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Wipneus

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Re: 2016 sea ice area and extent data
« Reply #800 on: August 30, 2016, 03:49:42 PM »
Here is the shadow CT-area report based on calibrated F18 NSIDC sea ice concentration data:

day  CT-date       NH               SH                Global
Mon 2016.6548  -52.5  2.756159  +81.7 14.851282   +29.2 17.607441
Tue 2016.6575  -57.5  2.698689  +53.3 14.904628    -4.1 17.603317
Wed 2016.6603  +27.5  2.726165  +41.6 14.946271   +69.1 17.672436
Thu 2016.6630  +44.4  2.770598  -41.4 14.904863    +3.0 17.675461


It is the CAB that does it: +43k.

Shadow NSIDC extent is 4.5471 dropping -159.6k. CAB (-89k) leads, ESS (-17k) is second. Other regions (Laptev, Kara, Greenland Sea, Baffin) contribute smaller portions.

There is of course an attached delta map. Studying it and comparing with previous day you may find that there is more than a simple un-reappearing act in the left Wrangel arm.

seaicesailor

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Re: 2016 sea ice area and extent data
« Reply #801 on: August 30, 2016, 04:27:56 PM »
...
On topic, recently, there's increasing interest towards the values of extent than simply area, among the more juvenile responders that disregarded extent in the past weeks. It is maybe the time of year when extent is switched from being less relevant to most relevant. Beat me if there was a real explanation behind, or only because it will keep falling and it is more suitable to make a goal. In reality, there are more accuracy of area now that there are no melt ponds. Extent is always as good except when more and more is closer to 15% in concentration hence the disgusting flash-unflash effects. In summary, if any there is a greater precision, if not acuracy, of area these days. However it does not feel certain goals. Lurker long-time question.

Yeah, you'll find today the trending number here is -159.6k whereas the +44.4k will be ignored.
On the contrary, at Wipneus' thread the extent change will be forgotten (...and the area too being a change so meager).

Actually extent is very accurate but very imprecise nowadays.
Area is accurate (for what it means) and more precise these days. No better, no worse. Each one reflects something different.

Iceismylife

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Re: 2016 sea ice area and extent data
« Reply #802 on: August 30, 2016, 05:16:37 PM »
I think that portends additional century drops as the clouds clear again. There is no way those gains are possible given what's ongoing over the Arctic.
Why do you leap to saying that the gain is inaccurate, rather than the preceding loss being inaccurate?  Both options are perfectly plausible.
Why I would say that is open ocean without cloud cover doesn't get counted as ice, but clouds get counted as ice sometimes.  Until we hit air temps conducive to freezing snow will melt back off.  So no real gain but real losses.

Peter Ellis

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Re: 2016 sea ice area and extent data
« Reply #803 on: August 30, 2016, 05:44:38 PM »
I think that portends additional century drops as the clouds clear again. There is no way those gains are possible given what's ongoing over the Arctic.
Why do you leap to saying that the gain is inaccurate, rather than the preceding loss being inaccurate?  Both options are perfectly plausible.
Why I would say that is open ocean without cloud cover doesn't get counted as ice, but clouds get counted as ice sometimes.  Until we hit air temps conducive to freezing snow will melt back off.  So no real gain but real losses.

But also... wet ice (e.g. melt ponds, after rain or after waves wash over it during a storm) doesn't get counted as ice, but reappears once the surface water drains away.

Both of these are plausible - so why assume that the losses are accurate and the gains are illusory, when it could as easily be vice versa?

oren

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Re: 2016 sea ice area and extent data
« Reply #804 on: August 30, 2016, 06:35:05 PM »
@ Neven, I will try to do so

Sterks, congratulations on deciding to unlurk. And bear in mind Neven's comment was directed not towards you, but towards abbotisgone who is notorious on quoting very long comments just to add a short sentence.

budmantis

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Re: 2016 sea ice area and extent data
« Reply #805 on: August 30, 2016, 08:55:06 PM »
I agree with Oren. Neven's comment was directed to Abbott and rightly so.

