Changing El Niño Patterns and the Possible Impact on DMS and Climate

Abstract:

El Niño patterns have been shifting from conventional Eastern Pacific scenarios to Central Pacific. With more cases of warmer ocean water recorded at Niño 3, 3.4 and 4 regions and similar pattern expected in impending warmer climate, we investigate the changes in dimethyl sulfide (DMS) flux as a result of these changing El Niño patterns. For example, our estimates show a drop of about 10 - 30% in DMS flux at regions 1+2 and 3 during 1997-1998 El Niño event and a respective reduction of 50% at region 4 for 1994-1995 Central Pacific El Niño period in comparison to the climatology. While regions just outside of these areas can experience greater DMS flux. Changes in DMS flux may serve as a proxy for flux of sea spray which is also wind driven. Less DMS flux over the equatorial region and increased DMS flux to the north and south could modify heat flux and Hadley cell circulation.

Atmospheric aerosols are contributors of absorption and reflection of incoming solar radiation. Hence, they are important in regulating the global radiation budget which ultimately determines global temperature. DMS is the source of nearly all of thesulfate aerosol in the remote marine atmosphere.The equatorial Pacific Ocean is an ideal region to illustrate the relationship between surface ocean concentrations, atmospheric abundance andclimate feedbacks of this molecule. The region remains biologically productive throughout the seasons. However, the alterations in sea surface temperatures and wind speed during El Niño events is crucial in determining sea-air flux of DMS. Our results suggest that Central Pacific El Nino might have more influence on sea-air flux of DMS compared to conventional Eastern Pacific El Nino. This may imply changing reflectivity and cloud albedo in a warming climate.