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anthropocene

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Can 2012 record minimum be beaten without a 2012 GAC?
« on: May 11, 2016, 12:25:21 AM »
The below was posted in the IJIS thread. Rather than clog up that thread I've started a new thread here to discuss it. I don't understand what "exhausted a lot of heat" means. Every other point I disagree with. What are the chances of beating 2012 record low extent without a GAC like the 2012 GAC? Discuss...

"The gac is way overrated
The differences with and without it would have been incredibly small.
The most amazing part was the speed in which large areas of Ice floes melted so fast.
But it also exhausted a lot of heat.  Where as a 2010 like dipole would have injected more heat into the basin and had a very similar end result"

magnamentis

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #1 on: May 11, 2016, 12:40:05 AM »
i tend to concur with your point of view, that GAC was the driving force to produce that 2012 record low IMO, hence it cannot be rated high enough. if we beat that record this year it's because we started into the melting season accordingly, 2012 was one of the later and higher maximums and until this day of the year the gap remains, all that made 2012 special happend in mid to late summer while this year can and probably will come close without any of that happening. all the parameters this year were and are close to or at the lowest, least, weakest, earliest and that kind of superlatives.

DavidR

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #2 on: May 11, 2016, 01:09:09 AM »
According to  at least one analysis teh cyclone was responsible for only about 150,000 km^2 of the record.

http://www.washington.edu/news/2013/01/31/cyclone-did-not-cause-2012-record-low-for-arctic-sea-ice/

The 2012 sea ice started plummeting on July 22nd and was well ahead of the previous record by the time the storm hit.

While 2012 was well below the previous record year, 2007, for nearly the next  3 months it was never as far ahead of the previous record as 2007 was ahead of 2005 the record year before 2007.

Record years are by definition different from previous years. So any prediction at this stage should really come with a likilihood. Weather is a major factor and we are not yet  good at that  three months out.

Toto, I've a feeling we're not in Kansas anymore

Glenn Tamblyn

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #3 on: May 11, 2016, 01:12:30 AM »
2012 had two standout events.

1. A major drop of around 1,000,000 km^2 in just over 10 days in early June. That moved it from a pretty average year to roughly on the edge of record breaking. The low extent in the Beaufort (and perhaps the Greenland Sea) mean we have already seen a similar break. If 2016 just continues an 'average trajectory' then it might likely match 2012 come mid June. However, since the cracking aa few weeks ago the Beaufort has plateaued. Cooler temps and thin refreeze has held it up. If the predicted warmer warmer temps in the next week hit, that refreeze will melt away and the Beaufort and CAB-above-Beaufort will drop again. So perhaps below 2012 by mid June.

2. 2012 saw a substantial drop during August where other years were starting to level out. Due to the GAC, or something else? Dunno. But 2016 would need to be well below 2012 heading into August, not just somewhat ahead to beat 2012 if it follows a 'normal' melt season trajectory. Another GAC would do it. Or perhaps the extensive cracking beyond the Beaufort we are seeing will prime enough of the other basins to progress more significantly.

crandles

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #4 on: May 11, 2016, 01:14:51 AM »
What do experts say?
Quote
an unusually strong cyclone in August helped to quickly break up the already thin and fragmented ice cover in the Chukchi Sea. This cyclone—remarkable in its intensity and its duration—lasted for thirteen days, of which ten days were spent in the Arctic basin.

While it appears that a record low extent would have been reached even without the cyclone, thinning over the last several decades has made the ice more vulnerable to such storms, compared to earlier decades when the Arctic Ocean was dominated by thick, multiyear ice.
http://nsidc.org/arcticseaicenews/2013/01/

There is still quite a bit of difference between ' a record low extent would have been reached' and the amount by which 2012 smashed the record low.

Volume was at a clear record low by the start of June and area by day 165.