Iceismylife

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Re: 2016 sea ice area and extent data
« Reply #806 on: August 30, 2016, 09:21:44 PM »
I think that portends additional century drops as the clouds clear again. There is no way those gains are possible given what's ongoing over the Arctic.
Why do you leap to saying that the gain is inaccurate, rather than the preceding loss being inaccurate?  Both options are perfectly plausible.
Why I would say that is open ocean without cloud cover doesn't get counted as ice, but clouds get counted as ice sometimes.  Until we hit air temps conducive to freezing snow will melt back off.  So no real gain but real losses.

But also... wet ice (e.g. melt ponds, after rain or after waves wash over it during a storm) doesn't get counted as ice, but reappears once the surface water drains away.

Both of these are plausible - so why assume that the losses are accurate and the gains are illusory, when it could as easily be vice versa?
Largely in the state the ice is in, no ponds, the ice is to small and broken.  How much water will mask the ice signature?  If the air temp is +0C then the surface should be wet From melting and in the summer months it should all be wet at least parts of the time.

Edit=Did a bit of thinking and reading. It you have an increase in area or extent this time of year you can chalk it up to clouds and ice drying out.  A decrease is more believable as melt rather than getting wet. IMO  But a decrease after an increase should be chalked up to the reverse rather than melt up to a reasonable dip in the trend line.
« Last Edit: August 30, 2016, 09:34:51 PM by Iceismylife »

BornFromTheVoid

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Re: 2016 sea ice area and extent data
« Reply #807 on: August 31, 2016, 03:53:28 PM »
With a drop of 78k on the single day NSIDC extent, we're just 136k and 128k off the 2011 and 2015 minimum respectively, with the 2007 min now 440k away.

5 day extent has now dropped below the 2010 min, and is just 8.4k off the 2008 min.

Wipneus

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Re: 2016 sea ice area and extent data
« Reply #808 on: August 31, 2016, 06:10:16 PM »
Here is the shadow CT-area report based on calibrated F18 NSIDC sea ice concentration data:

day  CT-date       NH               SH                Global
Tue 2016.6575  -57.5  2.698689  +53.3 14.904628    -4.1 17.603317
Wed 2016.6603  +27.5  2.726165  +41.6 14.946271   +69.1 17.672436
Thu 2016.6630  +44.5  2.770680  -41.3 14.904934    +3.2 17.675614
Fri 2016.6658  -52.5  2.718187 -105.3 14.799635  -157.8 17.517822


Declines in the CAB (-22k) and Laptev (-18k).

Shadow NSIDC extent is now 4.4687 dropping  -78.4k. The CAB does -48k and Laptev -27k.

The delta map has been attached.

Wipneus

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Re: 2016 sea ice area and extent data
« Reply #809 on: September 01, 2016, 04:35:48 PM »
Here is the shadow CT-area report based on calibrated F18 NSIDC sea ice concentration data:

day  CT-date       NH               SH                Global
Wed 2016.6603  +27.5  2.726165  +41.6 14.946271   +69.1 17.672436
Thu 2016.6630  +44.5  2.770680  -41.3 14.904934    +3.2 17.675614
Fri 2016.6658  -52.5  2.718149 -105.5 14.799451  -158.0 17.517600
Sat 2016.6685  -15.1  2.703045 -121.9 14.677568  -137.0 17.380613

Mostly the CAB: -25k.

Shadow NSIDC extent is 4.3875 dropping -81.1k. The CAB did -46k and Laptev declined -28k.

The attached delta image will answer all your questions about the growth and decline of arms and bites

Sourabh

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Re: 2016 sea ice area and extent data
« Reply #810 on: September 01, 2016, 04:38:49 PM »
BFV,

If possible, could you also show NSIDC comparison in form of chart as you do for IJIS extent? 

Thanks,
Sourabh

seaicesailor

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Re: 2016 sea ice area and extent data
« Reply #811 on: September 01, 2016, 04:56:52 PM »
Half a million gone in the last week of August, including the hiccup. If next week it dropped just half, the extent would reach the 4.1 mark, nearly the 2007 minimum (single day).

