The Arctic troposphere (0 to ca. 8 km) plays an important role in environmental concerns for global change. It is a unique chemical reactor influenced by human activity and the Arctic ocean. It is surrounded by industrialized continents that in winter contribute gaseous and particulate pollution (Arctic haze). It is underlain by the flat Arctic ocean from which it is separated by a crack-ridden ice membrane 3 to 4 m thick. Ocean to atmosphere exchange of heat, water vapor and marine biogenic gases influence the composition of the reactor. From September 21 to December 21 to March 21, the...