Aug Sea ice outlook using data to end of July ranged from 3.9 to 4.9 median 4.3 with actual at 3.6M Km^2 and previous record low at 4.61M Km^2
https://www.arcus.org/search-program/seaiceoutlook/2012/august

I would tend to disagree with both 'differences ..  incredibly small' and '[GAC] cannot be rated high enough'.

magnamentis

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #5 on: May 11, 2016, 01:18:19 AM »
yes, sounds good, predictions have to be taken with a prise of salt and they serve to sharpen the sensors or in other words, increase the exchange of thoughts and the intensity of discussions.

BTW, things are getting darker, ice in Kimmirut gets a darker blue tint every day and barrows snow is almost invisible underneath the soot.

Watching_from_Canberra

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #6 on: May 11, 2016, 01:34:24 AM »
I don't think that's ice at Kimmirut, I think it's just snow on top of the ice.  In fact, you can see tracks in the snow - there were a bunch of people out on the ice yesterday.  I suspect the blue-ish colour you're referring to is probably just due to the angle of the sun.  When it's higher, it will appear white.

Juan C. García

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #7 on: May 11, 2016, 01:39:44 AM »
The below was posted in the IJIS thread. Rather than clog up that thread I've started a new thread here to discuss it. I don't understand what "exhausted a lot of heat" means. Every other point I disagree with. What are the chances of beating 2012 record low extent without a GAC like the 2012 GAC? Discuss...

"The gac is way overrated
The differences with and without it would have been incredibly small.
The most amazing part was the speed in which large areas of Ice floes melted so fast.
But it also exhausted a lot of heat.  Where as a 2010 like dipole would have injected more heat into the basin and had a very similar end result"

Hi Anthropocene:

I believe that we can beat 2012 record without a GAC, specially if we continue with the downtrend on May.
But I don't believe that the GAC is overrated. I believe that is a way to lose a lot of Arctic sea ice, as you said when I made a poll about the importance of cyclones:

Most of what you say is most probably correct but I look at it a different way. I haven't done the calculations but I would guess there is more than enough energy in the arctic to melt all the ice. (There was a discussion many moons ago about the inflow of energy through the Bering Strait. iirc the amount of energy in a year alone would melt all the ice).  The issue is getting the energy to the ice in a way such that the ice melts. "cyclone merely speeds up the melt" downplays the impacts. I agree that the ice may have melted anyway but the speed up means that there is more time for other processes to occur (insolation, mixing of the cool 'just melted' water with warmer incoming water,increased contact area of ice to water etc.).  The above would be much clearer if upper ocean and ice were treated independently. In the (simple!) model in my head I treat them as separate systems. The problem then becomes getting the energy in the upper ocean to the ice. Cyclones are very effective at doing this.
« Last Edit: May 11, 2016, 01:46:09 AM by Juan C. García »
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.

magnamentis

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #8 on: May 11, 2016, 02:21:10 AM »
I don't think that's ice at Kimmirut, I think it's just snow on top of the ice.  In fact, you can see tracks in the snow - there were a bunch of people out on the ice yesterday.  I suspect the blue-ish colour you're referring to is probably just due to the angle of the sun.  When it's higher, it will appear white.

i talk about he blue part while on the edges is white snow, clearly distinguishable. further i watch that part closely for weeks and there were melt ponds a bout a week ago which now that the few mm of snow has melted are surfacing again, there is no shadow, at least not in my posted pic while now, later in the evening of course there are shadows :-)  and snow is not dark blueish. however wasn't meant to start a discussion, if this weather with temps above 0C will continue for another bit and at least some sunshine will occur we shall soon see. further outside of that fiord is a stripe of open water, hence things are certainly not as calm as the look, the natives even took their skidoos of the ice today, certainly for good reason. consider the 5C temps and full sunshine, at 5C snow is melting as is clearly visible closer to the cam and the snow cover was minor on top of those melt ponds. you find older pics in the melting season thread a few days back if you're really interested.

6roucho

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #9 on: May 11, 2016, 04:15:00 AM »
It seems possible this year that other systems might do the job of the GAC in breaking up weak ice and enabling increased advection through the Fram Strait, such as a continuation or extension of the  Beaufort Gyre to include parts of the CAB, along lines (sic) that have already been observed.

