Question

Which change might cause a cold spell in the northern united states

Answer 1

The answer is A. the polar jet stream moves south.

~apex

Answer 2

Jet Stream are narrow bands of strong winds from the upper levels of the atmosphere, and its location depends from year to year.

The winds blow from west to east in jet streams, but the flow often shifts to the north and south. Jet streams follow the boundaries between hot and cold air. They follow the boundaries between hot and cold air, so technically they take the heat with them wherever they travel: from north to south. Warming in the Arctic, i.e., melting sea ice, warming air temperatures and rising sea surface temperatures may also be intensifying the jet streams position which in the winter may cause extreme cold winter seen in places like the Northern United States.