Decadal increase in Arctic dimethylsulfide emission

Martí Galí , Emmanuel Devred , Marcel Babin (1) , Maurice Levasseur

1 Takuvik International Research Laboratory

Dimethylsulfide (DMS), a gas produced by marine microbial food webs, promotes aerosol formation in pristine atmospheres, altering cloud radiative forcing and precipitation. Recent studies suggest that DMS controls aerosol formation in the summertime Arctic atmosphere and call for an assessment of pan-Arctic DMS emission (EDMS) in a context of dramatic ecosystem changes. Using a new remote sensing algorithm, we show that summertime EDMS from ice-free waters increased at a mean rate of 13.3±6.7 Gg S decade-1 (∼33% decade-1) north of 70°N between 1998 and 2016. This trend, mostly explained by the reduction in sea ice extent, is consistent with independent atmospheric measurements showing an increasing trend of methane sulfonic acid, a DMS oxidation product. Extrapolation to an ice-free Arctic summer could imply a 2.4-fold (±1.2) increase in EDMS compared to present emission. However, unexpected regime shifts in Arctic geo-and ecosystems could result in future EDMS departure from the predicted range. Superimposed on the positive trend, EDMS shows substantial interannual changes and non-monotonic multiyear trends, reflecting the interplay between physical forcing, ice retreat patterns and phytoplankton productivity. Our results provide key constraints to determine whether increasing marine sulfur emissions, and resulting aerosol-cloud interactions, will moderate or accelerate Arctic warming in the context of sea ice retreat and increasing lowlevel cloud cover.

Domaines: Océanographie; Océan, Atmosphère

Martí Galí, Emmanuel Devred, Marcel Babin, Maurice Levasseur. Decadal increase in Arctic dimethylsulfide emission. Proceedings of the National Academy of Sciences of the United States of America, 2019, 116 (39), pp.19311-19317. ⟨10.1073/pnas.1904378116⟩. ⟨hal-03044166⟩