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crandles

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Re: Abrupt sea ice loss
« Reply #50 on: April 05, 2018, 07:53:03 PM »
Latest version (published Sept 2017) says
https://www.eea.europa.eu/data-and-maps/indicators/global-and-european-temperature-4/assessment

Quote
The global average temperature will continue to increase throughout this century as a result of projected further increases in greenhouse gas concentrations. The CMIP5 climate projections summarised in the IPCC AR5 project that global temperature will increase by mid-century (2046–2065 relative to 1986–2005) by 0.4–1.6 °C for RCP2.6, 0.9–2.0 °C for RCP4.5, 0.8–1.8 °C for RCP6.0 and 1.4–2.6 °C for RCP8.5; the warming projections for the end of the century (2081–2100) are 0.3–1.7 °C for RCP2.6, 1.1–2.6 °C for RCP4.5, 1.4–3.1 °C for RCP6.0 and 2.6–4.8 °C for RCP8.5. All projections show greater warming over land than over the oceans. Projected warming is strongest in the Arctic at about twice the global average. These patterns are consistent with the observations during the latter part of the 20th century

So global average 1.4–2.6 °C is reported but over 40-60 years.
Land temperatures are expected to rise faster and there is lots of land in mid latitudes (northern hemisphere).

Half it and add a bit does get to around 1C to 2C over land in 20-30 years. Still a little short of 1C per decade and this is mainly from GHGs whereas ice free for a month is a smaller forcing like a tenth of GHG forcing if my sums above are correct.

Still you got closer than I expected.

El Cid

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Re: Abrupt sea ice loss
« Reply #51 on: April 05, 2018, 09:19:30 PM »
Also let's not forget, that IF/WHEN the Arctic becomes ice-free, that would most likely cause changes to the atmospheric circulation.

Now, I know that this is very speculative but if the Arctic is ice free, then the Icelandic low could shift to the Arctic or to the Barents for example, most likely bringing warmer winds during the autumn/winter(?) to Northern/Central Europe...

jdallen

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Re: Abrupt sea ice loss
« Reply #52 on: April 06, 2018, 01:05:52 AM »
I'm finding the content presented in Jim Whites video very compelling, enough so I went ahead and watched the whole thing.

When, not if we have and blue Arctic summer, I find myself agreeing  that the rate of change in the northern hemisphere will accelerate abruptly, as we pass a tip over threshold that breaks the existing weather pattern and transitions rapidly into a new one.  I think it could happen in my remaining lifetime.
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Archimid

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Re: Abrupt sea ice loss
« Reply #53 on: April 06, 2018, 04:08:16 AM »
Halocarbons 0.36 W/m^2
CO2 1.88
Methane 0.49
N20 0.17
Ozone 0.4
Total 3.3

So the 0.3W/m^2 is only about a tenth of GHG forcing (maybe fifth of the warming we see taking areosols as masking half the effect of GHGs).

Warming appears less than 0.2 C per decade so a fifth of that is 0.04C per decade.

In the Arctic, the warming is 2, maybe 3 times higher than global temperatures. It is important differentiate between local and global effects.

Quote
Thus 1C per decade appears like 25 times stronger than what we are experiencing. For a 3 times stronger effect (of 0.3W/m^2 vs 0.1), this does not compute.

Albedo forcings are local to the Arctic and only during summer. CO2 forcing is global and uniform throughout the year. However in the Arctic the warming is 2-3 times higher than the global average. Albedo change is just one of the many forcings that are causing the temperature difference. It is a small one relative to others as you well said, however it's influence will increase as extent decreases.

I think the biggest forcing at work is the lack of volume to melt.  Because of the enthalpy of fusion of ice a lot of solar energy that would have gone to melt ice now goes to warm the Arctic. The funny thing about that is that it has no bearing on global warming except for the bit that gets irradiated out to space. If anything it cools the globe a bit.

I think the other large forcing is the atmosphere sending heat waves and water vapor into the Arctic. That's another factor that makes no direct difference in global temperatures but make a huge difference in Arctic temperatures.

