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Neven

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Re: The 2016 melting season
« Reply #50 on: March 19, 2016, 05:27:31 PM »
These are really interesting to look at - Many thanks for taking the trouble.

Probably should mention though that the comparisons for march all show the same date (March 18th) for 2016...

Yes, the 2016 SIC map on every page is hotlinked to the daily updated UB SIC map. I add the images from the archive once the melting season is over. It's too much of a hassle to do that every 6 days, especially when most people will want to look forward and not back.
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Neven

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Re: The 2016 melting season
« Reply #51 on: March 20, 2016, 09:51:53 AM »
Cracking event on the Siberian side of the Arctic due to a 1053 hPa monster (see Wipneus animation in the comment above).
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Lord M Vader

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Re: The 2016 melting season
« Reply #52 on: March 20, 2016, 11:03:57 AM »
ECMWFs most recent run suggest that we'll see a pattern change by the end of March with more cyclonic domination. Interestingly, it seems like the Arctic also is cooling now.....  :o A little late IMO.

Okhotsk is down quite rapid these days.Question is how fast melting will be.

plinius

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Re: The 2016 melting season
« Reply #53 on: March 20, 2016, 12:02:42 PM »
You mean in anomalies, or in real temperature? In anomalies, it will definitely cool, but that is just because we won't see a lot of summer temperature variation as long as there is some ice left in the arctic...

Jim Hunt

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Re: The 2016 melting season
« Reply #54 on: March 20, 2016, 03:16:25 PM »
An interesting paper has just become available for "discussion" at TCD:

The EUMETSAT sea ice climate record

Quote
An Arctic and Antarctic sea ice area and extent dataset has been generated by EUMETSAT’s Ocean and Sea Ice Satellite Application Facility (OSISAF) using the record of American microwave radiometer data from Nimbus 7 Scanning Multichannel Microwave radiometer (SMMR) and the Defense Meteorological satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) and Special Sensor Microwave Imager and Sounder (SSMIS) satellite sensors. The dataset covers the period from 1978 to 2014 and updates and further developments are planned for the next phase of the project.

The sea ice climate dataset is available for download at (www.osisaf.org) including documentation.

I'm guessing that this is the documentation referred to, but I am open to persuasion!

http://www.osi-saf.org/biblio/docs/osisaf_cdop2_ss2_pum_sea-ice-conc-reproc_2_1.pdf
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BornFromTheVoid

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Re: The 2016 melting season
« Reply #55 on: March 20, 2016, 04:23:08 PM »
Latest update with the NSIDC extent has resulted in a new extent high for 2016 using the 5 day rolling average.  The value to the 19th is 14,481,800km2, compared to the previous high of 14,477,600km2 set back on March 2nd.

jdallen

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Re: The 2016 melting season
« Reply #56 on: March 20, 2016, 05:02:30 PM »
Cracking event on the Siberian side of the Arctic due to a 1053 hPa monster (see Wipneus animation in the comment above).
Very dramatic, and in line with what we saw in the same region in 2015.
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epiphyte

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Re: The 2016 melting season
« Reply #57 on: March 20, 2016, 06:56:58 PM »
An interesting paper has just become available for "discussion" at TCD:

The EUMETSAT sea ice climate record

Quote
An Arctic and Antarctic sea ice area and extent dataset has been generated by EUMETSAT’s Ocean and Sea Ice Satellite Application Facility (OSISAF) using the record of American microwave radiometer data from Nimbus 7 Scanning Multichannel Microwave radiometer (SMMR) and the Defense Meteorological satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) and Special Sensor Microwave Imager and Sounder (SSMIS) satellite sensors. The dataset covers the period from 1978 to 2014 and updates and further developments are planned for the next phase of the project.

The sea ice climate dataset is available for download at (www.osisaf.org) including documentation.

I'm guessing that this is the documentation referred to, but I am open to persuasion!

http://www.osi-saf.org/biblio/docs/osisaf_cdop2_ss2_pum_sea-ice-conc-reproc_2_1.pdf

From the abstract:
Quote
A new algorithm has been developed to estimate the spatially and temporally varying sea ice concentration uncertainties. A comparison to sea ice charts from the Arctic and the Antarctic shows that ice concentrations are higher in the ice charts than estimated from the radiometer data at intermediate ice concentrations. The sea ice climate dataset is available for download at (www.osisaf.org) including documentation.

