File photo: The sun sets over Arctic ice near the 2011 Applied Physics Laboratory Ice Station north of Prudhoe Bay, Alaska in this Mar 18, 2011 picture. (Photo: REUTERS/Lucas Jackson)

GENEVA: Ozone depletion over the Arctic hit a "record level" in March, the biggest since 2011, but the hole has now closed, the UN World Meteorological Organization (WMO) said on Friday (May 1).