The only way i can understand it all Seb is 'energy in the system'. As I understand the MJO ( Madden Julian Oscillation?) tracks the stormy area of the equator as it tracks around but its positioning obviously messes up the full depth of the atmosphere ( like a monster hurricane tracking around the equator?
The other fly in the ointment are the winds high up in the atmosphere over the equator ( Quasi biennial oscillation or QBO?)
These winds used to be know as the time keeper of the climate system as their reversals from east to west and west to east used to be something you could set your watch by..... until the last reversal when they should have tracked east but they got near to the surface and then returned up without flipping east? This had never been observed before.
Both QBO and MJO appear to have suffered from the oddly positioned winter night jet ( Polar vortex) over recent years and anyone using Nullschool Earth at the 10 mb level of the atmosphere will have seen it reach down to the equator ( and obviously mess with the QBO winds)
So ,to me, it is like winding an elastic band on a balsa wood plane. Wind it too much and it all goes to Hel.
The open water Arctic has so messed with the Autumn/early winter atmosphere above it it has knocked the Winter night jet ( polar vortex) off kilter and that energy has passed on into the MJO/QBO winding them up beyond normal tolerances?
So it's like the whole atmosphere is a big wound up elastic band and every so often it goes 'Twang' and those 'twangs' , due to its off centred forcings, are appearing ever more extreme. Beyond what we have models for?
When we go blue ocean the forcings , being over the whole of the Arctic and not the Beaufort/Bering and the Barentsz/Kara edges, will be more extreme but in balance with the rotation of the planet so not building up odd, out of kilter, 'Twangs'?
But then that's just my 'understanding' allowing for my broad brush stroke understandings?