Here's the thing regarding the Kara, Barents and near-Atlantic pack. The significantly increased temperatures, and high temperature of the ice has a direct and measurable effect on the ice's compressive and tensile strength. The abstract of this article citation has a summary good enough for my purposes.
Strange. I always assumed the energy compressing ice was released via formation of pressure ridges. Keeping a 1 to 2 m ice cap compressed over thousands of km2 seems a mighty unstable situation to me.
Likewise, fractures quickly release the stretching of ice.
Ice seems a pretty fragile matter being a crystal. Shouldn't we be talking about resiliency/fragility rather than structural strengths?
The lower strengths - tensile similarly declines by a factor of 4 over that span of temperature - reduce the ice's resistance on a larger scale. It breaks into smaller pieces, and I would expect rather than forming durable ridges, shatters into melange - much as you see rock in fault zones ground into rubble. That may be a good metaphor for it as well - rather than being shaped into new structures, it gets ground into rubble, which while it might get lightly welded by some freezing, doesn't gain the durability required to be persistent.
It means also that larger structures - think multi KM stretches of ice - cease to have the strength required to resist internal stresses, and break down more easily into smaller elements than the colder, stronger ice.
We've seen very good evidence supportive of this over the last few years of observation in these forums.
This year becomes even more exceptional, as for significant stretches of the main basin, as well as the peripheral seas, we've seen temperatures so high that the pack has never had sufficient opportunity to consolidate, thicken, cool and strengthen. Buoy temperatures where we have them pretty consistently indicate temperatures considerably above -20C, which was not the case if you go back a few years. I vaguely recall looking at temperature profiles in late spring ice, 3M thick, with core temperatures still close to -20C.
The breakage issue is important mechanically for a number of reasons I think.
1) water column turnover. More movement of ice and direct access to sea surface by wind will increase Eckman pumping and transfer of heat from depth to the surface.
2) Lateral melt. Melting profiles in different studies tend to suggest that lateral melting does not contribute significantly to volume loss until your flow size drops down under about 100M or so. Once that threshold is reached, lateral melt contribution increases geometrically as the diameter decreases. It's pure arithmetic - you decrease flow size, you increase the area available to attack by sea water. You decrease the coherence of the ice - it's ability to maintain large expanses of unbroken ice - and you can see how the pack is evolving to a point where this will be an issue.
3) Mechanical attack by waves. We don't need collisions or compression to cause ruptures. With the ice significantly reduced in strength, where ever we see significant leads and fetch for wind, it will be far more prone to break up than in the past. Further, it will do so much earlier in the season.
4) More sea surface open to insolation. We won't need as much in the way of melt ponding to DEcrease albedo if, poorly consolidated ice ruptures, gets dispersed by movement, and opens sizeable leads. That was part of what was at work in 2015. I think it will only be worse this year, and may start earlier. *Has* started earlier.
Timing is important here. In the past, the ice would weaken, and that you would see significant reduction in strength over large stretches of the Arctic - but not until fairly late in the season. Even then, even in years like 2007, 2010, 2011 even 2012... you still had pretty sizeable stretches of ice which retained fairly high coherence. That really hasn't been true since 2013 onwards, if you consider the megacracking events we've seen, and the near complete atomization of the pack such as we saw in 2013. That year in particular, we were saved by nothing more than the whims of the weather and a cold freezing season.
We haven't had that for two years now.
I will be watching how the pack evolves over the early melt season with great interest.
[Edit: One more thing occurs to me - higher temperatures means brinier ice. It won't have had as much time or good conditions to "desalinate". That should translate into lower melting temperatures, closer to the current SST. Bottom melt will start sooner.]