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Jim Hunt

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Re: The 2015 melting season
« Reply #200 on: March 13, 2015, 05:13:06 PM »
Some slightly older material from David Barber on "rotten" multi-year ice. The video:



The learned paper:

http://onlinelibrary.wiley.com/doi/10.1029/2009GL041434/abstract
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Jim Hunt

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Re: The 2015 melting season
« Reply #201 on: March 13, 2015, 11:14:42 PM »
The sun is now above the horizon in the Beaufort Sea. It has melted most of the ice off the lens of the O-Buoy 11 camera. It reveals ITP 85 centre stage, with IMB 2014I on the right. Here's what they have to say for themselves currently:

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jdallen

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Re: The 2015 melting season
« Reply #202 on: March 14, 2015, 01:23:52 AM »
The sun is now above the horizon in the Beaufort Sea. It has melted most of the ice off the lens of the camera. .... Here's what they have to say for themselves currently:

Looks rather... warm.

We have a comparison with last year at about the same time?
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iceman

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Re: The 2015 melting season
« Reply #203 on: March 14, 2015, 02:46:13 AM »
  ....
But what we are interested in is how the March extent compares to the September extent. That is, for any two years, if the extent is lower in March in one year, is it also lower in September in that year? That is true only 36% of the time. (I wrote a program to compute these numbers for me. This was so low that I didn't believe it the first time and checked it again by hand.) This is low enough to suggest a negative correlation between March extent and September extent, meaning that after accounting for the fact that on average the extent decreases every year, a low extent in March actually implies a high extent in September.
  ....

That does seem counterintuitive at first, though it makes sense if you think of the open water losing more heat than it would if ice-covered.  By the same reasoning, I would expect a (weak positive) correlation between the date of the maximum and the September minimum (i.e., later max leads to higher min).

What's interesting about the latter relationship is the possibility of negative feedback under certain conditions. Think of a point in space and time where the ocean, on average, gains as much heat from insolation as it loses from radiation (and evaporation etc - the main idea being a balance of heat energy over the diurnal cycle).  Join all such points together to form a loop around the seas of the northern hemisphere.  It's neither a latitude line nor an isotherm, though influenced mainly by insolation and water temperature.  During the spring, the loop gradually moves northward: the sun's increasing warming power leads gains in SSTs.
   Now, where is the ice edge in relation to this moving line?  Let's say it's farther north, and extent is anomalously low.  Less insulation from ice cover, more heat radiated from water to air: negative feedback; faster ice growth (or slower melt).  Time passes, the equilibrium loop continues farther north and overtakes the ice edge.  Now we have either of two conditions.  If extent anomaly has remained low, there is more open water than normal to absorb the solar energy.  Positive feedback, the familiar albedo flip.  So we would expect - other things being equal - that anomaly measures continue downward and a low minimum obtains.
   But what if the ice has grown rapidly, taking extent anomaly to the high side?  That means more ice than normal to reflect sunlight back into space - under conditions where heat gain from insolation would otherwise exceed radiative heat loss.  So negative feedback would continue later into the season.  That might have happened in 2014, when extent rose rapidly to a late peak.  Not knowing where the equilibrium loop is and how it moves, this is only speculative.  But it could have been a contributing factor to the slow melt last year.

Sebastian

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Re: The 2015 melting season
« Reply #204 on: March 14, 2015, 07:59:22 AM »
I think we have to keep in mind that the Arctic is a big place made up of different regions. Any melting going on now is far away from where the action is in August and September, especially if you look at places like the Sea of Ohotsk.

So I think the extent numbers now are not that helpful when trying to figure out what will happen in summer. The warmer than usual temperatures over the Arctic Ocean might be a different thing though.

viddaloo

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Re: The 2015 melting season
« Reply #205 on: March 14, 2015, 08:26:28 AM »
From the SIAB, we get this commentary:

Quote from: Neven
The increase has come to a (temporary) halt, JAXA reports a small drop of 9498 km2. So that's another day gone by and 256K left to go.