BornFromTheVoid

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Re: 2016 sea ice area and extent data
« Reply #812 on: September 01, 2016, 05:38:53 PM »
BFV,

If possible, could you also show NSIDC comparison in form of chart as you do for IJIS extent? 

Thanks,
Sourabh

Sure. 5 day average or single day values? All years or just from 2007?

Sourabh

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Re: 2016 sea ice area and extent data
« Reply #813 on: September 01, 2016, 05:56:01 PM »
BFV,

If possible, could you also show NSIDC comparison in form of chart as you do for IJIS extent? 

Thanks,
Sourabh

Sure. 5 day average or single day values? All years or just from 2007?

Thanks.

From 2007 only. I think we already passed the minimum value of other years. Use whatever numbers (5 days or single day) you have used for comparison in previous posts in same thread.

BornFromTheVoid

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Re: 2016 sea ice area and extent data
« Reply #814 on: September 01, 2016, 07:19:17 PM »

Thanks.

From 2007 only. I think we already passed the minimum value of other years. Use whatever numbers (5 days or single day) you have used for comparison in previous posts in same thread.

Here they are.

Single day values


5 day trailing average

BornFromTheVoid

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Re: 2016 sea ice area and extent data
« Reply #815 on: September 02, 2016, 03:52:10 PM »
Another big drop in the single day NSIDC extent, -110k. This takes us below the minima of 2015 and 2011, securing at least the 3rd lowest minimum on record. We're also just 131k off the 2007 minimum.


Wipneus

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Re: 2016 sea ice area and extent data
« Reply #816 on: September 02, 2016, 05:30:20 PM »
Here is the shadow CT-area report based on calibrated F18 NSIDC sea ice concentration data:

day  CT-date       NH               SH                Global
Thu 2016.6630  +44.5  2.770680  -41.3 14.904934    +3.2 17.675614
Fri 2016.6658  -52.5  2.718149 -105.5 14.799451  -158.0 17.517600
Sat 2016.6685  -14.9  2.703242 -122.0 14.677490  -136.9 17.380732
Sun 2016.6712  -99.5  2.603781  -30.0 14.647455  -129.5 17.251236


The CAB lost -86k. Small losses in many other regions due to the first-of-the-month effect.

Shadow NSIDC extent is 4.2779 loosing -109.6k. Laptev leads with -36k, followed by CAB (-34k), Hudson (-31k) and Okhotsk (-16k). It is clear that the first-of-the-month effect has affected extent much more, even losses are reported in the Sea of Japan and the Gulf of Alaska (-10k).

You can spot these changes and more in the attached delta map.

I will have to take a few days break from these daily "shadow" CT-area and NSIDC extent reports for now (moving to a new home). If all goes well, I should be back online on Tuesday.

Lord M Vader

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Re: 2016 sea ice area and extent data
« Reply #817 on: September 02, 2016, 05:47:21 PM »
Interesting to see a (almost) century break by sunday. Should be a record or am I wrong? Also intersting to see that Antarctica will see two century breaks as they haven't reached their maxima yet.

seaicesailor

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Re: 2016 sea ice area and extent data
« Reply #818 on: September 02, 2016, 06:01:46 PM »
The UK-reminiscent shape of the Wrangel ice seems to be resisting the stress test. Was expecting reds where blues show. Today MODIS view is clear, shows some solid areas... We'll see.

Lord M Vader

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Re: 2016 sea ice area and extent data
« Reply #819 on: September 02, 2016, 06:41:11 PM »
12z op GFS run indicates that a moderate intensive cyclone with MSLP at 976 hpa will roar over the CAB by thursday-friday next week. If that forecast is to hold, then Wrangels arm should face hard times. In any case, Canadas ice service is producing daily ice charts over the North Pole as well for Wrangels arm if I'm not mistaken.

//LMV

RoxTheGeologist

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Re: 2016 sea ice area and extent data
« Reply #820 on: September 02, 2016, 08:02:00 PM »

I will have to take a few days break from these daily "shadow" CT-area and NSIDC extent reports for now (moving to a new home). If all goes well, I should be back online on Tuesday.

