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Neven

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Re: 2017 sea ice area and extent data
« Reply #200 on: May 30, 2017, 05:35:23 PM »
Hmmm, I think it's high time I retrieve some of your data, Wip, and look at compactness. What with SIA going low in the ranking, and SIE staying up (relatively speaking).
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Neven

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Re: 2017 sea ice area and extent data
« Reply #201 on: May 30, 2017, 10:46:40 PM »
As there is no more CT SIA, I've downloaded NSIDC extent and area data from Wipneus's site (is nsidc_arc_nt_main.txt the right file for that?) and made the compactness graph below. 2017 is currently second lowest. The lower the percentage, the more dispersed the ice pack is (either because it really is dispersed, or because melt ponds create this impression).
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Jim Williams

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Re: 2017 sea ice area and extent data
« Reply #202 on: May 30, 2017, 10:48:37 PM »
I'm beginning to think I want to know the total linear kilometers of cracks in the ice, and a comparison with previous years.  I think that would tell us a lot, but I haven't a clue how to go about it.

Even defining it could get hard.  Does one just measure the polynya, or do you measure the circumference of each block?

Reggie

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Re: 2017 sea ice area and extent data
« Reply #203 on: May 30, 2017, 11:02:47 PM »
As there is no more CT SIA, I've downloaded NSIDC extent and area data from Wipneus's site (is nsidc_arc_nt_main.txt the right file for that?) and made the compactness graph below. 2017 is currently second lowest. The lower the percentage, the more dispersed the ice pack is (either because it really is dispersed, or because melt ponds create this impression).

Would it be safe to conclude that there is minimal ponding at the present time and the low concentration is mostly due to dispersion?

Neven

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Re: 2017 sea ice area and extent data
« Reply #204 on: May 30, 2017, 11:24:23 PM »
Would it be safe to conclude that there is minimal ponding at the present time and the low concentration is mostly due to dispersion?

I'm not sure, but I don't think it's safe to conclude there is minimal ponding right now, as temps have been going up lately and skies are pretty clear over much of the Arctic.

At the same time things look pretty dispersed on the Atlantic side of the Arctic, especially in the vicinity of Novaya Zemlya:

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StopTheApocalypse

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Re: 2017 sea ice area and extent data
« Reply #205 on: May 30, 2017, 11:37:34 PM »
Related question: is there some index that tracks the "cloudiness" if you will, of the arctic? As a new follower of sea ice, I'm trying to get a handle on what a typical season might look like.

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Re: 2017 sea ice area and extent data
« Reply #206 on: May 30, 2017, 11:52:11 PM »
Would it be safe to conclude that there is minimal ponding at the present time and the low concentration is mostly due to dispersion?
Depends on the location. Take a look on Worldview at Hudson Bay, scroll back and forth over several weeks - the bluish color is now everywhere. Some other areas also became somewhat bluish recently.

magnamentis

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Re: 2017 sea ice area and extent data
« Reply #207 on: May 31, 2017, 12:07:27 AM »
Related question: is there some index that tracks the "cloudiness" if you will, of the arctic? As a new follower of sea ice, I'm trying to get a handle on what a typical season might look like.

i think that "typical" currently is and will be the last that applies. IMO it's even not recommended to rely on typical patterns when it comes to get the bigger picture, it nowadays often leads to false assumptions and the corresponding heated debates (at times LOL)

Reggie

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Re: 2017 sea ice area and extent data
« Reply #208 on: May 31, 2017, 12:26:47 AM »
@ Neven

 "I'm not sure, but I don't think it's safe to conclude there is minimal ponding right now, as temps have been going up lately and skies are pretty clear over much of the Arctic

At the same time things look pretty dispersed on the Atlantic side of the Arctic, especially in the vicinity of Novaya Zemlya:"

@ Oren
 "Depends on the location. Take a look on Worldview at Hudson Bay, scroll back and forth over several weeks - the bluish color is now everywhere. Some other areas also became somewhat bluish recently."

 I agree 100 percent.  My question regarding ponding was poorly phrased and should have excluded the last week or so. The effects of the recent "torching" on the North American side of the Arctic have become obvious on Worldview, particularly in Hudson Bay and Amundsen Gulf.
« Last Edit: May 31, 2017, 12:51:59 AM by Reggie »

Richard Rathbone

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Re: 2017 sea ice area and extent data
« Reply #209 on: June 01, 2017, 05:18:05 PM »
The compactness drop in the NSIDC measure is somewhat larger than the AMSR2 ones. This is not unusual for the time of year and usually gets put down to NSIDC being more sensitive to melt pond appearance.

