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Author Topic: Home brew AMSR2 extent & area calculation  (Read 1701967 times)

icefest

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Re: Home brew AMSR2 extent & area calculation
« Reply #700 on: March 12, 2014, 02:11:33 AM »
I found something:

"When the surface of water is disturbed by wave action, reflection increases by about 20% at low angles of incident light (ca. 5°) to approximately a 10%  increase at higher angles (5-15°). The difference is small at angles of incidence greater than 15° from the horizontal."

If I understand this correctly that means that the current 'holes' are less of a worry for early heat absorption.

From here: http://books.google.com.au/books?id=y9dvhm_pB58C&pg=PA53&lpg=PA53&dq=%22when+the+surface+of+water+is+disturbed+by+wave+action%22&source=bl&ots=5Jfbz0fkNK&sig=_RIPkJW7LMKjkWpqLcvbxqMt28w&hl=en&sa=X&ei=QbMfU6awIsOKlQXJuIGICQ&ved=0CCkQ6AEwAA#v=onepage&q=%22when%20the%20surface%20of%20water%20is%20disturbed%20by%20wave%20action%22&f=false
Open other end.

werther

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Re: Home brew AMSR2 extent & area calculation
« Reply #701 on: March 12, 2014, 08:48:26 AM »
Hi Icefest,

For me, the early absorption of the sun's energy in these open waters isn't the worrying part ( we discussed that before on the blog, it starts to be a major contributor in May).
It's the indication that the West Spitsbergen current, aided by the right winds, is now capable of keeping a part, about 100K, of the CAB perennially icefree.

DMI reports a stunning amount of red, positive anomalies, around and N of Svalbard. On its mean SST graph +1dC surface water is indicated,
That's at 81dN, right where the Atlantic Water is entering/starting the Arctic Boundary Current.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #702 on: March 12, 2014, 08:52:08 AM »
When the "torch" changes to a "freeze ray"

werther

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Re: Home brew AMSR2 extent & area calculation
« Reply #703 on: March 12, 2014, 08:55:49 AM »
Yes Wipneus,
That's the Northeaster coming in yesterday.

Andreas T

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Re: Home brew AMSR2 extent & area calculation
« Reply #704 on: March 12, 2014, 09:02:14 AM »
Icefest, in the quoted paragraph, angles are measured from horizontalvertical (sorry), so waves at the moment reduce reflection. You can relate this to observations most people will have made when being on a boat. A low sun glistens on the sea surface, a high sun doesn't even if you look down at the sea surface at the angle where you would expect reflection. Of course the big difference between ice and water which makes comparison difficult without measurement from all angles (hemispherical reflection) is that the water surface (and a smooth,clear ice surface) reflects strongly in one direction, nothing elsewhere, whereas a snowsurface reflects (scatters) strongly in all directions, some more so than others.
How significant this is, is not easy to quantify, waves clearly play a role, I just brought this up because I don't expect much warming from a sun which has low intensity in W/m2 because of its low incidence and is reflected at maybe 50%.
« Last Edit: March 12, 2014, 10:32:33 PM by Andreas T »

Chuck Yokota

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Re: Home brew AMSR2 extent & area calculation
« Reply #705 on: March 12, 2014, 02:28:17 PM »
I don't know how significant it is, but Rayleigh scattering can scatter up to 1/4 of the solar flux (making the sky blue).  This diffuse sky radiation would, I would think, have an advantage over low angle direct sunlight in penetrating the ocean surface.  Does anyone have any data on this?

crandles

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Re: Home brew AMSR2 extent & area calculation
« Reply #706 on: March 12, 2014, 02:43:26 PM »
I don't know how significant it is, but Rayleigh scattering can scatter up to 1/4 of the solar flux (making the sky blue).  This diffuse sky radiation would, I would think, have an advantage over low angle direct sunlight in penetrating the ocean surface.  Does anyone have any data on this?