This may of course be tongue–in–cheek, but still amazing how one can extrapolate from just *two* days of ice–growth in a long series of drops, and then from those *two* days expect gigantic and quite unprecedented — never before seen — gains of more than quarter of a million square kilometers in the second half of March.

Now, what if I went around, say, in 2014, and said after just *two* days of drops on February 23rd, that we'd go far down, quarter of a million or more, and that the previous top on February 21st constituted a record early winter maximum? Would I be eating crow much?  ;D
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viddaloo

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Re: The 2015 melting season
« Reply #206 on: March 14, 2015, 08:43:30 AM »
The 2nd half of March max gain — for the record — is 110 k km² (2010). 2010 is the *only* year to gain ice in the last half. 2014 lost 511 k km². The average loss is 209 k. Still people are seriously expecting 2 and a half times the record gain for last half of March?



I think the lessons learnt from last year should be you do not extrapolate from only a few days. It doesn't matter what direction — up or down — it's just not safe to assume a few days will expand to an endless loss or gain. Instead, it seems, the lesson we learnt was only to always expect colder climate and more freeze than we really think, no matter what.
« Last Edit: March 14, 2015, 09:01:08 AM by viddaloo »
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Neven

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Re: The 2015 melting season
« Reply #207 on: March 14, 2015, 10:47:08 AM »
From the SIAB, we get this commentary:

Quote from: Neven
The increase has come to a (temporary) halt, JAXA reports a small drop of 9498 km2. So that's another day gone by and 256K left to go.

This may of course be tongue–in–cheek, but still amazing how one can extrapolate from just *two* days of ice–growth in a long series of drops, and then from those *two* days expect gigantic and quite unprecedented — never before seen — gains of more than quarter of a million square kilometers in the second half of March.

Now, what if I went around, say, in 2014, and said after just *two* days of drops on February 23rd, that we'd go far down, quarter of a million or more, and that the previous top on February 21st constituted a record early winter maximum? Would I be eating crow much?  ;D

What's a SIAB?  ;D

Vid, unlike you, I don't look that much at statistics, but rather at the regional maps and what the weather forecasts say. If you have northerlies and cold temps in the regions that are relatively low right now (especially Bering and Barentsz), that quarter million can go poof in just one week. I think the early max will remain standing, but I'm far from 100% sure.

That said, I haven't looked at today's forecasts yet. They can change a lot from one day to the next.
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Jim Hunt

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Re: The 2015 melting season
« Reply #208 on: March 14, 2015, 11:01:49 AM »
We have a comparison with last year at about the same time?

Perhaps the graphs I posted on the blog? The same ice mass balance buoy (2013F), in approximately the same position, for two years running. Rather less snow (so far) this year, and about 15 cm thicker ice to show for the extra year in the Beaufort.

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viddaloo

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Re: The 2015 melting season
« Reply #209 on: March 14, 2015, 11:05:31 AM »
Neven, you're quite right that "another day gone by and 256K left to go" is an important point here. It doesn't matter if the daily drop's small (9498 km²) or even zero, the main damage is that we're one day later into the spring melt. The Sun is higher and lasts longer than yesterday, and the 256K even more pie–in–the–sky.

That said, you don't have to look at statistics to know the spring melt is here, or that *two days* is a very flimsy basis to build an assumption of amazing and twice–record–breaking early spring gains on. Two days is short enough that everyone can remember the long 9–day melt before those two days, and so not get overrun by emotional judgment.

Edit:

It's now been 26 days since the Feb 15 max, and this gives us a first batch of 13 days and a last batch. See if you can spot a trend here:

First 13 days: 5 days melt (38%), 8 days freeze.
Last 13 days: 10 days melt (77%), 3 days freeze.  ;D
« Last Edit: March 14, 2015, 11:17:20 AM by viddaloo »
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Neven

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Re: The 2015 melting season
« Reply #210 on: March 14, 2015, 11:06:40 AM »
Quote
*two days* is a very flimsy basis

That's not my basis.

Here, this is what I mean, the forecast for next Thursday:

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Jim Hunt

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Re: The 2015 melting season
« Reply #211 on: March 14, 2015, 11:21:35 AM »
Looks rather... warm.

