It wouldn't be much of a rebound anyways when you consider how thin all of the ice is.
What good is 4 year old ice that's under a meter thick
It’s more resilient than FYI under a meter.
<mass snippage>
Weather will be the determinant of the pack's survival, not the existing ice.
jdallen pretty convincing. I agree with almost everything you explain. Still that does not negate that, if we have that 7% of ice that has become older in the Western CAB post-2016, let’s count with its existence for future years. My belief is that it does matter, it is one of few negative feedbacks that the Arctic ice has to avoid imminent oblivion, that is: some regeneration of old ice if several years seasons do not push it away one direction or another.
I just happen to believe we are in for a gradual decline, which I know is not a popular opinion here. Yet some folks are noting that “this year would be creating big news if it wasn’t because of 2012”, yes, and that’s because of the current gradual decline of which 2012 was the exception.
I Used to believe 2030 was a good BOE prediction, but I am not so sure when one counts some negative feedbacks: extended falls after bad seasons lead to enormous late heat release, increased snowing, later springs, rebound years; years in a row with low or moderate CAB ice export lead to MYI rebound; warm ocean currents not easily reaching the western CAB ice...
mind you, I agree that a very bad year before 2030 might come and ice extent can go down even 1 m km2 but that would probably be exceptional, followed by rebounds, back to the gradual downhill track as it has happened post 2012, clearly.
Anyway, this is all speculation, reason why I post it here.
Thanks for shifting the discussion here.
I still think 2030-
ish is the way to bet as far as a BoE is concerned, and agree that we'll get years if not decades of "dead cat bounces" while the Arctic as a system languishes in a marginal condition between the previous and next "stable" state.
I think my primary criticism about the value of MYI is more nuanced than may have come across in my OP.
There is no question that MYI was key to buffering and balancing the Arctic as a system, especially pre-2007. The key function it served really didn't have to do with the implied latent energy uptake it represented. MYI doesn't absorb more energy that FYI when melting. The heat budget for phase change remains the same. Rather, it was it's mechanical strength, across vast stretches of the pack which helped stabilize the system as a whole.
Part of that strength depended seriously the temperature of the ice as much as it did on its salt content - ice at -20c is almost as hard as bedrock - and has nearly the same mechanical strength. So, pre-"modern" era conditions with millions of KM2 MYI and sub -10c temperatures meant that wind and other kinetic forces could be spread across very large areas with relatively little damage, and, that there would be little movement or disintegration of the ice outside of the pack margins. This has made the system more or less stable since the last of the Laurentide ice sheet vanished over 4500 years bce. (Prior to this, it was probably stronger.)
It's thickness ->at scale<- was important as well, as it meant year over year, it could lose 2+m of thickness, still remain in place, and provide a similarly broad-scale platform for re-deposition of new ice from below and new fresher ice refrozen from melt above. It tended to stay in place. It tended to keep albedo high, and by nature of strength and coverage, limit seasonal uptake of heat. These last were as if not more important than the thermal inertia the ice itself provides.
Scroll forward now to the modern era, particularly at key junctures like 2007, 2010 (an underrated melt year), 2011 and 2012. I'm adding a link to one of my favorite graphics by Jim Pettit here to help illustrate:
http://iwantsomeproof.com/extimg/siv_annual_max_loss_and_ice_remaining.pngThose years mentioned are key in they are points in which the melt season destroyed large areas of MYI. 2010 in particular is notable for that, as even though extent and area did not drop to record levels, it was the first year we observed volume drop below 5,000 km3. 2007 was the first below - WAY below - approximately 9000km3 (2006 was 8993km3). 2011 and 2012 were years that continued the trend, dropping volume under 5000km3 and progressively chipping away at what some of used to call "matrix pack"; called such because of the very regular way it would fracture, essentially creating what could be considered fault lines in the ice while mostly retaining strength and coherence.
Those losses of volume and by extension MYI are critical to set the stage for what we see starting most dramatically in 2016. The winter pack now fractures and recombines at much lower scales, eliminating the resistance it used to have to mechanical forces, and making the entire pack as a whole far more mobile. Combine this with increasing advection of heat from southerly seas, and you have the new seasonal regime we now see.
The result is, we have nothing like the larger expanses of MYI we used to see, which unbroken might cover 10's of thousands of km2. We are lucky if we see blocks of more than about 2500. And because of warmer temperatures overall, for longer periods of both the melt and refreeze seasons, that relict ice has nothing like the mechanical strength of the old pack.
So, to finish my thought for the moment and conclude, MYI was far more important for the structure and mechanical characteristics it provided than it was for any sort of thermal component. So while it exists now, it has nothing like the structure it had in the past, and because of that is only marginally less vulnerable than FYI when exposed to the conditions we now see during the melt season. Without that structure, it doesn't really provide a buffer against loss as it used to.