How do they manage the low fuel temps? A bit hard for a Twotter to descend to a lower level and increase mach number!
Apparently the fuel is preheated before loading - one reason for choosing the Twotter over the Hercules, 2500 lbs to heat instead of 60000.
The Twotter can carry a cabin auxiliary tank, which of course is not exposed to the cold until needed. (but I presume Herky-Birds have that option also).
They'll need the reserve tank just for the outbound leg, so there must be refueling capacity at the Polar base - and that fuel can be preheated also before the return.