CO2 is there of course, but it is more powerful as a global influencer of temperatures. Elevated global temperatures eventually lead to more heat into the Arctic, but CO2's direct impact as a greenhouse gas is not as large for Arctic amplification considerations. Methane and water vapor might be a different matter.
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Daniel B.

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Re: Abrupt sea ice loss
« Reply #54 on: April 06, 2018, 04:30:36 PM »

I think the biggest forcing at work is the lack of volume to melt.  Because of the enthalpy of fusion of ice a lot of solar energy that would have gone to melt ice now goes to warm the Arctic. The funny thing about that is that it has no bearing on global warming except for the bit that gets irradiated out to space. If anything it cools the globe a bit.


Yes, this is not trivial.  The heat of fusion of water is 333.55 J/g, while the specific heat of water is 4.186 J/g-C.  Using a straight-forward calculation, and an average volumetric loss of 320 km3/yr, the annual heat used to melt the ice is ~107 pJ (peta = 10^15).  That amount of heat would raise the surface temperature of the Arctic Ocean (14 million km2 to a depth of 200 m) by 0.37 C.  Obviously this is rather simplistic, and other factors will come into play (such as heat lost to space), but it is significant.

gerontocrat

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Re: Abrupt sea ice loss
« Reply #55 on: April 06, 2018, 05:03:53 PM »

I think the biggest forcing at work is the lack of volume to melt.  Because of the enthalpy of fusion of ice a lot of solar energy that would have gone to melt ice now goes to warm the Arctic. The funny thing about that is that it has no bearing on global warming except for the bit that gets irradiated out to space. If anything it cools the globe a bit.


Yes, this is not trivial.  The heat of fusion of water is 333.55 J/g, while the specific heat of water is 4.186 J/g-C.  Using a straight-forward calculation, and an average volumetric loss of 320 km3/yr, the annual heat used to melt the ice is ~107 pJ (peta = 10^15).  That amount of heat would raise the surface temperature of the Arctic Ocean (14 million km2 to a depth of 200 m) by 0.37 C.  Obviously this is rather simplistic, and other factors will come into play (such as heat lost to space), but it is significant.

Quote
a lot of solar energy that would have gone to melt ice now goes to warm the Arctic. The funny thing about that is that it has no bearing on global warming except for the bit that gets irradiated out to space.

I thought heating of the oceans is the number one factor in any longer term view of AGW.
No, I am totally convinced that an ocean body that has more than 1000 times the capacity to absorb and store energy than the atmosphere and is soaking up more than 90% of the excess energy trapped by rising co2 ppm is numero uno. Atmospheric temperature change is surely far more of a resulting side-effect of rising global ocean heat content and is quickly lost to space without further energy inputs.  So diminishing sea ice (especially early in the melting season) increases the energy available for long-term storage in the oceans (down to at least 2,000 metres). This energy can then be released at leisure to confound the predictions of atmospheric scientists.

My pure speculation is that a gradually warming Arctic ocean will gradually weaken winter sea ice volume allowing even lower winter maximum extents and even stronger early melt ........ until??
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RoxTheGeologist

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Re: Abrupt sea ice loss
« Reply #56 on: April 06, 2018, 05:49:15 PM »

I think the biggest forcing at work is the lack of volume to melt.  Because of the enthalpy of fusion of ice a lot of solar energy that would have gone to melt ice now goes to warm the Arctic. The funny thing about that is that it has no bearing on global warming except for the bit that gets irradiated out to space. If anything it cools the globe a bit.


Theses are old numbers - back from 2008.

Water: A greenhouse gas, like carbon dioxide, it represents around 80 percent of total greenhouse gas mass in the atmosphere and 90 percent of greenhouse gas volume. Water vapor and clouds account for 66 to 85 percent of the greenhouse effect, compared to a range of 9 to 26 percent for CO2.

Just off the top of my head, I would think a warm ice free Arctic is going to contribute much more water to the atmosphere than a cold one...


FishOutofWater

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Re: Abrupt sea ice loss
« Reply #57 on: April 06, 2018, 07:32:16 PM »
Water vapor acts as a multiplier of the effects of greenhouse gases such as CO2, methane and CFCs that have relatively long atmospheric lifetimes. Open ocean water is a continuous source of water vapor to the Arctic region so the loss of sea ice is a powerful amplifier of the greenhouse effect in the Arctic. Sublimation of snow and ice is not nearly as effective a means of getting water vapor into the atmosphere as winds blowing over open ocean. We're already seeing large warmings in the Barents and Bering sea regions where open water has replaced ice and the added water vapor is affecting the whole Arctic.