Can provide this diagram:



which probably doesn't help that much.

Phil.

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Re: Home brew AMSR2 extent & area calculation
« Reply #707 on: March 12, 2014, 03:58:59 PM »
I don't know how significant it is, but Rayleigh scattering can scatter up to 1/4 of the solar flux (making the sky blue).  This diffuse sky radiation would, I would think, have an advantage over low angle direct sunlight in penetrating the ocean surface.  Does anyone have any data on this?

Yes diffuse light will increase absorption, hence some light clouds, mist will significantly increase scattering over bigger angles and have an even bigger effect.  Between 25% (blue) and 5% (red) of direct light is Rayleigh scattered.  The scattering isn't uniform in angle the scattered intensity at right angles is about half the maximum value near direct forward and back scattering.  As I pointed out earlier polarization has an effect, this is why sunglasses cut the glare, at about 30º to the horizon all of the p-polarized light is absorbed, the 'glare' is all s-polarized.

Andreas T

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Re: Home brew AMSR2 extent & area calculation
« Reply #708 on: March 12, 2014, 10:42:57 PM »
Chuck, http://weather1.pme.gov.sa/applied-studies/majala9.pdf covers this, showing albedo of the water surface for different sunangles and different atmospheric transmittance, i.e. more or less diffuse light.

epiphyte

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Re: Home brew AMSR2 extent & area calculation
« Reply #709 on: March 13, 2014, 04:05:48 AM »
@crandles... probably this should qualify as a "silly question" - if so, apologies - but going by the diagram you posted above, most of the atmospheric absorption of reflected energy is due to co2 ( in the near IR) and water vapor ( in the far IR). Is it the case that the 100% long-wavelength absorption shown in the diagram is independent of temperature/humidity, or does some proportion of this energy escape back into space when the air is too cold to harbor much water vapor?

The reason I ask is that I'm wondering if arctic far-IR absorption increasing with air temperature (especially close to 0 degrees C) ,  is a positive-feedback mechanism that comes into play with the presence of early melt-season open water?

crandles

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Re: Home brew AMSR2 extent & area calculation
« Reply #710 on: March 13, 2014, 02:41:53 PM »
@crandles... probably this should qualify as a "silly question" - if so, apologies - but going by the diagram you posted above, most of the atmospheric absorption of reflected energy is due to co2 ( in the near IR) and water vapor ( in the far IR). Is it the case that the 100% long-wavelength absorption shown in the diagram is independent of temperature/humidity, or does some proportion of this energy escape back into space when the air is too cold to harbor much water vapor?

The reason I ask is that I'm wondering if arctic far-IR absorption increasing with air temperature (especially close to 0 degrees C) ,  is a positive-feedback mechanism that comes into play with the presence of early melt-season open water?

I think reflected energy is the same wavelength as incoming. So I assume 'reflected' in the first sentence quoted is just a mistake and you are really talking of Earth radiating heat in infra-red.

 I am not certain of the meaning of the pink, black and blue curves but assume these are something like radiation from earth at temperatures appropriate to equator, 45 degrees N or S and pole (maybe tropics, mid latitudes and Arctic/Antarctic circles).

Water vapour absorbs at near and far infra-red wavelengths. The window between these is partly covered by CO2 absorption. The window will be slightly larger for the poles because the atmosphere can hold less water vapour at polar temperature causing less widening of absorption bands with concentration of water vapour. There is also more outgoing radiation at the wavelengths covered by CO2 absorption in the window because Earth is colder at the poles as shown by black versus pink curve.

I am a bit unsure of even the above let alone speculating further.

I assume that virtually all radiation from earth escaping to space will be in or near the window. Is it fully 100% absorbed at longer wavelengths? From surface I would expect it is as near as makes no difference fully 100% absorbed. However, I would think that there must mbe some height from which some small part escapes - this will then be atmosphere emitting to space rather than re-absorption by atmospheredirect from earth. The distribution between wavelengths will then depend on atmosphere temperature rather than surface temperature so where atmosphere is warmer with temperature inversion there may be less radiation at those longer wavelengths. I expect this would only be a small effect near the top of the atmosphere for radiation emission.

