Potential contribution of marine biogenic emissions to the North Atlantic warming hole via cloud feedback

The North Atlantic warming hiatus has been linked to changes in ocean overturning circulation, modulated by radiation-cloud feedbacks and potentially influenced by aerosol-cloud interactions. The decline in anthropogenic aerosol concentrations, however, cannot account for the observed geographical patterns in low‑level cloud trends, including the increase in cloud droplet number concentrations north of 50°N between 2006 and 2015, a period marked by rapid North Atlantic cooling. This points to a role for marine biogenic aerosols in modulating cloud condensation nuclei variability. A machine learning reconstruction of seawater dimethylsulfide (DMS) concentrations over more than two decades reveals that the recent increase in cloud albedo has coincided with an increase of about 5.9% to 8.6% in sea-to-air DMS flux during such a decade of cooling. Interannual variations in sea surface temperature and shortwave radiation were in phase with biogenic emissions. These results indicate that marine biogenic aerosol-cloud feedbacks can modulate North Atlantic climate variability on interannual to decadal timescales.