Daniel B.

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Re: Abrupt sea ice loss
« Reply #58 on: April 06, 2018, 07:38:03 PM »
True, but not all that water will remain as vapor.  Some will condense into clouds, which will produce a negative feedback, blocking some of the 24-hour sunlight.

crandles

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Re: Abrupt sea ice loss
« Reply #59 on: April 06, 2018, 07:44:26 PM »
Usual explanation of water cycle with temperature change is
The water cycle is fast; 11 day average residency time. Absolute humidity will increase, relative humidity not much change. Contributes more..? yes and precipitates out quite quickly.

Arctic might be a little different with generally descending dry air that already gets moister as it travels south and warms up. Maybe it gets moister further north? Maybe that is still 'absolute humidity will increase, relative humidity not much change'?

FishOutofWater

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Re: Abrupt sea ice loss
« Reply #60 on: April 06, 2018, 08:26:09 PM »
Well we left out a major factor, storm tracks. We are seeing stormier conditions over open waters in the Arctic and subarctic as ocean water enhances baroclinic processes compared to sea ice. That's increasing atmospheric advection of heat from the north Atlantic and north Pacific basins.

This stormier situation way also change the relative humidity of an air column over the Arctic.

Thanks concerning the water residency time. I knew it was short but didn't remember the number.

jdallen

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Re: Abrupt sea ice loss
« Reply #61 on: April 06, 2018, 09:46:38 PM »
True, but not all that water will remain as vapor.  Some will condense into clouds, which will produce a negative feedback, blocking some of the 24-hour sunlight.
Clouds don't help in winter. In fact, they hurt.

Clouds may not help enough in summer.  There is still the matter of downwelling long wave radiation as well as the latent heat in the water vapor itself.

The feedback from clouds will be overtaken as total system enthalpy increases.
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Dharma Rupa

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Re: Abrupt sea ice loss
« Reply #62 on: April 06, 2018, 11:05:48 PM »

I think the biggest forcing at work is the lack of volume to melt.  Because of the enthalpy of fusion of ice a lot of solar energy that would have gone to melt ice now goes to warm the Arctic. The funny thing about that is that it has no bearing on global warming except for the bit that gets irradiated out to space. If anything it cools the globe a bit.


Theses are old numbers - back from 2008.

Water: A greenhouse gas, like carbon dioxide, it represents around 80 percent of total greenhouse gas mass in the atmosphere and 90 percent of greenhouse gas volume. Water vapor and clouds account for 66 to 85 percent of the greenhouse effect, compared to a range of 9 to 26 percent for CO2.

Just off the top of my head, I would think a warm ice free Arctic is going to contribute much more water to the atmosphere than a cold one...

CO2 is the trigger.  H2O is the bullet.

wili

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Re: Abrupt sea ice loss
« Reply #63 on: April 06, 2018, 11:33:46 PM »
" H2O is the bullet."

And heat

And wind

And drought...
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Daniel B.

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Re: Abrupt sea ice loss
« Reply #64 on: April 07, 2018, 12:13:14 AM »
True, but not all that water will remain as vapor.  Some will condense into clouds, which will produce a negative feedback, blocking some of the 24-hour sunlight.
Clouds don't help in winter. In fact, they hurt.

Clouds may not help enough in summer.  There is still the matter of downwelling long wave radiation as well as the latent heat in the water vapor itself.

The feedback from clouds will be overtaken as total system enthalpy increases.

There is a large albedo difference between clouds and open water.  Also, it reduces the water vapor effect in the atmosphere.

Cid_Yama

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Re: Abrupt sea ice loss
« Reply #65 on: April 09, 2018, 05:59:08 AM »
Quote
Of course, you will be able to find a few individuals like Prof Wadhams saying such things so preferably something that has widespread support not just some nutter saying it.

(IOW I think you need a reality check.)