Good luck with your move to a new home! I think we will also miss your analysis.

Lord M Vader

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Re: 2016 sea ice area and extent data
« Reply #821 on: September 02, 2016, 08:10:39 PM »
Good luck Wipneus! :) Big or small move? Have a great weekend anyways and thanks for all the job you are doing to the forum! :)

Neven

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Re: 2016 sea ice area and extent data
« Reply #822 on: September 02, 2016, 08:39:00 PM »
Interesting to see a (almost) century break by sunday. Should be a record or am I wrong? Also intersting to see that Antarctica will see two century breaks as they haven't reached their maxima yet.

Last year saw a drop of 107K on September 2nd, LMV.
Il faut comparer, comparer, comparer, et cultiver notre jardin

Lord M Vader

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Re: 2016 sea ice area and extent data
« Reply #823 on: September 02, 2016, 08:50:08 PM »
Thanks Neven! :)

Juan C. García

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Re: 2016 sea ice area and extent data
« Reply #824 on: September 02, 2016, 08:55:00 PM »
I had not noticed before that NSIDC publishes the Total Monthly Extent and the tendency graph of the last month, as early as today (September 2nd).
http://nsidc.org/data/seaice_index/

I take this opportunity to wish Wipneus the best in his move to a new home!
Good luck Wipneus! :) Big or small move? Have a great weekend anyways and thanks for all the job you are doing to the forum! :)
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Neven

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Re: 2016 sea ice area and extent data
« Reply #825 on: September 02, 2016, 09:53:50 PM »
Good luck, Wip! Don't drop the computer!  ;)
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Jim Pettit

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Re: 2016 sea ice area and extent data
« Reply #826 on: September 02, 2016, 10:00:56 PM »
Interesting to see a (almost) century break by sunday. Should be a record or am I wrong? Also intersting to see that Antarctica will see two century breaks as they haven't reached their maxima yet.

Last year saw a drop of 107K on September 2nd, LMV.

Last year also saw an SIA drop of 102k on October 3rd. But even so, area CBs in September are fairly rare; there have been only four in the past 20 years, including the one Neven mentioned.

BornFromTheVoid

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Re: 2016 sea ice area and extent data
« Reply #827 on: September 03, 2016, 02:31:57 PM »
Another large drop in the daily NSIDC extent, down 67k, and now just 64k off the 2007 minimum.

Interestingly, after setting the record for the latest date to see a 100k drop using the 5 days average during the week, the drop on Sept 2nd (99.2k) is now the largest September drop on record.
Again with the 5 day average, we have now dropped below the 2015 minimum and are just 34.4k off the 2011 minimum.

Rob Dekker

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Re: 2016 sea ice area and extent data
« Reply #828 on: September 04, 2016, 09:35:39 AM »
When I suggested a week ago that (based on "area" development) big extent drops were coming for the week ahead, I did not expect these drops would be THIS large.
And I am afraid we are not done yet.
Area is still running at (apart from 2012) record low, with much of the low concentration ice in lower latitude (the (broken) Wrangel arm and the Laptev arm).
Also temperature forecasts suggest higher than normal temps over the CAB over the week to come, so we will not yet see any significant freezing happening.

So I think 2016 still has a lot of potential to dip lower still, and will hit "minimum" late this year.
« Last Edit: September 04, 2016, 09:53:34 AM by Rob Dekker »
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Bill Fothergill

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Re: 2016 sea ice area and extent data
« Reply #829 on: September 04, 2016, 12:30:39 PM »
On the other hand...

When I refreshed my DMI tab this morning, everything from about mid-July onward has been hiked upwards by several hundred thousand square kilometres.
http://ocean.dmi.dk/arctic/icecover.uk.php

Does anyone (John C perhaps) know why this has happened?


Meanwhile, on the other, other hand...