Bearing in mind that 2014 was itself "rather warm".

P.S. Especially for any Guardian readers, click here to produce the winter 2014/15 temperature anomaly plot.
« Last Edit: May 07, 2015, 10:43:32 AM by Jim Hunt »
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lanevn

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Re: The 2015 melting season
« Reply #212 on: March 14, 2015, 12:28:52 PM »
Quote
*two days* is a very flimsy basis

That's not my basis.

Here, this is what I mean, the forecast for next Thursday:
Living in the cold place, I can say that in march temperature of air doesn't mean so much. 0C with clear sky melting much more snow than +5C cloudy weather.

BornFromTheVoid

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Re: The 2015 melting season
« Reply #213 on: March 14, 2015, 12:34:11 PM »
Vid, the variability is extent and area over short periods is governed entirely by weather conditions. The fact that we saw a drop in coverage from mid-late February until a few days ago was because of persistently mild temps and southerlies in key regions, namely the Barents and Bering seas and Okhotsk.

2014 was the largest "late" coverage increase at the time it happened, because it was near record lows and there was a switch to northerlies in both Barents and Kara. Now, going off statistics alone, you would never have predicted that to happen because it has never happened before.
We are in a similar state this year, a few days later perhaps, but northerlies through Barents and Bering are well capable of spreading ice southward and causing substantial increase in coverage. The Barents sea alone put on over 200k over the space of about a week this time last year, and given how low coverage is there now, the Bering sea is well capable of the same.

Even if things go as forecast, it's still not certain to beat the max set so far, but the chance of it happening is still worth taking note of.

Neven

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Re: The 2015 melting season
« Reply #214 on: March 14, 2015, 01:35:42 PM »
Living in the cold place, I can say that in march temperature of air doesn't mean so much. 0C with clear sky melting much more snow than +5C cloudy weather.

I believe it will be cloudy, and definitely a lot below zero, up to -30 °C. Will it be enough to surmount that 250K difference? I don't know. It's not even sure this forecast will play out.
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iceman

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Re: The 2015 melting season
« Reply #215 on: March 14, 2015, 04:44:56 PM »
Vid, the variability is extent and area over short periods is governed entirely by weather conditions.
  ....
Especially so a week from now, when shifting weather interacts with thin edge ice all over the place: in Bering and Baffin/Newfoundland in from extent growth, in Kara from short-term refreeze, and possibly some of each in northern and southern Barentsz.

2014 was the largest "late" coverage increase at the time it happened, because it was near record lows and there was a switch to northerlies in both Barents and Kara. Now, going off statistics alone, you would never have predicted that to happen because it has never happened before.
  ....
Agreed, though you could stretch the point and say that such an extreme event becomes statistically more likely as variability increases over time.  That's part of what makes the Arctic scene so engaging around the max and min.
    Also, Crandles noted that movements from low points (local minima) could have greater predictive value for the extent maximum.

   ....
Even if things go as forecast, it's still not certain to beat the max set so far, but the chance of it happening is still worth taking note of.
I'll stay on the fence for now with 50/50 odds - though I've been wrong so far about upward trending anomaly in Okhotsk.

cesium62

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Re: The 2015 melting season
« Reply #216 on: March 14, 2015, 04:53:58 PM »
The 2nd half of March max gain — for the record — is 110 k km² (2010).

What's the maximum gain in the 2nd half of March from 14.286 km²?

The current extent is a really strange starting location.  Extrapolating based on normal starting locations is meaningless.  The current extent occurs less than 5% of the time.  We are unlikely to keep rolling our 20-sided fair dice and keep seeing 1's come up.

viddaloo

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Re: The 2015 melting season
« Reply #217 on: March 14, 2015, 05:07:52 PM »
The 2nd half of March max gain — for the record — is 110 k km² (2010).

What's the maximum gain in the 2nd half of March from 14.286 km²?

The current extent is a really strange starting location.  Extrapolating based on normal starting locations is meaningless.
I agree, let's not go there. Some people are expecting more than double the 2010 end of March record gain of 110 k km². I find that unlikely. However, I do see us getting above the 13.94 million February 15th max again, but not before Feb 2016, or maybe January.
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Espen

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Re: The 2015 melting season
« Reply #218 on: March 14, 2015, 05:13:11 PM »

"However, I do see us getting above the 13.94 million February 15th max again, but not before Feb 2016, or maybe January."