I.e: "Wherever there's not much ice, there's less than you think there is."

...which makes perfect sense given the nature of the sensors, and the fact that models are ill-equipped to cope with the more complex and uncertain physics in <100% concentration environments.

...Which in turn is one reason that I have always said that the year the ice all melts, it will take everyone who goes by the numbers by surprise, and it will all go at once.


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Re: The 2016 melting season
« Reply #58 on: March 20, 2016, 08:25:03 PM »
No, it says the opposite - that the ice concentration in the sea ice charts (hand-compiled using multiple sources including direct observations and radar as well as microwave data) is generally higher that that estimated from microwave data alone.

This is nothing new - it's one of the main reasons MODIS shows more ice than the microwave imaging, for example.  Microwaves just aren't very good at picking up thin, sparse ice.

Jim Hunt

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Re: The 2016 melting season
« Reply #59 on: March 21, 2016, 01:48:13 AM »
If the preliminary CT area maximum holds it is significantly below all previous years in their record. Next lowest is 13.144 in 2011:

http://GreatWhiteCon.info/2016/02/the-2016-arctic-winter-sea-ice-puzzle/#comment-213940
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Treesong

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Re: The 2016 melting season
« Reply #60 on: March 21, 2016, 04:06:21 AM »
Latest update with the NSIDC extent has resulted in a new extent high for 2016 using the 5 day rolling average.  The value to the 19th is 14,481,800km2, compared to the previous high of 14,477,600km2 set back on March 2nd.

I've asked this before, but...can we really know the sea ice extent to six significant figures?
What are the chances that this new high is really a new high? Since it's a rolling average I imagine the trend is more meaningful than daily values, but still.

plinius

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Re: The 2016 melting season
« Reply #61 on: March 21, 2016, 09:53:44 AM »
rather 5 figures that you need for that difference. Out of painful own experience - yes, thank them for providing so many significant digits, otherwise people using those data would have to fight with rounding artefacts. Also please note that BftV talks about a new maximum in the index, and not the sea ice itself, which makes his statement very accurate.

BornFromTheVoid

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Re: The 2016 melting season
« Reply #62 on: March 21, 2016, 11:35:44 AM »

I've asked this before, but...can we really know the sea ice extent to six significant figures?
What are the chances that this new high is really a new high? Since it's a rolling average I imagine the trend is more meaningful than daily values, but still.

I'm pretty sure the daily values come with an error range that would make the current and previous high statistically indistinguishable, but as far as keeping the record consistent, March 19th will be ranked (so far) as the 2016 extent maximum.
It's definitely possible that the 5 day average will continue to increase over the coming days too.

DavidR

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Re: The 2016 melting season
« Reply #63 on: March 21, 2016, 12:58:27 PM »
Latest update with the NSIDC extent has resulted in a new extent high for 2016 using the 5 day rolling average.  The value to the 19th is 14,481,800km2, compared to the previous high of 14,477,600km2 set back on March 2nd.

I've asked this before, but...can we really know the sea ice extent to six significant figures?
What are the chances that this new high is really a new high? Since it's a rolling average I imagine the trend is more meaningful than daily values, but still.

In the last week or so both NSIDC extent and Area have changed by over 170,000 sq Km^2 in a single day, that is over 7000 Km^2 in an hour.  Any figure given is merely a best guess and should be treated as such.
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crandles

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Re: The 2016 melting season
« Reply #64 on: March 21, 2016, 01:22:54 PM »
Latest update with the NSIDC extent has resulted in a new extent high for 2016 using the 5 day rolling average.  The value to the 19th is 14,481,800km2, compared to the previous high of 14,477,600km2 set back on March 2nd.

I've asked this before, but...can we really know the sea ice extent to six significant figures?
What are the chances that this new high is really a new high? Since it's a rolling average I imagine the trend is more meaningful than daily values, but still.

What are the chances? About 50:50 if considering just 2 dates that are that close.

While we shouldn't expect accuracy, perhaps we shouldn't be too dismissive of relative values:

Can we use different measures:
NSIDC (daily)
2016,    02,  29,     14.557 (local max)
2016,    03,  19,     14.482

ADS/IJIS
29Feb 13.96 local maximum
19Mar 13.89

If they both find the same day as the maximum....
  If they both use same satellite data then that could easily be due to noise in satellite data that is not a result of level of ice. But if they are using different satellite data maybe reporting same day for max is indicative of that being the day the ice reached max?

