Ozone exhaustion over the Arctic hit a "record level" in March, the greatest since 2011, yet the gap has now shut, the UN World Meteorological Organization (WMO) said on Friday.

The springtime wonder in the northern side of the equator was driven by ozone-exhausting substances still in the air and freezing winter in the stratosphere, WMO representative Clare Nullis told UN instructions in Geneva.

"These two components joined to give an exceptionally significant level of exhaustion which was more terrible than we saw in 2011. It's presently back to typical again ... the ozone opening has shut," she said.

Nullis asked whether less contamination during the pandemic had assumed a job, stated: "It was irrelevant to COVID."