BornFromTheVoid

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Re: 2017 sea ice area and extent data
« Reply #210 on: June 04, 2017, 05:00:55 PM »
Update for the week to June 3rd

The current 5 day trailing average is on 11,858,000km2 while the 1 day extent is at 11,681,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -672,000km2, an increase from -612,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -179,000km2, an increase from -126,000km2 last week. We're currently 4th lowest on record, up from 7th lowest last week.



The average daily change over the last 7 days was -60.1k/day, compared to the long term average of -51.4k/day, and the 07, 11 and 12 average of -52.5k/day.
The average long term change over the next week is -52.4k/day, with the 07, 11, and 12 average being -75.5k/day.



The extent loss so far this June is the 7th largest on record. To achieve the largest loss, a drop of at least 98.7k/day is required (more than -99.5k/day with single day values), while the smallest loss requires a drop of less than 30.9k/day (less than 26.2k/day with single day values) and an average loss requires a drop of 53.3k/day (50.5k/day with single day values).



The extent loss in May was the 12th smallest on record while the average extent was the 5th smallest on record.




I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Csnavywx

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Re: 2017 sea ice area and extent data
« Reply #211 on: June 04, 2017, 07:08:34 PM »
That looks familiar:



Wipneus

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Re: 2017 sea ice area and extent data
« Reply #212 on: June 09, 2017, 04:44:43 PM »
Both extent and area calculated from NSIDC sea ice concentration have been overtaken by 2012 now.  Extent is 6th lowest, area is at place 5.

extent NH
datum: -06-08
2009-06-08 11.676325
2008-06-08 11.631845
2005-06-08 11.529974
2006-06-08 11.450210
2017-06-08 11.388661
2012-06-08 11.376244
2011-06-08 11.333488
2015-06-08 11.312987
2010-06-08 11.254079
2016-06-08 10.870105

area NH
2014-06-08 9.578384
2008-06-08 9.537484
2015-06-08 9.483089
2006-06-08 9.478056
2011-06-08 9.469125
2017-06-08 9.278360
2007-06-08 9.276071
2010-06-08 9.203477
2012-06-08 9.082649
2016-06-08 8.675202


Wipneus

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Re: 2017 sea ice area and extent data
« Reply #213 on: June 09, 2017, 04:50:32 PM »
In the restricted Arctic Basin, extent has now taken the first (lowest) place.
Area is still within a pack of several recent years. The melt pond induced cliff should come now fast to stay in competition.

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Re: 2017 sea ice area and extent data
« Reply #214 on: June 09, 2017, 05:27:38 PM »
In other words

RoxTheGeologist

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Re: 2017 sea ice area and extent data
« Reply #215 on: June 09, 2017, 05:53:33 PM »

The low area and the sparse number of FDDs would suggest that the ice in the CAB is in very poor shape despite the lack of darkening. If there is a lot of snow on the ice would that keep the reflectivity of the surface up but not have a huge impact on the resilience to bottom melt?

If the snow is concealing thin ice it would also make a precipitous decline more likely once the snow melts.

Wipneus

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Re: 2017 sea ice area and extent data
« Reply #216 on: June 13, 2017, 06:43:04 PM »
Double century drop in area calculated from NSIDC sea ice concentration. Surface melting seems to have begun.

Regional Arctic Sea Ice Extent and Area calculated from NSIDC NASA Team concentration data
Date: 2017-06-12 12:00  Values in 1000 km^2

Extent (value, one day change, anomaly):
   Central Arctic Basin       East Siberian Sea              Laptev Sea
  4435.3   +0.7   -14.8    885.3   +3.8   -43.0    704.8   -4.5    -3.8
               Kara Sea             Barents Sea           Greenland Sea
   727.1  -52.8  -148.1    289.0  +11.6  -238.4    570.7   +0.8   -80.3
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
   765.0  -24.5   -73.5      5.7   -4.2    -0.4   1065.7  +22.6   -42.1
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
   741.9   -0.6   +18.6    429.0   -5.1   -67.4    357.8  -10.0  -173.0
             Bering Sea          Sea of Okhotsk                   Lakes
    21.5   +5.4   -38.1     57.9  -12.3   -29.2    159.8   -4.0   +28.8
          Other regions       Total (ex. lakes)
    12.5   +3.4    +9.5  11069.4  -65.7  -923.9

