Best Vacuum Sealed Thermoses
If you are really going to the Arctic (or Antarctic) there are a lot more important considerations than KEEPING food hot, chiefly how one would GET enough food at all, hot or cold -- http://www.chow.com/grinder/1617
That said I will elaborate that the vacuum insulated mugs & bottles from Nissan/Thermos that have the "Thermax" designation are very good. I think that a glass vacuum bottle is capable of maintaining temperatures longer AND will suck out less heat from the food/beverage initially, but the fragile nature of such rules them out for any sort of outside use...
Will your dogsled have a cigarette lighter? If your dogsled will have
a cigarette lighter you might consider one of these:
But seriously, it's almost always better to carry fuel, then heat when
necessary. Cooling is proportional to the difference between the temperature
of the hot thing and the temperature of the surroundings, and the decay
is exponential. So given an extreme difference in temperature between your
food and the arctic air, and considering the fairly narrow range in R-values
of consumer grade thermoses, pretty much anything is going to get cold
fast and then stay slightly warmer than the surroundings for a long time.