The University of Bremen AMSR2 plot appears to have taken a scarcely credible nosedive.
http://www.iup.uni-bremen.de:8084/amsr2/extent_n_running_mean_amsr2_regular.png

oren

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Re: 2016 sea ice area and extent data
« Reply #830 on: September 04, 2016, 01:24:42 PM »
The University of Bremen AMSR2 plot appears to have taken a scarcely credible nosedive.
It's an error. It was mentioned in the IJIS thread.

Bill Fothergill

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Re: 2016 sea ice area and extent data
« Reply #831 on: September 04, 2016, 01:35:48 PM »
The University of Bremen AMSR2 plot appears to have taken a scarcely credible nosedive.
It's an error.

As a matter of course, I generally ignore any "one day wonders". The only reason I mentioned it today was as a counterpoint to DMI having simultaneously shifted about 6 weeks worth of data in an upward direction.

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Re: 2016 sea ice area and extent data
« Reply #832 on: September 04, 2016, 02:08:29 PM »
When I refreshed my DMI tab this morning, everything from about mid-July onward has been hiked upwards by several hundred thousand square kilometres

It does look rather more realistic now though?

http://GreatWhiteCon.info/2016/09/the-2016-arctic-sea-ice-metric-minima/#comment-215522

Hamburg Uni AMSR2 still looks sensible, though they may have filled in the gaps with data from the previous day?
« Last Edit: September 04, 2016, 04:12:11 PM by Jim Hunt »
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seaicesailor

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Re: 2016 sea ice area and extent data
« Reply #833 on: September 04, 2016, 03:54:56 PM »
There has been a nice 50k uptick of the daily NSIDC extent but as JC Garcia explained yesterday, the low-pass-filtered NSIDC number is now below 2011 minimum, at ~4.3 M.km2. Will be difficult this number does not reach 4.1 M km2 given the inertia it brings behind and possible drops still ahead.

Nightvid Cole

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Re: 2016 sea ice area and extent data
« Reply #834 on: September 04, 2016, 04:02:58 PM »

The University of Bremen AMSR2 plot appears to have taken a scarcely credible nosedive.
http://www.iup.uni-bremen.de:8084/amsr2/extent_n_running_mean_amsr2_regular.png

A large sector has gone missing from the map as well.


BornFromTheVoid

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Re: 2016 sea ice area and extent data
« Reply #835 on: September 04, 2016, 05:22:13 PM »
Update for the week to September 3rd

The current 5 day trailing average is on 4,322,000km2 while the 1 day extent is at 4,263,000km2.

(All the following data is based on a trailing 5 day average)
The daily anomaly (compared to 81-10) is at -2,136,000km2, an increase from -1,930,000km2 last week. The anomaly compared to the 07, 11 and 12 average is at +212,000km2, an increase from +85,000km2 last week. We're currently 2nd lowest on record, the same as last week.



The average daily change over the last 7 days was -68.8k/day, compared to the long term average of -38.9k/day, and the 07, 11 and 12 average of -45.2k/day.
The average long term change over the next week is -23.1k/day, with the 07, 11, and 12 average being -28.5k/day.



The extent change so far this September is the most negative on record. To achieve the largest monthly loss, a drop of at least 5.9k/day is required (requiring -3.9k/day with with single day values), while the largest gain requires an increase of at least 34.1k/day (+39.1k/day with single day values) and an average change requires an increase of 12.7k/day (increase of 16.1k/day with single day values).



The extent loss in August was the 3rd largest on record, while the average extent was the 3rd lowest on record.



A-Team

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Re: 2016 sea ice area and extent data
« Reply #836 on: September 04, 2016, 08:48:42 PM »
The Sept 4th Terra provides the clearest view we've had in a long while of the north pole to Barents sea. It's compared below with the Sept 3rd AMSR2 3.1k (latest available) at the same scale as well as a five day animation of sea ice concentration/motion change. The first two images need a click to display at WorldView resolution.

