Why is ozone de­ple­tion worse over Antarc­tica?

BBC Earth (Asia) - - Q&A -

Ozone de­ple­tion oc­curs when ozone mol­e­cules in the up­per at­mos­phere are de­stroyed by chem­i­cal re­ac­tions with halo­gen gases, such as chlo­rine. Cold con­di­tions above Antarc­tica in the win­ter months en­cour­age the for­ma­tion of ex­tremely cold, high-al­ti­tude clouds. These clouds pro­vide the ideal con­di­tions for chlo­rine that was pre­vi­ously trapped in sta­ble mol­e­cules to be trans­formed into highly re­ac­tive chlo­rine gas, which ac­cu­mu­lates over the long po­lar night. As win­ter ends, sun­light breaks apart the chlo­rine gas mol­e­cules, free­ing bil­lions of chlo­rine atoms, which go on to re­act with ozone mol­e­cules, caus­ing a sharp dip in ozone lev­els: the ozone ‘hole’. AC

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