I voted for 12 to 12.5...
Reasoning:
- Current sources of heat and moisture are N. Atlantic and N. Pacific. These areas will cool and mix with deeper coool water, as they do every winter, depriving the Arctic of the fuel for its anomalous water vapor feedback warming.
- A cold spell will eventually allow a thin layer of ice to form, even in the Kara and Barents seas. Once closed off, another source of water vapor will be lost.
- Many areas - CAB, E Siberian, Laptev, Can. Archipelago, and Beaufort - have already reached near 100% coverage (although CAB is currently dipping a bit). They will not contribute to any drastic extent shortfall. Chukchi will soon reach 100%
- Greenland Sea extent will be a function of Fram Export and circum-Greenland wind patterns. When Greenland Sea is higher, Baffin is lower, and vice versa. These two are unlikely to be drastically higher or lower in toto.
- Hudson Bay has always reached 100% by Dec 31. Winter is now finally arriving in Canada. Hudson Bay is unlikely to be much below 100% being surrounded by a very cold continent.
- St Lawrence is not important... usually near 0% on Dec 31.
- Okhotsk is below average temps. This is one of the marginal areas that will determine the extent during winter. It will freeze on time or even early.
- The N Pacific is cool. Extent could be above average in the Bering Sea once its shallow waters have cooled and overturned, and cool air and water flow north from the huge reservoir of coolth in the N Pacific.
That makes 10 areas with near normal extent. The 4 marginal areas that will determine the final year-end total are Okhotsk, Bering, Kara and Barents.
1. I think it is likely that Okhotsk will be above average due to its current below average temps, its proximity to very-much-below-average very cold Siberia, and its proximity to cool N pacific
2. I think Bering will be at or slightly above average extent - despite its current above average temps - for the same reasons as for Okhotsk.
3. Kara should eventually freeze, but it may be below average. It is anomalously warm right now, and there is no immediate source of coolth to bring it down.
4. Barents is very warm, has been highly variable in the past, and, like Kara, is upwind of cold Siberia so it cannot lose its heat easily. It should be far below average.
Sum total - eyeballing the excellent regional graphs by Wipneus - I think a new record low extent is possible for Dec 31, but just barely. Extent just above a record low is equally likely. So 12 - 12.5 encompasses my guesses. I would not be too surprised by a record low just below 12, but I would be very surprised by a return to near normal like the 2000's average of 12.75
The long-term effect of weaker and thinner ice from this alarmingly poor re-freeze is far more important than the extent... if it's a record low or near normal makes no difference. The thin ice will melt out early, barring a miraculously cold spring. Then albedo feedback at summer solstice will do its damage, even worse than last year.
The good news is the Trump/Bannon administration will cut the funding needed to monitor the Arctic so we can enjoy a brief interlude of blissful ignorance before the albedo/methane/water vapor feedbacks trigger the next hysteresis state-flip.
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