Increase in atmospheric carbonyl sulphide since the last glacial period

Abstract

Abstract Carbonyl sulphide (COS) is the most abundant atmospheric sulphur gas with links to terrestrial and oceanic productivity1. A 52,000-year COS record was recovered from a South Pole ice core. We find evidence for COS production in the ice sheet that alters the atmospheric signal in the ice but can be corrected for using sea salt sodium as a proxy. There was substantially less COS in the glacial atmosphere than the Holocene and the deglaciation is marked by a 2-4 fold rise, which is primarily source driven. Oceanic emissions in the form of COS, carbon disulphide (CS2), and dimethylsulphide (DMS) are collectively the largest natural source of atmospheric COS1-7. In the ocean, COS and CS2 are produced primarily by photochemical reactions involving organosulphur compounds3-7, and DMS is a byproduct of phytoplanktonic activity8-12. The large increase in ocean COS emissions during the deglaciation suggests enhancements in emissions of all three sulphur gases and associated climate feedbacks via processes that involve ocean productivity. DMS is a major source of marine sulphate aerosol, inducing negative direct and indirect climate feedbacks8-14. COS is a precursor for background stratospheric sulphate aerosol with impacts on stratospheric chemistry and a net negative radiative impact15-18.