Better keep a lower profile, we are not at Holmenkollen ;)
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Anne

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Re: The 2015 melting season
« Reply #219 on: March 14, 2015, 05:16:06 PM »
What is saddest is that the voices who should be considered the most expert are rarely heard from and that is the Inuit. They have members that have either died from or needed rescue from thin ice where 30 years ago that would never have happened, because they understood ice.
^^ This. I took an engineer friend to see Thin Ice a while back and the thing he was most contemptuous of, the thing that for him tainted the credibility of the whole film, was the personal testimony of Inuit and Saami. Sentimental and unscientific, he reckoned. While I can see that it's both, I still think their experience has its own truth, and not in some woo-ish way that means they are in a different world, rather they experience it more literally than those who make models of it.

This sort of personal testimony is a way of trying to convince others to share and act on your convictions. If someone already shares those convictions, they'll feel more motivated to act on them. If they don't share those convictions and are scientifically trained, they'll feel they are being conned.

Lord Lawson telling an anecdote about his friends' butlers shovelling snow might make a compelling image but it would be bad evidence for the lack of climate warming. Cherry picked testimony from a few Inuit as evidence for the state of the Arctic falls into the same category.
No, not really. I'd be inclined to give less credence to Lord Lawson's friend's butler re what's been happening in the Arctic than to anecdotal evidence from people who've lived there for generations. No, it's not scientific and it can't be measured. Doesn't mean it's absolutely worthless, or worth the same as some puff from a blowhard.

Nightvid Cole

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Re: The 2015 melting season
« Reply #220 on: March 14, 2015, 05:53:36 PM »
Let's not also forget the importance of the Gulf of Saint Lawrence in the timing of the maximum extent. It's usually the first ice to go in the spring, and it has an area of 236,000 square km. Some recent years have shown half of its ice melting by March 20-25 or so, which is over 100k. This is unlikely to happen this year given the forecast for continued cold weather and snow:

http://wx.hamweather.com/?config=&pass=&dpp=&forecast=zandh&config=&place=charlottetown&state=pe&country=ca

viddaloo

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Re: The 2015 melting season
« Reply #221 on: March 14, 2015, 06:06:28 PM »
Better keep a lower profile, we are not at Holmenkollen ;)
We're getting there, Espen, we're getting there! beginning to look like a ski–jump now.


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jdallen

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Re: The 2015 melting season
« Reply #222 on: March 14, 2015, 06:36:32 PM »
On a whim, I went to look at the Canadian Weather Service site that publishes the polar orbiting satellite images.  The first image is current state of the ice; there's a rather remarkable gap of open water in the Northern Baffin Bay.

There doesn't seem particularly a lot of open cracking in the North American side of the Arctic per se, but the ice does seem to be very scrambled.

As a happy coincidence, I happened to find an image I'd captured from about the same date in 2013.  This was just after one of the serious "shattering" events that took place and transformed the structure of the pack.  I've put it back up for contemplation.

(click to enlarge)
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jdallen

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Re: The 2015 melting season
« Reply #223 on: March 14, 2015, 07:01:09 PM »
Another reference article, harkening back to various discussions of lead-vs-melt pond discussions.

http://onlinelibrary.wiley.com/doi/10.1029/92JC01755/abstract?deniedAccessCustomisedMessage=&userIsAuthenticated=false
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Neven

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Re: The 2015 melting season
« Reply #224 on: March 14, 2015, 07:52:23 PM »
The first image is current state of the ice; there's a rather remarkable gap of open water in the Northern Baffin Bay.

