »
Thanks Wipneus,

So, melt extent, as Richard said, refers to area of ice with wet surface. But, how can you be sure that it is melt pond and not open water? Is this why you are using thickness maps to include only those areas that have non-zero thickness and some water/melt surface?

Also, is rapid rise in melt extent precursor to rapid drop in area? Because  area is declining rapidly for past three days (more than 320k), and in your graph, melt extent is also increasing.

oren

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Re: Home brew AMSR2 extent & area calculation
« Reply #2012 on: June 05, 2016, 07:25:42 PM »
If I recall correctly, the algorithm for sea ice area treats melt ponds as open water, which is why area is dropping when melt extent rises. (Am I right?)

Neven

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Re: Home brew AMSR2 extent & area calculation
« Reply #2013 on: June 05, 2016, 07:34:30 PM »
If I recall correctly, the algorithm for sea ice area treats melt ponds as open water, which is why area is dropping when melt extent rises. (Am I right?)

That's right. Melt ponds get counted as open water for area. And so when melt pond concentration goes up, sea ice area goes down.

If one grid cell is covered with more than 85% of melt ponds, it also gets counted for extent. Remember, as soon as more than 15% of a grid cell is covered with ice, it gets counted as 100% sea ice for extent.

This is the main reason there are two different ways of determining how much of the Arctic Ocean is covered with sea ice. Extent is seen as more accurate because it is less susceptible to melt ponds.
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Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2014 on: June 06, 2016, 07:17:08 AM »
I have no time now to analyse this, but instead of a race to the bottom extent and area increased. As a result 2016 lost over 20% of its lead to 2012.

Update 20160605.

Extent: +38.4 (-405k vs 2015, -672k vs 2014, -1084k vs 2013, -805k vs 2012)
Area: +20.7 (-700k vs 2015, -625k vs 2014, -1119k vs 2013, -714k vs 2012)

The details (in 1000 km2):


Extent:
   Central Arctic Basin       East Siberian Sea              Laptev Sea
                   10.3                    12.0                     0.0
               Kara Sea             Barents Sea           Greenland Sea
                    6.2                    -5.3                    14.1
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -15.7                     0.0                    10.1
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                    4.0                     7.3                    -0.2
             Bering Sea          Sea of Okhotsk            Total Extent
                   -1.5                    -2.9                    38.4

Area:
   Central Arctic Basin       East Siberian Sea              Laptev Sea
                   -1.1                    17.2                    -6.7
               Kara Sea             Barents Sea           Greenland Sea
                   17.6                    -5.7                    15.3
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -14.2                     0.0                     7.6
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                    2.8                     0.9                    -9.1
             Bering Sea          Sea of Okhotsk              Total Area
                   -1.6                    -2.2                    20.7


Andreas T

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Re: Home brew AMSR2 extent & area calculation
« Reply #2015 on: June 06, 2016, 08:41:59 AM »
The increases in the ESS are not surprising, the extensive surface water which showed as open water earlier was expected to drain at some point revealing the ice below. Melting is continuing there but it is reducing thickness rather than opening the sea surface at this point.
Kara I find more surprising, there is "easy ice" which should continue to melt away, whether there was  surface wetness influencing the sensor in the central part we will see when the clouds clear.

Buddy

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Re: Home brew AMSR2 extent & area calculation
« Reply #2016 on: June 06, 2016, 01:19:32 PM »
The plunge is coming.  From the graphic posted by Wipneus.....I can see 7 "points of attack":

1) Hudson Bay
2) Baffin Bay
3) northeastern half of Greenlands coast and inside Svalbard
4) Central northern Russia coast (Kara and Laptev)
5) East Siberian Sea....ice opening nicely
6) Bering Strait
7) Beaufort Sea

And the 5 day forecast max temperature is none too kind for ice.... That Siberian coast is especially toasty.




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seaicesailor

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Re: Home brew AMSR2 extent & area calculation
« Reply #2017 on: June 06, 2016, 02:47:48 PM »
The plunge is coming.  From the graphic posted by Wipneus.....I can see 7 "points of attack":

1) Hudson Bay
2) Baffin Bay
3) northeastern half of Greenlands coast and inside Svalbard
4) Central northern Russia coast (Kara and Laptev)
5) East Siberian Sea....ice opening nicely
6) Bering Strait
7) Beaufort Sea

And the 5 day forecast max temperature is none too kind for ice.... That Siberian coast is especially toasty.

