Arctic Sea Ice : Forum

Cryosphere => Arctic sea ice => Topic started by: Juan C. García on March 01, 2013, 09:12:01 PM

Title: Arctic sea ice free (extent)
Post by: Juan C. García on March 01, 2013, 09:12:01 PM
I will appreciate your comments about your answer  :)
Title: Re: Arctic sea ice free (extent)
Post by: gfwellman on March 01, 2013, 09:33:34 PM
If the question had been CT area, rather than NSIDC extent, I would have gone with 2017-2020, but I chose 2021-2030.  No deep science, just an eyeballed linear extrapolation.  Such extrapolation could be way off for longer time periods, but seems reasonable for 10 years or so.
Title: Re: Arctic sea ice free (extent)
Post by: Juan C. García on March 01, 2013, 09:54:10 PM
I agree with your forecast, gfwellman. It could be good to establish an equivalent “ice free” CT area and/or PIOMAS volume, before making a poll with these concepts.
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on March 01, 2013, 10:03:54 PM
Actually I've just removed my last message and edit and retract my vote.

I missed the 'monthly' criteria for the September minimum. In which case, I'd say early 2020s.
Title: Re: Arctic sea ice free (extent)
Post by: Neven on March 01, 2013, 10:14:21 PM
I'm with gfwellman. But if I had to bet, I would say the first day that sees a sea ice area below 1 million km2 could very well be before 2020.
Title: Re: Arctic sea ice free (extent)
Post by: crandles on March 01, 2013, 11:31:49 PM
Some extrapolations just in case people want them for guidance:

Gompertz fit of extent first below 1m in 2023 (RMSE .436)
Exponential fit of extent first below 1m in 2019 (RMSE .435)
'Linear plus exponential' fit of extent first below 1m in 2018 (RMSE .434 but 4 parameters instead of 3)


Exponential fit of volume reaches 0 in 2015
Gompertz fit of volume gets down to 232 Km^3 by 2020


1m Km^2 extent and volume of 232 Km^3 so thickness of .232m is about the normal ratio of area to extent, perhaps that is just a little thinner than average. So, if you believe the gompertz extrapolation of volume then whether 2020&before or after 2020 looks rather borderline to me perhaps marginally in favour of being under 1m km^2 extent in 2020.

The trend looks slightly faster than gompertz fit of volume, indeed the 'linear plus exponential' fit suggests it is faster than the exponential fit.

This suggest I should go for 2017 to 2020 and yet there are the models suggesting a tail and I think I do believe there will be some sort of a tail. I doubt it will be as fat as the gompertz tail based on evidence so far.

I would be happier with a 2019 to 2022 range but I think it might just make it by 2020 so I will select 2017 to 2020.
Title: Re: Arctic sea ice free (extent)
Post by: Dromicosuchus on March 02, 2013, 12:54:30 AM
Based solely on extent, I would have probably guessed 2021-2030 or 2031-2040, but considering the PIOMAS volume estimates, and the confirmation of those estimates by Cryosat-2, I think it'll probably be mostly gone by 2020 at the very latest, and more likely will have sunk below 1,000,000 km^2 by 2015-2017.  Since that covers more of option A's range than option B, count me in the 2013-2016 camp--with the caveat that I think it's extremely unlikely that the sea ice'll hit <1,000,000 km^2 in 2013, and pretty improbable that 2014 will have that dubious honor.
Title: Re: Arctic sea ice free (extent)
Post by: Jim on March 02, 2013, 02:03:22 AM
I voted for 2017-2020, but I really want to see this years minimum value. If it is another record, then we could see ice free conditions very soon (2015-16), but if there is a 'rebound' (like 2008 and 2009) then the date could be some time away - we might see a pattern like...

Big Drop
Rebound
Rebound
Big Drop
Rebound
Rebound
..... and so on.

I really think this year will give us a very big clue as to the future course of the summer ice melt.

Title: Re: Arctic sea ice free (extent)
Post by: Edheler on March 02, 2013, 02:54:14 AM
I wish the time periods allowed for a bit more choice. I chose 2017 to 2020 but wouldn't be surprised by it happening in the early 2020's.
Title: Re: Arctic sea ice free (extent)
Post by: FrankD on March 02, 2013, 03:14:52 AM
Extent is a bit tricky because of the three major metrics its the one most dependent on weather conditions (aggregated over the season).

I seem to be on the seams of the time periods in the poll. Like crandles, if there'd been a 2019-2022, that would match my sweet spot.

My gut, which has more nerve endings that my brain (cite: Colbert, 2006), together with some volume curve-fitting, roughs out:
Daily minimum <1 M: ~2015-2017
30 day running min <1 M (ear Sep to early Oct): ~2018-2020
September mean (which was the question) <1 M: 2019-2022

Conservatively, opted for 2021-2030, but I think it will be right at the beginning of that range, and would not be at all surprised if it occurred in the period before that. I would be surprised it if occurred before 2017.

But the Arctic is just full of surprises these days...
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on March 02, 2013, 06:09:35 AM
2016, +/- 3 years.

That implies a 5% chance of SIE < 1M km2 in 2013, a 50/50 chance in 2016, and 95% by 2019.
Title: Re: Arctic sea ice free (extent)
Post by: DungeonMaster on March 02, 2013, 07:22:39 AM
2013-2016
The Artic is mostly with thin ice on AARI now, and I fear that the last thick ice north of Greenland and Canada will start detaching from the coasts and moving as a whole towards warmer, ice-free areas - and start melting there those next years.

I'll closely watch the north-east coast of Greenland this summer to see how the last purple, thick areas resist - or die.
Title: Re: Arctic sea ice free (extent)
Post by: birthmark on March 02, 2013, 09:53:27 AM
A couple of years ago I said 2017. I don't remember what reason (if any) that I picked that year, but I'll stick with it.
Title: Re: Arctic sea ice free (extent)
Post by: Jim Williams on March 02, 2013, 02:23:16 PM
I'll agree with Lodger, though with extent you can have almost no ice and still use up a lot of sea surface.  I'll take the soonest category on the "aggression principle."
Title: Re: Arctic sea ice free (extent)
Post by: anonymous on March 03, 2013, 01:30:36 AM
Mmh, am I the only pessimist here? Remember how the big storm took out a million km² in a week? I would go with 2016 +/-1, but there is no category. Look, here's again PIOMAS raw plus anomaly, what might prolong that story after 2020?

(https://dl.dropbox.com/u/354885/Arctic/asinet/piomas-data-anom.gif)

I understand this poll is about extent, but how much extent is left given volume is zero?
Title: Re: Arctic sea ice free (extent)
Post by: icebgone on March 03, 2013, 01:59:27 AM
Ice melt reaches new records each year from 2013 through 2017.  Export of isolated and detached MYI by 2017 lowers remaining extent below 1,000,000.  Perennial ice free summer extent by 2030 and permanently ice free arctic before 2050.  Warmer water from Pacific and Atlantic plus albedo change trumps cold air and weather.  Another year like 2007 or a sudden release of co2 and/or methane in the arctic and all these dates could accelerate significantly.
Title: Re: Arctic sea ice free (extent)
Post by: Carex on March 03, 2013, 03:07:46 AM
I try, mainly for discussion with those with questions, to phrase my opinions in terms of climate, not weather.  So I like to say in the warmest year of the next ten or thirty.  Given that, I'll pick 2017-2020.  That would be within 10 years after the 2010 volume drop.  I'd say the chance is 90% to 95%.  And the chance of pre-2040 as 99.999%.  My reasoning is based completely on a visual review of photos and graphs.  A gut feeling that ocean warming could overwhelm this but do not have enough background in ocean currents or physics to assess my own opinions.
Title: Re: Arctic sea ice free (extent)
Post by: Wipneus on March 03, 2013, 03:16:00 PM
Given the choices I would guest about 2017-2018 frame.

That would be for a low straight average ice period of any 30 days.
The  NSIDC algorithm may compute a mean that is well above a straight average and the minimum may be in August.
Title: Re: Arctic sea ice free (extent)
Post by: benjamin on March 03, 2013, 05:14:33 PM
If one accepts the conclusion of Shepherd et al (http://xa.yimg.com/kq/groups/18383638/836588054/name/Science-2012-Shepherd-1183-9.pdf (http://xa.yimg.com/kq/groups/18383638/836588054/name/Science-2012-Shepherd-1183-9.pdf)  link kindly provided by Chris Reynolds) then 2,700Gtons (+/-980Gt error bar) more than usual (well, more than deposited in precipitation actually) has been dumped into the Artic between 1992 and 2011 from the Greenland Sheet  and if one believes the CRYOSAT Volume as being similar scale (no more than 5,000Gt) to that then you could argue that pretty much all the "sea" ice has already gone and we are "only" left with the excess from Greenland which in the record breaking 2012 must have contributed another net 400 to 600Gt I would guess.
But I know that is not the intent of the question.
Nevertheless, the CO2, the Methane the temperature are all going one way - up - and all are accelerating so I think the PIOMAS  exponential volume is likely right of 2015 or 2016. But I think that the ever growing extra ice contribution from Greenland may push it back to 2017
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on March 03, 2013, 05:25:36 PM
Whoa there Benjamin,  :o

A lot of the mass loss is actually from melt, and most of the calving is from the East and West Coasts, which are virtually sea ice free at the end of summer. We also know that ice growth is very vigorous in the Arctic over winter, and that the Drift Age Model (which tracks and ages parcels of sea ice) agrees pretty well with the ASCAT satellite system - without any input from glaciers.
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on March 03, 2013, 08:30:16 PM
I don't know what the relationship between date of extent minimum and extent is. I only really do area. But in terms of area there is no relationship, there is no trend in date of minimum despite area going down markedly. However I'm assuming that this is also the case for extent.

I'm also assuming most loss and gain increase will occur around the period of maximum rate of change of extent, where length of ice front is higher than at minimum, and to a lesser degree around the minimum.

I've taken the JAXA extent series for 2003 to 2012, September. For each daily value I have subtracted the extent at minimum for that year. This has the effect of pulling down the extent so that each year hits zero for one day, the minimum criteria for which one might claim a daily extent sea ice free.

Then I've taken the average extent for each of those adjusted Septembers. Only one year 2003 then has an average extent below 1M km^2, that's 2003 at 0.944M. 3 years have an average of >2M km^2

Having assumed that the date of min extent is set by insolation and is invariant as is the case for area, I've set all extent values prior to the date of minimum to zero. In other words the ocean is completely ice free entering September and refreeze starts after the date of minimum for each year 2003 to 2012.

There are 10 years, 4 have an average of well below 1M, 2 have an average of just below 1M, 4 have a September average of well above 1M.

So I prefer a later rather than an earlier date after 2020 for sea ice extent average to be less than 1M km^2.
Title: Re: Arctic sea ice free (extent)
Post by: gfwellman on March 03, 2013, 09:30:51 PM
I was under the impression there was a slight trend to later minimums (driven by albedo feedback).  Of course, that mechanism can't push the minimum much past the fall equinox.  Presumably when we reach ice-free summers, the ice-out date will be before the equinox (and move progressively earlier) while the refreeze gets a little later due to thermal inertia.

I don't think there's any trend in the date of the maximum.  It might be getting more variable because the thinner pack can be pushed around more by winds.

Anybody have actual statistical results?
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on March 04, 2013, 07:49:52 AM
Well I don't do extent, I consider it to be a virtually useless metric, and JAXA is too short to do this.

But a scatter plot of CT date of min vs CT area at min gives a slope of -0.0013, and R2 of 0.0001. Similarly the time series of dates of min has a slope of 0.038, R2 of 0.0029. Both based on linear trends. Therefore I conclude that the date of min is set by the solar cycle with some wiggle due to random weather.
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on March 04, 2013, 10:46:03 AM
...while the refreeze gets a little later due to thermal inertia.
Hi Greg,

Thermal inertia is an annual factor yes, but over decadal time-scales, increasing meridional heat transport will transform the Arctic Ocean into a lobe of the Atlantic, which also does not freeze during Winter.
Title: Re: Arctic sea ice free (extent)
Post by: Gray-Wolf on March 04, 2013, 12:53:39 PM
I think that we all suspect that "The end will come fast" so we should focus on the 'middle' i.e. the melt out of the bulk of the pack? With the thin ice ,this year, allowing for the scale of disruption we have seen so far I have to think that the bulk of the F.Y. ice will have gone by early Aug. Should we lose a section of the remaining multi-year over the same period (via transport through Fram) then we will have a lot of water to eat away at the remaining multi-year through Aug/early Sept?

Remember that some of that 'multi-year' also took a battering last year and so is really only a skim of older ice with a keel of FY ice. I believe that this factor was overlooked last year and allowed for a certain amount of 'solid' multi-year ice to retreat far faster than was expected?

I'd love to see a 'rebound' of ice levels this year but something keeps telling me that this is an unrealistic expectation this time around. In 08' and 09' part of the 'slowdown' of the melt season was the 'collapse and spread' of the remaining perennial ice (as prof Barber saw) and so a portion of that 'rebound' was really a collapse. Now we are without that perennial and so have no large floes to collapse and spread out (bolstering extent) only multi-year with FY ice below?

I think we wait until mid July and see just how much 'solid core' of the pack remains (previous years have the C.T. image of '100% ice' tracing out the pack that will remain come Sept?) I suspect that even this central core will prove less than 100% come Aug (Neven's 'Ice Islands' of Central Basin/Fram for the remaining ice come Sept?).

Any quirk of the weather over summer (high melt synoptics/high transport synoptics) may prove enough to finish off the remaining pack should they arise? The ice will continue to thin ,year on year, but another 'perfect storm' year arriving would finish off the ice over any of the years of the ice's final volume decline. In 07' we were told the 'perfect storm' years were cyclical around a 10 to 20yr time frame with the two previous of 07' being 10yrs apart. Does that favour 2017?
Title: Re: Arctic sea ice free (extent)
Post by: john_mann on March 04, 2013, 07:33:18 PM
Hi there all - sorry, new to this format.