Jim Pettit

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Re: The 2016 melting season
« Reply #65 on: March 21, 2016, 01:31:56 PM »
If the preliminary CT area maximum holds it is significantly below all previous years in their record. Next lowest is 13.144 in 2011:


Yes, indeed. Wrote about this a few days ago. 2016's max-to-date was 12.885 on Day 0.2000; that's 259k less than the 2011 max you mentioned. In order for this year to climb above that 2011 mark, area would have to somehow jump by roughly 500k over the next week or so.

That's not going to happen; the new 2016 record will stand.

On a similar note, it's unlikely, though not impossible, that area will grow enough in the next week or so to surpass the max-to-date of 12.885, meaning that it's likely, though not certain, that 2016 has passed its peak.

Bonus fact: 2016 SIA is, as of today, 1.035 million km2 below where 2012 was on this same date.
« Last Edit: March 21, 2016, 01:38:17 PM by Jim Pettit »

Neven

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Re: The 2016 melting season
« Reply #66 on: March 21, 2016, 01:35:14 PM »
They're both using passive microwave data from different satellite sensors. IJIS uses AMSR2, and the Sea Ice Index relies on DMSP and SSMIS. The Bootstrap algorithm is used for the former, the NASA Team algorithm is used for the latter.
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Jim Hunt

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Re: The 2016 melting season
« Reply #67 on: March 21, 2016, 01:40:46 PM »
Yes, indeed. Wrote about this a few days ago. 2016's max-to-date was 12.885 on Day 0.2000; that's 259k less than the 2011 max you mentioned. In order for this year to climb above that 2011 mark, area would have to somehow jump by about 478k over the next week or so.

That's not going to happen; the new 2016 record will stand.

That being the case:

http://GreatWhiteCon.info/2016/02/the-2016-arctic-winter-sea-ice-puzzle/#comment-213943
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Neven

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Re: The 2016 melting season
« Reply #68 on: March 21, 2016, 01:51:05 PM »
One fluke could be enough to top IJIS' preliminary peak (just a 48K difference), although I'm not seeing it in the forecast. CT SIA is a done deal, unless Wipneus sees extraordinary things coming our way in his crystal ball.
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Andreas T

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Re: The 2016 melting season
« Reply #69 on: March 21, 2016, 02:08:04 PM »
I don't claim to know a lot about this region, but just looking at the temperature of ice and land surface yesterday on worldview http://go.nasa.gov/1RctEMH I would guess that a drop in area could be not far off in this region.

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Re: The 2016 melting season
« Reply #70 on: March 21, 2016, 03:54:26 PM »
I don't claim to know a lot about this region, but just looking at the temperature of ice and land surface yesterday on worldview http://go.nasa.gov/1RctEMH I would guess that a drop in area could be not far off in this region.
Maybe.  I think a lot of what you are seeing is cloud tops, so I'm not sure it reflects what's actually going on at 2M or so.  Regardless, the ice in Okhotsk is very weak and thin, so when the right conditions arrive, it will vanish quickly.
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Pmt111500

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Re: The 2016 melting season
« Reply #71 on: March 21, 2016, 04:06:30 PM »
Yes, indeed. Wrote about this a few days ago. 2016's max-to-date was 12.885 on Day 0.2000; that's 259k less than the 2011 max you ... jump by about 478k...

That's not going to happen; the new 2016 record will stand.

That being the case:

http://GreatWhiteCon.info/2016/02/the-2016-arctic-winter-sea-ice-puzzle/#comment-213943


'k, still linear. As it should be. By ghgs alone. During winters. 'k. Tamino split his temperature response function for el nino in two parts in his recent post. Delays are 2 months and 10 months. Thisproduces a bit better fit than the previous one. I think the longer period could be for extratropical marine resposnse. October- November temperatures should be interesting in this respect.
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Andreas T

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Re: The 2016 melting season
« Reply #72 on: March 21, 2016, 04:22:16 PM »
jdallen, maybe you could use the link I provided and compare visible and IR image. These "cloudtops" you think I am seeing have oddly icefloe like shapes. Please consider the possibility that someone has thought about this before posting!
What I think it shows is exactly that the ice isn't very thick and warms quickly. But isn't it better to back this up with data than to just state an opinion?
What the weather will do I have no idea but I spotted this clear sky shot and thought it tells something about the situation at the surface. Lets see what happens next and whether this observation means anything.

epiphyte

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Re: The 2016 melting season
« Reply #73 on: March 21, 2016, 04:58:11 PM »
No, it says the opposite - that the ice concentration in the sea ice charts (hand-compiled using multiple sources including direct observations and radar as well as microwave data) is generally higher that that estimated from microwave data alone.