It's a commonly used trope on here that one day it might all just flow out the Fram. That's an (obviously extreme) example of the kind of macro-scale change that could enable a rapid decline to occur, and yet seem 'impossible' based on model extrapolations.

A GAC is just one example of a state-change trigger.
« Last Edit: May 11, 2016, 05:07:59 AM by 6roucho »

6roucho

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #10 on: May 11, 2016, 05:00:04 AM »
I'm reminded of Maslowski's list of climatic processes that are omitted from, or poorly represented in, most current-generation models (due to constraints such as the availability of data, the existence of algorithms, computational cost, our knowledge of physics, the amount of time scientists have, and the limitations of computability):

"Oceanic eddies, tides, fronts, buoyancy-driven coastal and boundary currents, cold halocline, dense water plumes and convection, double diffusion, surface/bottom mixed layer, sea ice–thickness distribution, concentration, deformation, drift and export, fast ice, snow cover, melt ponds and surface albedo, atmospheric loading, clouds and fronts, ice sheets/caps and mountain glaciers, permafrost, river runoff, and air–sea ice–land interactions and coupling."

That's a lot of 'unknowns' to potentially combine under a regime of substantially increased temperatures to produce a substantially different outcome.

6roucho

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #11 on: May 11, 2016, 05:12:44 AM »
Of course the set of substantially different outcomes includes a recovery, but with the amount of heat being added to the system, if we can consider the previous state to be a more ordered one, then entropy suggests not. Broken teacups reassembling themselves is a statistically rare event.

anthropocene

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #12 on: May 11, 2016, 09:31:49 PM »
OK - to put more meat on the bones. It is my contention that low pressure/cyclones is more destructive to ice (in particular ice volume which is the property which matters most) than high pressure. However there are factors which mean that it can look as if high pressures have more impact and which can mean that the impact of cyclones is underestimated. Below I list the main factors causing loss of ice and the main factors which mean that the amount of ice lost can be over-estimated (high pressure) or under-estimated (low pressure)

High pressure  - ice melt factors:

Insolation
Drift of higher temperatures from the south (especially if high pressure is part of a ridge in polar vortex)
Production of melt ponds

Reasons why impact of high pressure can be over-estimated:

high pressures compact ice
persistent winds from the south compact ice (by definition)
clear skies allow visibility of any loss of ice (Modis etc.)
Melt ponds fool satellites to under-estimate ice cover (especially in May/June)
Psychologically associate sunshine with warmth/ice melt because most people are at low latitudes. Sunshine has lower affect at higher latitudes especially at the pole in August/September
Higher temperatures may not come into contact with ice as much as expected

Low pressure - ice melt factors:

Pull warm air into arctic areas
Ekman pumping increases SSTs
waves physically attack ice
rain onto ice
spreads ice (increase of area which can be melted)


Reasons why impact of low pressure/cyclone can be under-estimated:

low pressure spreads ice (increases extent and to a lesser amount area)
clouds can fool satellites to detect false ice
freezing of melt ponds can cause extent and/or area to (falsely) increase
lack of "torching" temperatures psychologically means that massive melting is not expected
Same as above for sunshine
Clouds stop visible satellite view of loss of ice


Comparing the above (admittedly with no quantitative measures of the relative impact of each factor) it seems clear to me that cyclones can melt more ice. It can also be seen why it is easy to get the impression that impact of high pressure/clear skies is greater than it is.


Michael Hauber

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #13 on: May 12, 2016, 04:28:50 AM »
In 2010 an early season high pressure dominated pattern sent ice extent to well below the previous record.  When the pattern changed to a low pressure dominated pattern the melt hit a brick wall and melt was well above record at minimum.  2007 was high pressure dominated.  2103 was low pressure dominated.