I read a comment over the main articles about acoustic/seismic monitoring of ice sheet cracking. Can anyone elaborate on this?
Title: Re: Arctic sea ice free (extent)
Post by: Nightvid Cole on March 04, 2013, 10:39:02 PM
I picked 2017-2020, but I wouldn't be surprised if we have one last minimum slightly above 1 M km^2 again sometime in the early 2020s (and the deniers will proclaim it the beginning of a recovery). And the very next year it'll probably crash down to something like 500,000 km^2.
Title: Re: Arctic sea ice free (extent)
Post by: Juan C. García on March 05, 2013, 01:54:36 AM
Quote
John Mann:
I read a comment over the main articles about acoustic/seismic monitoring of ice sheet cracking. Can anyone elaborate on this?

Maybe they will help you on the topic: Arctic sea ice - Records and oddities.
http://forum.arctic-sea-ice.net/index.php/topic,35.50.html (http://forum.arctic-sea-ice.net/index.php/topic,35.50.html)
Title: Re: Arctic sea ice free (extent)
Post by: misfratz on March 06, 2013, 12:20:37 PM
I picked 2017-2020, but only because the question specified monthly average extent. I'm fairly confident that the daily minimum will breach the 1 million square km mark before then.

The basis for this is the validation of PIOMAS with the Cryosat observations. Before then I'd been fairly sceptical of PIOMAS on the basis that it was a model with unknown errors and biases. The decline in sea ice volume is more consistent then the decline in extent, so I judge the possibility of a temporary plateau to be much less.
Title: Re: Arctic sea ice free (extent)
Post by: Gray-Wolf on March 06, 2013, 02:00:00 PM
I to did the 2017-2020 slot but that was before we saw this ongoing fragmentation event?

Last year GAC12 made a mess of the ice surrounding the central pack but did not get into the main body proper.

Should a continuation of this fragmentation lead to the whole basin becoming fractured then any storms this summer would disrupt the central ice much more and lead to a lot more inundation of the central area (and higher melt rates).

This fragmentation event has also raised the spectre of high losses into Fram from the 'rump ice' of the Canadian Archipelago. If we continue to see the forecast pushing ice along the trans Arctic current whilst the fragmentation itself pushes further into this 'rump ice' then we could well lose a good portion of our best ice into Fram before May's start to the melt season proper?

All in all I'm begining to wonder whether recent events have upped the odds for this year being the first to have the pack drop below 1 million?
Title: Re: Arctic sea ice free (extent)
Post by: fred on March 06, 2013, 02:24:20 PM
My guess is 2014. I don't think there is anything linear about this.

Not only does open water earlier have more heating, open water has more currents. I think it's like dropping a pat of butter in a soup: as long as the soup isn't stirred, the pat remains insulated by its melt a bit. Stir the pot and the melts almost instantly (i.e. relatively instantly: within margins of error for size of pat, etc.)

If melting is on the same scale more or less as last year, it seems that the chances of another storm dealing serious damage, if not a death blow, seem larger each year. I think the edge or tipping point for loss of summer ice could be well more than 1 million skms.
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on March 06, 2013, 02:47:57 PM
I recall these chilling words from a Century-old poem:

Quote
Turning and turning in the widening gyre
The falcon cannot hear the falconer;
Things fall apart; the centre cannot hold;
Mere anarchy is loosed upon the world,
The blood-dimmed tide is loosed, and everywhere
The ceremony of innocence is drowned;
The best lack all conviction, while the worst
Are full of passionate intensity.


William Butler Yeats, 1919, from The Second Coming.

Yeats was Not a Climate Scientist, but 2019 may not be far off...
Title: Re: Arctic sea ice free (extent)
Post by: Bob Wallace on March 06, 2013, 09:17:41 PM
There's no apparent recovery during this freezing season.  Monthly PIOMAS volume figures continue to track downward on an exponential curve.  The ice appears to be fracturing very early this year.  No melt-slowing factors have been observed.  Volume of transportation continues to hold steady, even with thinner ice being transported.  More heat is available to melt less ice.  The ice is thinner which allows mechanical forces to have a larger impact.

I can see nothing but a crash coming.  And, as it has been amply pointed out, one cannot have area or extent with zero volume.

I would have liked to have been presented with a 2013 to 2019 option, but having to pick I took the shortest.  About six times in the last twenty-five years we have seen annual volume losses that would take us to near zero at today's level.  It would not take an extremely unusual melt to make 2013 the year that the ice melted, only a "normal big melt".
Title: Re: Arctic sea ice free (extent)
Post by: OldLeatherneck on March 06, 2013, 09:37:24 PM
I picked 2017-2020 solely because it is the "engineering mentality" I still have which causes me to vote on the conservative side.  That being said, I wouldn't bet someone else's money on my vote, because I can envision the various scenarios that have the melt occur by 2016, if not sooner.  After all, when you look at the poll results of the first 40 voters, many of which are some of the 'most knowledgeable individuals, on planet earth, when it comes to all things arctic', 85% predict an ice-free summer by 2020.
Title: Re: Arctic sea ice free (extent)
Post by: DavidR on March 07, 2013, 01:25:05 AM
2013-16,. You can't really  go past the fact that the PIOMAS volume has been declining by about 800 cu Km per year over the past 9 years. AS of 2012 it was down to  3.4K in September.  As this rate is increasing there is no reason to  consider the decline anything but  exponential.

This suggests 4 years will easily  see off the 1 Million sq km extent,  and with just one 'warmer' year we could see the ice completely  gone. 
Title: Re: Arctic sea ice free (extent)
Post by: Vergent on March 07, 2013, 02:49:20 PM
In 2002 they said we would have an ice free arctic in 100 years.
Quote
If this alleged trend were to continue, the poles would be ice-free in summer just under 100 years from now. Imagine the summer cruise opportunities!
http://www.worldclimatereport.com/archive/previous_issues/vol7/v7n22/feature.htm (http://www.worldclimatereport.com/archive/previous_issues/vol7/v7n22/feature.htm)


In 2006 it was 70 years.
Quote
Arctic sea ice could disappear within 70 years
http://www.greenpeace.org/international/en/campaigns/climate-change/impacts/habitat_loss/ (http://www.greenpeace.org/international/en/campaigns/climate-change/impacts/habitat_loss/)


late in 2007 it was 50 years.
Quote
According to the latest computer models, says Schauer, the Arctic could be ice free in less than 50 years...
http://www.ens-newswire.com/ens/sep2007/2007-09-14-03.asp (http://www.ens-newswire.com/ens/sep2007/2007-09-14-03.asp)

I figured they had a systemic error. A simple linear extrapolation of that error(in 2008) led me to the conclusion that we would be ice free in 2013.

Nothing since then has led me to doubt that conclusion.
Title: Re: Arctic sea ice free (extent)
Post by: Vergent on March 07, 2013, 03:09:08 PM
In 2011 it was 20-30 years, call it 25. . . Graph those points out and you get a graph that would make Wipneus blush.
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on March 07, 2013, 07:13:10 PM

I figured they had a systemic error. A simple linear extrapolation of that error(in 2008) led me to the conclusion that we would be ice free in 2013.

Nothing since then has led me to doubt that conclusion.

Thanks for sharing that, Vergent.

I also became aware of the trend in accelerated predictions during the Spring of 2006. At that time, I gave a talk to a lay audience on the validity of Arctic sea ice projections. I was met with blank stares and fidgeting. Crickets chirping.

Strong denial is another occurrence that has accelerated in the last 7 years. The most well-informed members of the public gather enough information to have a straw man for every reported scientific observation.

FWIW, in Spring 2006 I also predicted 2013 as the first sea ice free Summer, purely on my observations of the trend in decreasing predictions. Hah! Yet another 'Death Spiral'. My Audience was unimpressed.

I will return to speak to that group during the first sea ice-free September. I expect more blank stares and fidgeting. And the chorus of 'so what?' and 'it's a good thing'. However this time, I also expect a storm outside, as well as inside.
Title: Re: Arctic sea ice free (extent)
Post by: Vergent on March 07, 2013, 08:14:41 PM
x axis = year

y axis times 10 = "years until ice free"

It seems that the predictions are off by a factor of 10.
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on March 07, 2013, 08:33:58 PM
x axis = year

y axis times 10 = "years untill <sic> ice free"

It seems that the predictions are off by a factor of 10.

Hi Vergent,

There it is. The decline in Arctic see is IS linear.  ::)

"Nothing to worry about. Move along. Resume SHOPPING!"
Title: Re: Arctic sea ice free (extent)
Post by: gfwellman on March 07, 2013, 08:50:41 PM
Quote
The decline in Arctic see is IS linear.
Actually, if you look at that graph closely, it hints at a Gompertz  ;)

(Yes, I realize with 4 data points almost in a straight line, fitting anything other than a straight line isn't justified.  I'm just being a little funny because we like our Gompertz fits.)
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on March 07, 2013, 09:13:06 PM
Quote
The decline in Arctic see is IS linear.
Actually, if you look at that graph closely, it hints at a Gompertz  ;)

Hi gfwellman,

Are you MAD?!  >:(

This is CLEARLY a PARABOLA! The 3rd Recovery happened so quickly, we're already moving onto a 5th (of gin).  :P
Title: Re: Arctic sea ice free (extent)
Post by: Vergent on March 07, 2013, 09:59:56 PM
Quote
The decline in Arctic see is IS linear.
Actually, if you look at that graph closely, it hints at a Gompertz  ;)

(Yes, I realize with 4 data points almost in a straight line, fitting anything other than a straight line isn't justified.  I'm just being a little funny because we like our Gompertz fits.)

Quote
Arctic sea ice could disappear within 10 years as global warming increases speed of melting

http://www.dailymail.co.uk/sciencetech/article-2187346/Arctic-sea-ice-disappear-10-years-global-warming-increases-speed-melting.html (http://www.dailymail.co.uk/sciencetech/article-2187346/Arctic-sea-ice-disappear-10-years-global-warming-increases-speed-melting.html)

Gompertz this, and Dodger, your parabola needs some Viagra.

Title: Re: Arctic sea ice free (extent)
Post by: JMP on March 07, 2013, 10:06:15 PM
Sometime around 2012's minimum I came to (the somewhat alarming) conclusion, just based on the graphs that I was seeing, that 2015 looked like the most likely date.  But, what do I know? just read what I can -- so of course it's merely an edumakayted guess. 

I see two wild cards in the deck: one is weather (which is perhaps the most understood) and the other is that AGW is completely new, and although it may parallel past warming events in some ways, there isn't a way to study by any exact method these things that have never happened before (the future cannot be observed etc).  This thought ties in with the comments above about "systemic error" etc.

So, I think before 2020 is a safer bet, but yes I do think it could even happen this summer, (and as long as I'm making guesses mind you) I do think that it probably wont dip below 2.0 and around 3.6 is 2.2 and around 4.0 might be a more likely minimum for 2013.  (It'd probably be better for PR if the minimum was lower this year but so-far nature plus anthropogenic input has not - afaik - moved in quite this linearly obvious way and the minimums have mostly been followed by rebounds (this way of thinking may be scientifically described but I would not describe it as scientific  ;) just as luck would have it thinking etc. ))

I voted 2013-2016.       
Title: Re: Arctic sea ice free (extent)
Post by: OldLeatherneck on March 07, 2013, 10:27:03 PM
What I'm going to be looking for is the extent on or about the 1st of June, which is about the time the entire arctic begins to have sunlight 24 hours/day.  If by some chance the extent is 10.5 Million KM2 or less and the loss during June significantly exceeds other previous years, there will be a chance to reach a minimum below 1.0 Million KM2 this year, but I doubt it would occur soon enough to have an average below that for the entire month of September.
Title: Re: Arctic sea ice free (extent)
Post by: Espen on March 07, 2013, 10:35:32 PM
I think the vote should be: When do believe the Arctic Sea will be sea ice free below 1.000.000 km2 for the first time during the melt season?
Title: Re: Arctic sea ice free (extent)
Post by: JMP on March 07, 2013, 11:01:57 PM
I think the vote should be: When do believe the Arctic Sea will be sea ice free below 1.000.000 km2 for the first time during the melt season?

That was my understanding of what we're voting on, but just as measured by the NSIDC, and was thinking their standard measurement is a monthly average.   After checking I see now that their graphs are based on a 5 day average? and last years minimum of 3.41 million square kilometers was based on a daily average?  Is that right? -- Not that it would change my vote.
Title: Re: Arctic sea ice free (extent)
Post by: crandles on March 07, 2013, 11:45:14 PM
The monthly data is at

ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/Sep/N_09_area.txt

3.61 for Sept 2012 average.

The minimum 5 day average was 3.36855
 
Links to both monthly and daily figures are on the graphs page:
https://sites.google.com/site/arcticseaicegraphs/

(Should we have a link to above graphs page somewhere in the header of this blog?)
Title: Re: Arctic sea ice free (extent)
Post by: JMP on March 08, 2013, 12:23:19 AM
Thanks for the clarification!   It would be helpful it there was an obvious link to the graphs from the forum.  On the home page of the forum might be sufficient if it's easier.  Some of us need all the help we can get.   :D
Title: Re: Arctic sea ice free (extent)
Post by: Vergent on March 08, 2013, 06:03:17 PM
Thanks for the clarification!   It would be helpful it there was an obvious link to the graphs from the forum.  On the home page of the forum might be sufficient if it's easier.  Some of us need all the help we can get.   :D

Just bookmark Neven's graph page.

https://sites.google.com/site/arcticseaicegraphs/
Title: Re: Arctic sea ice free (extent)
Post by: JMP on March 08, 2013, 11:50:47 PM

Just bookmark Neven's graph page.

https://sites.google.com/site/arcticseaicegraphs/ (https://sites.google.com/site/arcticseaicegraphs/)

I think crandles was thinking about others too when he asked:
(Should we have a link to above graphs page somewhere in the header of this blog?)

