The history of Holocene atmospheric iodine over the North Atlantic

Atmospheric iodine chemistry has a large influence on the oxidizing capacity and associated radiativeimpacts on the troposphere.Direct instrumental measurements of atmospheric iodine are restricted to the last decades,preventing us from understanding the longterm biogeochemical cycle of iodine and furtherenvironmental and climatic implications. Ice core records partially overcome these limitations sincethese natural archives sensitively record continuous atmospheric iodine levels in polar regions.In this study we report (from the Greenland-ReCAP ice core record) the first and continuousreconstruction of iodine levels (i.e. iodine concentration [I] and iodine depositional fluxes (Iflux)) in theNorthern Hemisphere since the onset of the Holocene (last 11 700 years). This exceptional naturalarchive, provide us with an analyticalframework to investigate, for the first time, the evolution ofatmospheric iodine in the Arctic since the Holocene.The global 3D chemistry-climate model CAM-Chem, is used to study how the ozone-driven emissionsof iodine (HOI and I2) may have controlled the variability of atmospheric iodine during the 1950-2010time period.This study also provides a unique insight into the environmental drivers controlling the long termatmospheric iodine biogeochemical cycle in the Arctic