Area (value, one day change, anomaly):
   Central Arctic Basin       East Siberian Sea              Laptev Sea
  4222.6  -39.0   -28.4    778.2   +4.3   -45.4    590.7  -22.5    +3.5
               Kara Sea             Barents Sea           Greenland Sea
   454.6  -84.7  -257.2    150.6   +9.8  -171.9    382.7   +2.8   -32.8
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
   482.8  -39.0   -96.3      1.4   -0.9    -0.4    591.5  -12.1  -204.7
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
   635.5   -2.9    +9.0    339.7   -8.3   -66.5    295.9   -7.8  -159.5
             Bering Sea          Sea of Okhotsk                   Lakes
     5.9   +0.8   -14.0     19.5   -4.6   -17.9     96.8   -3.7   +27.8
          Other regions       Total (ex. lakes)
     3.8   +0.2    +2.8   8955.3 -203.8 -1079.8



gregcharles

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Re: 2017 sea ice area and extent data
« Reply #217 on: June 13, 2017, 10:59:09 PM »
@Wipneus I'm sure you've answered this before, but what is the basis for the anomalies? Is it an average of the whole satellite record, just recent years, or some other subset?

Meanwhile, Charctic, which I believe is the NSIDC 5-day rolling average extent, shows 2016 with a significant, but diminishing lead over 2011, 2012, 2015, and 2017, which are oddly knotted together in a near dead heat for second.

Wipneus

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Re: 2017 sea ice area and extent data
« Reply #218 on: June 14, 2017, 07:07:19 AM »
@Wipneus I'm sure you've answered this before, but what is the basis for the anomalies? Is it an average of the whole satellite record, just recent years, or some other subset?


Like NSIDC, it is the 1981-2010 mean.

Richard Rathbone

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Re: 2017 sea ice area and extent data
« Reply #219 on: June 14, 2017, 01:50:48 PM »
@Wipneus I'm sure you've answered this before, but what is the basis for the anomalies? Is it an average of the whole satellite record, just recent years, or some other subset?


Like NSIDC, it is the 1981-2010 mean.
Is what used to be the CT area anomaly graph available anywhere? That's what I used to use for judging just how cliffy June is.

 

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Re: 2017 sea ice area and extent data
« Reply #220 on: June 14, 2017, 07:15:26 PM »
Update for the week to June 10th

The current 5 day trailing average is on 11,371,000km2 while the 1 day extent is at 11,234,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -792,000km2, an increase from -672,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -136,000km2, a decrease from -179,000km2 last week. We're currently 4th lowest on record, the same as last week.



The average daily change over the last 7 days was -69.5k/day, compared to the long term average of -52.4k/day, and the 07, 11 and 12 average of -75.5k/day.
The average long term change over the next week is -46.1k/day, with the 07, 11, and 12 average being -82.6k/day.



The extent loss so far this June is the 7th largest on record. To achieve the largest loss, a drop of at least 109.0k/day is required (more than -113.4k/day with single day values), while the smallest loss requires a drop of less than 17.5k/day (less than 11.8k/day with single day values) and an average loss requires a drop of 47.6k/day (45.3k/day with single day values).

I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

magnamentis

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Re: 2017 sea ice area and extent data
« Reply #221 on: June 14, 2017, 08:24:35 PM »
@Wipneus I'm sure you've answered this before, but what is the basis for the anomalies? Is it an average of the whole satellite record, just recent years, or some other subset?


Like NSIDC, it is the 1981-2010 mean.
Is what used to be the CT area anomaly graph available anywhere? That's what I used to use for judging just how cliffy June is.

yes it is, at least if this is what you mean :-)

just scroll down a bit hope it's right

https://sites.google.com/view/pettitclimategraphs

Richard Rathbone

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Re: 2017 sea ice area and extent data
« Reply #222 on: June 15, 2017, 01:12:26 PM »
@Wipneus I'm sure you've answered this before, but what is the basis for the anomalies? Is it an average of the whole satellite record, just recent years, or some other subset?


Like NSIDC, it is the 1981-2010 mean.
Is what used to be the CT area anomaly graph available anywhere? That's what I used to use for judging just how cliffy June is.

yes it is, at least if this is what you mean :-)

just scroll down a bit hope it's right

https://sites.google.com/view/pettitclimategraphs

Those are all extent, not area.

magnamentis

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Re: 2017 sea ice area and extent data
« Reply #223 on: June 15, 2017, 05:12:05 PM »
@Wipneus I'm sure you've answered this before, but what is the basis for the anomalies? Is it an average of the whole satellite record, just recent years, or some other subset?


Like NSIDC, it is the 1981-2010 mean.
Is what used to be the CT area anomaly graph available anywhere? That's what I used to use for judging just how cliffy June is.

yes it is, at least if this is what you mean :-)

just scroll down a bit hope it's right

https://sites.google.com/view/pettitclimategraphs

Those are all extent, not area.

yep, i was fooled by the similarity and just assumed there would be one for area as well, next time i 1st look better before posting, sorry ;)

Steven

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Re: 2017 sea ice area and extent data
« Reply #224 on: June 16, 2017, 07:53:03 PM »
Is what used to be the CT area anomaly graph available anywhere? That's what I used to use for judging just how cliffy June is.