I think the impact of the GAC during 2012 was overrated.  As quoted earlier analysis estimates about 150k difference between minimum due to the GAC.  The rapid melt that occurred during the GAC was preconditioned by a major weakening of ice over a large area, and the partial detachment of a large area of ice towards ESS which made that area especially vulnerable to melting.  Before the GAC Neven had been speculating on flash melting due to these factors.  I think there are two important factors other than GAC that impacted the ice in 2012.  We had quite warm weather in early June which resulted in the earliest start to widespread surface melt for most of the central Arctic that I have been able to find.  During July there was a pattern of widespread weak ice over a huge area visible in MODIS, that I had not seen in watching MODIS since 2009.  It was in some ways similar to 2013, but in 2013 the floe size was much larger, and the surface more frequently frozen.  This pattern first appeared after a short sharp low pressure system around 20 June.  Everything poleward of the storm's track becomes dispersed, and most of this ice eventually melts out.  I suspect this unremarked storm had as much or even more impact on the ice than the GAC in August did.  It dispersed the ice, and warm, moderately sunny conditions afterwards melted the ice with the help of lots of small areas of water in between the floes.  Contrast to a pure high pressure system year where the ice becomes compact.  All the open water is in one continuous piece at the edge of the Arctic.  The sun soaks into the open water but it is too far from the ice to melt anything and instead the large area of open water reaches up to 10 degrees above average.  Contrast with 2013 where low pressure dispersed the pack and made it weak.  But there was too much low pressure and never any good sunny weather to attack the weakened ice.
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LRC1962

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #14 on: May 12, 2016, 01:44:38 PM »
In the past most highs and lows started and end in the Arctic thereby in effect isolated from the rest of the NH. The jet stream has weakened and is no wobbling so much the more and more, the majority of the systems in play are starting from the lower latitudes. This is a major shift and therefore those systems now bring far different variables to the table then the 2012 GAC.
As far as needing a GAC to beat 2012? No. The winter of 2015-2016 has set a table that IMO would take an extraordinary cold and isolated June-July to hold what ice is there from falling a part. Remember we have lost a lot of MYI this past winter and what is still there is not in the best spot for staying in the Arctic this summer.
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jdallen

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #15 on: May 12, 2016, 06:37:26 PM »
In the past most highs and lows started and end in the Arctic thereby in effect isolated from the rest of the NH. The jet stream has weakened and is no wobbling so much the more and more, the majority of the systems in play are starting from the lower latitudes. This is a major shift and therefore those systems now bring far different variables to the table then the 2012 GAC.
As far as needing a GAC to beat 2012? No. The winter of 2015-2016 has set a table that IMO would take an extraordinary cold and isolated June-July to hold what ice is there from falling a part. Remember we have lost a lot of MYI this past winter and what is still there is not in the best spot for staying in the Arctic this summer.
I've noticed the increase in systems reaching the arctic after starting at low latitudes as well.

That weakening of the jet stream is very much on my mind.  In particular, I am considering the "cyclone cannons" we've had on the eastern coasts of Asia and North America, which during fall and winter over the last two years have fired streams of explosively intensifying storms from low/mid latitudes into the arctic. 

So, for me, it's not so much the weather setting up in the arctic, as it is the break down of the circulation outside of it that I'm concerned about.

If we see an expansion of those "cyclone cannons" into early fall/last summer it could both significantly extend the melt season and intensify August and September melt.

But even more to the point, unlike 2012, what frames what's happening now isn't any individual event, but a long list of much smaller changes.  Winter weather heat.  Increased import of moisture.  Decreased MYI.  Decreased ice mechanical strength, higher net Arctic ocean enthalpy, decreased albedo, greater ice mobility, all these contribute.  Some of the changes are more or less dramatic, but no single factor really strikes me as the magic bullet that shatters the Arctic.  In aggregate though, they have the potential reduce the 2012 GAC to an "also ran" event.
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DavidR

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #16 on: May 12, 2016, 11:01:20 PM »
With temperatures the way they have been over the last 4 months we really are in a different ball park than in previous years. This shows temperatures as std deviations since 1948 for the globe, the Arctic and 80N+. As you can see 2016 is a complete outlier.
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anthropocene

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #17 on: May 15, 2016, 05:17:24 PM »
Thanks for all the (thoughtful) responses.

jdallen: Yes so the high pressure systems and cyclones are now having different characteristics to the past both of them now bringing more heat to the arctic system. Seems sensible.

