1) Of the last 10 years, only the last years volume freeze was below average. 2013 and 2014 were high but how can you attribute this to anything other than random variation?
I attribute that growth to the ice being very thin and the atmosphere almost as cold as average.
2) What do you mean by endogenous cold?
For example the temperature of the water under the Chukchi sea or the Beaufort. For most of the record those areas were almost completely covered in ice year round keeping them nice and cold. I imagine (can't find data) that since the 2007 cover changes the areas with significant cover changes are becoming warmer. That effect was barely noticeable from 2007-2014, but it accumulates By 2015 those cold spots lost their "endogenous cold" and no longer help with the freezing. The same happens with hot air intrusions. Once the endogenous cold of the Arctic kept the Arctic dry and the heat from the hemisphere away. But as the arctic warms, warmth is allowed in, warming it more.
3) "used up"? Huh? There is no sunlight every winter. The temperature rises come from a) heat stored in the ocean built up over summer, b transported by winds & currents, and c more GHG in atmosphere reducing rate of emission from atmosphere to space. I don't see any reason to think any of these will do anything other than slowly increase over long periods of time.
a) heat stored in the ocean built up over summer:
Like the Chukchi this year. It was hot and releasing heat to the atmosphere until very late in the freezing season. Eventually it covered in ice but I bet there is still extra heat underneath the ice. From the looks of thing this year the pattern will be reinforced.
b) transported by winds & currents
And that has increased over the years. The less ice, the more humid and the more warm air intrusions.
c) more GHG in atmosphere reducing rate of emission from atmosphere to space
I think that can best be appreciated in the baseline of winter temperatures in DMI N80. Even in winter temperatures seem to have a new baseline. that new baseline is induced by higher arctic water vapor and clouds who are bound to increase even more as more ocean remains open for longer. Hot air intrusions also add to the new baseline.
>"Why this doesn't happen now? All growth of ice that I have seen comes from the ice edge. not from random cold spots above the ocean."
Why would you get a cold spot above the ocean, unless there was wind coming from a direction where there was ice or snow. The further it gets from that ice or snow the more it has warmed up and is less able to cool the water sufficiently. We don't really have resolution to see small amounts of ice forming and match it to openings in clouds which allow faster radiation loss to space.
>"You speak as if the heat loss by the ocean magically disappears"
A small amount goes direct from ocean to space. Most is from ocean to atmosphere and then atmosphere to space. No idea why you are thinking I am thinking something other than that.
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Because if you are citing high ice growth rates because the oceans will vent heat. However high growth rates are also dependent on atmospheric temperatures. If the ocean vents heat to the atmosphere, the atmosphere will warm precluding ice formation. Also much of that heat will be in the form of water vapor, which serves to keep the warmth in during the winter night.
I guess that what I'm trying to say is that the fast growth you are counting on won't happen because it will simply be too warm for rapid ice growth.