There has been no "June cliff" in June 2017 so far, probably due to a lack of melt ponds.  In the graph below I used Arctic sea ice area data from Wipneus' site  (filename:  nsidc_arc_nt_main.txt), which he calculates from NSIDC gridded sea ice concentration data.  In the graph I used 5-day running means to smooth the data.



magnamentis

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Re: 2017 sea ice area and extent data
« Reply #225 on: June 16, 2017, 08:21:26 PM »
Is what used to be the CT area anomaly graph available anywhere? That's what I used to use for judging just how cliffy June is.

There has been no "June cliff" in June 2017 so far, probably due to a lack of melt ponds.  In the graph below I used Arctic sea ice area data from Wipneus' site  (filename:  nsidc_arc_nt_main.txt), which he calculates from NSIDC gridded sea ice concentration data.  In the graph I used 5-day running means to smooth the data.




this is misleading somehow, june is one of the biggest overal loosers due to steady instead of cliff-like losses in extent and most probably in volume as well. further as wip posted there are significant losses going on in area currently. further i sea only one real cliff that deserves the name in that graph and that is 2012 coming from relatively high.

i just try to understand the motives behind this kind of post. it's obvious that things are in bad shape and primed for the worse, including forecasted weather for the next few days.

if someone is reading that post he/she could get an entirely different picture about what's going on hence IMO, even, what i don't know, the data are correct thus far, they neither represent the current situation nor do they any good to make and keep people alert to the situation.

of course as usual i'm ready to listen and learn what i'm missing, just my 2 cents.

seaicesailor

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Re: 2017 sea ice area and extent data
« Reply #226 on: June 16, 2017, 08:49:18 PM »
Magnamentis there is no reason to distrust the motives behind what simply is a piece of information with no distortion of any kind in a nice plot (thank you Steven).
Now I am surprised that you have mentioned the bad shape of extent. Yes it is.
I partly agree, 2012 dwarves the other cliffs but I guess it is important as well where area ends in second mid of June, ☀️

magnamentis

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Re: 2017 sea ice area and extent data
« Reply #227 on: June 16, 2017, 10:12:07 PM »
Magnamentis there is no reason to distrust the motives behind what simply is a piece of information with no distortion of any kind in a nice plot (thank you Steven).
Now I am surprised that you have mentioned the bad shape of extent. Yes it is.
I partly agree, 2012 dwarves the other cliffs but I guess it is important as well where area ends in second mid of June, ☀️

yes there is no reason and i basically explicitly ASKED for something i overlooked which implies the possibility that i don't get a point. this is fair enough i think and more or less the opposite.

still ihave to consider things come across in that way, probably because of the term "misleading" while i said "THIS" is misleading "IN SOME WAY" and not the person is mislieading.

all good i think and i hope i could clear that out and to i i submit my thanks for making me aware of possible misunderstandings and giving me the opportunity to clarify :-)

BTW to avoid OT i had such a nice private message ready ;) "big smile"

cheers

EDIT: my apologies to steven, nothing personal for sure and no offence meant, mea culpa for any bad wording.
« Last Edit: June 16, 2017, 10:24:41 PM by magnamentis »

Neven

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Re: 2017 sea ice area and extent data
« Reply #228 on: June 16, 2017, 11:34:53 PM »
yes there is no reason and i basically explicitly ASKED for something i overlooked which implies the possibility that i don't get a point. this is fair enough i think and more or less the opposite.

What you're missing is simply melt ponds, or to be more precise, the lack thereof. If there had been a lot of melt ponds (like in 2007 and 2012), area would have fallen off a cliff. And that's because for area melt ponds counts as open water, which is why scientists came up with the 15% threshold (ie extent) to dampen the influence of melt ponds on the numbers.

SIA hasn't fallen off a cliff so far, because there are relatively few melt ponds. Useful information, just like sea ice extent is.
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magnamentis

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Re: 2017 sea ice area and extent data
« Reply #229 on: June 16, 2017, 11:38:45 PM »
yes there is no reason and i basically explicitly ASKED for something i overlooked which implies the possibility that i don't get a point. this is fair enough i think and more or less the opposite.

What you're missing is simply melt ponds, or to be more precise, the lack thereof. If there had been a lot of melt ponds (like in 2007 and 2012), area would have fallen off a cliff. And that's because for area melt ponds counts as open water, which is why scientists came up with the 15% threshold (ie extent) to dampen the influence of melt ponds on the numbers.

SIA hasn't fallen off a cliff so far, because there are relatively few melt ponds. Useful information, just like sea ice extent is.

great, thanks, so melt ponds somehow simulate water which lowers area numbers, just didn't have that present (stupid i) should have know that by now ;)

Neven

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Re: 2017 sea ice area and extent data
« Reply #230 on: June 16, 2017, 11:41:24 PM »
great, thanks, so melt ponds somehow simulate water which lowers area numbers, just didn't have that present (stupid i) should have know that by now ;)

No problem. But keep it mind before calling data useless or misleading again. All data is useful, it's what we do with it that can sometimes be wrong.  :)
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Tor Bejnar

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Re: 2017 sea ice area and extent data
« Reply #231 on: June 17, 2017, 01:17:01 AM »
...
so melt ponds somehow simulate water which lowers area numbers, just didn't have that present (stupid i) should have know that by now ;)
Melt ponds are water!  But because it is water on top of ice floes, it shouldn't count as being ocean water.  But the satellite sensors cannot distinguish between salty (sometimes diluted with fresh water) ocean water and fresh (or brackish) melt pond water.

Before melt-ponding starts in May (and after they freeze over in October), extent:area ratios put numbers to ice floe compression or dispersion.  With melt ponds present, interpreting the ratio is much more complex.  If we could get a numerical sense of the amount of melt ponding, that would be quite cool.  How about pixel counting of the pale blue ice that others report (in cloud-free sections of the Arctic)?  (I sometimes think I see the tint of blue in Worldview images, but mostly I don't get it - I presume it is due to some degree of color blindness on my part.)
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

oren

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Re: 2017 sea ice area and extent data
« Reply #232 on: June 17, 2017, 08:50:27 AM »
How about pixel counting of the pale blue ice that others report (in cloud-free sections of the Arctic)?  (I sometimes think I see the tint of blue in Worldview images, but mostly I don't get it - I presume it is due to some degree of color blindness on my part.)
Tor - first you need to see a good example, and then it becomes easier. Best to look at fast ice, or at zoomed-out images of large areas. Jump a few days at a time.
Here's something I made for you as an example, posted in the Nares thread to avoid going further OT.
http://forum.arctic-sea-ice.net/index.php/topic,176.msg117326.html#msg117326

gerontocrat

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Re: 2017 sea ice area and extent data
« Reply #233 on: June 17, 2017, 12:24:54 PM »
Some more boring numbers (derived from Jaxa). I look at previous years' melt from the latest daily extent to minimum and the average for the last 10 years. The increase in June melt over the last week or two has made a 2nd lowest minimum for 2017 seem much more possible per the table below.

 As At June 16     Melt required     As % of 2007/2016 average
 For 2016 Result     6,089,458    100.7%
 For 2012 Result     6,929,267    114.6%
 For 2007 Result     6,040,983    99.9%

However, there is little change in the large additional percentage melt required for a lower than 2012 minimum. There are now just 90 days melting season remaining of which one would expect only 80 to be significant.

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Re: 2017 sea ice area and extent data
« Reply #234 on: June 17, 2017, 02:21:38 PM »
(I sometimes think I see the tint of blue in Worldview images, but mostly I don't get it - I presume it is due to some degree of color blindness on my part.)

Have you tried using MODIS bands 7-2-1? See for example:

https://go.nasa.gov/2tyHgL7

then compare with June 10th.
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Re: 2017 sea ice area and extent data
« Reply #235 on: June 17, 2017, 05:30:05 PM »
Just for kicks (and because I'm at a temporary stopping place in my dev work), I went ahead and made an NSIDC extent graph somewhat based on Espen's longstanding daily IJIS graphic:



(Anyone interested can find it in the NSIDC section on my graphics page.)

That graph shows just how low extent is at the moment, despite May's slow decrease. But this graph shows it even better, I think:



Tor Bejnar

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Re: 2017 sea ice area and extent data
« Reply #236 on: June 17, 2017, 05:51:52 PM »
(I sometimes think I see the tint of blue in Worldview images, but mostly I don't get it ...)
Have you tried using MODIS bands 7-2-1? See for example: https://go.nasa.gov/2tyHgL7 then compare with June 10th.
'Never viewed selected MODIS bands on my own.  And yes! I definitely see the different blues!
Has anyone attempted to use this data to discern the melt-pond faction of [extent - area]?
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

magnamentis

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Re: 2017 sea ice area and extent data
« Reply #237 on: June 17, 2017, 05:59:03 PM »
great, thanks, so melt ponds somehow simulate water which lowers area numbers, just didn't have that present (stupid i) should have know that by now ;)

No problem. But keep it mind before calling data useless or misleading again. All data is useful, it's what we do with it that can sometimes be wrong.  :)

yeah, useless is a hard word you're right. sometimes i'm writing too much per day and just loose patience or get carried away. always try to do better but at times fail, sorry for that.

cheers and a nice weekend @all

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Re: 2017 sea ice area and extent data
« Reply #238 on: June 17, 2017, 06:30:04 PM »
Re: melt ponds and MODIS.

