Instead of extent, area & volume, has anyone ever calculated a total Arctic Sea Ice thermal mass index?
Such a value could incorporate all three of the current measures (E, A, V), along with an average salinity % of the ice to estimate how many megajoules of melt energy would be required to transition it all from ice to water.
It might also include a measure of fracturing or average floe size to represent the surface area of remaining ice. A square meter of ice as a separate little chunk surround by ocean water has a lot more exposure to warm water (and a tiny bit more to solar energy) than a square meter of ice embedded in a solid pack.
Going even farther, it might be possible to add in the average transport speed relative to floe size, and use that to include an estimate of exposure to loss by export into the Fram Strait or another ice killing zone. It seems to me that as ASI decline continues, a point will be reached where mobility will become a huge factor. But neither E, A, or V will reflect that as it happens, only after the effect of increased mobility leading to increased export losses occurs.
With so many levels of estimation, the resulting index would have a large noise to signal ratio. But an attempt to include all the relevant factors into one index to rule them all would be interesting for comparison to the standard measures. Even with internal variability, because it represents a broader range of influences, a long term trend of a thermal mass index might have lower interannual variability than E, A, or V because it accounts for factors they overlook. And it might be a better indicator and predictor for where we are in the process of losing summer Arctic sea ice.
The main point is that the existing metrics do not include any measure of the quality of the ice beyond thickness. A thermal mass index would represent the fact that the ice that remains has a much higher portion of "rotten ice". Volume by itself represents the thin vs. thick ice factor, but not the fact that thin ice not only has less volume, but has higher salinity and lower melt temperature, which in addition to structural aspects, makes it qualitatively different and less resistant to melt, i.e. has less thermal mass per unit volume.
So the index would be S (avg. salinity) * M (avg. mobility, due to fracturing and floe size vs. continuity of ice cover) * X (avg. exposure to melt energy through solar energy on top and ocean water on the side) = Q (qualitative measure of ice quality). That cumulative value Q * the Volume would be the Thermal Mass Index. Hey it's the "Stupid Question" forum, right?