There are bound to be others far more expert on this than me.
« Last Edit: March 14, 2014, 12:44:39 PM by crandles »

Andreas T

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Re: Home brew AMSR2 extent & area calculation
« Reply #711 on: March 13, 2014, 06:45:23 PM »
Crandles is right to be cautious about speculating what changed temperatures in the arctic would do to outgoing radiation. Ray Pierrehumbert always points out that what matters for earth's heat budget is top of atmosphere radiation. For different wavelengths that will come from various depths in the atmosphere, even the surface in the windows if the sky is clear. The AVHRR images on the DMI Greenland I have been watching for the first time this winter show increased infrared into space for low clouds. Of course that is only part of the spectrum, but clearly a snow covered surface will drop to a very low temperature and radiate less according to that temperature, the same surface will stay warmer under a cloudy sky, but the clouds, which result from warmer more humid air also radiate outwards and if warmer than the cloudless surface radiate more. The curves shown in the graph (for 210 to 310K) are clearly standardized to a fixed height, absolute intensity is lower for lower temperature. These clouds of course would cool through this and precipitate unless they are maintained by some advection I guess. That is why people build models for this stuff, trying to factor in all these complexities.

epiphyte

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Re: Home brew AMSR2 extent & area calculation
« Reply #712 on: March 14, 2014, 06:10:02 AM »
Wow. I'm tempted to just say "Right then, it's complicated. Get that." and retire into the shadows after all that... but just can't resist wondering if the increased radiation to space under cloudy conditions is due to incoming light which was absorbed by those same clouds, and then partially re-radiated as IR, or from IR which was radiated from the ground, absorbed by the clouds, and then re-radiated to space.

In either case the cloudless, low-humidity alternative (at least when it is cold and ice is present) would seem to be that much of the energy coming in gets reflected, or alternatively absorbed and then radiated, directly,  from the high-albedo ice?

Complexities aside - is there a possible rule-of-thumb here... I.e. "The simpler the path that incoming solar energy has back to space, the less will be retained by the overall system"?

crandles

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Re: Home brew AMSR2 extent & area calculation
« Reply #713 on: March 14, 2014, 12:41:29 PM »
Complexities aside - is there a possible rule-of-thumb here... I.e. "The simpler the path that incoming solar energy has back to space, the less will be retained by the overall system"?

I have wondered if it is reasonably correct to say that

The more complex the path that outgoing radiation takes to get to space, the longer the heat is retained in the system and the higher the surface temperature. So if on average heat is radiated and absorbed say 32 times before it reaches the effective radiating height to be emitted to space while in a pre-industrial climate it only took on average 30 radiations to reach the effective radiating height this might give a sense of how much effect we are having on the atmosphere.

However, experts seem to stress the increase in the effective radiating height.

I don't quite follow why that is stressed rather than average number of times heat is radiated. It seems to me that effective radiating height understates the effect if average radiation distance / height gain is declining due to a more opaque atmosphere. Perhaps it is complicated by the average height gained by heat via convection rather than by radiation.

Chuck Yokota

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Re: Home brew AMSR2 extent & area calculation
« Reply #714 on: March 14, 2014, 03:32:11 PM »
It is not the length of time it takes the infrared energy to get to the top of the atmosphere and escape, but the fact that the energy is absorbed and then re-emitted non-directionally, as likely downward as upward.  This means that in order to get enough energy up to the top of the atmosphere, the surface and lower part of the atmosphere have to heat up (using the downward-emitted energy) to produce enough infrared energy that the part of it that is emitted from the top of the atmosphere balances the incoming solar energy.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #715 on: March 19, 2014, 07:21:06 AM »
Time for an update of the Fram/Barents section. Transport through the Fram is quite active.
The broken sea ice around Svalbard and Frans Jozef land is very movable and some spectacular cracks are appearing in what looked like the consolidated ice pack.