For instance someone could conceivably come here who has never seen the (other) blog.   I'm not so very familiar with the blog myself and do not recall seeing the graphs page.  Bookmarking it now isn't an issue.    I was looking at data on the NSIDC site here: http://nsidc.org/arcticseaicenews/2012/09/arctic-sea-ice-extent-settles-at-record-seasonal-minimum/ (http://nsidc.org/arcticseaicenews/2012/09/arctic-sea-ice-extent-settles-at-record-seasonal-minimum/) to get  "On September 16, Arctic sea ice appeared to have reached its minimum extent for the year of 3.41 million square kilometers (1.32 million square miles)." and then here: http://nsidc.org/arcticseaicenews/about-the-data/ (http://nsidc.org/arcticseaicenews/about-the-data/) to get "NSIDC produces the daily extent image and graph using a five-day trailing mean. Please note, the values provided are the individual daily values, not the five-day average values that NSIDC displays for its daily extent image and graph."   

Of course I now see my error. 
Title: Re: Arctic sea ice free (extent)
Post by: idunno on March 12, 2013, 12:03:25 PM
My vote is for 2017-20, my reasoning expressed better than I can manage by Lodger above in this thread. If the vote was for the first occurrence of <1million of area on a single day, I would pick 2013-6.
Title: Re: Arctic sea ice free (extent)
Post by: ivica on March 12, 2013, 02:12:10 PM
Ditto from above,
I'm with Lodger et all. on it.
Title: Re: Arctic sea ice free (extent)
Post by: Vergent on March 12, 2013, 03:41:50 PM
This definition of "ice free" is silly.

1,000,000 km^2 of "Extent" could be as little as ;

150,000 km^2 of area

that is the area of Bangladesh.

If that had a thickness of 10cm it would be 15 km^3 of volume.

If the arctic goes ice free by this definition, its going to be truly ice free(except for ice shelves and bergs) a day or two later.

Verg ;-)
Title: Re: Arctic sea ice free (extent)
Post by: slow wing on March 14, 2013, 12:15:50 PM
Long time lurker on Neven's Arctic sea ice blog but this is my first post. I would like to express my appreciation to Neven and the other posters for the outstanding standard of the information and analysis provided there and here.

I voted 2013-16 because firstly the ice volume trend when naively extrapolated shows only a few years left anyway, with an end-point perhaps around 2016 +/- 3. Secondly, it appears likely that the deviation from a naive extrapolation should likely be in the direction of a quicker melt-out. The FYI that now predominates is more saline and should melt more easily than the MYI used to, volume-for-volume. And there have been reports documented on the blog that at least some of the MYI is 'rotten', with little mechanical strength. Thirdly, the ice is already observed to be breaking up on a scale that is unusual and perhaps unprecedented in the satellite record for this time of year. I am largely convinced by Artful Dodger's analysis from the 'Fragmentation event' thread (http://forum.arctic-sea-ice.net/index.php/topic,94.msg1663.html#msg1663) that this should allow all the MYI ice in particular to be transported around to areas where it can more easily melt. Additionally, broken up ice can more efficiently absorb the local heat and salt content. The large scale break-up may be a prelude to break-up into smaller pieces that can melt out quickly.



Title: Re: Arctic sea ice free (extent)
Post by: deep octopus on March 14, 2013, 03:31:58 PM
I'm also pinning a seasonally sea ice-free Arctic in the 2013-2016 range, tending to the lower end of the spectrum. The satellite images of the multiyear ice north of the CAA don't lie. The MYI looks like a set of brittle teeth in dire need of root canals, when really, they are just going to be pulled. By late June, the new ice that has filled the spaces where the MYI has just fractured will be gone under the full intensity of the five-month Arctic summer day, leaving only the MYI stranded in open water once again, whose floes only gradually deteriorate. As a conservative estimate, most of the MYI will be gone by September 2013, with the relicts going through consolidation heading into the desperate 2013-2014 freeze season, and then delivering its final words by September 2014.

Forlorn sadness is an emotion that comes to mind as I watch the gravely wounded ice lay bleeding. It's almost voyeuristic to be doing so, knowing that there is nothing to stop it as it happens, so I can only watch and try to understand.
Title: Re: Arctic sea ice free (extent)
Post by: Juan C. García on March 16, 2013, 08:15:04 PM
I will be writing about the characteristics of NSIDC SIE monthly averages and the difficulty of reaching sea ice extent less than one million km2. So I just want to show how it is the poll right now, before I start to talk about it.
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fi1275.photobucket.com%2Falbums%2Fy449%2Fjuancgarcia22%2FNSIDC_DailyValuesAvg%2FPollASIfree130316_zps13d91345.jpg&hash=0d20f77dc418d669a2d3993118f5136b)
The discussion will be held at the Forum topic: Models of projected Arctic sea ice decline:
With “https”:
https://forum.arctic-sea-ice.net/index.php/topic,83.0.html (https://forum.arctic-sea-ice.net/index.php/topic,83.0.html)
With “http”:
http://forum.arctic-sea-ice.net/index.php/topic,83.0.html (http://forum.arctic-sea-ice.net/index.php/topic,83.0.html)
Title: Re: Arctic sea ice free (extent)
Post by: Jim Hunt on March 16, 2013, 09:40:55 PM
Here are some "predictions" from the scientists amongst the panelists at The Arctic Summit (http://forum.arctic-sea-ice.net/index.php/topic,105.0.html) last week, in descending order:

Stefan Rahmstorf - 2040
Ellen Baum - 2027
Jan-Gunnar Winther - 2023-2033
Rear Admiral Jonathan White - 2023

Personally, I'm inside all of them!

Here's the audio - https://soundcloud.com/water-connects-us/ice-free-summer-arctic-numbers (https://soundcloud.com/water-connects-us/ice-free-summer-arctic-numbers)


Title: Re: Arctic sea ice free (extent)
Post by: mmghosh on March 17, 2013, 04:15:21 AM
2017-2020

I would have chosen 2013-2016 if it wasn't for decreasing insolation over the past decade.
Title: Re: Arctic sea ice free (extent)
Post by: slow wing on March 18, 2013, 09:51:07 PM
Jim Hunt,

  Thanks for going to that conference and reporting back. It was very interesting to read that.

  Did any of those scientists happen to say how they reconcile their predictions stated above with what is observed for year-on-year ice volume loss? What are they thinking might be physical reasons for the volume loss to pull up before volume reaches zero? Thanks.
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on March 18, 2013, 10:31:53 PM
Slow wing,

If you scroll further up this thread you can read a post where I calculate that even if September has no sea ice up to the time the ice starts forming a sub 1M km^2 Sept average is not guaranteed.

The experts who are saying it won't be <1M km^2 extent this decade are right.
Title: Re: Arctic sea ice free (extent)
Post by: Glenn Tamblyn on March 20, 2013, 09:17:38 AM
I went for 2013/2016

With the volume decline from PIOMAS (supported by CS2) we are looking at basic quantities of heat being added each year. Apart from fluctuations in yearly weather, there is no reason to think that that heat accumulation will suddenly stop. Yet for figures much beyond 2016 to be possible, something has to change that rate of volume decline. And it has to happen NOW!

The only scenario where I can imagine it holding out longer is if the last bastion above Ellesmere/Greenland somehow hunkers down and stays put. None of it is lost to the Fram or Beaufort, no major polynyas open up within it, and thinning of it doesn't increase sunlight penetration to warm the water below it. Everything would need to line up perfectly for the remnant to mount any sort of fightback. Anything other than that perfect outcome and the trend continues.

What are the odds of that perfect outcome happening? There are plenty of factors that can accelerate melt. Not many that can retard it.
Title: Re: Arctic sea ice free (extent)
Post by: Jim Hunt on March 20, 2013, 11:57:38 AM
Hi Slow Wing,

Did any of those scientists happen to say how they reconcile their predictions stated above with what is observed for year-on-year ice volume loss?

The shindig (http://forum.arctic-sea-ice.net/index.php/topic,105.msg1916.html#msg1916) was organised by The Economist, so it wasn't really that sort of conference. The scientists were on first, with a few minutes each in which to try and get their message across. By way of example, Stefan Rahmstorf said things like:

Quote
Sea ice volume has shrunk by 80% compared to 1979.... This loss of sea ice is disturbing the weather patterns.

He also happened to mention his latest paper on that very topic!

"Quasiresonant amplification of planetary waves and recent Northern Hemisphere weather extremes (http://www.pnas.org/content/early/2013/02/28/1222000110.full.pdf+html?with-ds=yes)"
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on March 20, 2013, 07:05:20 PM
...Yet for figures much beyond 2016 to be possible, something has to change that rate of volume decline. And it has to happen NOW!

All that has to happen for September average to stay above 1M km^2 is for September up to the date ice starts to grow not to be ice free. It is highly likely that it will be next decade before we have Septembers starting without sea ice.
Title: Re: Arctic sea ice free (extent)
Post by: crandles on March 20, 2013, 07:25:51 PM
There are plenty of factors that can accelerate melt. Not many that can retard it.

Well, there is:

1. We have been melting areas that have net transport of ice out of those regions. To get under 1m km^2 we might have to melt areas that have net transport into those areas piling up thick ice out of thin ice.

2. We are largely melting shallow areas where the seas warm up. Deeper ocean areas may have tendency for any Atlantic Water to sink so that there is much less upward heat flux from AW and it will take much longer to warm ocean there.

3. There is a lot of melt around the edge of the pack. As the pack diminishes the circumference declines so the rate of ice volume loss may well decline.

There are probably others.
Title: Re: Arctic sea ice free (extent)
Post by: Bob Wallace on March 20, 2013, 11:46:36 PM


The only scenario where I can imagine it holding out longer is if the last bastion above Ellesmere/Greenland somehow hunkers down and stays put.


The land masses just south of the thickest ice is loosing its snow cover and heating up.  The channels between the islands are opening and allowing ice to move into melting zones.

The upper side of Ellesmere/Greenland may not be as safe a haven for ice as some thought it might be.

It will likely be the last place where ice is to be found simply because remaining ice which is not swept out the Fram will tend to be moved there by wind and current.  But it's not a safe zone where the ice will be provided any protection from the heat.

It's where the last ice will circle the drain....

Title: Re: Arctic sea ice free (extent)
Post by: pikaia on March 26, 2013, 10:28:51 AM
I voted 2013-16, based on an extrapolation of the volume, which I think is a better indicator than area or extent. I see no reason to believe the Gompertz curve, I expect the decline to accelerate.
Title: Re: Arctic sea ice free (extent)
Post by: fishmahboi on March 26, 2013, 10:38:19 AM
2013 to 2016 for the cracking event has made it practically inevitable that the only Multi Year Ice in the Arctic will be flushed out into the Fram leaving us with extremely weak First Year Ice that is likely to melt out during the first month of summer or so.
Title: Re: Arctic sea ice free (extent)
Post by: Richard Rathbone on March 27, 2013, 12:45:36 AM
Piomas extrapolation has June heading to zero before 2020, so I really don't see any reason to go beyond 2017-2020.

NSIDC uses an averaging method that makes their monthly value biassed towards the high end of the spread of daily values in a month, so it will be a conservative measure of when the Arctic has an ice free month. Ice could vanish on August 10th and reappear on Sept 20th and neither month qualify. Consequently I don't see it happening by 2016, even though PIOMAS might well have a couple of months virtually ice free in 2016.
Title: Re: Arctic sea ice free (extent)
Post by: Juan C. García on March 28, 2013, 05:10:45 AM
Well, if you haven’t vote, there are only three days left, so I invite you to do it.
On the other hand, I thank the votes and replies to this topic. I find very interesting that almost 90% (at this moment) expect an Arctic Sea ice free before or at 2020, even that the question was with NSIDC extent monthly average, that is a tricky way to measure the Arctic sea ice.
So thanks for your participation and we will continue following the 2013 melting season, which seems that will have an early and strong start.
Title: Re: Arctic sea ice free (extent)
Post by: TerryM on March 28, 2013, 08:00:16 PM
I opted for the third choice, 21-30. I have little doubt that we'll experience a 30 day period without ice shortly after our first ice free day based mainly on the sensible heat released when we've run out of ice to melt. Centering that 30 days of ice free conditions on a calender month is where I see problems.


Ice free day by 2015
Ice free 30 day period 2017
Ice free month by NSIDC 2022


All simply WAGs


As an aside. Does anyone have any thoughts on the ramifications of a 30 day ice free Arctic?


Terry
Title: Re: Arctic sea ice free (extent)
Post by: ritter on March 28, 2013, 11:40:02 PM
As an aside. Does anyone have any thoughts on the ramifications of a 30 day ice free Arctic?

Yeah. Bad.  ;)
Title: Re: Arctic sea ice free (extent)
Post by: Jim Williams on March 29, 2013, 12:40:17 PM
As an aside. Does anyone have any thoughts on the ramifications of a 30 day ice free Arctic?

Yeah. Bad.  ;)

Probably will confirm Greenland as the Cold Pole.  Pretty much certain that Winter in North-North America and Europe will either be unusually cold or unusually warm.  Hate to say it, but I think more likely cold.

