Monthly resolved modelled oceanic emissions of carbonyl sulphide and carbon disulphide for the period 2000–2019

Abstract

Carbonyl sulphide (OCS) is the most abundant, long-lived sulphur gas in the atmosphere and a major supplier of sulphur to the stratospheric sulphate aerosol layer. The short-lived gas carbon disulphide (CS2) is oxidized to OCS and constitutes a major indirect source to the atmospheric OCS budget. The atmospheric budget of OCS is not well constrained due to a large missing source needed to compensate for substantial evidence that was provided for significantly higher sinks. Oceanic emissions are associated with major uncertainties. Here we provide a first, monthly resolved ocean emission inventory of both gases for the period 2000–2019 (available at https://doi.org/10.5281/zenodo.4297010) (Lennartz et al., 2020a). Emissions are calculated with a numerical box model (2.8∘×2.8∘ resolution at the Equator, T42 grid) for the oceanic surface mixed layer, driven by ERA5 data from ECMWF and chromophoric dissolved organic matter (CDOM) from Aqua MODIS. We find that interannual variability in OCS emissions is smaller than seasonal variability and is mainly driven by variations in CDOM, which influences both photochemical and light-independent production. A comparison with a global database of more than 2500 measurements reveals overall good agreement. Emissions of CS2 constitute a larger sulphur source to the atmosphere than OCS and equally show interannual variability connected to variability in CDOM. The emission estimate of CS2 is associated with higher uncertainties as process understanding of the marine cycling of CS2 is incomplete. We encourage the use of the data provided here as input for atmospheric modelling studies to further assess the atmospheric OCS budget and the role of OCS in climate.