Time to go on the record: Is this going to be the year?

[muriel_volestrangler]

10. I agree volume is important

though what is important depends on what you're considering. The amount of old ice does seem important when considering what each year's minimum will be - we're at the stage in which pretty much all ice formed since the last year's minimum is bound to melt during the summer, and the question is how much multi-year ice will go too, and the volume gives us a good idea of what goes each year. Yes, you're right that warmer water (eg from currents from the Atlantic or Pacific) can reduce the volume even if the area isn't decreasing significantly.

For some things, the measure of the area may still be more 'important', though - for instance, in the feedback due to albedo. It doesn't matter how thick the ice is for that, it's just how much sunlight it reflected back by the surface. And that actually means weighting the area figures according to the sunlight reaching the surface, which is most in high summer, with hours of daylight and the angle the sun is in the sky, and the latitude the ice is at (and cloud cover, though that's going to be harder to allow for).

Luckily, the mathematician 'tamino' (I forget his real name) who write the 'Open Mind' blog has done some calculations for this, up to and including 2011 (not trying to include cloud cover, and modelling Arctic sea ice as a perfect circle, and Antarctic as a perfect ring): http://tamino.wordpress.com/2012/10/01/sea-ice-insolation/

average annual insolation:



For your final bit ("Once the ice fails, with it the thermal inertia decreases and more rapid increase in water temperature will happen, not just from albedo, but the physics as well&quot - yes, I think that would happen in the surface layer. However, water mixes, so there's the potential for the extra heat to be spread far further down than it is with ice. You'd need someone who understands the dynamics of ocean warming to explain what people think happens to temperatures (and at what depth) when ice cover goes.