(click the image for an animation)

epiphyte

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Re: Home brew AMSR2 extent & area calculation
« Reply #716 on: March 19, 2014, 08:06:52 AM »
So this is what a record March increase in extent looks like...

In the words of Bilbo Baggins :
... Sort of thin - Stretched - like butter scraped over too much bread.

sofouuk

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Re: Home brew AMSR2 extent & area calculation
« Reply #717 on: March 19, 2014, 02:54:31 PM »
lol

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Re: Home brew AMSR2 extent & area calculation
« Reply #718 on: March 19, 2014, 03:52:15 PM »
Time for an update of the Fram/Barents section. Transport through the Fram is quite active.
The broken sea ice around Svalbard and Frans Jozef land is very movable and some spectacular cracks are appearing in what looked like the consolidated ice pack.

(click the image for an animation)

It sure looks like the transport of ice is not simply through the Fram. The ice also appears to be moving rapidly towards the Atlantic both south and north of Frans Jozef.

Given the fragile state of the Atlantic side of the CAB, if a persistent high were to set up over a cold Greenland, could we see this kind of ice transport through the summer? With the current water temperature anomalies in the Barents and Greenland Seas, this ice would meet a quick demise.

jdallen

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Re: Home brew AMSR2 extent & area calculation
« Reply #719 on: March 19, 2014, 05:53:29 PM »
Time for an update of the Fram/Barents section. Transport through the Fram is quite active.
The broken sea ice around Svalbard and Frans Jozef land is very movable and some spectacular cracks are appearing in what looked like the consolidated ice pack.

(click the image for an animation)

It sure looks like the transport of ice is not simply through the Fram. The ice also appears to be moving rapidly towards the Atlantic both south and north of Frans Jozef.

Given the fragile state of the Atlantic side of the CAB, if a persistent high were to set up over a cold Greenland, could we see this kind of ice transport through the summer? With the current water temperature anomalies in the Barents and Greenland Seas, this ice would meet a quick demise.

I concur with SH. This could be a very significant change in behavior, and a direct consequence of the increased fracturing of the pack.  Combine the movement with the massive increases in heat content of the Barents, and we now have a new ice grinder.
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Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #720 on: March 22, 2014, 08:45:43 AM »
Animation of Laptev/Kara. Mobility of the ice is great, even the "stubborn" ice in Kara in 2013 showing big cracks now.

(click image for animation)

jdallen

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Re: Home brew AMSR2 extent & area calculation
« Reply #721 on: March 23, 2014, 05:44:38 AM »
That looks bad. Note the lowconcentration as well.
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Re: Home brew AMSR2 extent & area calculation
« Reply #722 on: March 24, 2014, 08:05:17 AM »
Melting season start with a fat century drop in extent ( -112k for the "home brew extent" ).

The decline is in the lowest latitude regions (Okhotsk and St Lawrence), other regions: not much change.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #723 on: March 27, 2014, 07:43:08 AM »
Small overall increase today (+6k), with the St.Lawrence the leader (+26k).


Yuha

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Re: Home brew AMSR2 extent & area calculation
« Reply #724 on: March 27, 2014, 07:53:03 PM »
Small overall increase today (+6k), with the St.Lawrence the leader (+26k).

Some of the reported new ice in St. Lawrence appears to be true but some of it is clearly false.
There was a thick cloud cover in the area on the 26th.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #725 on: March 31, 2014, 08:10:22 AM »
Time for a look at the Fram Strait. Transport of sea ice looks strong. The source of the sea ice is not just from the central Arctic, but also from the north of Greenland now. This would imply an increase in export of thick multi-year ice.