This is nothing new - it's one of the main reasons MODIS shows more ice than the microwave imaging, for example.  Microwaves just aren't very good at picking up thin, sparse ice.

Holy SnowBalls, Batman! You're right I completely misread it.

Laurent

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Re: The 2016 melting season
« Reply #74 on: March 21, 2016, 06:20:05 PM »
Colorado Bob posted this video of a US nuclear Submarine piercing through the Arctic Ice : https://www.rt.com/viral/336319-nuclear-submarine-arctic-ice/

I do not see the ice as being meters thick. Eye balling it does seem to be at max 50 cm thick... What do you think ? They have chosen a very weak spot ?

(I have watched Mad Max recently for the first time, but it is so cute not at all the hard rock punkish thing I thought it was... ;))
« Last Edit: March 21, 2016, 06:35:33 PM by Laurent »

jai mitchell

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Re: The 2016 melting season
« Reply #75 on: March 21, 2016, 07:43:06 PM »
Colorado Bob posted this video of a US nuclear Submarine piercing through the Arctic Ice : https://www.rt.com/viral/336319-nuclear-submarine-arctic-ice/

I do not see the ice as being meters thick. Eye balling it does seem to be at max 50 cm thick... What do you think ? They have chosen a very weak spot ?

(I have watched Mad Max recently for the first time, but it is so cute not at all the hard rock punkish thing I thought it was... ;))

They use a sub-ice sonar to locate thin areas of ice to breach.  The thinnest that they can find.
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jdallen

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Re: The 2016 melting season
« Reply #76 on: March 21, 2016, 07:47:08 PM »
jdallen, maybe you could use the link I provided and compare visible and IR image. These "cloudtops" you think I am seeing have oddly icefloe like shapes. Please consider the possibility that someone has thought about this before posting!
What I think it shows is exactly that the ice isn't very thick and warms quickly. But isn't it better to back this up with data than to just state an opinion?
What the weather will do I have no idea but I spotted this clear sky shot and thought it tells something about the situation at the surface. Lets see what happens next and whether this observation means anything.
Sorry, AndreasT - I did use the link and spent quite some time tinkering with various settings in Worldview to get a sense of it.   I just came to a different conclusion, that's all.
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NeilT

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Re: The 2016 melting season
« Reply #77 on: March 21, 2016, 09:49:42 PM »
Is it not the case that if the CT area continues to fall and the NSIDC extent continues to rise, that the same, or less, ice is simply being distributed over a larger area of sea.

This does not, to my mind, really give much weight to the fact that NSIDC didn't create a new record.  Just that the ice is more mobile than it used to be.

Or did I get that wrong?
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Stephen

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Re: The 2016 melting season
« Reply #78 on: March 22, 2016, 09:45:04 AM »
As an amateur, I can only say that it's kind of freaky watching how closely the 2016 peak season is following the 2015 season.  An early March bump, then a sharp decline that has us all fooled, then a late season steady climb.

Maybe the spirit of Viddaloo is haunting the ice pack?
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Re: The 2016 melting season
« Reply #79 on: March 22, 2016, 03:57:53 PM »
I think some of us are still fooled. This doesn't look very 2015-ish to me.

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Re: The 2016 melting season
« Reply #80 on: March 22, 2016, 04:57:48 PM »
Colorado Bob posted this video of a US nuclear Submarine piercing through the Arctic Ice : https://www.rt.com/viral/336319-nuclear-submarine-arctic-ice/

I do not see the ice as being meters thick. Eye balling it does seem to be at max 50 cm thick... What do you think ? They have chosen a very weak spot ?

(I have watched Mad Max recently for the first time, but it is so cute not at all the hard rock punkish thing I thought it was... ;))

They use a sub-ice sonar to locate thin areas of ice to breach.  The thinnest that they can find.