Go ahead Crandles, bury your head in the sand.  You aren't using it anyway.  If you think I'm about to reiterate all of the self-reinforcing feedbacks already identified, you need to rub your two brain cells together and try to get a spark.

BTW, Peter Wadhams credentials speak for themselves.  Some anonymous nutter on a website disparaging him, doesn't change the facts.

Go crawl back under your denier rock.  I hear WUWT calling you. 

« Last Edit: April 09, 2018, 06:13:33 AM by Cid_Yama »
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Neven

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Re: Abrupt sea ice loss
« Reply #66 on: April 09, 2018, 09:24:41 AM »
Or maybe you hear Neven calling, saying you shouldn't get this worked up.  :)
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Daniel B.

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Re: Abrupt sea ice loss
« Reply #67 on: April 10, 2018, 03:27:31 PM »
Quote
Of course, you will be able to find a few individuals like Prof Wadhams saying such things so preferably something that has widespread support not just some nutter saying it.

(IOW I think you need a reality check.)

Go ahead Crandles, bury your head in the sand.  You aren't using it anyway.  If you think I'm about to reiterate all of the self-reinforcing feedbacks already identified, you need to rub your two brain cells together and try to get a spark.

BTW, Peter Wadhams credentials speak for themselves.  Some anonymous nutter on a website disparaging him, doesn't change the facts.

Go crawl back under your denier rock.  I hear WUWT calling you.

Cid, yes his credentials speak for themselves.  However, some of his recent claims are a bit eccentric, don't you think?  Like three British scientists being murdered? 

Jim Hunt

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Re: Abrupt sea ice loss
« Reply #68 on: April 11, 2018, 11:41:11 AM »
However, some of his recent claims are a bit eccentric, don't you think?

Prof. Wadhams is a very nice fellow. Perhaps too nice for his own good? For much more on that "story" see:

http://GreatWhiteCon.info/2015/07/professor-peter-wadhams-complaint-to-ipso/

My conclusion?

Quote
The moral of this tale would seem to be “Don’t speak to journalists without taping the conversation” and “Don’t speak to journalists without saying the magic words ‘off the record’ first” or quite possibly simply “Don’t speak to journalists”!
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Daniel B.

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Re: Abrupt sea ice loss
« Reply #69 on: April 11, 2018, 01:48:28 PM »
However, some of his recent claims are a bit eccentric, don't you think?

Prof. Wadhams is a very nice fellow. Perhaps too nice for his own good? For much more on that "story" see:

http://GreatWhiteCon.info/2015/07/professor-peter-wadhams-complaint-to-ipso/

My conclusion?

Quote
The moral of this tale would seem to be “Don’t speak to journalists without taping the conversation” and “Don’t speak to journalists without saying the magic words ‘off the record’ first” or quite possibly simply “Don’t speak to journalists”!

I think your last statement sums it up best.  Journalists are not objective.  They have their own agenda, and are just looking for anything that supports their own views.  Still, he should have never made those innuendos - especially to a journalist.

Steven

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Re: Abrupt sea ice loss
« Reply #70 on: April 11, 2018, 07:12:01 PM »
I think it's pretty clear that Wadhams shouldn't be taken seriously anymore.  He's promoting pseudo-scientific nonsense about ghosts, mediumship and paranormality as well as various conspiracy theories.  He seriously believes that he has precognitive dreams in which he can foresee future events.  That is probably the reason for the unscientific predictions that he has been making in recent years (e.g. here), which are an easy target for climate deniers who use extremists like Wadhams to ridiculize the entire climate science community.

Cid_Yama

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Re: Abrupt sea ice loss
« Reply #71 on: April 12, 2018, 10:35:58 AM »
Yes, and he also believes that Christ existed.  I myself have experienced Déjà vu and it seemed I had experienced it earlier, perhaps in a dream.

We all have personal beliefs that perhaps can't (as of yet) be proven by science.  I'll bet you do to.  Does that make everything else about you suspect?

Jung spoke of synchronicity and wrote a book.  He hung out with the Madame Blavatsky crowd.

Quote
“Broadly speaking, although there are some differences, I think Buddhist philosophy and Quantum Mechanics can shake hands on their view of the world. We can see in these great examples the fruits of human thinking. Regardless of the admiration we feel for these great thinkers, we should not lose sight of the fact that they were human beings just as we are.”