Ice has not been so near north Svalbard for a while.  The ice in the Barents Sea is extending still, the cover is probably thin ( I will have a look at SMOS soon) and could vanish as quickly as it came.

(click image for an animation)

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Re: Home brew AMSR2 extent & area calculation
« Reply #726 on: March 31, 2014, 05:35:02 PM »
I have only been visiting here for a couple of years but does that ice along the northeast coast of Greenland look more fragile than usual?

jdallen

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Re: Home brew AMSR2 extent & area calculation
« Reply #727 on: March 31, 2014, 05:37:32 PM »
I have only been visiting here for a couple of years but does that ice along the northeast coast of Greenland look more fragile than usual?
It has become more fragile. There is considerably less land fast ice than two years ago.
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Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #728 on: April 11, 2014, 01:24:46 PM »
The last two weeks in the Laptev and Kara sectors. Maybe not that unusual, but the ice is very mobile: sloshing to an fro. Further to the North Pole, the ice seems to have decided not to wait and is taking the Transpolar Drift Express.

(click that picture, I hope it animates)

Jim Hunt

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Re: Home brew AMSR2 extent & area calculation
« Reply #729 on: April 11, 2014, 01:33:07 PM »
Maybe not that unusual, but the ice is very mobile: sloshing to an fro.

See also the current DMI ice temperature map:

http://GreatWhiteCon.info/resources/arctic-sea-ice-graphs/#DmiTemp

I hope that page is OK with you Wipneus? Please let me know ASAP if you spot any obvious errors or omissions!
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lanevn

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Re: Home brew AMSR2 extent & area calculation
« Reply #730 on: April 11, 2014, 03:46:50 PM »
Can you say where to get AMSR2 map for any day. I can find only for last day, and the day before last.

Jim Hunt

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Re: Home brew AMSR2 extent & area calculation
« Reply #731 on: April 11, 2014, 04:23:05 PM »
Can you say where to get AMSR2 map for any day.

The University of Hamburg flavour are all available via FTP from: ftp://ftp-projects.zmaw.de/seaice/AMSR2/
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #732 on: April 11, 2014, 04:23:59 PM »
You can find the images created by the people of the University of Hamburg here:

ftp://ftp-projects.zmaw.de/seaice/AMSR2/3.125km/

some people like the images that I create (from the NETCDF data files from Uni Hamburg). These (last 5 months or so) are here:

https://sites.google.com/site/apamsr2/home/pngcby32

(reason could be that my files are a lot smaller)

lanevn

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Re: Home brew AMSR2 extent & area calculation
« Reply #733 on: April 11, 2014, 11:50:19 PM »
Thanks

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Re: Home brew AMSR2 extent & area calculation
« Reply #734 on: April 12, 2014, 09:23:04 AM »
A big crack develops through the East Siberian Sea, a (first) sign that the ice may not be that solid here as it appeared to be.

(must click for an animation)

BornFromTheVoid

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Re: Home brew AMSR2 extent & area calculation
« Reply #735 on: April 12, 2014, 10:35:25 AM »
Nice work Wipneus. I suspect that crack is in response to the storm that moved over the New Siberian Islands over the last 36 hours.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

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Re: Home brew AMSR2 extent & area calculation
« Reply #736 on: April 12, 2014, 10:40:55 AM »
Morning all!
Thanks Wipneus. Yes BFTV, it was driven open from Pevek Bay to Kotelnyi Island in about two days, today up to 40 km wide, total surface around 25K. Doesn't refreeze much up to this moment. Must have an influence on CT SIA soon.