It does look pretty thin - but the technique used to break through looks as though it would probably work just fine on considerably thicker ice... Notice how he's rising straight upwards (i.e. with zero forward motion), trimmed up at the bow so that the initial breakthrough force is straight up and down, concentrated at two points in sequence (first the sail, then the bow). Judging by how far the bow comes out of the water he probably has more than a few truckloads of positive buoyancy pushing straight up on a very small area.

Neven

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Re: The 2016 melting season
« Reply #81 on: March 22, 2016, 10:30:50 PM »
Was I too early to unsticky the freezing season thread and sticky this thread? Both JAXA SIE and CT SIA can top their preliminary peaks tomorrow. I didn't know I could jinx it this way too.  ;D 8)
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Re: The 2016 melting season
« Reply #82 on: March 22, 2016, 11:33:42 PM »
I think we are all waiting with bated breath to see the start of a plummeting ice extent.  It feels like watching a slow motion train wreck.... thin ice, multiyear ready to escape, loud cracks, naked Svalbard & today looks like a full moon so next the remaining glaciers will crack !  If it (the max)hangs on a little longer - great.

epiphyte

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Re: The 2016 melting season
« Reply #83 on: March 23, 2016, 01:51:58 AM »
Was I too early to unsticky the freezing season thread and sticky this thread? Both JAXA SIE and CT SIA can top their preliminary peaks tomorrow. I didn't know I could jinx it this way too.  ;D 8)

Oh there's melting going on, alright. (look at the ice edge nw of Svalbard - it's advancing southward, but also melting at the edges).

...But on the whole it seems that there's maybe still more freezing than melting ;)

Jim Pettit

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Re: The 2016 melting season
« Reply #84 on: March 23, 2016, 01:39:12 PM »
Was I too early to unsticky the freezing season thread and sticky this thread? Both JAXA SIE and CT SIA can top their preliminary peaks tomorrow. I didn't know I could jinx it this way too.  ;D 8)
JAXA extent could easily surpass its max-to-date of, as it's currently just 16k below it. But my guess is that CT area's max-to-date is safe; even with Wipneus's expected 80k+ increase tomorrow, it'll still be nearly 90k below the Day 0.2000 reading. Then again, 2012 managed to add more ice this week on its way to the latest maximum on record. If 2016 reaches a new peak in the next several days, it'll come in as the second latest. Normal distribution:


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Re: The 2016 melting season
« Reply #85 on: March 23, 2016, 01:54:24 PM »
the less ice there at this time of the year, means the more retreated to the north the ice edge is, the later spring will reach the edge and the higher the chance for partial refreezes. what we see now is that currently the edge advances on the atlantic side and retreats in the okhotsk while 10 days ago it was vice versa. the later in winter the less the chance that the cold will persist on a certain latitude around the entire globe but still it can happen that while one part of the arcitc just started refreezing a bit while the other just ended refreezing there is an overlap of a day or two which can produce short lived peaks while the general possibility of refreezing due to higher latitude average ice edges remains. hence the record years tending to peak later IMO

Edit: i'm neither a scientist nor an native english speaker hence be tolerant as to my wording please  ;)
« Last Edit: March 23, 2016, 02:08:00 PM by magnamentis »

crandles

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Re: The 2016 melting season
« Reply #86 on: March 23, 2016, 02:48:44 PM »
NSIDC  14.575 for 21 Mar is higher than 14.557 of 29 Feb
5Day average of 14.487 is also new peak (but only 2 days later than last peak)

92, 97, 99 2003 and 2010 had later 5 day peaks. So would have to continue upwards quite a bit longer to become record or second latest peak for extent.

IIRC the area minimum is generally a little before the extent minimum because northern areas getting increased ice coverage matters for area but not for extent.  Melting presumably tends to start at the edges rather than freezing starting in the middle. So I am not sure there is much difference or reason for a difference in the date or variability of that date in maximum between area and extent.

Perhaps just a matter of chance that we are near a very late area maximum but further from a very late extent maximum?

pauldry600

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Re: The 2016 melting season
« Reply #87 on: March 23, 2016, 03:23:23 PM »
Im quite amazed at how quickly the melted ice can refreeze and appear once again.

