Polar Vortex

In 2014 we became familiar with the term “polar vortex” as unusually cold air descended upon us. The term polar vortex is not new though - this meteorological term was first coined in 1853 to describe strong winds and cold air masses that circle the polar regions of the globe.

In the Northern Hemisphere, these wind flow in a counterclockwise direction while in the Southern Hemisphere the winds travel clockwise. The polar vortex strengthens in the winter and weakens in the summer due to temperature differentials between the Polar Regions and the equator. As temperatures decrease in the fall, circumpolar winds increase around the poles, forming a coherent air mass known as the polar vortex. These winds reach about 80 miles per hour, causing this cold air mass to increase in size.

As winter progresses and it gets warmer, the winds decrease in velocity and the size of the vortex diminishes. In the Northern Hemisphere the polar vortex begins to decrease sometime between March and May. If the vortex decreases early in the year, we get an early spring; the later it stays intact, the longer winter’s grasp.

Due to global warming, however, Earth has lost a lot of Arctic sea ice, transforming a highly reflective icy surface to a dark absorptive and warmer surface. As explained by Paul Ullrich, associate professor of regional climate modeling at UC Davis, the change is warming higher latitudes and reducing the temperature difference between the warmer mid-latitude and the Polar Regions. This diminishes the circulation and thereby the strength of the vortex, allowing sections of the masses to splinter off and migrate southward, bringing cold arctic air to our region –and even further south, while at times also allowing warmer air to creep up into the arctic.

Future climate change will further weaken the polar jet stream, bringing rise to more extreme and unusual weather patterns. The temperatures and weather patterns do not only impact us humans and our decisions on what to wear and what to do in the great outdoors. The changing weather patterns affect what species of trees and types of forests can grow where, which in turn affects what fauna can survive where, what foods will grow, animal migration patterns, water availability, and so much more.

Article by FCFCDB

Nature Notes for 12/16/2022