The map of composite maximum temperatures is a bit tricky Buddy. See the one below. The perfect one for Bastardi :)

Richard Rathbone

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Re: Home brew AMSR2 extent & area calculation
« Reply #2018 on: June 06, 2016, 04:58:28 PM »
Thanks Wipneus,

So, melt extent, as Richard said, refers to area of ice with wet surface. But, how can you be sure that it is melt pond and not open water? Is this why you are using thickness maps to include only those areas that have non-zero thickness and some water/melt surface?

Also, is rapid rise in melt extent precursor to rapid drop in area? Because  area is declining rapidly for past three days (more than 320k), and in your graph, melt extent is also increasing.

Wipneus has it right. It is a melt pond index. Its not a good index, and there are clearly large biasses and errors in it, but melt ponds are what it purports to show.

Buddy

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Re: Home brew AMSR2 extent & area calculation
« Reply #2019 on: June 06, 2016, 05:13:51 PM »
Quote
The map of composite maximum temperatures is a bit tricky Buddy. See the one below. The perfect one for Bastardi :)

Joe would photoshop the "minimum" out of your graphic.....and maximum would "magically" appear... ;)
FOX (RT) News....."The Trump Channel.....where truth and journalism are dead."

budmantis

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Re: Home brew AMSR2 extent & area calculation
« Reply #2020 on: June 07, 2016, 12:58:25 AM »
Quote
The map of composite maximum temperatures is a bit tricky Buddy. See the one below. The perfect one for Bastardi :)

Joe would photoshop the "minimum" out of your graphic.....and maximum would "magically" appear... ;)
I think we all tend to bend the facts to fit our own concept of reality, which is why this blog is so helpful.

Hey Buddy, do you mind if I ask the bartender to put my beer on your "bill"?!

Buddy

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Re: Home brew AMSR2 extent & area calculation
« Reply #2021 on: June 07, 2016, 01:11:32 AM »
Quote
I think we all tend to bend the facts to fit our own concept of reality, which is why this blog is so helpful.

I would disagree with you there.  I have had the great opportunity to work around at least 2 people who were very good and "looking for the truth".  They were (and still are) very TRUTHFUL people.....and they always LOOKED for the truth.  They also took what they did VERY SERIOUSLY....but didn't take themselves seriously.  In other words......their "ego's were in check."  I think that is the biggest issue that humans have to deal with (and yes....Donald Trump is PRIME EXAMPLE #1). 


Quote
Hey Buddy, do you mind if I ask the bartender to put my beer on your "bill"?!

Absolutely.....just remember that a Duck's "bill" is right by his mouth....so your beer will be gone "pronto" once it is on my "bill".... :o
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budmantis

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Re: Home brew AMSR2 extent & area calculation
« Reply #2022 on: June 07, 2016, 01:41:58 AM »
I hear what you're saying. I greatly value logic and objectivity and keeping one's ego in check is important. Nevertheless, we are human and we have to be aware of our own personal biases and above all, remain humble. As for the Donald, I take consolation that Republicans are just as concerned with him being president as I am!

By the way, thanks for the beer! I think.

oren

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Re: Home brew AMSR2 extent & area calculation
« Reply #2023 on: June 07, 2016, 07:07:54 AM »
Ahem. You are going way off topic in this very popular thread.

budmantis

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Re: Home brew AMSR2 extent & area calculation
« Reply #2024 on: June 07, 2016, 07:27:40 AM »
Ahem. You are going way off topic in this very popular thread.
Point taken and my apologies, but I was simply responding to Buddy's comments.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2025 on: June 07, 2016, 01:35:47 PM »
A slow day, which lets 2012 come a century nearer by extent) and even two cent's for area.

Update 20160606.

Extent: -14.3 (-367k vs 2015, -628k vs 2014, -989k vs 2013, -684k vs 2012)
Area: -10.9 (-633k vs 2015, -631k vs 2014, -977k vs 2013, -503k vs 2012)

Regionally the extent changes are small as well, Kara (+13k) and Greenland Sea (-15k) changed most.

Regional area saw a big increases in the ESS (+42k) and Kara (+18k).  CAA dropped -21k, Laptev -18k, Hudson -16k and Greenland Sea -15k.

Region of the day is the CAA. The apparent ice concentration has dropped considerably in the Amundsen Gulf, in places below 15%. Also the crack north of the islands can be seen widening.
 