Expect a lot of extremely negative AO with persistent highs over Greenland, and a continuing pooling of warm water south and south-west of Greenland.
Title: Re: Arctic sea ice free (extent)
Post by: icebgone on March 30, 2013, 02:28:33 AM
I agree with you Jim.  Summer drought in the U.S. and Europe/Russia is more likely due to sluggish weather patterns.  Cold in winter/Hot in Summer and much much drier during growing season.  All-in-all a truly ugly and dangerous long-term change for mankind.  Planning for change is difficult for all living things.  Unfortunately, failure is an option.
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on March 30, 2013, 08:19:08 AM
Does anyone have any thoughts on the ramifications of a 30 day ice free Arctic?
Hi Terry,

I'm in the camp that believes the FIRST ice free Summer will last 30 days. That's not to say the first Summer <1M km2 SIE. But once ALL the ice is gone in the CAB (ignore side shows like Baffin Bay or E. Greenland), then the storms of Autumn will blow in from the N. Atlantic and churn the surface of the Arctic ocean.

There is LOTS of heat down there already. Only the tenuously thin fresh water lens in the Central Basin keeps a cap on it. When that heat comes to the surface, the freeze will be greatly delayed.  :o

I'm also on record predicting 30-40 years from first sea ice-free Summer to the first sea ice-free Winter. There's some science (Eisenman & Wettlaufer, 2008 (http://www.pnas.org/content/106/1/28.short)) to back this up, in that it only takes another 3 wm-2 increase in forcings to go from seasonally ice-free to perennially ice-free. Contrast that with 15 to 20 wm-2 needed to go from perennially ice-covered to seasonally ice-free.

Even in the 1960s, RAND Corporation scientists predicted* it would require just 40 wm-2 to melt the Arctic ice cap (you have to convert from BTUs per fortnight).  ;)

Ramifications? How about the cessation of Arctic deep water creation, causing an interruption of global oceanic circulation? Recall, it is this vertical current and a similar one in Antarctica that carries oxygen into the depths of the ocean. Anoxia in the deep ocean caused 4 of the 5 mass extinction events in deep time. Like seafood? Like breathing?  >:(

* Fletcher, J. O., Ed. (1966). Symposium on the Arctic Heat Budget and Atmospheric Circulation (http://www.rand.org/pubs/research_memoranda/RM5233.html). Proceedings. Santa Monica, CA: RAND Corp. (available in hardcopy only)

* Fletcher, J. O. (1969). Managing Climatic Resources (http://www.rand.org/pubs/papers/P4000-1.html). RAND Corp. (ebook PDF download)
Abstract excerpt: "it does appear to be within man's engineering capacity to influence the global system by altering patterns of thermal forcing."

* Rand Corporation Memorandum 6093-PR / November 1969, by G. A. Maykut & N. Untersteiner Numerical Prediction of the Thermodynamic Response of Arctic Sea Ice to Environmental Changes (http://www.rand.org/pubs/research_memoranda/RM6093.html)"  (ebook PDF download)

Full text for the attached figure: (Eisenman & Wettlaufer, 2008)
http://www.pnas.org/content/106/1/28/F3.expansion.html (http://www.pnas.org/content/106/1/28/F3.expansion.html)
Title: Re: Arctic sea ice free (extent)
Post by: Jim on March 30, 2013, 04:57:22 PM
Hi Artful Dodger,
This is scary stuff!  :-[
I especially don't like the
 "the wintertime sea ice cover abruptly disappears in an irreversible process"
part of the Eisenman & Wettlaufer article - irreversible sounds so, well, final!  :-\
Jim
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on March 30, 2013, 08:33:22 PM
Forgive me if I misremember, but E&W don't only find rapid removal of winter cover, and Eisenman's later paper on bifurcations finds such behaviour to be one of four scenarios, with only simple 'toy' models showing it.

As I say - correct me if I've misremembered, but could people not selectively use the worst cases to reinforce their worst fears?
Title: Re: Arctic sea ice free (extent)
Post by: Jim on March 31, 2013, 03:14:22 AM
Hi Chris,
Yes, worst-case scenarios do attract more attention  :)

Having a look at the whole paper, it seems that they examined a number of levels of surface heating and considered 'bifurcation thresholds' (tipping points) that could possibly push the arctic into a perennial ice-free state.

Although they consider such a situation unlikely when only albedo feedback is taken into account, they do think it could occur if warming continues.

From their conclusion...

"Our analysis suggests that a sea-ice bifurcation
threshold (or “tipping point”) caused by the ice–albedo feedback
is not expected to occur in the transition from current perennial
sea ice conditions to a seasonally ice-free Arctic Ocean, but that
a bifurcation threshold associated with the sudden loss of the
remaining seasonal ice cover may occur in response to further
heating
"
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on March 31, 2013, 09:40:50 AM
I was more wondering if you folks would notice what the science was saying in 1968:

The Polar Ocean and World Climate (http://www.rand.org/pubs/papers/P3801.html) by J. O. Fletcher

Quote
About 10 percent of the northern hemisphere ocean area and 13 percent of the southern is covered in winter by floating ice of variable extent. As the ice pack recedes, storm tracks go farther north and midlatitude rainfall patterns shift eastward.

This is a SUMMARY of established research as of 1968, fully FORTY-FIVE years ago. European Winter much? Drought much?

Then (cautionary hand-waving redacted) Fletcher states:

Quote
After examining the possible effects of removing the ice pack, and the possibilities of doing so, the study concludes that we probably do have the technological ability to eliminate the ice

This was 45 YEARS AGO. And no, Fletcher was no rogue, or renegade scientist. He wrote this paper for the premier defense industry think-tank of the era, the RAND Corporation (http://en.wikipedia.org/wiki/RAND).

Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on March 31, 2013, 09:49:52 AM
As another example, this translated paper was released in the U.S. in 1964 (the title tells you what the Soviets were thinking at the time):

Toporkov, L. G. (April 1964) "Is it Possible to Remove the Ice Cover of the Northern Arctic Ocean (http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0611038)" Foreign Technology Division, Wright-Patterson AFB, Ohio, Report Number: AD0611038 (13 pages)

Abstract: The feasibility of a plan for the removal of the ice cover of the northern Arctic Ocean is discussed. The plan involves the construction of a dam across the Bering Straits and transferring 150,000 cubic km/year of water from the northern Arctic Ocean into the Pacific Ocean and an inflow of the Atlantic Ocean into the northern Arctic Ocean.

Descriptors: (*CLIMATE, ARCTIC OCEAN), (*OCEANOGRAPHY, ARCTIC OCEAN), (*ARCTIC OCEAN, CLIMATE), ICE ISLANDS, MELTING, OCEAN CURRENTS, HEAT TRANSFER, DAMS, BERING SEA, MARINE METEOROLOGY, THEORY, FEASIBILITY STUDIES, PACIFIC OCEAN

Distribution Statement: APPROVED FOR PUBLIC RELEASE



This is one of the DISCARDED schemes that Fletcher writes about in '68. But the MISGUIDED DESIRE to eliminate the Arctic sea ice pack goes back far further.
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on March 31, 2013, 10:11:05 AM
How about this paper from 1975? (PDF (http://onlinelibrary.wiley.com/doi/10.1029/EO056i007p00484/pdf) download available)

Aagaard, K., and Coachman, L. (1975), Toward an ice-free Arctic ocean (http://onlinelibrary.wiley.com/doi/10.1029/EO056i007p00484/abstract), Eos Trans. AGU, 56(7), 484–486, doi:10.1029/EO056i007p00484.

Quote
ABSTRACT: The strong salinity stratification of the Arctic Ocean prevents substantial ice-free conditions in winter by suppressing convection and reducing upward heat flux from the Atlantic Water. These conditions would be significantly altered in the sensitive southern Eurasian basin if suggested diversions of western Siberian rivers were accomplished.
The point is that your grandfathers knew this, they had a clear goal, and they were working on ways to achieve it.

There are STILL plans around proposing to divert Northern rivers to irrigate the parched Southern grain belt. Google it (https://www.google.com/search?q=divert+northern+rivers&hs=eMZ&tbs=qdr:y). Any such plan freshens the Central Arctic Basin, and turns the Arctic over to the Atlantic. Which by the way is the plan. Time to face the facts, shake yourself awake, and realize what is going on, and why.

You are not fighting the Science or Ignorance or Complacency. You are fighting Industrial rapacious greed. First rule of warfare: Know your enemy.
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on March 31, 2013, 11:47:53 AM
Jim,

"Yes, worst-case scenarios do attract more attention"

Yes indeed they do. I'm just trying to argue for context. There are various papers about the transition from seasonally sea ice free to perennially sea ice free. At present I suspect that seasonally sea ice free may be an unstable state, but that's just a suspicion.
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on March 31, 2013, 12:13:53 PM
This Letter to Nature was 40 years old on Jan 5th, and the Publishing Journal still wants $32 to download it.  :o

R. L. NEWSON (1973) "Response of a General Circulation Model of the Atmosphere to Removal of the Arctic Ice-cap (http://www.nature.com/nature/journal/v241/n5384/abs/241039b0.html#References)" Letters to Nature 241, 39 - 40 (05 January 1973); doi:10.1038/241039b0

Quote
OVER the past few years, numerical models have been developed for investigating the general circulation of the atmosphere and studying its long term behaviour. (See, for example, Smargorinsky et al. 1 Kasahara and Washington2.) These models are firmly based on the equations of fluid motion and thermodynamics and simulate in mathematical terms the chief physical processes which are thought to be of importance in determining large scale atmospheric motions over long periods of time (a month or more). The advent of very high speed computers has made numerical experiments with these models reasonably easy.

References:

Seems like they were beavering quite hard on the problem 40 years ago. And according to Newson, they had the high speed computers needed to solve it. Well, it was almost a month since the final Apollo Mission to the Moon (also done with the computers of the era).  ::)

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2Fthumb%2F7%2F76%2FApollo_17-insignia.png%2F201px-Apollo_17-insignia.png&hash=1ee91d4cdb73be196bdd813163d43aa3)
Title: Re: Arctic sea ice free (extent)
Post by: Jim on March 31, 2013, 02:01:00 PM
Hi Chris,
If we can cap future temperature rise, then the seasonal ice-free scenario could be stable. If, later, we can even get a reduction in Arctic warmth, then a return to present conditions might be possible - but if CO2 levels continue to rise, and the Arctic continues to warm, then a perennial ice-free Arctic could result. It might take decades, or more, but on our current trajectory this seems to be the eventual state of the Arctic.
Jim


Jim,

"Yes, worst-case scenarios do attract more attention"

Yes indeed they do. I'm just trying to argue for context. There are various papers about the transition from seasonally sea ice free to perennially sea ice free. At present I suspect that seasonally sea ice free may be an unstable state, but that's just a suspicion.
Title: Re: Arctic sea ice free (extent)
Post by: Juan C. García on April 01, 2013, 06:58:16 AM
Last day to vote...  ;)
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on April 01, 2013, 05:15:34 PM
Jim,

I'm afraid I think it a virtual inevitability that we'll burn all the fossil fuels we have access to, unless a new energy source becomes more cost effective and cheap. Therefore when considering the issue of whether the Arctic will become perennially ice free my consideration is restricted to what CO2 level this is possible. That leaves open the question of feedbacks etc and possible bifurcations.
Title: Re: Arctic sea ice free (extent)
Post by: Jim on April 01, 2013, 07:42:29 PM
Let's see what Obama does with the XL Pipeline - I don't hold out much hope, but you never know!
If he were to stop the pipeline, and possibly roll-back on other dirty oil/gas projects, then that could send a positive message to other countries.
China and India are already looking to alternatives to fossil fuels, if only to limit their increasingly chronic pollution and infrastructure problems.
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on April 01, 2013, 10:02:01 PM
Jim,

Economics and the situation regards oil depletion and oil price make it a certainty.

I've just done some digging regards the Keystone XL and Alberta Tarsands. There's a paper from Nature in 2012 from Swart & Weaver. Swart's page on the paper is here:http://climate.uvic.ca/people/nswart/Alberta_Oil_Sands_climate.html

And here is a graphic showing the GWP from various sources:
http://climate.uvic.ca/people/nswart/oil_sands_images/warming_global_resources.gif (http://climate.uvic.ca/people/nswart/oil_sands_images/warming_global_resources.gif)

That's around 0.36degC warming if all the estimated reserves prove economically extractable, 0.03degC warming if the proven economically extractable reserves are burned. Looking at their pdf of calculations they seem to be assuming that all bitumen is converted to oil. This covers the fact that once conversion has taken place a carbon rich slag is left, which can be burnt as dirty coal. So those warmings are upper bounds. If Swart & Weaver are right Keystone XL adds to warming but it's not 'game over' as some have said.

What that graph does suggest is that if coal reserves are half accurate we have a big problem.
Title: Re: Arctic sea ice free (extent)
Post by: Csnavywx on April 02, 2013, 01:40:50 AM
With paleo-evidence of Antarctic glaciation occurring in the 400-500 ppm range, how much time do we reasonably expect to have with even seasonal Arctic sea ice? Even though these values are close to the full equilibrium response, we can't truly be serious about believing the models that say in upwards of 1000 ppm must be reached before perennially ice-free conditions are met.
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on April 02, 2013, 03:36:21 PM
To glaciate what is needed it that the ice survive through the summer. Therefore the threshold of glaciation is likely lower than that needed to keep a polar region above zero year round.
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on April 03, 2013, 09:48:30 AM
Let's see what Obama does with the XL Pipeline <snip>
Hi Jim,

This is the Forum >> Cryosphere >> Arctic Sea Ice.

Your discussion belongs in an appropriate thread under Policy and Solutions.