 – The Dalai Lama

According to Quantum Physics there is no such thing as matter, it is all energy that is constantly coming into existence and disappearing at time scales so small we can't comprehend.

Can you tell me what consciousness is?  No?

You act as if reality is fixed and known by you and can therefore judge others.
   
You also demonstrate a form of bifurcation fallacy.  Binary thinking.  Perhaps you should look to the plank in your own eye.
 
« Last Edit: April 12, 2018, 10:49:26 AM by Cid_Yama »
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be cause

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Re: Abrupt sea ice loss
« Reply #72 on: April 12, 2018, 11:17:22 AM »
 As a shamanic  Christian I would consider limiting myself to the world of non-quantum science about as drastic as losing both my arms . I even dare predict that abrupt sea ice loss is upon us . :)
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gerontocrat

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Re: Abrupt sea ice loss
« Reply #73 on: April 12, 2018, 11:53:59 AM »
Prof. Wadhams is in good company.

https://en.wikipedia.org/wiki/Isaac_Newton%27s_occult_studies

Quote
Isaac Newton's occult studies
English physicist and mathematician Isaac Newton produced many works that would now be classified as occult studies. These works explored chronology, alchemy, and Biblical interpretation (especially of the Apocalypse). Newton's scientific work may have been of lesser personal importance to him, as he placed emphasis on rediscovering the occult wisdom of the ancients. In this sense, some[1] believe that any reference to a "Newtonian Worldview" as being purely mechanical in nature is somewhat inaccurate.

After purchasing and studying Newton's alchemical works, economist John Maynard Keynes, for example, opined in 1942 at the tercentenary of his birth that "Newton was not the first of the age of reason, he was the last of the magicians." In the Early Modern Period of Newton's lifetime, the educated embraced a world view different from that of later centuries. Distinctions between science, superstition, and pseudoscience were still being formulated, and a devoutly Christian biblical perspective permeated Western culture.
Note: He suggested a  date for the apocalypse of 2060.

Is Prof. Wadhams still publishing science stuff? He is still writing articles for the papers

https://www.washingtonpost.com/news/theworldpost/wp/2018/01/08/carbon-emissions/?noredirect=on&utm_term=.e5e93534636d

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El Cid

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Re: Abrupt sea ice loss
« Reply #74 on: April 12, 2018, 01:30:28 PM »
Science is science, religion is religion. Mixing up the two is not very lucky. Science is and should be based on observations, facts, and replicable experiments not on visions. I dare say this exactly because I had out-of-body experiences. They had nothing to do with abrupt sea ice loss  :)

Dharma Rupa

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Re: Abrupt sea ice loss
« Reply #75 on: April 12, 2018, 01:35:54 PM »
Science is science, religion is religion. Mixing up the two is not very lucky. Science is and should be based on observations, facts, and replicable experiments not on visions. I dare say this exactly because I had out-of-body experiences. They had nothing to do with abrupt sea ice loss  :)

Science is a religion.  Can we get back to discussing the ice?

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Re: Abrupt sea ice loss
« Reply #76 on: April 12, 2018, 02:33:11 PM »
And then, abruptly, they discussed sea ice loss again.  ;) ;D
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Re: Abrupt sea ice loss
« Reply #77 on: April 12, 2018, 05:24:40 PM »
Science is science, religion is religion. Mixing up the two is not very lucky. Science is and should be based on observations, facts, and replicable experiments not on visions. I dare say this exactly because I had out-of-body experiences. They had nothing to do with abrupt sea ice loss  :)

Science is a religion.  Can we get back to discussing the ice?

super off topic but absolutely necessary: science is NOT a religion.
Now back to discussing the ice if you wish

Daniel B.

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Re: Abrupt sea ice loss
« Reply #78 on: April 12, 2018, 06:02:31 PM »
Sorry, but couldn't resist.


