naa a22 4500 530098474 20181026074614.0 cr unu---uuuuu 181026s2010 xx s 000 0 eng 10.3929/ethz-b-000159120 doi 10.5194/acp-10-7545-2010 doi (ETHRESEARCH)oai:www.research-collection.ethz.ch:20.500.11850/159120 Low sensitivity of cloud condensation nuclei to changes in the sea-air flux of dimethyl-sulphide [Elektronische Daten] [M.T. Woodhouse, Kenneth S. Carslaw, Graham W. Mann, Sergio M. Vallina, Meike Vogt, Paul R. Halloran, O. Boucher] Atmos. chem. phys. Open access ethresearch The emission of dimethyl-sulphide (DMS) gas by phytoplankton and the subsequent formation of aerosol has long been suggested as an important climate regulation mechanism. The key aerosol quantity is the number concentration of cloud condensation nuclei (CCN), but until recently global models did not include the necessary aerosol physics to quantify CCN. Here we use a global aerosol microphysics model to calculate the sensitivity of CCN to changes in DMS emission using multiple present-day and future sea-surface DMS climatologies. Calculated annual fluxes of DMS to the atmosphere for the five model-derived and one observations based present day climatologies are in the range 15.1 to 32.3 Tg a−1 sulphur. The impact of DMS climatology on surface level CCN concentrations was calculated in terms of summer and winter hemispheric mean values of ΔCCN/ΔFluxDMS, which varied between −43 and +166 cm−3/(mg m−2 day−1 sulphur), with a mean of 63 cm−3/(mg m−2 day−1 sulphur). The range is due to CCN production in the atmosphere being strongly dependent on the spatial distribution of the emitted DMS. The relative sensitivity of CCN to DMS (i.e. fractional change in CCN divided by fractional change in DMS flux) depends on the abundance of non-DMS derived aerosol in each hemisphere. The relative sensitivity averaged over the five present day DMS climatologies is estimated to be 0.02 in the northern hemisphere (i.e. a 0.02% change in CCN for a 1% change in DMS) and 0.07 in the southern hemisphere where aerosol abundance is lower. In a globally warmed scenario in which the DMS flux increases by ~1% relative to present day we estimate a ~0.1% increase in global mean CCN at the surface. The largest CCN response occurs in the Southern Ocean, contributing to a Southern Hemisphere mean annual increase of less than 0.2%. We show that the changes in DMS flux and CCN concentration between the present day and global warming scenario are similar to interannual differences due to variability in windspeed. In summary, although DMS makes a significant contribution to global marine CCN concentrations, the sensitivity of CCN to potential future changes in DMS flux is very low. This finding, together with the predicted small changes in future seawater DMS concentrations, suggests that the role of DMS in climate regulation is very weak. Creative Commons Attribution 3.0 Unported http://creativecommons.org/licenses/by/3.0 ethresearch Woodhouse M.T. joint author Carslaw Kenneth S. joint author Mann Graham W. joint author Vallina Sergio M. joint author Vogt Meike joint author Halloran Paul R. joint author Boucher O. joint author Atmospheric Chemistry and Physics Göttingen : Copernicus 10 (16), pp. 7545-7559 1680-7375 http://hdl.handle.net/20.500.11850/159120 text/html WWW-Backlink auf das Repository (Open access) 1 Journal Article ethresearch ETHRESEARCH 856 40 http://hdl.handle.net/20.500.11850/159120 text/html WWW-Backlink auf das Repository (Open access) ETHRESEARCH 700 1- Woodhouse M.T. joint author ETHRESEARCH 700 1- Carslaw Kenneth S. joint author ETHRESEARCH 700 1- Mann Graham W. joint author ETHRESEARCH 700 1- Vallina Sergio M. joint author ETHRESEARCH 700 1- Vogt Meike joint author ETHRESEARCH 700 1- Halloran Paul R. joint author ETHRESEARCH 700 1- Boucher O. joint author ETHRESEARCH 773 0- Atmospheric Chemistry and Physics Göttingen : Copernicus 10 (16), pp. 7545-7559 1680-7375 BK010053 XK010053 XK010000 ETHRESEARCH ETHRESEARCH ETHRESEARCH Journal Article Open access