That's the North Water Polynya, jdallen, one of yearly recurring polynyas in the Arctic.
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lisa

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Re: The 2015 melting season
« Reply #225 on: March 14, 2015, 10:21:03 PM »
re: #226
Yes, I've been thinking about the melt pond post and discussion from last year. 

viddaloo

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Re: The 2015 melting season
« Reply #226 on: March 15, 2015, 03:18:48 PM »
Icelook mar15: Average extent 4th lowest in 48 days, average volume will be 6th in 8 weeks, and p1k (Piomas minus 1000) will be 5th in 9 months. Volume figures, however dubious you may think those are, have finally arrived and thus also made the daily PIOMAS estimates more reliable than earlier this week. These have been up a tick, so now current annual average volume is closer to that of 2008 — percentagewise — than current annual average extent is to that of 2011. That's why the tightest zoom is now on volume, which is uneventful: We are scheduled to go from 5th lowest to 6th on May 8th by crossing the 2010 line out of chart. Much more interesting this time of year is extent, which has already been fading away for an entire month in the peripheral seas. Sea ice is melting, or blown together and compacted, reported as losses in extent in the south. This has given us a record early extent maximum of Feb 15, and for the first time in recent history we maxed out below the 14 million mark, at 13.94 million km². This also has current annual average extent dropping like a ball: Faster than ever before in 2015, faster than all of 2014 and 2013, and the algorithm now has to resort to 2012 to find a match for daily drop deltas. Earlier in the week, Mar 14–17 was estimated for passing the 10.3 million line. We're not quite there yet, but 3 more days to go before we can say it was wrong. Graph says Mar 16, and the weekly drop pace agrees with it. Current weekly AAE drop pace of 9490 km²/week enables us to lose almost 40 grand per month, which will take us below the 10.26 million line before mid April. According to the graph, this line is crossed on April 9th. The forecast is of course more reliable in the short term, but has us crossing into 4th lowest territory on May 2nd, though April is more likely, going by background figures. Despite all these record–low ice extent measurements for over a month, CH₄ releases have been calm and generally with even the monthly peaks well below 2400 ppb, which is good, although extent hasn't really been low where the biggest leaks are. It will be interesting to see what happens to methane as record–low extent enters the Arctic Basin later in spring and summer.


[chart faq]
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jdallen

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Re: The 2015 melting season
« Reply #227 on: March 15, 2015, 05:27:59 PM »
The first image is current state of the ice; there's a rather remarkable gap of open water in the Northern Baffin Bay.

That's the North Water Polynya, jdallen, one of yearly recurring polynyas in the Arctic.
Thank you, Neven. Oddly, the first time I've heard it named.  Makes perfect sense systemically; ice bridge in Nares stops ice flow, not water, and the movement will force Baffin ice south.

What struck me more about the two images was the comparative states of Beaufort sea ice cover.  There actually seems more open water in 2013, but the ice of 2015 has very little structure.  It is yet to be demonstrated to me (in spite of my expectations) that the fractured ice will lead to a new low minimum.  Weather just hasn't attacked in the ways I thought it would. Perhaps this year will prove different.
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DavidR

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Re: The 2015 melting season
« Reply #228 on: March 16, 2015, 12:21:55 AM »
The 2nd half of March max gain — for the record — is 110 k km² (2010).

What's the maximum gain in the 2nd half of March from 14.286 km²?

The current extent is a really strange starting location.  Extrapolating based on normal starting locations is meaningless.
I agree, let's not go there. Some people are expecting more than double the 2010 end of March record gain of 110 k km². I find that unlikely. However, I do see us getting above the 13.94 million February 15th max again, but not before Feb 2016, or maybe January.
There have been gains of around 300 K km^2 in both Cryosphere area(2011 from 23 Mar, 2014 from 13 Mar) and NSIDC extent (2010 from 22 Mar)  after the latest dates we have for both measures. There is still a lot of variation possible so it is feasible for the ice to  go above the late February figures.
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Michael Hauber

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Re: The 2015 melting season
« Reply #229 on: March 16, 2015, 05:44:42 AM »
According to CT Barents, Kara and Okotsk have lost about 400k combined in the last week or two.  All three regions have been impacted by strong storms and strong southerly winds.  At the same time Bering Sea has gone up by over 100k.  In the coming week this pattern is forecast to change with strong cold and northerlies in the Barents/Kara region developing in 2-3 days, and coolish conditions already in place and continuing in Barents and Okhotsk.  I expect this should see the Barents expansion continue, and much of the 400k lost to be regained.  I also expect some gain in Okhostk as although conditions won't be great for ice gain we are very low there even compared to recent years and temps will be near normal for this time of year.  300k gain in the next week or two does not look out of the question.
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BornFromTheVoid