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2026 on: June 07, 2016, 01:42:43 PM »
The uptick in Kara does not seem to be very importnt/lasting.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2027 on: June 07, 2016, 01:48:07 PM »
Two days of slow extent and area changes come with a similar stall in the "ice melt extent" (whatever that means). 2016 is similar to 2014, a little bit above 2013 and 2015, also just an observation. 

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2028 on: June 08, 2016, 07:53:20 AM »
Perhaps the short stall has come to an end. At least the extent figures a dropping again, loosing only 40k of the lead to 2012.

Update 20160607.

Extent: -86.0 (-405k vs 2015, -661k vs 2014, -977k vs 2013, -644k vs 2012)
Area: -30.1 (-590k vs 2015, -565k vs 2014, -769k vs 2013, -470k vs 2012)

A large part of the extent drop happened in the Greenland Sea (-35k). Hudson, CAA and Kara lost extents of -16k, -14k and -14k.
The apparent concentration was still rising in the ESS, gaining +32k in area. Laptev, Greenland Sea and Hudson lost -20k, -20k and -16k.

Todays's region Greenland Sea shows big losses in the south and some gains near the Fram Strait. The ice is getting nearer the north of Svalbard.
 

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2029 on: June 08, 2016, 08:03:12 AM »
The melting is clearly on in the ESS and Laptev regions. The wait now when the fast ice becomes mobile.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2030 on: June 08, 2016, 08:08:41 AM »
And the melting situation. Not a big change, lost some "melt pond extent" in Chukchi and eastern ESS, gained some in Laptev and CAA.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2031 on: June 09, 2016, 08:41:23 AM »
It is risky to draw conclusions from two day's observations, but the end of the stall seems to be there. Not enough to match 2012's nose dive yet (lost 65k of the 2016 lead), but that can still come.

Update 20160608.

Extent: -66.8 (-435k vs 2015, -726k vs 2014, -980k vs 2013, -579k vs 2012)
Area: -140.5 (-623k vs 2015, -654k vs 2014, -791k vs 2013, -441k vs 2012)
 
You will find the updated graphs in the top post


Extent drop is evenly distributed over many regions: ESS, Laptev, Kara, Greenland Sea, Hudson and CAA all declined about -12k.

Area drop is concentrated to a few regions. Hot spots are ESS (-48k), Laptev (-44k) and CAA (-33k).

I am high-lighting the CAA again. First the melting has not moved firmly to the center of the archipelago. Second there is increasing open water (<15% SIC). That could either be real, or excessive amount of melting ponds one the surface. Third melting is starting in the Kane basin, helping to break down the Nares Strait blockage.


Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2032 on: June 09, 2016, 08:48:08 AM »
Animated SIC in Chukchi. The ice edge that was retreating for some time is now expanding again. The fast ice patch on the north Alaskan coast seems to be shattered.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2033 on: June 09, 2016, 08:57:54 AM »
And the surface melting situation as calculated by ADS/Jaxa from AMSR2 microwave measurements.
We see the same as in the sea ice concentration data, melting increased a lot in the last data. 2016 "melt pond extent" has now reached levels eralier than 2013-2015.

oren

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Re: Home brew AMSR2 extent & area calculation
« Reply #2034 on: June 09, 2016, 11:31:25 AM »
Wipneus thanks again for your wonderful work here.
Do you have the last chart (melt vs extent) in a direct link that I can bookmark?

iceman

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Re: Home brew AMSR2 extent & area calculation
« Reply #2035 on: June 09, 2016, 01:29:03 PM »
   ....
 The fast ice patch on the north Alaskan coast seems to be shattered.

For the Isthmus of Neven there may be a kind of see-saw effect this coming week, with ice moving toward the coast on one side of Barrow and away from it on the other, as a succession of lows pass by.

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Re: Home brew AMSR2 extent & area calculation
« Reply #2036 on: June 09, 2016, 04:25:00 PM »
Quote
Animated SIC in Chukchi #2038
That improbable visionary prediction of a splitting ice pack made five days ago by Hycom seems to be coming in on schedule.
« Last Edit: June 09, 2016, 04:30:16 PM by A-Team »

magnamentis

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Re: Home brew AMSR2 extent & area calculation
« Reply #2037 on: June 09, 2016, 06:35:46 PM »
Quote
Animated SIC in Chukchi #2038
That improbable visionary prediction of a splitting ice pack made five days ago by Hycom seems to be coming in on schedule.

