What is the layer of the atmosphere that is thinnest over the poles?

The troposphere is the layer of the atmosphere that is indeed thinnest over the poles. This layer extends from the Earth's surface up to about 8 to 15 kilometers (5 to 9 miles) in altitude, depending on the geographic location. At the poles, the lower temperatures lead to less vertical mixing of air and thus a reduced thickness compared to the equatorial regions, where the troposphere is generally thicker due to warmer temperatures.

This atmospheric phenomenon is dynamic, with the troposphere being where most weather events occur and where air density is highest. The temperature profile of the troposphere also plays a significant role, with it usually getting colder with increasing altitude, further impacting how thick the layer appears in polar versus equatorial regions.

Other layers such as the stratosphere, mesosphere, and thermosphere do not exhibit the same geographical thickness variations in response to latitude and temperature as the troposphere. The stratosphere lies above the troposphere and contains the ozone layer, while the mesosphere and thermosphere are located even higher up and do not typically have the same thickness disparity influenced by polar temperatures.