This is a continuation of Part 1, wherein I posted several graphs and maps depicting the 2015 minimum, and the weather conditions leading up to it (Tamino has a great blog post showing the long-term sea ice extent trends, all of them, not just the cherry-picked, meaningless one the GWPF selected to mislead).
Before jumping into the ice age and volume data that is (perhaps) most interesting, intriguing, but also incomplete, I want to refer to one more factor that - besides weather conditions and ocean heat flux - can play an important role in how a single melting season plays out: land snow cover.
Here are the monthly Northern Hemisphere snow cover anomaly graphs from the Rutger University Global Snow Lab during the melting season:
It's clear snow cover got pretty low during June and July. It's a bit of a chicken-or-the-egg kind of mutual influence thing, with an albedo feedback leading to warming over land, leading to increased snow melt, etc. which then starts to influence the Arctic and its sea ice as well. There's been ongoing speculation on this correlation between land snow cover and sea ice for years now, and my guess is that there's a there there, but as it isn't the only influence, it's hard to quantify it. Either way, it has to do with (global) warming, as attested by commenter Al Rodger's guest blog a few years ago: The untold drama of Northern snow cover.
And so we turn to multi-year ice. I'll repost this animation from a blog post I posted two weeks ago, showing how virtually all of the older, thicker multi-year ice on the Pacific side of the Arctic has melted out this melting season: