The ozone hole over Antarctica is largest during which period?

• A. Winter
• B. Summer
• C. Early spring
• D. Autumn

Answer: (C)

Ozone depletion in Antarctica is a seasonal process tied to sunlight and very cold temperatures in the stratosphere. In the Antarctic winter, darkness and extreme cold lead to the formation of polar stratospheric clouds, which transform stable chlorine compounds into reactive forms. Without sunlight, those reactions can’t destroy ozone yet, so the hole isn’t at its maximum during winter.

When spring arrives and sunlight returns, photochemical reactions become active. The activated chlorine and bromine radicals rapidly catalytically destroy ozone, and because the air remains cold and the polar vortex keeps the air isolated, a large amount of ozone is removed. This combination causes the ozone hole to reach its largest extent in early spring.

As temperatures rise and PSCs disappear later in spring and into summer, ozone destruction slows and it begins to recover. So the period when the ozone hole is largest is early spring in Antarctica.