It keeps the Arctic air bottled up in these areas.

它能使这些区域的极寒空气保持密闭。

It keeps the Artic air bottled up in these areas.

它使这些地区的空气保持密闭。

The low-pressure system usually keeps Artic air bottled up at the North Pole but when it gets unstable in winter, as it is now, the polar vortex allows that air to spill south and then, well cold.

低压系统通常会将北极的空气封闭起来，但当它在冬季变得不稳定时，就像现在一样，极地涡旋会使空气向南溢出，之后带来寒冷天气。