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Re: The 2015 melting season
« Reply #230 on: March 16, 2015, 09:42:20 AM »
An increase of over 100k in the last 5 days on JAXA, and that's before the northerlies arrive in the Bering and Barents seas tomorrow. The latest ECM shows the northerlies continuing for at least another 5 days too.
I'd say the chance of beating the February maximum is quite substantial now.

Interesting that all this is coming about due to the emergence of the old dipole pattern.

viddaloo

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Re: The 2015 melting season
« Reply #231 on: March 16, 2015, 05:17:55 PM »
We're down .1 million since the start of the month, same as 2007. 2012's up .2 million km², despite its first century drop of the year. 2015 still has the lowest extent, the most drop centuries and the biggest total during those drops among the three years.



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Jim Hunt

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Re: The 2015 melting season
« Reply #232 on: March 16, 2015, 09:46:57 PM »
Continuing a conversation with Chris Reynolds from the blog, where videos don't embed in comments, here's a few extracts from:

http://GreatWhiteCon.info/resources/arctic-sea-ice-videos/winter-201415-videos/

Firstly a slightly out of date Drift Age Model map, from 2015 week 5:



which shows some 5 year plus ice in close proximity to the Beaufort Sea coast of Alaska. The trouble is that if I look at RadarSat (see attachment below) or ASCAT:



or JAXA RGB:



or HYCOM/GOFS 3.1:



I don't see any old, thick ice in that location, even though PIOMAS appears to:



All of which leads me to continue to wonder if PIOMAS really has a good handle on what's going on in the Arctic as the majority of the sea ice gets younger, and thinner and more mobile.
 
« Last Edit: March 16, 2015, 09:54:31 PM by Jim Hunt »
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viddaloo

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Re: The 2015 melting season
« Reply #233 on: March 16, 2015, 10:11:06 PM »
At best, my model is a "GUESStimator" rather than a scientific predictor.  However, I have learned a great deal in the process of developing this tool.

Learning is half the fun! Getting a useful view of the situation and being right/wrong is the other half.

2011 is a great model low year that peaks on Monday 16th. It ended 3rd lowest in both ext and vol. We are currently 3 weeks ahead of it. I'm betting we can keep our huge 350 000 km² lead on 2011 and improve because of self–reinforcing feedbacks, week by week. Therefore, here are my minimal melt demands for the next 4 weeks:

Week 12:   209417 km²/week   29917 km²/day
Week 13:   -41847 km²/week   -5978 km²/day
Week 14:   114218 km²/week   16317 km²/day
Week 15:   128792 km²/week   18399 km²/day
[]

LRC1962

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Re: The 2015 melting season
« Reply #234 on: March 17, 2015, 08:01:52 AM »
I don't see any old, thick ice in that location, even though PIOMAS appears to:
ue to wonder if PIOMAS really has a good handle on what's going on in the Arctic as the majority of the sea ice gets younger, and thinner and more mobile.
From Mar-3 charts at Canadian ice service.
Quick and very dirty as ZZzzz time. Going to this page. and going to the different areas. Scroll to the very bottom and you will find developmental  ice maps of each area. In each case you will find first year ice of various thickness and what is called old ice. The question that comes into play is how do you interpret old ice. Is it old school where you will find 5+ meter thick ice. New reality of a lot of 'old' ice this is in large part very degraded thin ice that keeps hanging around. Or is it somewhere in the middle. The problem is that Satellites do not give a clear picture although they are getting much better. So it is left to models and human interpretation.
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Jim Hunt

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Re: The 2015 melting season
« Reply #235 on: March 17, 2015, 11:16:33 AM »
Scroll to the very bottom and you will find developmental  ice maps of each area. In each case you will find first year ice of various thickness and what is called old ice.