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Re: Abrupt sea ice loss
« Reply #79 on: April 20, 2018, 11:40:04 AM »
I think that we have been nudging toward what will appear on paper as a 'sudden drop' in sea ice because of the changes going on in the central region and the way the 15% or more measure skews the picture?
As I understand it the measure was not intended for the central pack but to capture ice edge ice cover?
As such we have been seeing central arctic square becoming less and less ice covered by seasons end but still over the 25% 'cut off' and so still measured as 100% covered.
Over the past 4 years we may have seen more and more fragmentation over the high Arctic with 20 or 30% less ice cover yet still end up with 'high' ( 4th /5th/6th lowest) finishes?
If we continue on this path then we may find that all of a sudden we appear to make a sudden lurch down as more open water introduces less than 15% covered sqaures and that 'permanent ice' blinking out?
With the central region I imagine more ice is lost to export than to melt in-situ. As we enter a time where both ocean entrances see rapid transition to open water ice has far more space to roam into as the season progresses ( and melt there in lower lat/warmer waters) leaving even more space for ice to drift into.
Early rapid melt of the peripherals and unfavourable winds could see the central ice 'drifted' away from the pole and so uncover lots of squares usually permanently ice covered?
The DMI 80N graph will be our first warning as it rises above the 'near freezing values' that the ice melt ( and latent heat of fusion) pegs it to.
Will it be this year?
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Dharma Rupa

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Re: Abrupt sea ice loss
« Reply #80 on: April 20, 2018, 02:06:28 PM »
The DMI 80N graph will be our first warning as it rises above the 'near freezing values' that the ice melt ( and latent heat of fusion) pegs it to.

I have to agree with this as the correct signal for a Blue Ocean Event rather than some arbitrary number.  When there is no longer enough ice to keep the temp in the far north pegged near 0 the Arctic will be effectively ice free.

gerontocrat

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Re: Abrupt sea ice loss
« Reply #81 on: April 20, 2018, 02:11:16 PM »
I think that we have been nudging toward what will appear on paper as a 'sudden drop' in sea ice because of the changes going on in the central region and the way the 15% or more measure skews the picture?

I have also wondered if the extent measure was grossly underestimating the true loss of sea ice coverage. So I've been looking at area as well (NSIDC spreadsheets).

The answer is - no. Area decline tracks extent decline very closely. (In addition, since January 2008 the dreaded pole hole has been a mere 0.029 million km2 and so cannot screw up the data over the central arctic).

Mind you, I think at some time there will be a sudden extent/area drop when volume loss reduces the average thickness of remaining ice to n cms, where n is just under 1 metre? Mere speculation by a gerontocrat who might see it, or might not.

The graphs below are for September and March 1979 to 2017 averages. Similar or what.
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Daniel B.

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Re: Abrupt sea ice loss
« Reply #82 on: April 20, 2018, 03:50:57 PM »
Yes, over time both area and extent have tracked each other quite well.  According to NSIDC, the seasonal difference between the two is due to melt ponds; area measurements see these as open water, while they are too small to be detected by extent.  Hence, summer area is proportionally lower than winter.  Hence, extent is more readily used.

gerontocrat

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Re: Abrupt sea ice loss
« Reply #83 on: April 20, 2018, 05:32:57 PM »
Yes, over time both area and extent have tracked each other quite well.  According to NSIDC, the seasonal difference between the two is due to melt ponds; area measurements see these as open water, while they are too small to be detected by extent.  Hence, summer area is proportionally lower than winter.  Hence, extent is more readily used.

"True yeah, man" as we used to say in Liberia when I was there. BUT (there is always a "but" ), this thread is "Abrupt sea ice loss". The divergence of area from extent decline is modest over time.

What I am suggesting is that there is no historical data to support a major abrupt sea ice loss sustained over time. The 2007 and 2012 events have been submerged into the long-term trend. I admit that in both 2007 and 2012 I was at least half-convinced the tipping point had come. But it had not.

Wait and see? N'est ce pas?
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Tor Bejnar

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Re: Abrupt sea ice loss
« Reply #84 on: April 20, 2018, 06:36:31 PM »
Just came across this old projection made soon after the 2012 record was achieved.  A lot of us on Neven's blog, at the time, thought this might come to pass.

Note: 2018 would achieve < 1 million km2 per this projection.
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Dharma Rupa

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Re: Abrupt sea ice loss
« Reply #85 on: April 20, 2018, 06:48:33 PM »
What I am suggesting is that there is no historical data to support a major abrupt sea ice loss sustained over time.