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Re: Home brew AMSR2 extent & area calculation
« Reply #737 on: April 15, 2014, 07:49:46 AM »
Time for an updated animation of the Greenland Sea sector. The ice in the Fram Strait continues to move south.
The icepack in the Central Basin seems to make a 90 degrees turn: cracks that run more or less east-west in the beginning are south-north oriented in the last two frames/

(click the picture for that animation)

werther

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Re: Home brew AMSR2 extent & area calculation
« Reply #738 on: April 15, 2014, 01:18:13 PM »
Thanks again, Wipneus!
Must have an influence on CT SIA soon.
Funny, it does.... CT SIA has gone down about 400K in four days. Impressive performance, that Low!

werther

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Re: Home brew AMSR2 extent & area calculation
« Reply #739 on: April 15, 2014, 08:58:40 PM »
A detail 100x130 km in the East Siberian Sea, 15 April:



This enhances what a potent Low can do to the ice in mid April.

The initial stress lead (drawn in red lines) that opened the 11th has lost its shape. The tearing force of wind and tide cracked the adjacent ice. That goes for the pack ice on the left, which is splintering up like it did summer 12 and 13. The fast ice gives in too, breaking in 60 km wide swaths.

This is straight in ‘old’ ice that made it through last summer. The thin arm has been recognizable on ASCAT all winter. It doesn’t look to have gained much strength, nor thickness.
It makes me wonder, what role did this winters’ snowpack play on the ice? The members of Expedition Hope mentioned the snow cover, too (even though they’re 2100 km further on the ice).

Winter power wasn’t great. PIOMAS confirmed on volume. Where‘s this going this season?

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #740 on: April 18, 2014, 08:56:26 AM »
A spectacular decrease today:

Update 20140417.

Extent: -171.3 (-297k vs 2013)
Area: -285.8 (-428k vs 2013)

The usual regions are Okhotsk, Bering and St.Lawrence. Today they get help from Baffin, Greenland Sea and Barents. Especially the ice in the Barents Sea and near New Foundland looks ready for a quick disappearance.

The details (in 1000 km2):


Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                    4.1                     0.7                    -0.5
               Kara Sea             Barents Sea           Greenland Sea
                    0.2                   -25.0                   -16.8
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -54.5                   -12.3                   -25.4
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                   -0.5                     0.1                    -2.0
             Bering Sea          Sea of Okhotsk            Total Extent
                  -13.3                   -26.2                  -171.3

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   -3.0                    -8.5                   -12.0
               Kara Sea             Barents Sea           Greenland Sea
                   -4.3                   -30.8                   -22.5
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                 -113.4                   -13.9                   -33.0
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                    1.0                     0.5                    -5.3
             Bering Sea          Sea of Okhotsk              Total Area
                  -12.9                   -27.8                  -285.8



jdallen

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Re: Home brew AMSR2 extent & area calculation
« Reply #741 on: April 18, 2014, 10:00:05 AM »
That's stunning, Wipneus, even if most of the activity is peripheral.
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Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #742 on: April 19, 2014, 08:15:02 AM »
Another day in the Arctic, another day with un-seasonal massive sea ice losses:

Update 20140418.

Extent: -167.6 (-424k vs 2013)
Area: -213.5 (-613k vs 2013)

As observed yesterday the decrease is strong in Barents and Baffin regions.

Extent:
           Arctic Basin       East Siberian Sea              Laptev Sea
                   -2.6                    -1.0                    -8.4
               Kara Sea             Barents Sea           Greenland Sea
                  -11.0                   -63.5                    -1.5
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -45.2                    -0.7                    -9.0
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                    0.7                     0.7                    -2.0
             Bering Sea          Sea of Okhotsk            Total Extent
                   -2.7                   -21.6                  -167.6

Area:
           Arctic Basin       East Siberian Sea              Laptev Sea
                  -30.8                    -1.5                   -18.2
               Kara Sea             Barents Sea           Greenland Sea
                  -17.2                   -86.5                    10.1
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
                  -45.9                     0.6                    -8.6
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
                    8.7                     1.4                    -0.6
             Bering Sea          Sea of Okhotsk              Total Area
                   -4.6                   -20.5                  -213.5


jdallen

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Re: Home brew AMSR2 extent & area calculation
« Reply #743 on: April 19, 2014, 08:57:03 AM »
Another day in the Arctic, another day with un-seasonal massive sea ice losses:

Update 20140418.