Just to make sure that everyone is aware that a method is described:

http://icdc.cen.uni-hamburg.de/fileadmin/user_upload/icdc_Dokumente/roeseletal_MeltPondsonArcticSeaIceDeterminedfromMODISSatelliteDatausinganArtificialNeuralNetwork_TC_6_2012.pdf

You will find  how clouds are filtered, the MODIS spectral bands to use and the influence that melt ponds have on the spectral bands.

Caution: the calculation to compute melt pond fraction from color band intensities is done with a neural net. This is completely unneeded, the equations in the paper can be solved directly. That would make redoing this relatively simple, just need some time.

BornFromTheVoid

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Re: 2017 sea ice area and extent data
« Reply #239 on: June 18, 2017, 06:26:58 PM »
Update for the week to June 17th

The current 5 day trailing average is on 10,780,000km2 while the 1 day extent is at 10,605,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -1,061,000km2, an increase from -792,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -150,000km2, an increase from -136,000km2 last week. We're currently 4th lowest on record, the same as last week.



The average daily change over the last 7 days was -84.5k/day, compared to the long term average of -46.1k/day, and the 07, 11 and 12 average of -82.6k/day.
The average long term change over the next week is -59.1k/day, with the 07, 11, and 12 average being -78.1k/day.



The extent loss so far this June is the 2nd largest on record. To achieve the largest loss, a drop of at least 122.1k/day is required (more than -128.3k/day with single day values), while the smallest loss requires an increase of at least 18.7k/day (at least 38.0k/day with single day values) and an average loss requires a drop of 27.8k/day (16.9k/day with single day values).

I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

gerontocrat

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Re: 2017 sea ice area and extent data
« Reply #240 on: June 22, 2017, 02:12:08 PM »
A few days of strongish melting makes quite a difference.

On June 1st 2017 JAXA sea ice extent was 733,000 km2 greater than 2016, and average daily melting (from April 1) was 22% less than 2016.
As at 21st June that difference is down to 157,000 km2 and the average daily melting rate (again from April 1 ) is now only 2% less than 2016.

If melting from now to minimum is at the average of the previous 10 years, the 2017 minimum would tie with 2016 as 2nd lowest at 4.02 million km2. This is a significant change from earlier this month when a 5% above average melt would have been required.
However, to be a new record low (i.e. less than 2102) still requires remaining melting to be 15% above the 10 year average.
This is summarised in the little table below:-

 As At June 21       Melt required     As % av      Resulting Minimum
 For 2016 Result     5,711,402    100.0%    4,017,264
 For 2012 Result     6,551,211    114.8%    3,177,455
 For 2007 Result     5,662,927      99.2%    4,065,739
 Average 7-16 melt     5,708,577                4,020,089

The data illustrates how extraordinary the 2012 melting season was. (A similar story can be told on Greenland's melting in 2012).

There are about 85 days of the melting season left, of which perhaps 75 are significant in an average year. Although the Arctic temperatures are not yet at maximum, peak insolation day was yesterday.
If all other things are equal, a 2nd lowest minimum despite not particularly favourable climatic conditions seems eminently possible. However, not all other things are or will be equal. When will the thickness of the ice in the CAB reduce to below the point of no return?


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"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

magnamentis

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Re: 2017 sea ice area and extent data
« Reply #241 on: June 22, 2017, 07:04:32 PM »
A few days of strongish melting makes quite a difference.

On June 1st 2017 JAXA sea ice extent was 733,000 km2 greater than 2016, and average daily melting (from April 1) was 22% less than 2016.
As at 21st June that difference is down to 157,000 km2 and the average daily melting rate (again from April 1 ) is now only 2% less than 2016.