LRC1962 & DavidR:  Good points that the arctic is becoming warmer. I'm not arguing that the arctic is not becoming warmer or that eventually the warmer arctic will mean 2012 is beaten. My personal prediction is that the arctic will be ice free at minimum in 2030 +- 10 years. To reach that by 2020 then it almost certainly means having a lower minimum than 2012 in the next year or two.

By the way there is an excellent post by Artful Dodger on the fresh water lens here http://neven1.typepad.com/blog/2016/05/beaufort-under-relentless-high-pressure.html?cid=6a0133f03a1e37970b01bb08fde8f1970d#comment-6a0133f03a1e37970b01bb08fde8f1970d

This is the type of inertia that I propose means new mechanisms are required if new lower levels of sea ice minimum are going to be reached. In other words it will take a few years for the increasing heat to melt significantly more ice.  Cyclones and Ekman pumping are one way that the fresh water lens can be broken down.

 

jdallen

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #18 on: May 16, 2016, 12:17:30 AM »
<snippage>  Cyclones and Ekman pumping are one way that the fresh water lens can be broken down.

Hmmm.  I wonder if the models are taking that into consideration?  That might be an unanticipated feedback?
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Laurent

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #19 on: May 16, 2016, 09:40:03 AM »
Now that the entire ice pack is in rotation, isn't there Ekman pumping ? How many times before we can notice it in the buoys data ?

philiponfire

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #20 on: May 16, 2016, 10:26:57 AM »
I do not think this is the right question any more. in my opinion we are int territory where we need to be thinking in terms of how much not if.
as I mentioned in the melt season thread, MASIE just announced over 400,000 sq km drop in 3 days.
MASIE records show that on this day 2016 is already over 880,000 sq km lower than in 2012. It matters not the difference between MASIE and the other measurement systems. In a year to year comparison 880,000 is a big number. going to be hard to claw back that much slow down as we move into summer.

oren

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #21 on: May 16, 2016, 10:55:27 AM »
I do not think this is the right question any more. in my opinion we are int territory where we need to be thinking in terms of how much not if.
as I mentioned in the melt season thread, MASIE just announced over 400,000 sq km drop in 3 days.
MASIE records show that on this day 2016 is already over 880,000 sq km lower than in 2012. It matters not the difference between MASIE and the other measurement systems. In a year to year comparison 880,000 is a big number. going to be hard to claw back that much slow down as we move into summer.

Not necessarily such a big number. Note that 2015 was lower than 2012 by 650k sqkm on June 5th, only to be left 180k sqkm behind on June 13th, a relative change of 830,000 sq km in eight days. 2012 was consistently high all through the spring, so comparing to 2012 gives wrong impressions at this time. I'm not saying this year could not beat 2012 - it could, but it's not going to be easy. Check back at mid-June and the certainty level could be much higher.
« Last Edit: May 16, 2016, 03:08:36 PM by oren »

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #22 on: May 16, 2016, 02:32:21 PM »
I do not think this is the right question any more. in my opinion we are int territory where we need to be thinking in terms of how much not if.
as I mentioned in the melt season thread, MASIE just announced over 400,000 sq km drop in 3 days.
MASIE records show that on this day 2016 is already over 880,000 sq km lower than in 2012. It matters not the difference between MASIE and the other measurement systems. In a year to year comparison 880,000 is a big number. going to be hard to claw back that much slow down as we move into summer.

Not necessarily such a big number. Note that 2015 was higher than 2012 by 650k sqkm on June 5th, only to be left 180k sqkm behind on June 13th, a relative change of 830,000 sq km in eight days. 2012 was consistently high all through the spring, so comparing to 2012 gives wrong impressions at this time. I'm not saying this year could not beat 2012 - it could, but it's not going to be easy. Check back at mid-June and the certainty level could be much higher.
2012 passed 10M km^2 on June 17th, becoming the earliest that milestone has been passed.  The smallest decline in the record since 2007 will put 2016 more than 200 K km^2 below that and the largest 2, apart, from 2012 itself,  would put 2016,  800 K km^2 below 2012.  Only the 2004 drop of 1.08 M km^2 would see 2012 catch 2016 by then.