Thanks everyone for keeping on topic, and putting in the tiny extra effort it takes to post in the appropriate thread.  8)
Title: Re: Arctic sea ice free (extent)
Post by: Jim on April 03, 2013, 12:25:24 PM
Hi Lodger,
A tricky one this, the subject had already been raised, and these issues are all tightly inter-related. Nevertheless, I will endeavour to remain 'on topic' in future  :)
Jim


Let's see what Obama does with the XL Pipeline <snip>
Hi Jim,

This is the Forum >> Cryosphere >> Arctic Sea Ice.

Your discussion belongs in an appropriate thread under Policy and Solutions.

Thanks everyone for keeping on topic, and putting in the tiny extra effort it takes to post in the appropriate thread.  8)
Title: Re: Arctic sea ice free (extent)
Post by: Chuck Yokota on April 03, 2013, 01:29:26 PM
Over on Skeptical Science, a moderator pointed out a follow-up on Eisenman & Wettlaufer, 2008, at http://eisenman.ucsd.edu/reprints/Eisenman-2012.pdf (http://eisenman.ucsd.edu/reprints/Eisenman-2012.pdf) which I have just started to study.  It discusses the underlying processes that cause different global climate models to show smooth or discontinuous transition from seasonally ice-free to year-around ice free.
Title: Re: Arctic sea ice free (extent)
Post by: Jim Williams on April 03, 2013, 01:56:39 PM
This figure from the NSIDC's report for March ( http://nsidc.org/arcticseaicenews/ (http://nsidc.org/arcticseaicenews/) ) would seem to indicate that a rebound this year is rather unlikely.  It also indicates that my guess of a melt-out this year isn't too likely either.   Seems it's the second year ice that is really suffering, though the old ice has detached from Greenland; which probably signals the beginning of the end.
Title: Re: Arctic sea ice free (extent)
Post by: Peter Ellis on April 03, 2013, 03:03:22 PM
This figure from the NSIDC's report for March ( http://nsidc.org/arcticseaicenews/ (http://nsidc.org/arcticseaicenews/) ) would seem to indicate that a rebound this year is rather unlikely. 

Why so?  Sure, it shows a drop in older ice compared to last year, but the drop from 2007-2008 was far greater, and yet 2008 and 2009 both bounced back noticeably.
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on April 03, 2013, 10:27:26 PM
Thanks Chuck,

That's the paper I was referring to when I had a moan about people choosing worst case scenarios.
Title: Re: Arctic sea ice free (extent)
Post by: Shared Humanity on April 04, 2013, 01:01:57 AM
I have some questions about using ice age as evidence of health. Does 5 YO ice mean the same thing that it did 20 years ago or even 10 years ago? Sure the ice has hung around for a while but has it been able to thicken as in the past?

If not, is this rebound since 2007 really as dramatic as the chart suggests?
Title: Re: Arctic sea ice free (extent)
Post by: crandles on April 04, 2013, 01:55:38 AM
I have some questions about using ice age as evidence of health. Does 5 YO ice mean the same thing that it did 20 years ago or even 10 years ago? Sure the ice has hung around for a while but has it been able to thicken as in the past?

If not, is this rebound since 2007 really as dramatic as the chart suggests?

Surely that depends on what do you take it mean:

If you take it to mean thickness, then I think PIOMAS and ICESAT are clear enough that it isn't as thick. That of course looks at total thickness of the ice. It seems quite likely that a greater proportion of the thickness is now FYI rather than it almost all being MYI in the past. In the past it was thick enough that it wouldn't gain any thickness except by mechanical thickening. These days it gets quite thin in summer and gains thickness thermodynamically in winter (ie FYI added to bottom of MYI).

Is it as extensive within the pixel concerned? I would suggest that more cracking means more FYI forms in cracks then gets squashed up between flows. So I suspect the actual arial coverage has declined more than the age data shows. (If there is more than 15% MYI coverage in a block of ice I think it is all taken to be the oldest category for which there is over 15% coverage.)

So if you are thinking thickness, area or volume then it is probably worse than the data suggests.

However, if you are thinking old ice = fresh ice which is harder to melt then things might in one way be better than the data suggests. The more frequently the temperatures get above freezing and the more by which temperatures rise above freezing can cause brine rejection. So x year ice might now be fresher than it was in the past.

So the volume is probably worse than the data shows but it might be fresher meaning more energy to melt for a fixed volume.

I would suspect, but it is only a pure guess, that the energy required to melt is rather worse than the data shows. Based on suspecting thickness is a much more important element than area or freshness.

Re rebound since 2007:
Is it a better like with like comparison to compare current levels with 2008 and say there isn't much change in percent of area since 2008? (3+ down while 1-3 up slightly more than 3+ is down though I expect a net decline for March 2008 to 2014.) Or would comparing to 2009 be better?

I really don't understand why those graphs are in percent of area rather than just area which would be a little easier to see if you are comparing like with like.
Title: Re: Arctic sea ice free (extent)
Post by: Jim Williams on April 04, 2013, 03:31:32 AM
This figure from the NSIDC's report for March ( http://nsidc.org/arcticseaicenews/ (http://nsidc.org/arcticseaicenews/) ) would seem to indicate that a rebound this year is rather unlikely. 

Why so?  Sure, it shows a drop in older ice compared to last year, but the drop from 2007-2008 was far greater, and yet 2008 and 2009 both bounced back noticeably.

I'm basing that on the comparative lack of second year ice. After 2007 it returned to trend.  After 2012 the trend looks a whole lot like the 2007 low did.

On the other hand, the older ice is about the same as it has been.  So that seems against complete melt-out.
Title: Re: Arctic sea ice free (extent)
Post by: wanderer on April 04, 2013, 11:22:26 AM
Huge Extent drop: (200k)
http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm (http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm)

Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on April 06, 2013, 02:11:10 PM
Over on Skeptical Science, a moderator pointed out a follow-up on Eisenman & Wettlaufer, 2008

John Wettlaufer and Ian Eisenman have separately authored two follow-on papers to their seminal 2008 study:

Moon, W., and J. S. Wettlaufer. "On the existence of stable seasonally varying Arctic sea ice (http://pantheon.yale.edu/%7Ejw378/articles/TwoSeason_JGR_2012.pdf)." arXiv preprint arXiv:1202.5506 (2012).

Eisenman, Ian. "Factors controlling the bifurcation structure of sea ice retreat (http://arxiv.org/pdf/1202.5506)." Journal of Geophysical Research: Atmospheres (1984–2012) 117.D1 (2012).
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on April 08, 2013, 01:57:42 PM
I'm in the camp that believes the FIRST ice free Summer will last 30 days. That's not to say the first Summer <1M km2 SIE. But once ALL the ice is gone in the CAB
MORE idle talk unless it's backed with some real science! Here it is: ;)

Eisenman, Ian. "Factors controlling the bifurcation structure of sea ice retreat. (http://www.agu.org/pubs/crossref/2012/2011JD016164.shtml)" Journal of Geophysical Research: Atmospheres (1984–2012) 117.D1 (2012).

A PDF (http://authors.library.caltech.edu/29296/1/Eisenman2012p17064J_Geophys_Res-Atmos.pdf) is freely available (yes, this is the same Ian Eisenman who with John Wettlaufer wrote the seminal 2009 paper "Nonlinear threshold behavior during the loss of Arctic sea ice (http://ateson.com/ws/r/www.pnas.org/content/106/1/28.full)").

Panel C of Figure 8 of Eisenman2012 (attached below) clearly shows that the first time sea ice touches zero, that year remains sea ice free for over 70 days (~20% of a year).  :o

Further, Panel C shows that 1st sea ice free day occurring around Day 240, which is August 28th in a normal year. Freeze-up would not begin until Day 310, or November 6th.  :-[

Figure 8. Poincaré maps (http://en.wikipedia.org/wiki/Poincar%C3%A9_map) and ~E(~t) trajectories. (a) Poincaré map with default parameter values... (b) Same as Figure 8a but with... initial conditions slightly warmer and colder (c) One-year trajectories of E (Surface enthalpy (http://en.wikipedia.org/wiki/Enthalpy#Relationship_to_heat)) associated with the green circles in Figure 8b.

Eisenman2012 (http://authors.library.caltech.edu/29296/1/Eisenman2012p17064J_Geophys_Res-Atmos.pdf), page 11, Figure 8:
Title: Re: Arctic sea ice free (extent)
Post by: TerryM on April 08, 2013, 07:48:19 PM
Lodger


Haven't read the paper yet, but could you synopsize what they're postulating would be sufficient to keep things open so late in the year?


I apologize for commenting before reading, but it's one of those days with a lot of things backing up & the subject is fascinating.


Terry
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on April 08, 2013, 09:55:37 PM
...could you synopsize what they're postulating would be sufficient to keep things open so late in the year?
yes, latent heat going into the sea ice quickly switches to sensible heat going into the ocean after the last of the sea ice is gone. It takes time to give back all that heat.
Title: Re: Arctic sea ice free (extent)
Post by: TerryM on April 09, 2013, 05:07:23 AM
Thanx


I'll try to get the paper read tonight.


I've been very interested in the release of sensible heat when the ice is gone, but suspected that it wouldn't  be a factor until the year after the first melt.


Terry
Title: Re: Arctic sea ice free (extent)
Post by: Richard Rathbone on April 09, 2013, 06:40:34 PM
I think it depends how early in the season it hits zero the first time it does. If it just makes it there in late September, its not going to stay ice free long. So if it only goes to zero the first time this year because there was an unusually favourable September for melt, its not going to be ice free for 70 days. However, a couple of years of unfavourable weather, followed by a high rate melt season, and it could easily go ice free at the beginning of August and pick up enough heat to stay that way through October.

If you look at the trend lines for how fast each month is heading to zero, there are several not far behind September. September takes a year longer than trend, or they take a year less, and you could have a 100 day ice free Arctic the first time it happens.

This year I'd say if it happens its probably only for a few days and people will argue about whether it was technically "ice-free" during those days. If it doesn't happen until 2015 or 2016 it could easily be 100.
Title: Re: Arctic sea ice free (extent)
Post by: fishmahboi on April 09, 2013, 06:46:14 PM
Is it possible for the Arctic Ice to his zero possibly during June or July and if not, what conditions would be needed for such an occurrence to ensue?

Title: Re: Arctic sea ice free (extent)
Post by: TerryM on April 09, 2013, 07:02:03 PM
Lodger


They're using a 50 m mixing layer in the model. In 2011 a British group found mixing down to 200 m under FYI. Would the much larger mixing layer act as a damper on seasonal variations even though it would result in higher temperatures at the ice/water interface?


I'd assumed that the first melt out year would be similar to the previous year, but that in the following year sensible heat would be released when there was no more ice to melt.


Terry
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on April 09, 2013, 07:57:01 PM
Is it possible for the Arctic Ice to his zero possibly during June or July and if not, what conditions would be needed for such an occurrence to ensue?

This June/July?

Not at all possible.    

Monthly Average Volumes for 2012.

April 21.73
Loss of 6.16
July 14.70
Loss of 10.33
September 4.36

Therefore it is not going to happen, and you can rest assured that anyone telling you that it will, or even could, doesn't have the vaguest brush with the data or the physics.   

 ::)
Title: Re: Arctic sea ice free (extent)
Post by: fishmahboi on April 09, 2013, 08:56:17 PM
Is it possible for the Arctic Ice to his zero possibly during June or July and if not, what conditions would be needed for such an occurrence to ensue?

This June/July?

Not at all possible.    

Monthly Average Volumes for 2012.

April 21.73
Loss of 6.16
July 14.70
Loss of 10.33
September 4.36

Therefore it is not going to happen, and you can rest assured that anyone telling you that it will, or even could, doesn't have the vaguest brush with the data or the physics.   

 ::)

Would the fracture event not have an effect on that (I probably should have included this in my initial question) in the sense that there is much more open water and the Multi Year Ice on the north of Greenland is quite mobile this year.
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on April 09, 2013, 09:29:45 PM
Between April and July the loss in 2012 was 6.16.

Between July and September the loss in 2012 was 10.33.

Will the fracturing mean that 10330 cubic KILOMETRES of ice just go 'puff'?

Will it f.....

 ;D
Title: Re: Arctic sea ice free (extent)
Post by: anonymous on April 10, 2013, 01:20:37 AM
Will the fracturing mean that 10330 cubic KILOMETRES of ice just go 'puff'?

Chris, don't spoil the game. Actually, I would find it interesting if someone calculates the energy needed to melt 10³km³ ice, and put this in context. I'm sure you don't need sun going supernovae. Last in Greenland a cloud cover with just the right thickness forced a lot of melting. Also, there is enough warm water below 200m to melt all the ice. The question itself is not wrongful, if there is a plausible cause for such a melt I'd like to know, even if it is not much likely to happen.
Title: Re: Arctic sea ice free (extent)
Post by: slow wing on April 10, 2013, 02:27:32 AM
Hi Arcticio,

If you only need plausible then, sure, I will wave my hands...  ;D

The area of the Arctic Ocean is 14 million km^2.

Let's suppose the ice volume is 14,000 km^3 at the start of July, but it is all broken up into chunks and spread throughout the Arctic Ocean, with gaps everywhere exposing water to the sun.

Let's define the effective critical albedo as the fraction of the incident sunlight required to melt all the ice in the month of July.

In mid-summer, the sun shines 24 hours/day at the pole. I seem to recall that the incident sunlight energy/day there is more than at any other place in the world. I don't remember exactly, but lets assume 20 MJ/(day.m^2) x 31 days in July ~ 600 MJ/m^2 in July.

We know the average ice thickness is 14,000 km^3 / 14,000,000 km^2 = 1m. Therefore, we need to melt 1 tonne of ice per m^2.

The latent heat of fusion for ice is 334 J/g = 334 MJ/tonne.

Putting it altogether,

effective critical albedo ~  334 MJ/tonne x 1 tonne/m^2 / 600 MJ/m^2 ~ 0.56.