Extent: -167.6 (-424k vs 2013)
Area: -213.5 (-613k vs 2013)


Looks like my "toboggan" has definitely dropped off the edge of the cliff...

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Shared Humanity

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Re: Home brew AMSR2 extent & area calculation
« Reply #744 on: April 19, 2014, 02:51:22 PM »
Given the dramatic drops are occurring in peripheral areas, is it possible we could see significant reductions in these drops over the next several weeks as these peripheral lose their ability to drive such rapid ice loss?

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #745 on: April 19, 2014, 04:20:40 PM »
Given the dramatic drops are occurring in peripheral areas, is it possible we could see significant reductions in these drops over the next several weeks as these peripheral lose their ability to drive such rapid ice loss?

That is what I think too. If you look at the spaghetti of the Jaxa/IJIS graph you see that all lines come close together in the mid of May. The extent at that time signifies little, 2012 is medium and 2004 is one of the lowest, yet in September 2004 has one of the highest ice covers of the bunch and 2012 ...

So unless 2014 is seriously outside of that bottle neck in May, that is probably the time when the real differences only start to become clear.


crandles

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Re: Home brew AMSR2 extent & area calculation
« Reply #746 on: April 19, 2014, 04:29:29 PM »
Given the dramatic drops are occurring in peripheral areas, is it possible we could see significant reductions in these drops over the next several weeks as these peripheral lose their ability to drive such rapid ice loss?

It is possible of course but my impression is of large movement of ice into Barents meaning that some places must be being left thin which will start to melt out earlier than usual. Despite the large movement the ice in Barents look sparse and thin suggesting water has been warm enought to melt a lot of ice.

Similarly not much ice in Bering and Chukchi looks well broken up.

Without modis images for last year perhaps my memory is not good enough?

Yes the mid May lines are usually closer together and maybe that will happen again.

-285k then -212k. Wow! Sounds like CT could get near low edge of 2007 for the time of year.
(IJIS only needs to lose 48k in 3 days (though 2004 was lower than 2007).)

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #747 on: April 19, 2014, 04:34:08 PM »

-285k then -212k. Wow! Sounds like CT could get near low edge of 2007 for the time of year.
(IJIS only needs to lose 48k in 3 days (though 2004 was lower than 2007).)

My estimates for CT changes in the coming days (reported on Sat,Sun,Mon):

-49.7 -211.1 -191.4

crandles

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Re: Home brew AMSR2 extent & area calculation
« Reply #748 on: April 19, 2014, 05:06:13 PM »

-285k then -212k. Wow! Sounds like CT could get near low edge of 2007 for the time of year.
(IJIS only needs to lose 48k in 3 days (though 2004 was lower than 2007).)

My estimates for CT changes in the coming days (reported on Sat,Sun,Mon):

-49.7 -211.1 -191.4

 12.603 -49.7-211.1-191.4 = 12.151

CT day 109 in 2007 = 12.133
just 18k above 2007 seems to agree with my earlier "could get near" :)

(it is a lot nearer than the current day 106 values of 12.603 vs 2007's 12.267 a 336k difference)

Thanks for the numbers Wipneus.

Wipneus

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Re: Home brew AMSR2 extent & area calculation
« Reply #749 on: April 20, 2014, 09:13:21 AM »
The decline continues with a somewhat more believable but still big stride:

Extent: -90.5 (-502k vs 2013)
Area: -142.7 (-773k vs 2013)

The Barents region is still on the decline and is accompanied today by Kara.
As can be seen on the attached animation (you must click for that) the remaining sea ice in the Barents Sea is "not much soup" (Dutch expression, you get the meaning), it may be gone soon depending on the mercy of the weather. The Fram is exporting ice that looks like it is sourced from north of Greenland: probably multi year ice.