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If we define Arctic sea ice free as less than one million of square kilometers measured with the official NSIDC sea ice extent (monthly average), when do you believe that the Arctic will be sea ice free?

2013-2016
44 (45.4%)
2017-2020
41 (42.3%)
2021-2030
9 (9.3%)
2031-2040
2 (2.1%)
2041-2060
1 (1%)
2061-2100
0 (0%)
Later than 2100
0 (0%)

Total Members Voted: 96

Voting closed: April 01, 2013, 10:12:01 PM

Author Topic: Arctic sea ice free (extent)  (Read 92732 times)

JMP

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Re: Arctic sea ice free (extent)
« Reply #50 on: March 08, 2013, 11:50:47 PM »

Just bookmark Neven's graph page.

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/ 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/ 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. 
« Last Edit: March 08, 2013, 11:58:29 PM by JMP »

idunno

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Re: Arctic sea ice free (extent)
« Reply #51 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.

ivica

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Re: Arctic sea ice free (extent)
« Reply #52 on: March 12, 2013, 02:12:10 PM »
Ditto from above,
I'm with Lodger et all. on it.

Vergent

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Re: Arctic sea ice free (extent)
« Reply #53 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 ;-)

slow wing

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Re: Arctic sea ice free (extent)
« Reply #54 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 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.




deep octopus

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Re: Arctic sea ice free (extent)
« Reply #55 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.

Juan C. García

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Re: Arctic sea ice free (extent)
« Reply #56 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.

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
With “http”:
http://forum.arctic-sea-ice.net/index.php/topic,83.0.html
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

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

Jim Hunt

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Re: Arctic sea ice free (extent)
« Reply #57 on: March 16, 2013, 09:40:55 PM »
Here are some "predictions" from the scientists amongst the panelists at The Arctic Summit 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


« Last Edit: August 05, 2014, 01:13:41 PM by Jim Hunt »
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

mmghosh

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Re: Arctic sea ice free (extent)
« Reply #58 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.

slow wing

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Re: Arctic sea ice free (extent)
« Reply #59 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.

ChrisReynolds

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Re: Arctic sea ice free (extent)
« Reply #60 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.

Glenn Tamblyn

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Re: Arctic sea ice free (extent)
« Reply #61 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.

Jim Hunt

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Re: Arctic sea ice free (extent)
« Reply #62 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 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"
« Last Edit: March 20, 2013, 12:18:41 PM by Jim Hunt »
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

ChrisReynolds

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Re: Arctic sea ice free (extent)
« Reply #63 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.

crandles

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Re: Arctic sea ice free (extent)
« Reply #64 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.

Bob Wallace

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Re: Arctic sea ice free (extent)
« Reply #65 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....


pikaia

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Re: Arctic sea ice free (extent)
« Reply #66 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.

fishmahboi

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Re: Arctic sea ice free (extent)
« Reply #67 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.

Richard Rathbone

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Re: Arctic sea ice free (extent)
« Reply #68 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.

Juan C. García

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Re: Arctic sea ice free (extent)
« Reply #69 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.
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

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

TerryM

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Re: Arctic sea ice free (extent)
« Reply #70 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

ritter

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Re: Arctic sea ice free (extent)
« Reply #71 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.  ;)

Jim Williams

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Re: Arctic sea ice free (extent)
« Reply #72 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.

icebgone

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Re: Arctic sea ice free (extent)
« Reply #73 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.

Artful Dodger

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Re: Arctic sea ice free (extent)
« Reply #74 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) 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. Proceedings. Santa Monica, CA: RAND Corp. (available in hardcopy only)

* Fletcher, J. O. (1969). Managing Climatic Resources. 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"  (ebook PDF download)

Full text for the attached figure: (Eisenman & Wettlaufer, 2008)
http://www.pnas.org/content/106/1/28/F3.expansion.html
« Last Edit: March 31, 2013, 10:17:45 AM by Artful Dodger »
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Jim

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Re: Arctic sea ice free (extent)
« Reply #75 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

ChrisReynolds

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Re: Arctic sea ice free (extent)
« Reply #76 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?

Jim

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Re: Arctic sea ice free (extent)
« Reply #77 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
"

Artful Dodger

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Re: Arctic sea ice free (extent)
« Reply #78 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 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.

« Last Edit: March 31, 2013, 10:15:45 AM by Artful Dodger »
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Artful Dodger

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Re: Arctic sea ice free (extent)
« Reply #79 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" 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.
« Last Edit: March 31, 2013, 09:57:04 AM by Artful Dodger »
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Artful Dodger

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Re: Arctic sea ice free (extent)
« Reply #80 on: March 31, 2013, 10:11:05 AM »
How about this paper from 1975? (PDF download available)

Aagaard, K., and Coachman, L. (1975), Toward an ice-free Arctic ocean, 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. 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.
« Last Edit: March 31, 2013, 10:35:44 AM by Artful Dodger »
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Re: Arctic sea ice free (extent)
« Reply #81 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.

Artful Dodger

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Re: Arctic sea ice free (extent)
« Reply #82 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" 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:
  • Smarorinsky, J., Manabe, S., and Holloway, J. L., Monthly Weather Review, 93, 727 (1965).
  • Kasahara, A., and Washington, W. M., Monthly Weather Review, 95, 389 (1967).
  • Corby, G. A., Gilchrist, A., and Newson, R. L., Quart. J. Roy. Met. Soc., 98, 809 (1972).
  • Warshaw, M., and Rapp, R. R., R-908-ARPA (1972).

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).  ::)

Cheers!
Lodger

Jim

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Re: Arctic sea ice free (extent)
« Reply #83 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.

Juan C. García

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Re: Arctic sea ice free (extent)
« Reply #84 on: April 01, 2013, 06:58:16 AM »
Last day to vote...  ;)
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

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

ChrisReynolds

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Re: Arctic sea ice free (extent)
« Reply #85 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.

Jim

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Re: Arctic sea ice free (extent)
« Reply #86 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.

ChrisReynolds

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Re: Arctic sea ice free (extent)
« Reply #87 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

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.

Csnavywx

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Re: Arctic sea ice free (extent)
« Reply #88 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.

ChrisReynolds

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Re: Arctic sea ice free (extent)
« Reply #89 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.

Artful Dodger

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Re: Arctic sea ice free (extent)
« Reply #90 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)
Cheers!
Lodger

Jim

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Re: Arctic sea ice free (extent)
« Reply #91 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)

Chuck Yokota

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Re: Arctic sea ice free (extent)
« Reply #92 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 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.

Jim Williams

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Re: Arctic sea ice free (extent)
« Reply #93 on: April 03, 2013, 01:56:39 PM »
This figure from the NSIDC's report for March ( 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.

Peter Ellis

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Re: Arctic sea ice free (extent)
« Reply #94 on: April 03, 2013, 03:03:22 PM »
This figure from the NSIDC's report for March ( 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.

ChrisReynolds

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Re: Arctic sea ice free (extent)
« Reply #95 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.

Shared Humanity

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Re: Arctic sea ice free (extent)
« Reply #96 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?

crandles

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Re: Arctic sea ice free (extent)
« Reply #97 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.

Jim Williams

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Re: Arctic sea ice free (extent)
« Reply #98 on: April 04, 2013, 03:31:32 AM »
This figure from the NSIDC's report for March ( 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.

wanderer

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Re: Arctic sea ice free (extent)
« Reply #99 on: April 04, 2013, 11:22:26 AM »