i think i mentioned this possibility several weeks ago, just like a gear-wheel that is loosing one tooth after another, sooner or later this thing will become a "polar gyre" with all the loosing of integrity that spiraling matter
generally comes with and this, IF it happens this year, will be due to that extremely week ice cover after this winter. interesting times lay ahead and thanks for you daily contribution, very educational and entertaining.
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Re: Home brew AMSR2 extent & area calculation
« Reply #2038 on: June 09, 2016, 07:39:34 PM »
Could be, A-team and Magna,
We might be looking at the late-July icepack boundary out there on the Pacific side....
Still it could also remain above '12 extent.
Maybe not so much on volume.
Which might get this thing to the '17 black swan-event haunting me since the beginning of the last ENSO-cycle.

oren

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Re: Home brew AMSR2 extent & area calculation
« Reply #2039 on: June 09, 2016, 08:19:10 PM »
Wipneus thanks again for your wonderful work here.
Do you have the last chart (melt vs extent) in a direct link that I can bookmark?

Never mind, found it.
https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/grf/jaxa-amsr2-melt-extent.png

Laurent

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Re: Home brew AMSR2 extent & area calculation
« Reply #2040 on: June 09, 2016, 08:41:42 PM »
I don't know if it is real but I see two bridges one crossing the entire Arctic and an other one from ESS to Barentz. It seem to me that Hycom forecast an other lead in around 84° shown in green ?

http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn_nowcast_anim30d.gif

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2041 on: June 10, 2016, 08:11:51 AM »
The leads with 2012 are receiving heavy blows. Area's lead lost 65k and by extent nearly 160k. That may tell you of course more about 2012 than about the current year.

Update 20160609.

Extent: -46.2 (-465k vs 2015, -741k vs 2014, -976k vs 2013, -420k vs 2012)
Area: -124.8 (-694k vs 2015, -723k vs 2014, -880k vs 2013, -376k vs 2012)
 
You will find the updated graphs in the top post

The only regions with significant extent changes are Kara (-42k) and Baffin (-12k).

By area, its also Kara that leads the pack: -73k. More moderate declines are in CAA, Baffin and ESS, each about -20k. Area increased in the CAB (+16k) and Hudson (+13k).

Today's region must be Kara, top scorer of the day.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2042 on: June 10, 2016, 08:23:28 AM »
Animated ice transport in Greenland Sea, scaled to 6.25 km/pix for size.
 The ice is getting restricted more and more in the north. There the fast ice can be seen cracking, while the pack ice has stopped moving.

The ice within the basin is diverging towards Svalbard, it is one of the reasons extent is currently gaining.


Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2043 on: June 10, 2016, 08:31:55 AM »
And the surface melting images. The "melt pond extent" has increased again.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2044 on: June 10, 2016, 08:49:53 AM »
Wipneus thanks again for your wonderful work here.
Do you have the last chart (melt vs extent) in a direct link that I can bookmark?

Never mind, found it.
https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/grf/jaxa-amsr2-melt-extent.png

Currently I prefer the AMSR2 data from the  Ascending semi orbits. The melting seems to respond earlier and it does not exhibit such unrealistic thick ice when ice in reality is dispersed. So I use this one:
https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/grf/jaxa-amsr2-melt-extentA.png

You can make your own choice of course. This is more research than anything else.

oren

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Re: Home brew AMSR2 extent & area calculation
« Reply #2045 on: June 10, 2016, 08:55:39 AM »
Thanks!

Rob Dekker

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Re: Home brew AMSR2 extent & area calculation
« Reply #2046 on: June 10, 2016, 09:46:49 AM »
Thanks Wipneus,
Just one question : Why is 2012 missing from the "melt extent" graphs ?
This is our planet. This is our time.
Let's not waste either.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #2047 on: June 10, 2016, 09:59:40 AM »
Thanks Wipneus,
Just one question : Why is 2012 missing from the "melt extent" graphs ?

NO DATA.

(AMSR2 did not start delivering data until end of July 2012)

notjonathon

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Re: Home brew AMSR2 extent & area calculation
« Reply #2048 on: June 10, 2016, 03:15:49 PM »
Quote
The ice within the basin is diverging towards Svalbard, it is one of the reasons extent is currently gaining.
And no ice goes beyond the invisible barrier. Either someone built a huge transparent fence to hold it in, or it simply melts in place once it gets there.

epiphyte

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Re: Home brew AMSR2 extent & area calculation
« Reply #2049 on: June 10, 2016, 07:58:09 PM »

The ice within the basin is diverging towards Svalbard, it is one of the reasons extent is currently gaining.

Which it's hardly news to mention is not likely to be a good thing when the chips get counted at the end of the day.