Based on the thinness of the ice there appears to be little chance of 2012 catching 2016 before July, barring an exceptionally long, exceptionally cold, spell; and that is highly unlikely in the middle of the hottest year on record.

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LRC1962

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #23 on: May 16, 2016, 11:02:29 PM »
Some things to think about maybe.
Extent is closer to zero than ever before at this time.
The ice is thinner than ever before.
The extent boundary is farther north on both Pacific and Atlantic sides.
Put this together then you will see wave action impacting deeper into the pack than ever before.
If you apply the same calculation that they give to the Hurricane season and how bad it was, If you stretch the GAC storm out over 4 month period, then you will not need big storms to break down the ice to the same degree, just need to over that time period. Also, remember that storms creating those waves do not need to be on top of the central pack anymore to cause destruction. All they need to do is send them in the right direction.
IMO even if we have low temps and low sunlight levels, if we get waves from even 100's of miles away the ice will still disappear. Get all 3 working together and we may be in for a cliff drop.
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anthropocene

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #24 on: May 16, 2016, 11:43:44 PM »
Laurent: "Now that the entire ice pack is in rotation, isn't there Ekman pumping ? How many times before we can notice it in the buoys data ?"

Good point - I hadn't really thought about that before. No idea whether Ekman pumping occurs and what impact that has.

Philiponfire: "I do not think this is the right question any more"

I disagree - some of the responses posted have made me more certain that it is exactly the right type of question to be asking.  Melt in May has very little in common with melt occurring after the middle of August. The majority of melting in the later part of the melt season is bottom melt. Maybe it'll be better to phrase the question another way as a thought experiment. It is the middle of August and ice cover is approximately equivalent to 2012 sea-ice minimum. Since ice extent is so low, the ice edge is at a high latitude and where the ice melt is occurring it is unlikely that air temperatures will be much above 0degC for long periods in the day.  On day 1, melting occurs across a 1000 km range and melts a band 5km across. For arguments sake lets say this occurs 100% by bottom melt. 5000 sq. km of ice has been melted which is quite a large bite out of the remaining ice. But now the warm water is now up to 5km from the ice edge. On day 2 how much ice is melted and by what mechanism does that happen?

anthropocene

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #25 on: May 20, 2016, 08:10:16 PM »
So nobody wants to take up the challenge of answering the thought experiment? I've either defeated you all or bored you to death. The second option seems more likely.

I have two answers to the above question
1) Cheat. Make the situation happen 1 month earlier in mid-July when it will be easier to get ice melting air temperatures to those high latitudes and insolation will be that much greater. 2016 is making a good attempt to reach that state but the change required to reach 2012 minimum in mid-July is (hopefully) a few years off.

2) A different mechanism is required to transfer the energy in the system to the ice. This could be in the form of waves physically smashing the ice, rain on the ice or wind pushing the ice over the warm water or to maximise ice melt all three. A bit of Ekman pumping would help (once the ice becomes broken enough to allow that to happen).  A GAC would quite easily do that along a 1000km front.

Sorry but all the posts elsewhere using previous amount of melts from the current date onwards to predict this years minimum add little value. Melting ice in seas surrounding the CAB is not the same as melting ice in high latitudes in late August. More open ocean makes cyclones in the arctic more likely but not certain.

jdallen

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #26 on: May 20, 2016, 08:30:38 PM »
So nobody wants to take up the challenge of answering the thought experiment? I've either defeated you all or bored you to death. The second option seems more likely.

Nah, mostly busy or distracted.

I think key to answering your question is an understanding of starting conditions.

*If* we had the same conditions as 2012, I think the answer is no, we could not reach that low without a GAC.