Because of swath timing differences, clouds, ice movement, compaction, flashing, atmospheric artifacts, and processing algorithms, the two images are not strictly synchronous so not fully comparable overlays. Comparison restricted to the best wedge is the easiest to evaluate, 2nd animation. Accurate placement of critical latitudes and pole holes onto WV is explained over at #2775 and prior on Home Brew.
« Last Edit: September 06, 2016, 01:23:37 AM by A-Team »

prokaryotes

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Re: 2016 sea ice area and extent data
« Reply #837 on: September 05, 2016, 12:39:18 PM »
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Nightvid Cole

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Re: 2016 sea ice area and extent data
« Reply #838 on: September 05, 2016, 02:45:15 PM »
Can someone elaborate on this



http://www.iup.uni-bremen.de:8084/amsr2/extent_n_running_mean_amsr2_regular.png

This would actually seem to agree with IJIS that we are at the second lowest on record for extent, after 2012 which is mysteriously omitted from the graph...

Jim Hunt

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Re: 2016 sea ice area and extent data
« Reply #839 on: September 05, 2016, 04:43:57 PM »
This would actually seem to agree with IJIS that we are at the second lowest on record for extent, after 2012 which is mysteriously omitted from the graph...

There is another version of that graph:
« Last Edit: September 05, 2016, 06:43:28 PM by Jim Hunt »
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Lord M Vader

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Re: 2016 sea ice area and extent data
« Reply #840 on: September 05, 2016, 05:39:52 PM »
IMO, it's a shame that 2007 and 2012 aren't in the same graph as both are significant years to the SIE.

NSIDC is closing the gap to 2007, now down to 4,28 Mn km2. 2007 minimum saw 4,15 Mn km2 so 130K to go which shouldn't be too impossible.

Shared Humanity

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Re: 2016 sea ice area and extent data
« Reply #841 on: September 05, 2016, 07:24:01 PM »
The Sept 4th Terra provides the clearest view we've had in a long while of the north pole to Barents sea. It's compared below with the Sept 3rd AMSR2 3.1k (latest available) at the same scale as well as a five day animation of sea ice concentration/motion change. The first two images need a click to display at WorldView resolution.

Because of swath timing differences, clouds, ice movement, compaction, flashing, atmospheric artifacts, and processing algorithms, the two images are not exact overlays. Comparison restricted to the best wedge is the easiest to evaluate, 2nd animation. Accurate placement of critical latitudes and pole holes onto WV is explained over at #2775 and prior on Home Brew.

The comparison of terra visible and AMSR2 makes a clear argument for the increasing importance of visible images. In the past, high concentrations seen on AMSR2 were typically populated with very large floes of MYI, interspersed with smaller floes. The high concentrations are now more likely composed of relatively small floes, mixed in with thousands of tiny floes, highly mobile and susceptible to melt. Extent and Area are still important metrics but it is this entirely novel mechanical state of the ice that is eye opening and frightening.

Acts5v29

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Re: 2016 sea ice area and extent data
« Reply #842 on: September 05, 2016, 11:31:46 PM »
We will have an "ice-free summer" at the pole in a matter of a few years.   So as a matter of interest, what will be the focus thereafter?  Whatever it is, shouldn't we be looking at it in earnest now?

Michael J

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Re: 2016 sea ice area and extent data
« Reply #843 on: September 06, 2016, 02:39:33 AM »
We will have an "ice-free summer" at the pole in a matter of a few years.   So as a matter of interest, what will be the focus thereafter?  Whatever it is, shouldn't we be looking at it in earnest now?

I think that the first time we hit it, it will be an outlier like 2012 and 2007 were.  We could then have many years before the second year. I think that this is the reason that IPCC changed their definition of ice-free to being 5years of minimums below 1m square km instead of the first year reached.

However, there could be feedback mechanisms both positive and negative that could change this.


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Re: 2016 sea ice area and extent data
« Reply #844 on: September 06, 2016, 04:40:18 AM »
We will have an "ice-free summer" at the pole in a matter of a few years.   So as a matter of interest, what will be the focus thereafter?  Whatever it is, shouldn't we be looking at it in earnest now?

As I understand it, we are seeing 'the focus thereafter' to a degree already.  While it may be impossible to assign any particular feature of the global climate today to increased extent of water surface near the North Pole, there will be effects relating to heat transfer, jet stream location and all other mischief which this is giving rise to. 

