"With the climate being warmer, there's less cities that can sustain natural ice, so this gives them the opportunity to skate longer.
"The air heated by the skin, being warmer and less dense than the surrounding air, rises naturally according to Archimedes' Principle," he says.
The vulnerability of the affluent south-east was a surprise to scientists because it was not simply due to the region being warmer on average.
Whether the cold snap in the stratosphere "is related to it being warmer than it typically is lower down is intriguing," Dr. Livesey said, "but the connection has yet to be made".
"It's a way of being warmer, more genuine, more welcoming, when you call yourself what everyone else calls you," said Kate Coleman, the organization's senior vice president and chief marketing officer.
Elsewhere, normal temperatures range between 5° and 15° C (41° and 59° F), the western oceanic margins being warmer owing to currents from the equator and the eastern margins receiving colder boreal currents and experiencing upwelling.
