The discovery of the Antarctic ozone hole in 1985 (Farman et al., 1985) led to much scientific and public debate on anthropogenic ozone depletion. A similar ozone loss above the Arctic was initially considered less likely because of higher stratospheric temperatures and different dynamics observed in the Arctic polar region. However, since the beginning of the early 90s, reduced total ozone were observed during Arctic spring (McPeters et al., 1996, Newman et al., 1997). Record low northern polar total ozone amounts inside the vortex has been observed Newman et al., 1997, Santee et al., 1997) in 1995/96. Despite the large dynamic ozone variability observed in the northern hemisphere, chemical ozone loss due to heterogeneous chemical processes similar to that observed in the Antarctic have been recently identified (Müller et al., 1997, Rex et al., 1997).
In winter/spring 1997 record low stratospheric temperatures sufficient to form polar stratospheric clouds (PSCs) persisted in late March (Coy et al., 1997). PSCs drive the heterogeneous reactions, which activates chlorine compounds responsible for the rapid catalytic ozone depletion when the spring sun enters the polar night. During March/April 1997 a chemical ozone loss of 70-80 Dobson units (DU) in the total column were observed inside the vortex (Müller et al., 1997). The NH winter/spring 1997/98 was warmer than in the previous years and less ozone depletion was observed by GOME in the Arctic. The Full Retrieval Method FURM, which derive ozone profile from GOME satellite data have been for the first time applied to derive NH vertical ozone distributions. Results for selected days during the Arctic spring in 1997 and 1998 are presented and discussed.
Low ozone can be also frequently observed in northern mid-latitude region outside the vortex and are termed ozone mini-holes (Newman et al., 1988, Hood et al., 1997). During such events exchange of ozone-poor airmasses from the sub-tropics and the polar vortex occur, which leads to further adiabatic cooling and possible PSC formation (Grewe et al., 1997). During March 1998 GOME ozone profiles inside an ozone mini-hole have been observed for the first time.