Note that there is no lag in the reaction of the system to these physical and chemical changes.  If situation x demands a response by change to climate y, it will happen forthwith.  It doesn't need a committee meeting and a white paper to decide to act.

The ice-free day, month or year will not be a singular event which suddenly precipitates these changes, they will travel hand in hand with the changing ice conditions as a cause-effect loop from yesterday until that sad day.  It is unlikely that these changes will be for the benefit of humankind.  And they will continue to get worse, until... 

But the eventual melting of the last bit of floating ice in the Arctic will be a landmark moment.  Human's being what they are, the last ice block will probably be surrounded by fossil-fuel burning boats carrying the international Press Corp, plus government representatives, Greenpeace and Uncle Tom Cobley and All.  The irony of their presence being utterly lost on most of them.

Juan C. García

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Re: 2016 sea ice area and extent data
« Reply #845 on: September 06, 2016, 05:10:02 AM »
Bremen is showing less extent than any other source. I would like to know why, but the difference between 2016 and 2011 is significant. We should remember that -according to Bremen- 2011 went lower than 2007. So 2007 is 4th lowest on record, following 2012, 2016 and 2011.

Edit: From NSIDC:
Quote
Other sea ice data are available from other data providers, using different satellite sensors and sea ice algorithms. For example, data from the University of Bremen indicate that sea ice extent from their algorithm fell below the 2007 minimum. They employ an algorithm that uses high resolution information from the JAXA AMSR-E sensor on the NASA Aqua satellite. This resolution allows small ice and open water features to be detected that are not observed by other products. This year the ice cover is more dispersed than 2007 with many of these small open water areas within the ice pack. While the University of Bremen and other data may show slightly different numbers, all of the data agree that Arctic sea ice is continuing its long-term decline.
http://nsidc.org/arcticseaicenews/2011/09/
« Last Edit: September 06, 2016, 05:28:02 AM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Adam Ash

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Re: 2016 sea ice area and extent data
« Reply #846 on: September 06, 2016, 05:51:13 AM »
The CAA is like a vacuum cleaner!  The last time there was virtually no 100% concentration pack ice against the CAA was...?  (Answers rounded to the nearest million years will be accepted!)

slow wing

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Re: 2016 sea ice area and extent data
« Reply #847 on: September 06, 2016, 06:25:26 AM »
The CAA is like a vacuum cleaner!  The last time there was virtually no 100% concentration pack ice against the CAA was...?  (Answers rounded to the nearest million years will be accepted!)
It occasionally loses suction...

Rob Dekker

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Re: 2016 sea ice area and extent data
« Reply #848 on: September 06, 2016, 06:52:58 AM »
We will have an "ice-free summer" at the pole in a matter of a few years.   So as a matter of interest, what will be the focus thereafter?  Whatever it is, shouldn't we be looking at it in earnest now?

I think that the first time we hit it, it will be an outlier like 2012 and 2007 were.  We could then have many years before the second year. I think that this is the reason that IPCC changed their definition of ice-free to being 5years of minimums below 1m square km instead of the first year reached.

However, there could be feedback mechanisms both positive and negative that could change this.

Acts5v29, it is likely that we will get an "ice-free summer at the pole" way before we hit an "ice free Arctic" (less than 1 M km^2 left over in September).

Realize that there is a very big difference between the current (4 M km^2 minimum) and an ice free Arctic. There will be a host of other weather effects that will come into play before that.

So about that ice free Arctic, Michael, can you please reference exactly where the IPCC changed their definition of ice-free to being 5years of minimums below 1m square km ?

I'd like to know who exactly initiated and executed that change in definition.

After all, it seems bizarre that IPCC would change this definition, when even a single year below 1 M km^2 is not supposed to happen for another 50 years at least, even according to the latest GCMs.
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timallard

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Re: 2016 sea ice area and extent data
« Reply #849 on: September 06, 2016, 08:02:48 AM »
2016 mapped to 2011 well until recently, now looks to be going to less than 2007, if you show-all it's outside them all except for 2012 ... http://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/
-tom