Wdmn, the phase change itself needs energy.
Link >> http://hydrogen.physik.uni-wuppertal.de/hyperphysics/hyperphysics/hbase/thermo/phase.html
Sorry, no facts to add to the question, but here some perspectives for those of us who don't work with ice physics every day.
It always shocks me when reminded that the heat exchange between frozen vs. melted ice is 80% of the heat energy change required to change water temperature from 0C to 100C.
That huge energy budget to melt ice has been a defense mechanism for preserving the Arctic sea ice. Consider the 75+% ice volume losses since 1979, the amount of heat input that required is huge. As the Arctic loses that defensive wall (the ice phase transition energy requirement), the continued energy input into a decreasing portion of ice and an increasing portion of open water means that things will soon be getting even stranger even faster.
All of us on ASIF are interested in seeing the volume minimum this year. We don't get daily updates and images for volume like we do for extent and area, so volume gets a lot less discussion. But it really is the key number (with a respectful nod to Area as the factor that directly affects albedo). The 2020 minimum volume will almost certainly be closer to the 2012 record low than either extent or area.
Thickness is also difficult to measure and visualize. But it also deserves more respect. Lots of discussion recently about slow down in extent and area trends, with simultaneous comments about how terrible the ice looks. It is too bad we don't have regular reports and images about qualitative measures of ice condition like thickness, mechanical strength, continuity etc. Concentration is a qualitative measure of ice pack condition, but it is highly variable and apparently is difficult to accurately measure because of sensor errors caused by water on the ice surface and water vapor in the air.
One of the key things I've learned this year is to mentally blur the dark areas on the much appreciated and repeatedly viewed AMSR2, U. Bremen, U. Hamburg, and Hycom animations posted by ArticMelt, Blumenkraft, Born from the Void, and others. I think it was a great idea somebody had on the 2020 Melt Season thread to create 5-day average values for such images as a way to smudge some of the spurious readings and highlight what are the more likely true indications of low-concentration and softening ice
The 2020 story seems to continue the narrative from 2019 -- continued decline but no replacement of the 2012 record-low quantitative measurements, with progressive rot in the qualitative impressions of ice condition. Continuation of that trend leads to a point where ice thickness and qualitative melt resistance, exacerbated by increased forces of albedo, ice mobility, fracturing (and thus surface area and lateral melt by contact with ocean water as noted by JD Allen) reach a tipping point at which the right conditions create a major "Poof Event" where huge number of extent and area km2 disappear in a short time period.
The math backs up this theoretical scenario. At some point the flatter Extent decline curve has to catchup to the steeper Volume decline curve. The closer to the end point at which that occurs, the more radically steep the change in Extnet curve has to be. I thought that Exent would begin that catch up process by now, but I've been wrong about that so far. Thickness going below 1 meter could be a key tipping point for that Extent decline acceleration to occur. We are very close to reaching that tipping point.
Of course, it isn't a smooth incremental process. What happens in the real world depends on the chaotic vagaries of the weather. And the early 2020 melt season seems to have been a doozy among those vagaries. The rot evident in the former MYI bastion of the Ellesmere - Greenland - North Pole triangle is notable as both a qualitative and quantitative highlight of 2020 so far.
In earlier years, for a total melt season to reach "Poof Event" intensity would have required prolonged, extreme and unusual conditions. But with each year of progressive qualitative decline (i.e. ice pack rot), the conditions required for a severe melting event to occur become less extreme and less far beyond the normal range, and thus more likely to occur. That is exacerbated by the fact that as the Arctic continues to warm, the "normal range" for the amount of energy in melting events increases, thus making the required intensity for a catastrophic "Poof Event" even more likely to occur.
As for 2020, it ain't over til the fat lady sings. The amount of low-resistance ice hovering just over the 15% concentration threshold to be counted as a 100% extent pixel could still result in some dramatic drop days. IMHO, those values, while interesting to watch, are the daily news that is more noise than signal. The signal is the qualitative decline in ASI overall and the increasingly dire setup for a knockout punch.
I didn't mean for this reply to get so long. Oren, if this is the wrong thread for a sermon, please relocate as needed. Here is some more positive news - Tesla Inc.'s Battery Day, scheduled for Sept. 22, could bring big news to help us dig out of this mess. Getting back to doom and gloom, it will be interesting to see what adjectives Friv has saved up for the first big Poof Event.