However, we do not have the same conditions.  To briefly and incompletely summarize:

  • The ice is not of the same quality
  • The total heat content of the Arctic ocean has increased significantly
  • CO2 has increased by 2 1/2%, with a somewhat lesser but still significant effect on trapped heat
  • Weather patterns have shifted, bringing more heat year round into the Arctic
  • Total global enthalpy has increased

...And there are more, I'm sure.

So as our base state has changed considerably in the direction which favors the Arctic melting out, no, I do not believe we need a GAC to reach or beat 2012.

To use a metaphor, if the annual melt/refreeze is a pendulum, the total heat in the system determines where the walls are around it.  Increase the heat, we close the walls in and lower the amplitude of the swing.  Eventually  they compress so far it can no longer swing at all.
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Dundee

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #27 on: May 21, 2016, 01:41:20 AM »
jdallen has hit the key to the question, and why it is not as interesting as it may seem.

Accepting that global temperatures are generally rising, plot out whatever future slope and shape you wish. At some future date we can expect the 2012 record to be routinely broken, and at some date beyond that, to be a forlorn memory.

In this sense, the general answer is "of course". The question reduces to ". . . be beaten in 2016 without a 2012 GAC?". This may seem interesting this year, but in five years it probably won't.

To stray a bit, it is like asking if we will see CO2 at 400ppm this fall. Maybe, maybe not, but certainly not 2-3 years hence. We will (in fewer years than we wish) have the opportunity to ask the same question about 500ppm or (returning to the thread) "Can the 2016 record be beaten without a 2016 El Nino". Perhaps not in 2020 (or whenever) but if you are patient, almost certainly, and not so very far in the future.

To stray again (perhaps unforgivably) the question wrt blocking the Bering Strait should not be "why not?" but just how many years might it buy us, and how would they compare to how long it would take (given some very significant engineering uncertainties). To a certainty, it (and any other solution that does not restore the atmosphere to an acceptable spectral transparency) is absolutely not a long term fix.

As exciting as the result of extreme weather events may be, what should make the hair on the back of our neck bristle is what we now see happening in years whose weather represents the new normal - average to cooler than average melting seasons. Even should any particular black swan or tipping point (or all of them) turn out to be nothing exciting, we are still frogs who are, in fact, boiling.
« Last Edit: May 21, 2016, 06:17:50 AM by Dundee »

philiponfire

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #28 on: May 21, 2016, 02:59:06 AM »


  "Melt in May has very little in common with melt occurring after the middle of August."

Agreed! but you seem to be missing the point. The high latitude ice does not exist in isolation. It is all part of one system and that system this year is already being loaded with visibly extra heat.

"The majority of melting in the later part of the melt season is bottom melt."
If there is an ever larger area of ice free water surrounding the CAB then that is inevitably warmer water than the average temperature of the remaining ice is it not?
Unless you want to assume that the water does not move or mix then the water at the ice edge will become warmer and more ice will slowly melt until refreeze begins.
Where is the mechanism that is going to dramatically slow down the ice loss now so that small levels of August ice loss are unimportant?

Neven

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #29 on: May 21, 2016, 11:30:31 AM »
Welcome, Dundee, and nice first post. I have released your comment and profile (anti-spam measure), so you can post freely now.
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anthropocene

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #30 on: August 16, 2016, 09:31:51 PM »
Just bumping the thread before someone starts a new thread on similar lines  ;)

seaicesailor

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #31 on: August 16, 2016, 09:54:57 PM »
Nice. Thx for bumping.
 I don't know who wrote what is quoted in the OP but it has a point. The energy available at the periphery of the ice pack is finite and at some point it cannot keep melting what is thrown away from the storm.
The predicted August 24 (extremely improbable under-960 hPa) storm would probably help ice pack extent stay above 2007 because of its central location and because it is late in the season. If it is not that central, but somewhere at the peripheral seas, then it can really hurt, even if it is weaker.
« Last Edit: August 16, 2016, 10:03:40 PM by seaicesailor »

Michael Hauber

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #32 on: August 16, 2016, 11:15:37 PM »
According to Canadian weather office charts the current cyclone bottomed out at 968hp.  According to Simmonds and Rudeva the bottom pressure for GAC 2012 was 966hp.  So getting there, and comparing to the list of top 4 August storms the current storm would make number 3 on this list.  How comparable the Canadian Weather office central pressure and the Simmonds Rudeva central pressures are I'm not sure.