Sure. Here's the chart (scroll to the bottom), revealing a nice wide band of first year ice all along the Alaskan coast as per RadarSat.

Off Barrow the ice is classified as "medium" rather than "thick" first year ice. Compare with Chris's PIOMAS thickness chart above!
« Last Edit: March 17, 2015, 02:44:46 PM by Jim Hunt »
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LRC1962

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Re: The 2015 melting season
« Reply #236 on: March 17, 2015, 11:44:51 AM »
JH FYI that link goes nowhere, because the sites setup gives the same link for ALL charts. That is why I didn't link in the 1st place.
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Jim Hunt

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Re: The 2015 melting season
« Reply #237 on: March 17, 2015, 11:56:33 AM »
FYI that link goes nowhere

Curious. It seems to work OK for me?
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jbatteen

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Re: The 2015 melting season
« Reply #238 on: March 17, 2015, 02:07:36 PM »
It might have something to do with cookies?  I don't get an image from it either, just an oddly empty webpage.

iceman

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Re: The 2015 melting season
« Reply #239 on: March 17, 2015, 02:10:54 PM »
According to CT Barents, Kara and Okotsk have lost about 400k combined in the last week or two.  All three regions have been impacted by strong storms and strong southerly winds.  At the same time Bering Sea has gone up by over 100k.  In the coming week this pattern is forecast to change with strong cold and northerlies in the Barents/Kara region developing in 2-3 days, and coolish conditions already in place and continuing in Barents and Okhotsk.  I expect this should see the Barents expansion continue, and much of the 400k lost to be regained.  I also expect some gain in Okhostk as although conditions won't be great for ice gain we are very low there even compared to recent years and temps will be near normal for this time of year.  300k gain in the next week or two does not look out of the question.
An increase of over 100k in the last 5 days on JAXA, and that's before the northerlies arrive in the Bering and Barents seas tomorrow. The latest ECM shows the northerlies continuing for at least another 5 days too.
I'd say the chance of beating the February maximum is quite substantial now.

Interesting that all this is coming about due to the emergence of the old dipole pattern.

Looks to be running very close a week out.  Conditions in Okhotsk finally turn favorable for ice formation around the 24th, but extent gains in Bering and Barentsz will be trailing off by then.  My take is the outcome hinges on how much ice cover Baffin/Newfoundland loses and then regains with shifting winds and temperature in the coming week.

johnm33

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Re: The 2015 melting season
« Reply #240 on: March 17, 2015, 02:27:40 PM »
Jim the only way piomas makes sense to me is if it seeing deep fresh[ish] snow starting close to the light end of this density range as ice. http://sciencelearn.org.nz/Contexts/Icy-Ecosystems/Looking-closer/Snow-and-ice-density

Jim Hunt

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Re: The 2015 melting season
« Reply #241 on: March 17, 2015, 02:32:31 PM »
It might have something to do with cookies?

I guess so. Mine must have expired, and now I also only see a blank page. I've updated the link, to see if that one works.
« Last Edit: March 17, 2015, 02:46:30 PM by Jim Hunt »
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BornFromTheVoid

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Re: The 2015 melting season
« Reply #242 on: March 17, 2015, 04:10:12 PM »
Daily NSIDC extent up 50k, now above 2006 and just 168k off the daily max set back in February. I'd say a better odds are now in favour of setting a new max in the next 7 days.

Susan Anderson

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Re: The 2015 melting season
« Reply #243 on: March 17, 2015, 06:01:07 PM »
Thanks everyone.  Nothing to add, just thanks for the info.

Peter Ellis

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Re: The 2015 melting season
« Reply #244 on: March 17, 2015, 08:56:12 PM »
Jim the only way piomas makes sense to me is if it seeing deep fresh[ish] snow starting close to the light end of this density range as ice. http://sciencelearn.org.nz/Contexts/Icy-Ecosystems/Looking-closer/Snow-and-ice-density

PIOMAS isn't "seeing" anything, it's a model.  It's over-predicting the thickness in that region.