Think the Arctic is just volatile this year,

while melt will be interesting I wouldnt be surprised to see the min extent in September just a smidgeon below what it was last year.

Looking on a worldwide basis Europe is a lot colder this year especially Spain and Med so there may be no roaster of a Summer just normal weather.

Still this is more in hope than expectation

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Re: The 2016 melting season
« Reply #88 on: March 23, 2016, 05:27:16 PM »
 I am afraid that this many consecutive late freezes is an ominous sign.

https://www.quantamagazine.org/20151117-natures-critical-warning-system/

Quote
The signal, a phenomenon called “critical slowing down,” is a lengthening of the time that a system takes to recover from small disturbances, such as a disease that reduces the minnow population, in the vicinity of a critical transition. It occurs because a system’s internal stabilizing forces — whatever they might be — become weaker near the point at which they suddenly propel the system toward a different state.



I am an energy reservoir seemingly intent on lowering entropy for self preservation.

seaicesailor

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Re: The 2016 melting season
« Reply #89 on: March 23, 2016, 09:50:17 PM »
the less ice there at this time of the year, means the more retreated to the north the ice edge is, the later spring will reach the edge and the higher the chance for partial refreezes. what we see now is that currently the edge advances on the atlantic side and retreats in the okhotsk while 10 days ago it was vice versa. the later in winter the less the chance that the cold will persist on a certain latitude around the entire globe but still it can happen that while one part of the arcitc just started refreezing a bit while the other just ended refreezing there is an overlap of a day or two which can produce short lived peaks while the general possibility of refreezing due to higher latitude average ice edges remains. hence the record years tending to peak later IMO

Edit: i'm neither a scientist nor an native english speaker hence be tolerant as to my wording please  ;)

That has a lot to do with the plateau hypothesis
http://forum.arctic-sea-ice.net/index.php/topic,1211.0.html

As NH gets warmer, freezing progressess less staying in higher latitudes in average (this year was the turn of the Atlantic side, last year the Pacific). Extent "virtually" peaks earlier, in February, but then there is a period where ice edge retreats and advances in different seas out of Arctic ocean properly speaking. So extent says in a nearly steady value. Geoghaphical constraints also avoid that extent starts to drop seriously until April (my opinion).

magnamentis

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Re: The 2016 melting season
« Reply #90 on: March 23, 2016, 10:18:43 PM »
that's well explained what i meant to express in layman's terms, thanks for the complementary support   ;)

crandles

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Re: The 2016 melting season
« Reply #91 on: March 24, 2016, 01:55:39 PM »
the less ice there at this time of the year, means the more retreated to the north the ice edge is, the later spring will reach the edge and the higher the chance for partial refreezes.

This has been discussed. There seems little if any evidence for it.

Had another go, and this seems to indicate peak day is if anything getting earlier with lower extent.

Obviously weather can cause peaks and troughs so to minimise the effect I used 31 day average NSIDC extent.

The day seems if anything to be getting later over time particularly since 2007 (but with 2015 looking very oddly early).

crandles

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Re: The 2016 melting season
« Reply #92 on: March 24, 2016, 02:00:33 PM »
Try again with graph over time.

crandles

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Re: The 2016 melting season
« Reply #93 on: March 24, 2016, 02:12:32 PM »
Not sure there is any relationship - perhaps what we see is just noise. But speculating a bit, maybe I can suggest:

Maybe lower extent does mean later maximum other things being equal as the post 2007 jump indicates but there is also something acting in other direction. Probably too early for snow cover over land disappearing leading to earlier max. Perhaps just higher GHG levels over time mean the ice extent line can be held in check with a slightly lower sun angle.

Something like this would then mean over long periods the two effects mainly cancel out possible leaving a small residual effect possibly in direction of earlier minimum with time/CO2.

However, year to year, if there is a large difference in extent then you tend to get a later maximum with lower extent.

crandles

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Re: The 2016 melting season
« Reply #94 on: March 24, 2016, 03:55:12 PM »
However, year to year, if there is a large difference in extent then you tend to get a later maximum with lower extent.

No, that doesn't work. For consecutive years, there seems a stronger relationship that higher maximum is associated with later maximum.