If melting from now to minimum is at the average of the previous 10 years, the 2017 minimum would tie with 2016 as 2nd lowest at 4.02 million km2. This is a significant change from earlier this month when a 5% above average melt would have been required.
However, to be a new record low (i.e. less than 2102) still requires remaining melting to be 15% above the 10 year average.
This is summarised in the little table below:-

 As At June 21       Melt required     As % av      Resulting Minimum
 For 2016 Result     5,711,402    100.0%    4,017,264
 For 2012 Result     6,551,211    114.8%    3,177,455
 For 2007 Result     5,662,927      99.2%    4,065,739
 Average 7-16 melt     5,708,577                4,020,089

The data illustrates how extraordinary the 2012 melting season was. (A similar story can be told on Greenland's melting in 2012).

There are about 85 days of the melting season left, of which perhaps 75 are significant in an average year. Although the Arctic temperatures are not yet at maximum, peak insolation day was yesterday.
If all other things are equal, a 2nd lowest minimum despite not particularly favourable climatic conditions seems eminently possible. However, not all other things are or will be equal. When will the thickness of the ice in the CAB reduce to below the point of no return?

this only applies if you mean area or extent, in fact we need much less melting  to reach the same amount of ice in september because the amount of ice in cubic-kilometers is much lower than any other year before.

that means that much less energy = melt is needed to reach the "non-goal" so to say.

again, if you refer to area and in parts extent only, your calculation has a point, just that i think we should go slowly away from optical to physical values, extent is optical, it's not real, it just is an impression, while volume is the only value that provides amount of ice = energy needed to melt it.

at the end of the story, once all the ice is gone in a given year, that amount of energy needed to melt the ice is what counts, else it can't happen, while extent numbers can vary so much.

a) example 1 :  5 meters thick and 20% cover
b) example 2 :  2 meters thick and 20% cover
c) example 3 :  5 meters thick and 100% cover etc.

if one's gonna calculate the difference in ice mass between exmaples 1 and 3 and the energy equivalent needed to melt it, we find ourselves in two totally different worlds (scenarious)

this and nothing personal is why i over and over spoil the game of so many hinting at that.
our live energy for a change should be used the most efficient way, more i don't say, else
some will be jumping again LOL

cheers all and enjoy further

Jim Pettit

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Re: 2017 sea ice area and extent data
« Reply #242 on: June 24, 2017, 01:48:08 PM »
Because IJIS will be out of commission until at least Monday, I'll post these NSIDC SIE graphs here for those anyone experiencing the early stages of withdrawal:







Wipneus

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Re: 2017 sea ice area and extent data
« Reply #243 on: June 25, 2017, 08:11:03 AM »
Sea ice extent within the restricted Arctic Basin (you know which regions that are) stays record low in the NSIDC satellite era. Area not so much, it is "only" 5th lowest place or so.
Something more about that in the next post.

Wipneus

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Re: 2017 sea ice area and extent data
« Reply #244 on: June 25, 2017, 08:53:20 AM »
Comparing with other sea ice concentration data, Jaxa (AMSR2 sensor, bootstrap method) and Uni Hamburg (AMSR2 sensor, ASI method) all three agree that in the Arctic Basin extent is at the lowest (for Jaxa and UH that means since 2012) for the day of year.
However with area Jaxa and UH see it very different than NSIDC. They place area at record low too, while NSIDC places it in the middle of the recent-year-pack.

That makes it a little puzzle: I have gotten accustomed to NSIDC area to lead the other two when  making the summer dive. The summer dive is driven in large part by surface melting for which the NSIDC method (the Nasa Team algorithm) is hyper sensitive. So why not this year?

The last piece of the puzzle is Jaxa's melt ratio (calculated from its thickness and melt ice concentration maps) that is definitely showing less relatively melting this year in agreement with NSIDC area (even if I have not calculated the proper Arctic Basin melt ratio yet).

(Uni Hamburg data is only available up to 18th June but it seems we can safely assume that more recent data would change the picture much).

epiphyte

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Re: 2017 sea ice area and extent data
« Reply #245 on: June 25, 2017, 09:34:28 AM »
Comparing with other sea ice concentration data, Jaxa (AMSR2 sensor, bootstrap method) and Uni Hamburg (AMSR2 sensor, ASI method) all three agree that in the Arctic Basin extent is at the lowest (for Jaxa and UH that means since 2012) for the day of year.
However with area Jaxa and UH see it very different than NSIDC. They place area at record low too, while NSIDC places it in the middle of the recent-year-pack.

That makes it a little puzzle: I have gotten accustomed to NSIDC area to lead the other two when  making the summer dive. The summer dive is driven in large part by surface melting for which the NSIDC method (the Nasa Team algorithm) is hyper sensitive. So why not this year?

The last piece of the puzzle is Jaxa's melt ratio (calculated from its thickness and melt ice concentration maps) that is definitely showing less relatively melting this year in agreement with NSIDC area (even if I have not calculated the proper Arctic Basin melt ratio yet).