So, given the roughness of the calculation, it seems that about half the incident sunlight in July  would have to go towards melting the ice in order to melt it all that month.


But then we could move to a more plausible model than that - where the ice has all broken up by the beginning of June and then has both June and July to all melt out. The effective critical albedo in that case might only be about 0.3 - which doesn't look crazy to me if there is a lot of water exposed.

Then we could look at where the ice has all broken up by the beginning of May, where maybe we are down to an effective critical albedo of 0.2...

Then we can wave our hands a bit more about the currents, the wind and layer mixing bringing in extra heat as well, and maybe some extra export through the straits...


So I say the scenario is unlikely but it is not physically impossible for the ice to all melt out by the end of this July, due to it all breaking up into small chunks.




Title: Re: Arctic sea ice free (extent)
Post by: Vergent on April 10, 2013, 02:57:57 AM
Slow Wing,

The actual figure is a little over 500 W/m2 at peak If you use 450, you get 39 megajoules/day. So your argument is on the conservative side.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.physicalgeography.net%2Ffundamentals%2Fimages%2Finsolation_latitude.gif&hash=a8e1cc23311451c7f6209a2b0451db8a)

V
Title: Re: Arctic sea ice free (extent)
Post by: slow wing on April 10, 2013, 03:14:58 AM
 Cheers, Vergent. Wow, that's nearly a factor of 2 higher than I had assumed!  So the scenario becomes less implausible so far as I can tell.

  A question though to people who know about sea ice: is it plausible that it might continue to break up throughout much of the Arctic until it reaches small chunks of typically only a metre, or a few metres, on a side?
Title: Re: Arctic sea ice free (extent)
Post by: Vergent on April 10, 2013, 03:24:57 AM
Cheers, Vergent. Wow, that's nearly a factor of 2 higher than I had assumed!  So the scenario becomes less implausible so far as I can tell.

  A question though to people who know about sea ice: is it plausible that it might continue to break up throughout much of the Arctic until it reaches small chunks of typically only a metre, or a few metres, on a side?

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ficefloe.net%2FAloftcon_Photos%2Falbums%2F2012%2F20120908-0301.jpeg&hash=d8c2b2fec82be8cd9d9d8acb4f6f9d7e)

It did last year

http://icefloe.net/Aloftcon_Photos/index.php?album=2012 (http://icefloe.net/Aloftcon_Photos/index.php?album=2012)

V
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on April 10, 2013, 07:12:17 AM
Therefore, we need to melt 1 tonne of ice per m^2... The latent heat of fusion for ice is 334 J/g = 334 MJ/tonne.
Hi slow wing,

Um, no. Sea ice contains brine and air bubbles, both of which decrease the density and latent heat of fusion for sea ice. First year sea ice (FYI) is saltier than multiyear ice (MYI). Winter 2013 has a record high ratio of FYI to MYI.

These are empirical issues. It's helpful to provide a reference when you quote figures. For instance, a trivia Google search finds this paper:

Ohshima, K. I., Mizuta, G., Itoh, M., Fukamachi, Y., Watanabe, T., Nabae, Y., ... & Wakatsuchi, M. (2001). Winter oceanographic conditions in the southwestern part of the Okhotsk Sea and their relation to sea ice. Journal of oceanography (http://faculty.petra.ac.id/dwikris/docs/cvitae/docroot/html/www.terrapub.co.jp/journals/JO/pdf/5704/57040451.pdf), 57(4), 451-460.

Searching within the PDF for "latent heat of fusion for sea ice" finds this, on Page 6:

Quote
the density of sea ice and the latent heat of fusion for sea ice are taken as 900 kg m–3 and 0.276 MJ kg–1, respectively

So the latent heat of fusion of FYI is about 276 MJ/tonne. And since 1 M3 of FYI has a mass of 900 kg, the heat of fusion of 1 cubic meter of sea ice is 248.4 MJ. The figure you use is 34.5% higher. ;)

Note that this study was conducted in the Southwestern part of the Okhotsk sea, which guarantees that the values obtained are for FYI.

BTW, searching the ASI blog is productive. This issue has been discussed extensively. The important metric we call CAPIE (http://neven1.typepad.com/blog/2011/08/capie-hits-record-low.html?cid=6a0133f03a1e37970b014e8ac76042970d#comment-6a0133f03a1e37970b014e8ac76042970d) is an estimate of the ratio of open water to sea ice within the pack ice. Insolation is discussed there as well.

Wipneus posted this chart and this comment (http://neven1.typepad.com/blog/2011/10/september-2011-sea-ice-extent-looking-ahead.html?cid=6a0133f03a1e37970b014e8c17ba8b970d#comment-6a0133f03a1e37970b014e8c17ba8b970d) on the ASI blog: (quoted below)

(https://sites.google.com/site/arctischepinguin/home/asib/insol120-219.png)

Quote
Here is my version of the graphic (100 days high summer): So indeed in high summer, the north pole receives more energy than a place on the polar circle. The difference for these 100 days is about 7%.

Note: Day 120 is April 30, and Day 219 is Aug 07 in a normal year. This is the 100 day 'top-melt season' centered around the Northern Summer solstice. On the ASI blog, we've come to refer to the lower insolation days of late summer as the 'bottom-melt season'.
Title: Re: Arctic sea ice free (extent)
Post by: fishmahboi on April 10, 2013, 09:17:37 AM
I recognise that it is indeed possible for the Arctic to melt out in June or July depending on the amount of open water and the size of the Arctic Ice as a whole, it cannot survive it there is a large extent, but it mainly consists of broken ice, and thus I have to wonder about how long the Arctic would stay ice free if the ice did melt out as early as June.

I would ask about the impacts, but that's for the consequences subforum.
Title: Re: Arctic sea ice free (extent)
Post by: anonymous on April 10, 2013, 09:42:44 AM
Slow wing, great. Let me throw in data from buoy 2006C (http://imb.crrel.usace.army.mil/2006Csum.htm), showing bottom melting of ~1m per month happened in summer 2007.

(https://dl.dropbox.com/u/354885/Arctic/asinet/buoy2006c.jpg)
Title: Re: Arctic sea ice free (extent)
Post by: slow wing on April 10, 2013, 09:44:56 AM
Hi Vergent and Dodger,

  Yes Vergent, the state of the ice in that photo should do the trick.

Dodger, thanks for information in the references. It was just a plausibility argument so I didn't worry too much about 10-20% effects. That factor of 2 in the insolation needed to be fixed though.

So, re-running the argument with the factors rounded to 1 significant figure:

Ice is all broken up by the end of May: could it melt out by the end of July? Assume:

1 tonne/m^2 of ice left at end of May (this is about 15,500 km^3 at a density of 0.9 tonnes/m^3)
300 J/g = 300 MJ/tonne = heat of fusion
Insolation is 40 MJ/(day.m^2) (question: does that allow for clouds?)
60 days (OK, is 61)

critical absorbtion fraction to just melt the ice =

300 MJ/tonne x 1 tonne/m^2 / (40 MJ/(day.m^2) x 60 days) = 1/8

So, in this simple model and neglecting other heat sources and sinks...

 If only 1/8th of the solar energy goes into melting the ice then the Arctic Ocean could be ice free by the end of this July.

So the scenario is at least plausible imo.










Title: Re: Arctic sea ice free (extent)
Post by: slow wing on April 10, 2013, 09:48:45 AM
Slow wing, great. Let me throw in data from buoy 2006C (http://imb.crrel.usace.army.mil/2006Csum.htm), showing bottom melting of ~1m per month happened in summer 2007.
Wow! That's a lot!

Am I right that the general consensus was that about twice the normal amount of heat to melt the ice flowed in through the Bering Strait that year? It could be carnage if it happens again this year.
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on April 10, 2013, 10:30:48 AM
Am I right that the general consensus was that about twice the normal amount of heat to melt the ice flowed in through the Bering Strait that year? It could be carnage if it happens again this year.
Hi slow wing,

Yes, twice the normal heat influx in Summer 2007 is about right.

Woodgate, Rebecca A., Tom Weingartner, and Ron Lindsay. "The 2007 Bering Strait oceanic heat flux and anomalous Arctic sea-ice retreat (http://neven1.typepad.com/files/2009-woodgate-et-al.---2007-bering-strait-heat-flux.pdf)." Geophysical Research Letters 37.1 (2010): L01602.

This level of heat influx seems to be about a once-in-20-years event. Dr. Wieslaw Maslowski of the Naval Postgraduate School provides more data in Table 1 of this paper:

Maslowski, Wieslaw, et al. "The future of arctic sea ice (http://www2.bren.ucsb.edu/~dozier/Class/ESM203Fall2008/Reading/Overland_GRL2007.pdf)." Annual Review of Earth and Planetary Sciences 40 (2012): 625-654.
Title: Re: Arctic sea ice free (extent)
Post by: anonymous on April 10, 2013, 11:47:59 AM
I think two more effects happened in 2007 to the floe carrying buoy 2006C. There was open water, clear sky and mostly southerly wind. The surface water on the luv side was heated first and then driven below the ice. But my pet theory is once all the surface water got transported away it was replaced by upwelling with warm water from below, also then blown under the ice. All three effects together lead to turbo melting, so watch out for long lasting Arctic Dipoles.
Title: Re: Arctic sea ice free (extent)
Post by: ael on April 10, 2013, 03:44:58 PM
Um, no. Sea ice contains brine and air bubbles, both of which decrease the density and latent heat of fusion for sea ice.

I am confused how brine would decrease the density of sea ice.  Is not salt water denser than ice?
Title: Re: Arctic sea ice free (extent)
Post by: TerryM on April 10, 2013, 07:25:22 PM
Wow


I had no idea that latent heat for sea ice was different than for fresh ice. Since reading Lodgers post I've done some reading that indicates that not only is latent heat much less with sea ice - one of the figures I got was 246 kJ kg-1 at -2C - but also that there was a 2% difference between freezing and melting latent heat, with freezing being lower than melting.


David N. Thomas, Gerhard S. Dieckmann 2009 - page


Back to the drawing board - with a big eraser.


Terry





Title: Re: Arctic sea ice free (extent)
Post by: crandles on April 10, 2013, 07:26:22 PM
I am confused how brine would decrease the density of sea ice.  Is not salt water denser than ice?

If you exclude the weight of the brine but include the volume that it takes up then you end up with a lower density. While that may seem to be not comparing like with like, it is presumably what you would do for working out the latent heat needed to melt the block of ice that contains some brine.
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on April 10, 2013, 07:55:06 PM
Let me repeat.

April 21.73
Loss of 6.16
July 14.70
Loss of 10.33
September 4.36

In other words there would have to be a melt of 267% of ice volume from April to July for July to end up near zero.

Slow Wing,

In June 2012 most of the ice was just under 2m thick, with thinner ice in Barents and Beaufort. Peak volume loss is in July, at a typical 7k km^3 loss between June and July, 12k km^3 loss between August and June. You cannot move that loss forward because it is insolation driven and insolation is fixed. Vergent's figures for insolation are for top of atmosphere insolation, due to the low angle of incidence figures hitting the surface are lower, and due to low angle of incidence albedo is higher due to reflection of oblique rays off the surface.

If you're getting calculated results that show that a loss of 267% of ice volume from April to June is feasible with only 1/8 of insolation your assumptions are wrong. For a start, it comes before the bulk of the region's annual volume loss.

Here's the profile of volumes and losses on the first day of the month for 2012

4, 21.65, 1.757
5, 21.447, -0.203
6, 17.809, -3.638
7, 10.879, -6.93
8, 5.718, -5.161
9, 3.455, -2.263

i.e. for 6 (june) the negative number is the change from 1st May to 1st June.

After July there is a total of ~7.3 thousand cubic kilometers of ice. To get ice free in July you must melt this before July. Bearing in mind that the loss to the end of July from 1 May is ~10.7k km^3.

Frankly, I am staggered I'm even spending time replying to this.

Vergent,

I seriously doubt next year will see a melt out by July for the reasons I've already given. Sea ice in the Arctic basin will still grow to 2m thick over winter even if all the MYI goes, so net volume for the Arctic ocean will still exceed about 20k km^3. Until we see significant warming over winter this will continue to be the case. So against such a gain of volume over winter the question becomes how much can we reasonably expect the ice to loose during the melt season? The answer is that to get a sea ice free Arctic the total loss must be over 20k km^3. Here are the volume losses for the 2000s, but these include ice outside the Arctic Ocean.

2000 16.342
2001 15.574
2002 16.746
2003 17.079
2004 15.93
2005 17.022
2006 16.198
2007 17.407
2008 18.087
2009 18.189
2010 18.974
2011 17.944
2012 18.662

Now the peak volume for the last three years* has been around 21.9k km^3, which gives an indication of the start volume for these losses. *Assuming this year will be around that.

I said above I was staggered I was bothering to reply to this. I've decided it's not a useful expenditure of my time. Go ahead and dream up what you all want, I'll leave the ice to give the answer.
Title: Re: Arctic sea ice free (extent)
Post by: anonymous on April 10, 2013, 09:08:24 PM
Regarding turbo melting, didn't that happen at a regional level in 2011? The famous Laptev Bite? IIRC two weeks with ~20°C offshore wind was the reason. And I think Chris is right: Insolation has a well known upper level. Let's hope the other factors behave like the years before.
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on April 10, 2013, 09:16:27 PM
"Could you use your superior skills with data and physics to estimate how much ice an inrush like this could melt?"

When has such an inrush occurred in reality?

Really you're just chasing ghosts. You want to believe in them fine, it's your mind. But don't expect me to waste my time on it.