There might not be much historical evidence, but there is quite a bit of geological evidence.

Pmt111500

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Re: Abrupt sea ice loss
« Reply #86 on: April 20, 2018, 07:06:37 PM »
What I am suggesting is that there is no historical data to support a major abrupt sea ice loss sustained over time.

There might not be much historical evidence, but there is quite a bit of geological evidence.


Plus the older ice has been mostly lost already.
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RoxTheGeologist

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Re: Abrupt sea ice loss
« Reply #87 on: April 20, 2018, 07:52:48 PM »
What I am suggesting is that there is no historical data to support a major abrupt sea ice loss sustained over time.

There might not be much historical evidence, but there is quite a bit of geological evidence.


Plus the older ice has been mostly lost already.

It's really hard to define 'abrupt' geologically. That could mean 1000 years in the Pliocene or millions years in the Cambrian. If you want to get down to decade time scales,  then the only real resolution is in Quaternary ice logs.

e.g.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC34297/

where they have shown rapid changes occur over 40 years.

Wherestheice

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Re: Abrupt sea ice loss
« Reply #88 on: April 21, 2018, 11:09:59 AM »
could anyone provide some info on the current status of the multi-year ice in the arctic?
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gerontocrat

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Re: Abrupt sea ice loss
« Reply #89 on: April 21, 2018, 12:18:23 PM »
Found the attached maps in this Article. Not a lot of old ice left

http://nsidc.org/cryosphere/sotc/sea_ice.html

Note to the Maps:-
Old v. new ice in Arctic, March 1990 and 2016: These maps show sea ice age of late March 1990 (left) and 2016 (right), around the time of the winter maximum. Younger, thinner ice appears in shades of blue; older, thicker ice appears in shades of pale green and white. Ice-free ocean water is dark gray, and land areas are light gray. Image courtesy NOAA Climate.gov.
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crandles

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Re: Abrupt sea ice loss
« Reply #90 on: April 21, 2018, 12:19:45 PM »

high res:
http://nsidc.org/arcticseaicenews/files/2018/03/Figure4.png

Quote
Figure 5. This figure shows the distribution of Arctic sea ice according to stage of development, , as of February 22, 2018. Pink shows new ice; purple shows young ice; blue shows first year thin ice; orange shows first year medium ice, red shows first year thick ice, brown shows old ice, and while shows glacial ice.

Credit: U.S. National Ice Center

.



http://nsidc.org/arcticseaicenews/2017/10/
Quote
Figure 4b. Sea ice age distribution at the annual minimum extent for 1985 (upper left) and 2017 (upper right). Time series (bottom) of different age categories the minimum extent for 1985 to 2017. Note that the ice age product does not include ice in the Canadian Archipelago. Data from Tschudi et al., EASE-Grid Sea Ice Age, Version 3

Credit: W. Meier/National Snow and Ice Data Center, M. Tschudi et al.


gerontocrat

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Re: Abrupt sea ice loss
« Reply #91 on: April 21, 2018, 12:29:25 PM »
could anyone provide some info on the current status of the multi-year ice in the arctic?

And this :-
https://www.climate.gov/news-features/featured-images/2017-arctic-report-card-arctic-sea-ice-keeps-getting-younger-and

As reported in the 2017 Arctic Report Card, sea ice older than four winters made up 16 percent of the Arctic sea ice pack in March 1985. In March 2017, it made up less than 1 percent.  Meanwhile, first-year ice constituted roughly 55 percent of the Arctic sea ice pack in March through the 1980s. In March 2017, first-year ice comprised nearly 80 percent of the ice pack.

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Shared Humanity

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Re: Abrupt sea ice loss
« Reply #92 on: April 21, 2018, 02:00:58 PM »
If the increase in stored heat in the oceans is the most significant factor in the long term loss of sea ice and some here have argued that it is, then the obvious progression of MYI to FYI all along the Pacific side of the Arctic must indicate a tremendous growth in ocean heat.

