TIBAGS: Tropospheric Iodine Monoxide and Its Coupling to Biospheric and Atmospheric Variables—a Global Satellite Study

In the framework of the TIBAGS project, spatial and temporal variations of iodine monoxide, IO, in the Earth’s atmosphere were analysed, and relations between IO and further variables of the biosphere and atmosphere were investigated. The abundances and variations of IO are not well known on a global scale, partly because IO amounts are comparably low. However, due to strong reactivity, also small amounts of IO may have a substantial impact on tropospheric composition. In the present study, satellite data from the SCIAMACHY (Scanning Imaging Absorption spectrometer for Atmospheric CHartographY) sensor on board the ENVISAT satellite is used and a more global view on the subject is obtained. IO amounts are retrieved from measurements of scattered sunlight by using an absorption spectroscopy technique. Two consistent IO data sets are retrieved, one based on near real-time data (2004–2011) and one based on reprocessed consolidated data (2003–2010). Largest amounts of IO are found in the Polar Regions of Antarctica, for example in the Weddell Sea area in spring time. In addition, enhanced IO amounts are detected above some but not all biologically active ocean areas which show high Chlorophyll-a (Chl-a) signals. Correlations between IO and diatom distributions are in some areas stronger than between IO and Chl-a in general, indicating the importance of the specific phytoplankton species present in the ocean water.