I am lost trying to explain that. Any ideas anyone?
« Last Edit: March 24, 2016, 04:20:36 PM by crandles »

magnamentis

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Re: The 2016 melting season
« Reply #95 on: March 24, 2016, 04:16:56 PM »
perhaps we need a hypothetical extreme example to explain:

assuming the pole were ice-free in march, until when do you think could even larger re-freeze occur, i say may, even june would be possible. on the other hand if the ice edge were very far south in march what chance do you see that significant re-freeze could occour in june, may or even april, close to zero chance IMO.

so now please don't argue that it cannot be ice-free in march and seas around iceland cannot be frozen in march as well. it's just the extremes to illustrate the logics and then there "is" evidence just watch all the recent years with relatively late re-freezes before a steep drop. and we were not explicitely talking abou the max but about the latest ups in ice extent, re-freezes on significant scale very late in the season, it does not matter in this context whether the re-freeze will lead to new highs like in 2012 or not like last year. of course thickness has an impact as well, hence we could agree to replace the term extent to a certain degree with volume, but only if that volume is not boosted by extreme volumes in few places like the canadian archipelago. IMO it's absolutely logical and if you can't see this now we gonna talk again in 5-10 years when this and last years pattern became more regular and probably closer to the extreme i mentioned above ( only closer, of coure there will be always ice in winter for the coming milleniums for sure)

EDIT: since the pattern is relatively new and things are ever changing very rapidly of course no-one is able to come up with evidence gathered over decades like extent and area development, which is why i refer to the logic  and used those extrem examples, quasi as an eye opener.

crandles

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Re: The 2016 melting season
« Reply #96 on: March 24, 2016, 05:03:03 PM »
So far we have postulated effects that:

1. Northern location for ice edge means it is later for sun to reach adequate angle to stop expansion so causing later maximum.
2. GHG levels over time cause earlier maximum.
and magnamentis extremes consideration which seems to me to boil down to
3. Extent higher than trend causes early maximum.

On average extent will be on trend, so that can't explain trends but could be useful for explaining year to year variation. This says that of 2 consecutive years if one has higher extent the maximum day will tend to be earlier as you tend to get reversion towards trend. However the last scatter plot seems to show just the opposite.

On trends

There is a possibly a slight trend towards later maximum. This agrees with effect 1 but disagrees with effect 2.
It can't be just effect 1 as this would be seen perhaps more strongly in year to year data but the year to year data disagrees.

There is negligible trend possibly later maximum with higher extent. This disagrees with 1.
A combination of effects 1 and 2 could explain trends, but the consecutive years again show opposite of what you expect from those two effects.


Seems there either must be more effects in operation and/or I am trying to explain random noise and/or I am completely miscalculating/misinterpreting what I see.

Still lost.

Shared Humanity

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Re: The 2016 melting season
« Reply #97 on: March 24, 2016, 11:12:23 PM »
However, year to year, if there is a large difference in extent then you tend to get a later maximum with lower extent.

No, that doesn't work. For consecutive years, there seems a stronger relationship that higher maximum is associated with later maximum.

I am lost trying to explain that. Any ideas anyone?

Given the increasing positive temperature anomalies in the Arctic winter, couldn't this simply be evidence of the shortening of the freeze season?

crandles

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Re: The 2016 melting season
« Reply #98 on: March 24, 2016, 11:34:12 PM »

Given the increasing positive temperature anomalies in the Arctic winter, couldn't this simply be evidence of the shortening of the freeze season?

That is effectively the same as postulated second effect (GHG levels over time cause earlier maximum).

That would show up as a trend towards earlier maximums but there is a slight (ie not at all significant) trend towards later maximums. Of course it might be there but outweighed by something else.

crandles

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Re: The 2016 melting season
« Reply #99 on: March 24, 2016, 11:54:56 PM »
Perhaps it is the simple: weather dominates:

If cold near time when maximum should occur, then extent tends to go above trend and you also tend to have a late maximum. If warm near time of maximum, extent tends to go below average and you also tend to get an early maximum.

Over a long time period there is very little trend as observed. If you look at consecutive years then you get a strong effect of high extent goes with late maximums.

This does seem likely to dominate over any other effects, and seems to adequately explain the change in consecutive year effect.

It shouldn't have a large effect over long periods of time and leaves effects 1 and 2 competing to leave little trend.

Not sure there is much evidence to support these effects actually being the major effects rather than them being made up in order to try to fit the facts.