FishOutofWater

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Re: Abrupt sea ice loss
« Reply #93 on: April 21, 2018, 02:56:27 PM »
Yes, there has been a tremendous increase in ocean heat in the NH oceans and seas. The heat has worked its way into the Arctic seas.



Compare that to what it was like sixty years ago.


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Re: Abrupt sea ice loss
« Reply #94 on: April 21, 2018, 02:57:16 PM »
Reading this thread, I see two different issues somewhat confused.
1) Summer Arctic sea ice loss
2) Year round Arctic sea ice loss.

The first is discussed in https://doi.org/10.1016/j.quascirev.2013.10.022
This study suggests that there was a period of very low summer ice cover. This might be abrupt, but is a much smaller change to the climate system than winter loss of sea ice. Figure 5 shows that the modeled size of the abrupt change is roughly 0.5W/m^2, compared with double CO2 of 3.7 W/m^2. Also the ice cover impact is regional rather than global. We are likely to see most summer Arctic sea ice free by roughly mid-century, according to the IPCC and other sources.

The second is discussed in https://doi.org/10.1038/ncomms6608
The last time that the winter ice cover might have been not present was the mid Pliocene warm period. This is probably beyond 2100. The possible impacts are larger.

gerontocrat

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Re: Abrupt sea ice loss
« Reply #95 on: April 21, 2018, 03:15:17 PM »
Reading this thread, I see two different issues somewhat confused.
1) Summer Arctic sea ice loss
2) Year round Arctic sea ice loss.

We are likely to see most summer Arctic sea ice free by roughly mid-century, according to the IPCC and other sources.

The last time that the winter ice cover might have been not present was the mid Pliocene warm period. This is probably beyond 2100. The possible impacts are larger.

The IPCC reports are a consensus, and have to get through a final process which is highly political. Each five years a new set of reports comes out, each time the dates seem to come somewhat closer. They also assume that CO2 mitigation efforts (and later BECCS etc) will happen on schedule. So far they have not - the Paris Accord commitments are insufficient to keep AGW below 2 degrees, and Government actions are already below those commitments.

The IPCC scenarios are also either completely lacking or optimistic about a host of other stuff - e.g. methane stored in the shallow Arctic Seas and the treeless high latitudes of Asia and Canada especially.

I probably am one of those comparative optimists who see a continuation of current rates of decline in extent/area/volume for some years yet.  But mid-century for ice-free summer and 2100 for ice-free winter? No - only if there is a vast investment by Governments in changing how the world works.
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Rascal Dog

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Re: Abrupt sea ice loss
« Reply #96 on: April 21, 2018, 03:54:43 PM »
Quote
But mid-century for ice-free summer

I'll learn sometime how to be both brief and cover enough. OK, maybe not, I'm an old dog and that is a new trick.

There is a fairly tiny change of an ice-free summer any year now. There is a tiny chance the first ice free summer would be after 2060 or so. I wrote "mid-century", too brief. Even with perfect knowledge of the dynamics, random variations aka weather will vary the first summer of ice free by decades.

Year round Arctic sea ice free is a still harder problem.

Shared Humanity

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Re: Abrupt sea ice loss
« Reply #97 on: April 21, 2018, 06:00:48 PM »
With regards to year round ice free, I still have a very hard time trying to understand what would prevent ice forming in the long, relatively cold winter night any time soon. Would it look like today's ice? No. Will some form of ice form on large sections of the Arctic Ocean and peripheral sees? How could it not?

mitch

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Re: Abrupt sea ice loss
« Reply #98 on: April 21, 2018, 06:39:45 PM »
A year round ice free Arctic requires a couple of things: (1) relatively warm water coming into the Arctic Basin and sufficient stirring by storms to bury the large fresh water runoff into the basin, (2) relatively high greenhouse gases to provide a heat cap, and (3) development of winter cloud cover to trap outgoing heat. 

If it truly was ice-free in the early Pliocene, the estimated atmospheric CO2 content was about 400 ppm, like the last couple of years. However, the Pliocene oceans were a huge heat reservoir because the deep ocean was much warmer then.

Dharma Rupa

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Re: Abrupt sea ice loss
« Reply #99 on: April 22, 2018, 12:21:41 AM »
I'd like to point out that we have had a devil of a time trying to define "ice free."