That could be due to errors or simplifications in the model, or in the weather data it's been fed.  It will have been fed with satellite data for ice concentration, but that will simply have been showing ~100% ice cover since the re-freeze, so there's no way there to tell the model whether the ice is thick or thin.

viddaloo

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Re: The 2015 melting season
« Reply #245 on: March 18, 2015, 12:39:39 AM »
Neven's new blog post alerted me to the fact that 2011 is also the lowest max on record, which makes it even more ideal for a tight race:

2011 is a great model *record* low max year that peaked on Monday 16th and ended 3rd lowest in both ext and vol. We are currently 3 weeks ahead of it.

2011 is a great model low year that peaks on Monday 16th. It ended 3rd lowest in both ext and vol. We are currently 3 weeks ahead of it. I'm betting we can keep our huge 350 000 km² lead on 2011 and improve because of self–reinforcing feedbacks, week by week. Therefore, here are my minimal melt demands for the next 4 weeks:

Week 12:   209417 km²/week   29917 km²/day
Week 13:   -41847 km²/week   -5978 km²/day
Week 14:   114218 km²/week   16317 km²/day
Week 15:   128792 km²/week   18399 km²/day
[]

johnm33

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Re: The 2015 melting season
« Reply #246 on: March 18, 2015, 12:45:31 AM »
Jim the only way piomas makes sense to me is if it seeing deep fresh[ish] snow starting close to the light end of this density range as ice. http://sciencelearn.org.nz/Contexts/Icy-Ecosystems/Looking-closer/Snow-and-ice-density

PIOMAS isn't "seeing" anything, it's a model.  It's over-predicting the thickness in that region.

That could be due to errors or simplifications in the model, or in the weather data it's been fed.  It will have been fed with satellite data for ice concentration, but that will simply have been showing ~100% ice cover since the re-freeze, so there's no way there to tell the model whether the ice is thick or thin.
Well of course it's not seeing, it's a machine/process, the point being that 70-90cm[?] of snow may have the same freeboard as 5m ice and gets interpreted as such. Especially when all the 'local' surfaces also have a snow topping.
http://forum.arctic-sea-ice.net/index.php/topic,119.msg41670.html#msg41670

LRC1962

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Re: The 2015 melting season
« Reply #247 on: March 18, 2015, 02:20:47 AM »
The Canadian ice Service web site uses a curious format. If you go to the pages tat show all their links you are then directed to the proper page. If you copy the link on that page is goes to an error page because all links will give you the same address. Not sure why it is done that way, but that is how it works.
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Sonia

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Re: The 2015 melting season
« Reply #248 on: March 18, 2015, 02:44:02 AM »
Look what defrosted!  I'd been hoping for this camera to open its eyes.

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Re: The 2015 melting season
« Reply #249 on: March 18, 2015, 08:13:08 AM »
Jim the only way piomas makes sense to me is if it seeing deep fresh[ish] snow starting close to the light end of this density range as ice. http://sciencelearn.org.nz/Contexts/Icy-Ecosystems/Looking-closer/Snow-and-ice-density

PIOMAS isn't "seeing" anything, it's a model.  It's over-predicting the thickness in that region.

That could be due to errors or simplifications in the model, or in the weather data it's been fed.  It will have been fed with satellite data for ice concentration, but that will simply have been showing ~100% ice cover since the re-freeze, so there's no way there to tell the model whether the ice is thick or thin.
Well of course it's not seeing, it's a machine/process, the point being that 70-90cm[?] of snow may have the same freeboard as 5m ice and gets interpreted as such. Especially when all the 'local' surfaces also have a snow topping.
http://forum.arctic-sea-ice.net/index.php/topic,119.msg41670.html#msg41670
So how is PIOMAs getting its figures. 

Snow weighs slightly less than a quarter the weight of ice.

One metre thick ice would have a freeboard of about 13cm. 50 cm of snow on top of that ice would push the ice down to water level but the snow would still sit 50 cm above water .

Would PIOMAS recognise the snow and discount it somehow, or would it assume that  because the freeboard is 50 cm the ice thickness is actually 4m?

That  would obviously cause big variations if a lot of snow fell and then melted quickly?

Hopefully  someone with a technical understanding of how PIOMAS works can explain.
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