Do you know what conformation bias is?
Title: Re: Arctic sea ice free (extent)
Post by: SATire on April 10, 2013, 10:08:11 PM
Dear colleagues,

I would like to ask you to calm down a bit. The topic is interesting, the changes are steep - but please get cool a bit. The worst thing here is to get called "Alarmist" without reason - so reason ist important. Errors are often made, like big ones by myself - but agree, when you missed something important or calculated in stupid way. That is normal and nothing bad - bad is only, if you are the only one not able to see, when you are wrong...

Something in the discussion above is misleading by exaggeration and/or misunderstanding - that could be ruled out easily. E.g. End of July is not 1. July. Ice free July is not ice free after July. Next year July is not end of this years June, a picture of ice condition in Sept. 2012 does not indicate albedo of this years May...

I think the strength of this site is the interdisciplinarity - experts discuss with noobs and both learn and are surprised again and again by daily novel pictures. Please take the comments serious in any case - there is no truth anymore but todays observations. Risks should be rated, but not hyped because that is dangerous for credibility.

I am sorry if I disturbed again. I just love to read all the comments here because of their style without bickering. 

Title: Re: Arctic sea ice free (extent)
Post by: Espen on April 10, 2013, 10:28:18 PM
SATire;

I appreciate your comments, and hope it will be read by all our colleagues and friends, and yes it is one of very few blogs with important issues without bickering, and that is what is making it so special  and important!!
Title: Re: Arctic sea ice free (extent)
Post by: ChrisReynolds on April 10, 2013, 10:40:05 PM
No bickering from me SATire, I'm not bothering, not worth my time.
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on April 11, 2013, 11:01:29 AM
I am confused how brine would decrease the density of sea ice.  Is not salt water denser than ice?
Hi ael,

Compare pure water ice to brine ice. With pure ice, 100% of the mass is ice. With FYI, perhaps 90% (I'm choosing an arbitrary number here for the explanation) is ice, and 10% is liquid.

Now it still occupies 1 cubic meter of volume, but only 90% of the mass is ice. So the density of the ice is decreased, because it contains water.

It's not that hard really. Just ask yourself why FYI floats. It's less dense than the sea water that formed it.

HTH  ???
Title: Re: Arctic sea ice free (extent)
Post by: Wipneus on April 11, 2013, 11:24:40 AM
Thanks Lodger, that makes even less sense than before.

So when we are talking about volume of sea ice we include the inclusions of brine.
And when we are talking about the mass of sea ice, we take out the inclusions of brine.

And on another day, we can just reverse and say hey, density increases.

Quote
It's not that hard really. Just ask yourself why FYI floats. It's less dense than the sea water that formed it.

Well excluding the mass of the brine does make the ice float higher than it does. Just ask Archimedes.

Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on April 11, 2013, 11:30:24 AM
If it does not melt out this summer, it may melt out in late December!

The Met Office global model had a nightmare last fall. It envisioned about 1 Mkm^3 of warm Atlantic water flowing into the Arctic Basin between -50m and -300m. In December this water began convection to the surface. In early January the pole was ice free. Around the 10th of January they substituted in new historically normal water and ice layers. They have since shut down the model access.

Hi Verge,

You're on to some good stuff in this line, which IIRC has not been previously discussed here or on the ASI blog (pls correct me if i missed it).

Could you tell us where you got the model outputs? Are they still available online? Can you post a link, and perhaps provide some background?

Thanks in advance!  8)

BTW, your calculations are interesting too, but you need to re-examine your units for volume, area, and thickness. Showing your work is always appreciated. Clearly the model run ran the numbers, but we should be able to calculate the mean easily enough by hand!
Title: Re: Arctic sea ice free (extent)
Post by: Vergent on April 11, 2013, 05:28:19 PM
Lodger,

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2F24.media.tumblr.com%2F43da4c1d63eff0fa55ccf985205b9de9%2Ftumblr_mg6npv5MvL1rz9v16o1_400.jpg&hash=52f0972e3334a31babae65ff8d938562)

All estimates, approximations, absolutes, and global negatives are, by definition, false(including this one).

V

edit

Yes, that is a white crow.
Title: Re: Arctic sea ice free (extent)
Post by: Vergent on April 11, 2013, 05:53:57 PM
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Ficefloe.net%2FAloftcon_Photos%2Falbums%2F2012%2F20120912-0001.jpeg&hash=105fd3ed20bd39809bd054e464806d14)

Our mighty MYI. As last seen.
Title: Re: Arctic sea ice free (extent)
Post by: Vergent on April 11, 2013, 07:51:00 PM

Hi Verge,


Could you tell us where you got the model outputs? Are they still available online? Can you post a link, and perhaps provide some background?

Thanks in advance!  8)

BTW, your calculations are interesting too, but you need to re-examine your units for volume, area, and thickness. Showing your work is always appreciated. Clearly the model run ran the numbers, but we should be able to calculate the mean easily enough by hand!

http://data.ncof.co.uk:8080/ncWMS/godiva2.html (http://data.ncof.co.uk:8080/ncWMS/godiva2.html)

The link broke down in late January. Totally bummed me out. It was like losing google earth.

I stopped saving screenshots when I got banned for impiety at AmWx. The most recent I have was Dec. 1413(saved on 12/14).

DISCLAIMER: This did not happen, this is a model that diverged with reality.
 
Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on April 12, 2013, 09:38:25 AM
Statistician George E P Box, in "Science and statistics", Journal of the
American Statistical Association 71:791-799
Quote
All models are wrong, but some are useful
Hi Verge,

That's why i don't hang out on denier sites, there's nothing there to learn ;)

Your model 'screenies' are more entertaining than a Charlie Sheen meltdown, and twice as eye-opening. This is how i envision the final collapse of the Arctic.

BTW, do you have any associated depth/salinity profiles for the big event? I'm curious what the model thought happens to the halocline.

"Impiety"? That's when you ate too much PI, wot?

Laters! and have a good'un!

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.uproxx.com%2Fwp-content%2Fuploads%2F2011%2F02%2Fsheen-crazy-gif.gif&hash=840d72607868aad4dc61a3f5e6e193a3)
Title: Re: Arctic sea ice free (extent)
Post by: Vergent on April 12, 2013, 03:38:14 PM
Lodger,

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.eoearth.org%2Ffiles%2F123701_123800%2F123774%2FAbrupt_Climate_Change_4-2.png&hash=d811f59fce0383f1371596e2a1e3f303)
Quote
The background color shading depicts a zonally averaged density profile from observational data.
http://www.eoearth.org/article/The_Potential_for_Abrupt_Change_in_the_Atlantic_Meridional_Overturning_Circulation (http://www.eoearth.org/article/The_Potential_for_Abrupt_Change_in_the_Atlantic_Meridional_Overturning_Circulation)

I think depth/density is what is needed. The Fram outflow is limited to the in flow, which is restricted. Take away the restriction on inflow... Well its not much more complicated than a toilet flushing. Density seeks its level. 

The arctic basin has an area of 4.2Mkm2(CT). the dense depths are from -500m down. The Fram is 2,500m deep. So there is about 8.4Mkm3 poised to flow out.

V
Title: Re: Arctic sea ice free (extent)
Post by: johnm33 on April 12, 2013, 05:09:15 PM
Another scenario for a complete meltdown is imo strongly related to the cracks.  Last year a large anomoly showed up in Mackenzie bay, at its most extreme IIRC  there were 12 bands each indicating 2deg. implying 24deg.C on the actual temperature map. This was the implied temperature of the ocean closest to the shore, although it wasn't sustained at this level for more than a few days the anomoly persisted past the date of the max. The only other feature that showed any similarity to this was the anomoly on the western shore of greenland, it wasn't so extreme but it too had a gradient, was warmest by the coast and isolated from any similarly warm water.This seems to be best explained by the restratification of waters by eddy kinetic energy, caused by the currents returning north having traversed the east coast of greenland.  A number of papers are available search EKE, eddy kinetic energy, labrador sea, I've previously linked a couple on ASIB.
 The only likely supply of kinetic energy to effect the anomoly in Mackenzie bay is the Pacific. Looking at the tidal ranges at Point Barrow and Tin City http://www.americantides.com/ (http://www.americantides.com/) It's clear that Arctic tides [.4m] have about a third the range of the Pacific [1.1m] ones in this area, implying that whenever high tides occur in the north Pacific an extended pulse of Pacific water will enter the arctic. If you look further south in Alaska http://www.americantides.com/tide-predictions/black-rock-walrus-islands-alaska (http://www.americantides.com/tide-predictions/black-rock-walrus-islands-alaska) where the range is more than 4m some sense of the inertia in this dynamic can be grasped.
My contention is that once this "Pacific" water passes through the strait, it is lost to the pacific due to the diference in rotational speed between its origin and where it now finds itself. Going from 60N to 75N effectively halves the distance to the rotational axis and the local speed of the earths surface, a large fraction of that energy is posessed by the inflowing water which would be more energetically comfortable further south, but is compelled eastwards by the excess of kinetic energy carried with it through the strait.
Although this is the warmest/least saline of Pacific water it is nevertheless denser than the ice/fresh water floating atop the Arctic ocean and consequently dives below it. My guess is that before 2007 what it found there was an endless inverted landscape of ponds and small freshwater lakes formed by the mechanically impacted ice, and whatever damage/melt it caused was confined to these or merely spilled into the next [inverted] pond, and should this fresh water spill over and reach the surface that too was largely contained within the arctic by the extensive permanent ice, like an inverted freshwater sea contained by an ice mountain  range. Ready for the next freeze.It may have happened before but I think there was a breakthrough for that fresher water towards the end of July last year.
You'll have to form your own impression of the action of EKE but my veiw is that  as it rolls like a tidal wave across the inverted landscape, the 'surf' before it is the heat both of its own motion and that carried to the surface from the warm saline Atlantic waters at depth, and just like a wave when it meets an obstacle it waits until the trough is filled or the barrier overcome before  proceeding. Thus wherever a gap appears in the ice warm water will be brought to the surface and wherever the ice changes thickness a similar build up will enhance the probability of cracks forming as the wave swells before moving on. In time however the landscape will erode to a much leveller plane. Whilst this process has been happening since at latest 2007 I think the cracking this year indicates a more 'mature' inverted landscape beneath the ice, and the likelyhood of all the bottom/meltwater with nowhere to hide, being shunted out of Fram or through the archipelago by the energetically charged influx coming twice a day from the Pacific.
All the above is compounded by the fact that last year over vast areas the air temps were too high for ice to form but cold enough for snow to settle, yet it appeared this snow was being counted as ice in some of the models, well over the winter no doubt some of it became ice of sorts, probably the sort easily melted by increasingly unimpeded Pacific water on its way to Fram/Baffin.
 Just two last points, prior to 2007 I'm sure the kinetic energy was expended before it reached across the arctic, after the breakthrough I expect the flow slowly accelerated, just as it will this year, if theres anything at all in this, and as it does the ice disappears never mind the weather.
If this is indeed what's happening, and i think it is even though what evidence i see is somewhat ambiguous, we need a north wind through Bering because without it the fresh water lens will disappear south leaving nothing for the Atlantic water to dive beneath and consequently nothing to stop the sudden evacuation of the extreme saline basal waters through Frams basement etc.etc.
Title: Re: Arctic sea ice free (extent)
Post by: PhilGChapman on April 12, 2013, 05:11:39 PM
I haven't seen it mentioned; if it has been and I missed it apologies.

A February 2013 paper in Geophysical Research Letters by Overland and Wang "When will the Summer Arctic be Nearly Sea Ice Free?", updating their earlier work (that I know has been mentioned), compared what they categorise as the three approaches to answering the question. I've uploaded the full paper here (http://www.personal.soton.ac.uk/pgc1g08/Overland_2013.pdf) for anyone interested.
Title: Re: Arctic sea ice free (extent)
Post by: Jim Williams on April 12, 2013, 05:55:30 PM
I haven't seen it mentioned; if it has been and I missed it apologies.

A February 2013 paper in Geophysical Research Letters by Overland and Wang "When will the Summer Arctic be Nearly Sea Ice Free?", updating their earlier work (that I know has been mentioned), compared what they categorise as the three approaches to answering the question. I've uploaded the full paper here (http://www.personal.soton.ac.uk/pgc1g08/Overland_2013.pdf) for anyone interested.

I was doing fine until I realized it was an apologia for modelling.  I will agree that EVENTUALLY modelling is the answer.  The problem is that eventually may not be at all soon.
Title: Re: Arctic sea ice free (extent)
Post by: slow wing on April 13, 2013, 05:29:08 AM
...
Slow Wing,
...Vergent's figures for insolation are for top of atmosphere insolation, due to the low angle of incidence figures hitting the surface are lower, and due to low angle of incidence albedo is higher due to reflection of oblique rays off the surface...
Hi Chris,

Thanks for your comments and particularly the point quoted above.

It makes sense to look up the actual Summer insolation at the North Pole in Summer.
The appropriate insolation values can be obtained from https://eosweb.larc.nasa.gov/:

Monthly Averaged Insolation Incident On A Horizontal Surface (kWh/m2/day)
Lat 90
Lon 0   
22-year Average   
Jan 0.00
Feb 0.00
Mar 0.17
Apr 2.93
May 6.78, x 3.6 MJ/kWh = 24.4  MJ/(day.m^2)
Jun 7.49, x 3.6 MJ/kWh = 27.0  MJ/(day.m^2)
Jul 6.70, x 3.6 MJ/kWh = 24.1  MJ/(day.m^2)
Aug 4.03
Sep 0.82
Oct 0.00
Nov 0.00
Dec 0.00


In my first hand-waving post I simply guessed mid-Summer insolation of 20 MJ/(day.m^2),  x 1 kWh/3.6 MJ = 5.6  kWh/(day.m^2). This is seen to be a bit less than the measured value at the North Pole, but actually fairly close when averaged over the Arctic Ocean - try out a few different latitudes and longitudes on that website above. So it was a reasonable guess.