(Uni Hamburg data is only available up to 18th June but it seems we can safely assume that more recent data would change the picture much).

If I had to sum up the 2016/2017 winter in a sentence it would be" "More snow on top of less ice."
This may show no sign of melt at all until a very short time before it's gone. So it doesn't surprise me that NSIDC is on the high side for area, any more than it's surprising that the May melt pond fraction was low in areas (e.g. Laptev) that are now rapidly disintegrating.

Wipneus

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Re: 2017 sea ice area and extent data
« Reply #246 on: June 25, 2017, 02:23:28 PM »
Area is understanding the situation and responds with a near two and a half century drop.
Chukchi, Beaufort, CAB and the CAA contribute most to the drop in area.


Regional Arctic Sea Ice Extent and Area calculated from NSIDC NASA Team concentration data
Date: 2017-06-24 12:00  Values in 1000 km^2

Extent (value, one day change, anomaly):
   Central Arctic Basin       East Siberian Sea              Laptev Sea
  4456.6   +1.3   +10.6    861.8  +15.2   -59.0    669.9  +17.4   -20.4
               Kara Sea             Barents Sea           Greenland Sea
   678.6   +2.0  -146.3    165.2  -15.9  -242.5    540.4   -6.3   -65.9
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
   620.7  +11.3   -79.8     12.5   +0.5    +6.1    572.3  -77.3  -340.4
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
   728.7   -1.9   +14.2    355.9   +2.0  -118.4    295.1  -17.0  -179.1
             Bering Sea          Sea of Okhotsk                   Lakes
    14.0   -3.7   -28.0     52.8  -17.0   -21.4    209.6  +28.1   +83.5
          Other regions       Total (ex. lakes)
     9.6   -0.4    +6.7  10034.1  -89.7 -1263.4

Area (value, one day change, anomaly):
   Central Arctic Basin       East Siberian Sea              Laptev Sea
  4142.8  -97.9    -1.5    639.5   -0.7  -101.1    434.5   +9.4   -84.5
               Kara Sea             Barents Sea           Greenland Sea
   423.3  -16.0  -194.1     88.8   -1.7  -144.3    332.0   +0.9   -18.8
Baffin/Newfoundland Bay            St. Lawrence              Hudson Bay
   375.9  -20.5   -61.3      4.7   +2.4    +3.0    276.9  -19.6  -287.0
   Canadian Archipelago            Beaufort Sea             Chukchi Sea
   550.9  -34.7   +14.6    184.5  -30.6  -178.6    176.0  -31.7  -196.6
             Bering Sea          Sea of Okhotsk                   Lakes
     3.6   -0.0    -8.5     16.6   -6.2   -10.8    108.3   +4.5   +44.0
          Other regions       Total (ex. lakes)
     3.4   -0.6    +2.4   7653.4 -247.4 -1267.2


Delta map attached: red/blue means the concentration went below/over the 15% cut-off. Reddish/bluish means the concentration decreased/increased by more than 7%.

BornFromTheVoid

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Re: 2017 sea ice area and extent data
« Reply #247 on: June 25, 2017, 04:07:24 PM »
Update for the week to June 24th

The current 5 day trailing average is on 10,214,000km2 while the 1 day extent is at 10,034,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -1,213,000km2, an increase from -1,061,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at -169,000km2, an increase from -150,000km2 last week. We're currently 4th lowest on record, the same as last week.



The average daily change over the last 7 days was -80.9k/day, compared to the long term average of -59.1k/day, and the 07, 11 and 12 average of -78.1k/day.
The average long term change over the next week is -69.4k/day, with the 07, 11, and 12 average being -100.2k/day.



The extent loss so far this June is the 4th largest on record. To achieve the largest loss, a drop of at least 170.1k/day is required (more than -210.2k/day with single day values), while the smallest loss requires an increase of at least 134.8k/day (at least 247.1k/day with single day values) and an average loss requires an increase of 32.4k/day (96.2k/day with single day values).

I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

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Re: 2017 sea ice area and extent data
« Reply #248 on: June 25, 2017, 04:19:39 PM »
Quote
The average long term change over the next week is -69.4k/day, with the 07, 11, and 12 average being -100.2k/day.
Wow, the average of three different (yes, big) years over this next week is a century per day!
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

Shared Humanity

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Re: 2017 sea ice area and extent data
« Reply #249 on: June 25, 2017, 04:35:02 PM »
Quote
The average long term change over the next week is -69.4k/day, with the 07, 11, and 12 average being -100.2k/day.
Wow, the average of three different (yes, big) years over this next week is a century per day!

Tough acts to follow.