It does look increasingly likely that we will see some sort of significant follow up, even if it doesn't get as extreme as some of the current models are suggesting.  If that occurs I would guess we've had a stronger storm influence on the Arctic this year than in 2012, and we may have some confirmation of research suggesting that the impact of the GAC 2012 was relatively minor.  Or perhaps further evidence that such storms have a big impact.
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Nick_Naylor

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #33 on: August 16, 2016, 11:18:53 PM »
We are starting to see some evidence that such storms may no longer be rare :o

bbr2314

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #34 on: August 17, 2016, 12:08:23 AM »
We are starting to see some evidence that such storms may no longer be rare :o
This season the storms have clearly tracked along areas that opened early (and continue "following" the newly-opened areas of ocean). I think it is strong evidence that the GAC was a result of the overall state in 2012 vs an independent outcome and supports the idea that the tipping point between 2M KM2 @ minimum & 0 may be very small indeed.

RoxTheGeologist

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #35 on: August 17, 2016, 03:13:09 AM »
Nice. Thx for bumping.
 I don't know who wrote what is quoted in the OP but it has a point. The energy available at the periphery of the ice pack is finite and at some point it cannot keep melting what is thrown away from the storm.
The predicted August 24 (extremely improbable under-960 hPa) storm would probably help ice pack extent stay above 2007 because of its central location and because it is late in the season. If it is not that central, but somewhere at the peripheral seas, then it can really hurt, even if it is weaker.

There is enough heat in the Atlantic layer to melt the surface ice multiple times over. Hundreds of meters of saline +2°C water, compared to, at best, a few meters of surface ice, at worst a few cms.   

seaicesailor

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #36 on: August 17, 2016, 07:55:20 AM »
Nice. Thx for bumping.
 I don't know who wrote what is quoted in the OP but it has a point. The energy available at the periphery of the ice pack is finite and at some point it cannot keep melting what is thrown away from the storm.
The predicted August 24 (extremely improbable under-960 hPa) storm would probably help ice pack extent stay above 2007 because of its central location and because it is late in the season. If it is not that central, but somewhere at the peripheral seas, then it can really hurt, even if it is weaker.

There is enough heat in the Atlantic layer to melt the surface ice multiple times over. Hundreds of meters of saline +2°C water, compared to, at best, a few meters of surface ice, at worst a few cms.
Sure, but I was not meaning the Atlantic exclusively. A centered storm inflates the pack in all directions. This storm has surely enabled grater heat transfer rate to melt ice (water mixing, waves, floe breaking) to make up for that and more, but at some point the energy rate you need to keep melting is higher and higher as it gets colder.
I don't think the August 7 GAC melting effect was overrated, but at August 24, if it happened, and central,  might help extent keep up. And halt the season.
Let's see what happens with our August 16th GAC aftermath.

epiphyte

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Re: Can 2012 record minimum be beaten without a 2012 GAC?
« Reply #37 on: August 17, 2016, 09:07:55 AM »
I'm in two minds about this. On the one hand, IIRC, the biggest hurricane in recent memory dumped ~50km3/day of warm water on the US east coast. right now that's about 1% of the remaining ice volume, so if something of similar magnitude went on for a few days it would still be hard put to transport enough energy through the atmosphere to put much of a dent in 3-4000km3 of ice even if it was raining boiling oil.

OTOH, if it just stirs things up enough to homogenize the water down to a few meters of depth, and a few degrees of latitude, we could be looking at a record loss a week from now.

 - either way, on balance, IMO anything dramatic which happens between now and mid-September would likely not have happened absent this storm, so I guess for this year at least, the answer to the headline question of this thread is probably "No"...