 In the second post I doubled the value based on Vergent's number, which turned out to be for the top of the atmosphere. That was a mistake and too optimistic. Going back to my original guess of 20 MJ/(day.m^2) gives...


critical absorbtion fraction to just melt the ice =

300 MJ/tonne x 1 tonne/m^2 / (20 MJ/(day.m^2) x 60 days) = 1/4

So, in this simple model and neglecting other heat sources and sinks...

 If 1/4 of the direct solar energy goes into melting the ice then the Arctic Ocean could be ice free by the end of this July.


That much is now pushing it but the scenario is still at least plausible imo if the ice has already broken up some more - which is all that I was trying to address.

Title: Re: Arctic sea ice free (extent)
Post by: Artful Dodger on April 13, 2013, 11:41:08 AM
critical absorbtion fraction to just melt the ice =

300 MJ/tonne x 1 tonne/m^2 / (20 MJ/(day.m^2) x 60 days) = 1/4

So, in this simple model and neglecting other heat sources and sinks...

If 1/4 of the direct solar energy goes into melting the ice then the Arctic Ocean could be ice free by the end of this July.
Hi slow wing,

You're getting closer with the math. Several points:
Last year, CAPIE reached 0.75 on about day 177 (or Jun 25, 2012 and about 5 days after peak insolation). CAPIE bottomed out (http://neven1.typepad.com/blog/2012/08/asi-2012-update-9-stormy-weather.html) at around 0.57 from day 214 to 222 (Aug 1 to Aug 9, 2012)

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fneven1.typepad.com%2F.a%2F6a0133f03a1e37970b017d3c3c782f970c-pi&hash=60b1feb676d868b68cc513bd52e4cb96)

The difference in solar heat absorbed each day as reflective ice turns to dark water means that the melt curve is asymmetrical about the solstice. Even though there is less insolation after the solstice, the peak in heat absorbed didn't come last year until about day 200 (July 18, 2012 or fully 4 weeks after the solstice)! That's the Peak of Summer for the Arctic ocean. :o

I created a chart in Excel last year for the ASI blog showing solar melt potential as the relationship between insolation vs CAPIE, a little metric I dubbed "Solar gain (http://neven1.typepad.com/blog/2012/08/new-capie-record.html?cid=6a0133f03a1e37970b0167691116bc970b#comment-6a0133f03a1e37970b0167691116bc970b)":

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fi785.photobucket.com%2Falbums%2Fyy131%2Farcticdodger%2FSolargain-2012.gif&hash=57389f1a0b5835fb812f173e0afa21e5)

* Note: the actual fraction of solar heat absorbed is slightly different than 1 - CAPIE. The albedo (http://en.wikipedia.org/wiki/Albedo) of open sea water is approx 0.07 while sea ice albedo varies from 0.8 for dry thick sea ice down to 0.6 for wet thinning sea ice as the melt season progresses ( constant of 0.7 used as approximation). Thus, the solar heat absorbed fraction in the pack ice region as used in the chart above is calculated like this:  8)

( total absorption ) =
( Ice absorption ) + ( Water absorption ) =
((1- Ice albedo) x (Ice fraction)) + ((1 - Water albedo) x Water fraction)) =
((1-0.7) x (CAPIE)) + ((1-0.07) x (1-CAPIE)) =
( 0.3 x CAPIE ) + ( 0.93 x (1-CAPIE)) =
( 0.3 CAPIE + 0.93 - 0.93 CAPIE)) =
( -0.63 CAPIE + 0.93 )

Note that there is a linear relationship between CAPIE and solar heat absorbed within the main ice pack (always a mix of ice and water). Here's an important milestone for the coming melt season: when CAPIE equals 68% then about 50% of the solar energy reaching the surface is absorbed by the pack ice.  :o

Using chart values for top melt (due to insolation), and given daily sea ice area and total volume melt from PIOMAS history, you should then be able to solve for 'bottom melt' (due to heat from external ocean currents). We got SkyNet (http://) by the balls now, don't we? Let's book! ;)

Terminator 2 soundtrack09 John amp Dyson Into Vault (http://www.youtube.com/watch?v=XwdXUOBNogs#)
Title: Re: Arctic sea ice free (extent)
Post by: slow wing on April 14, 2013, 12:08:12 PM
Hi Lodger

  Thanks for the information. Yes, the simple model is too optimistic in assuming that the ice is evenly spread throughout the Arctic Ocean as a mish mash of ice chunks and water gaps. In reality this Summer, there are going to be areas of thicker and thinner ice and also large areas of exposed water where the ice has melted out completely.

That is why the CAPIE value is too optimistic for this prediction. In regions where there is no ice nearby, the sun's energy cannot melt ice even if it is absorbed and heating up the water. And where the ice is thickest, it won't melt out by the end of July even if 25% of the insolation in that region goes into melting the ice.

  Stepping away from the July question for a moment, it is noted that the ice cover this year is more even than it was last year. Although the volume is the same for March according to PIOMAS, there is less ice thicker than 3 metres and on the other hand the ice is not so thin as last year on the Russian side. That more even spread appears to favour more melting this year than last as it is closer to the situation in the simple model.


Title: Re: Arctic sea ice free (extent)
Post by: johnm33 on April 15, 2013, 12:35:12 PM
Further to my comment above, whilst the cracks, upwelling heat between them and the transport of warmer/fresher water through to Baffin are all implied, and may have other causes, further signs are anticipated. The disconnection of the ice from the coast, at the grounding line, should occur in Mackenzie bay on Axel Heiberg and the north of greenland in Lincoln. A repitition of the Mackenzie anomoly should be followed by similar anomolies in both the above mentioned areas, unless there's a massive breakthrough to Baffin at NWP and through the archipelago generally, sufficient to allow the dissipation of the Pacific waters south, this would lead to a large anomoly of sea temps through the islands and in northern Baffin.
Title: Re: Arctic sea ice free (extent)
Post by: Juan C. García on June 19, 2013, 09:12:01 PM
NSIDC announces a change on the baseline climatological period for Arctic Sea Ice News and Analysis: from 1979-2000 to a 30-year reference period, from 1981 to 2010:

Quote
This July, NSIDC plans to change the baseline climatological period for Arctic Sea Ice News and Analysis and the Sea Ice Index, the data set we use for our sea ice analysis. We are making this change to match the comparison time frames used by other climate research.

Until now, we have used the 22-year period 1979 to 2000 when comparing current sea ice extent to past conditions. When NSIDC first began to monitor and analyze sea ice extent, a longer period was not available. Since the satellite record is now extended, we are choosing to move to a more standard 30-year reference period, from 1981 to 2010.

http://nsidc.org/arcticseaicenews/2013/06/updating-the-sea-ice-baseline/ (http://nsidc.org/arcticseaicenews/2013/06/updating-the-sea-ice-baseline/)

Title: Re: Arctic sea ice free (extent)
Post by: ghoti on June 19, 2013, 10:34:39 PM
Which makes anomalies seem smaller and less frightening. "A new normal"
Title: Re: Arctic sea ice free (extent)
Post by: Juan C. García on June 20, 2013, 12:14:20 AM
That's right. The new standard will have lower values. But I believe that the difference will not be so much, in regards to the lower values of 2005-2012.
Title: Re: Arctic sea ice free (extent)
Post by: Glenn Tamblyn on June 20, 2013, 03:11:54 AM
The change will alter the anomalies, but it won't alter how much the anomalies have changed over time which is the key thing of interest.

This is just bringing NSIDC more into line with WMO standards for climatology. To fully match they would need to use 1961-1990 or 1991-2020 as their baseline - obviously not possible.
Title: Re: Arctic sea ice free (extent)
Post by: Shared Humanity on June 20, 2013, 05:23:36 PM
Which makes anomalies seem smaller and less frightening. "A new normal"

Yes and I am certain they know this is the effect. I've always felt a decade was adequate for calculating a baseline and, if we look at the area and extent loss as compared to this base, it looks very scary.
Title: Re: Arctic sea ice free (extent)
Post by: crandles on June 20, 2013, 05:46:03 PM
I've always felt a decade was adequate for calculating a baseline

For some climate things, a 30 year base period seems sensible to be able to tell how unusual something is. For other things you do not need as long as 30 years and for some events, particularly rare ones you need more than 30 years. However, when you know the climate is changing showing 3 decadal averages does seem a lot more useful than one 30 year average.

Why does
http://ocean.dmi.dk/arctic/plots/meanTarchive/meanT_2013.png (http://ocean.dmi.dk/arctic/plots/meanTarchive/meanT_2013.png)
use a 50 year average of 1958 to 2002? 5 decadal averages would appear to me to be much better.

If you are only plotting anomalies only then making all records consistently use 1981 to 2010 as the base period would seem sensible as satellite records often start around 1979 so 1981 to 2010 seems the only consistent choice available.
Title: Re: Arctic sea ice free (extent)
Post by: Juan C. García on June 20, 2013, 06:51:51 PM

However, when you know the climate is changing showing 3 decadal averages does seem a lot more useful than one 30 year average.

I totally agree. Maybe the best way to see it is to see the IJIS/JAXA SIE graph. Right now NSIDC is giving the approximated average (discarding 1979 and 1980 or 2000) of the first two lines (80´s and 90´s). With the new standard, NSIDC is going to give the approximated average of the first three lines (80´s, 90´s and 2000´s). The graphs of 2007, 2011 and 2012 are too low in values, so it doesn`t matter if you use standard 1979-2000 or 1981-2010. The differences are clear.
But the true is that you can see AGW better if you have the three decadal lines, instead of just one.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fi1275.photobucket.com%2Falbums%2Fy449%2Fjuancgarcia22%2FNSIDC_DailyValuesAvg%2FIJIS_130619_zps43413c3d.jpg&hash=11d8e7f85536ec7c3485c0be37316f37) (http://s1275.photobucket.com/user/juancgarcia22/media/NSIDC_DailyValuesAvg/IJIS_130619_zps43413c3d.jpg.html)
Title: Re: Arctic sea ice free (extent)
Post by: Laurent on June 18, 2014, 09:55:06 AM
Scientists Predict Arctic Will Be Ice-Free By Summer 2050, So... We're All Screwed
http://www.huffingtonpost.co.uk/2014/06/17/global-warming-arctic-ice_n_5502396.html (http://www.huffingtonpost.co.uk/2014/06/17/global-warming-arctic-ice_n_5502396.html)

Ice free in summer by 2050...really...that's strange, I am not seeing the volume decline the same way... not in 2014 but 2017 why not...
Title: Re: Arctic sea ice free (extent)
Post by: wili on February 12, 2015, 07:00:13 PM
Interesting to look back at our predictions. Probably few of us anymore would be predicting virtually ice free conditions by 2016.

Here, though is something on how the Arctic will likely manage to remain icefree throughout the year at some point:

"in warm “equable” climates the Arctic was blanketed by clouds in winter (picture horizon-to-horizon grey skies that most UK readers will be familiar with), which trapped warmth, keeping the Arctic largely ice-free. "

https://www.skepticalscience.com/Why_the_Miocene_Matters.html#commenthead (https://www.skepticalscience.com/Why_the_Miocene_Matters.html#commenthead)
Title: Re: Arctic sea ice free (extent)
Post by: AbruptSLR on February 12, 2015, 07:18:41 PM
I suspect that many who follow this thread do not realize that anthropogenic aerosols have been both more effective at global cooling than previously projected; but as the linked reference shows anthropogenic aerosols have been more effective still at masking/damping Arctic Amplification even than it has been at masking/damping the increase in mean global surface temperature.  Thus as aerosols are cleaned-up (projected to occur very rapidly in China, which is only of the largest sources of aerosols) the Arctic will warm faster than previously estimated.  This means that looking at the old trend lines many not be a good indication of how much Arctic sea ice loss will occur in the coming couple of decades (certainly a seasonally ice free Arctic in 2017 is not in the cards at this time, but I think it could happen by 2030 to 2035):

Najafi, M.R., et al. (2015) Attribution of Arctic temperature change to greenhouse-gas and aerosol influences, Nature Climate Change, doi:10.1038/nclimate2524

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2524.html (http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2524.html)

Abstract: "The Arctic has warmed significantly more than global mean surface air temperature over recent decades, as expected from amplification mechanisms. Previous studies have attributed the observed Arctic warming to the combined effect of greenhouse gases and other anthropogenic influences. However, given the sensitivity of the Arctic to external forcing and the intense interest in the effects of aerosols on its climate, it is important to examine and quantify the effects of individual groups of anthropogenic forcing agents. Here we quantify the separate contributions to observed Arctic land temperature change from greenhouse gases, other anthropogenic forcing agents (which are dominated by aerosols) and natural forcing agents. We show that although increases in greenhouse-gas concentrations have driven the observed warming over the past century, approximately 60% of the greenhouse-gas-induced warming has been offset by the combined response to other anthropogenic forcings, which is substantially greater than the fraction of global greenhouse-gas-induced warming that has been offset by these forcings. The climate models considered on average simulate the amplitude of response to anthropogenic forcings well, increasing confidence in their projections of profound future Arctic climate change."
See also (both extract and image):

http://www.carbonbrief.org/blog/2015/02/aerosols-dampen-pace-of-arctic-warming-for-now-say-scientists/ (http://www.carbonbrief.org/blog/2015/02/aerosols-dampen-pace-of-arctic-warming-for-now-say-scientists/)

Extract: "And the results suggest the cooling effect from aerosols is much larger in the Arctic than elsewhere in the world, Najafi adds. A separate study finds aerosols were responsible for offsetting around five per cent of global greenhouse gas warming between 1901 and 2010, and around 27 per cent for the shorter period of 1951 to 2010.