Seasonal and interannual variability in sinking particle fluxes in the 10°N thermocline ridge area of the northeastern equatorial Pacific

Abstract

The influence of ENSO variability on sinking particle fluxes was evaluated from time-series sediment trap experiments carried out for 8 years at a station located in the 10°N thermocline ridge of the northeastern equatorial Pacific. Six El Niño/La Niña events were observed over the monitoring period. During the normal periods, sinking particle fluxes had distinct seasonal fluctuations, with high fluxes in winter-spring and low values in summer-fall. This seasonal variability was caused by seasonal shifts in the location of the intertropical convergence zone (ITCZ). A weak(2004/05) and moderate(2006/07) El Niño events were accompanied by a significant reduction of sinking particle fluxes. In contrast, La Niña(2007/08) was associated with an increase in sinking particle fluxes to a level of three times higher than that during the normal periods. These results are consistent with the results of previous studies in the equatorial Pacific. However, the strong El Niño events(1997/98 and 2009/10) caused three-fold increase of sinking particle fluxes compared to the average particle flux during the normal period, which is completely opposite to the general trend observed in the equatorial Pacific. The chemical composition of settling material quite differences between two strong El Niño events.x El Niño/La Niña events were observed over the monitoring period. During the normal periods, sinking particle fluxes had distinct seasonal fluctuations, with high fluxes in winter-spring and low values in summer-fall. This seasonal variability was caused by seasonal shifts in the location of the intertropical convergence zone (ITCZ). A weak(2004/05) and moderate(2006/07) El Niño events were accompanied by a significant reduction of sinking particle fluxes. In contrast, La Niña(2007/08) was associated with an increase in sinking particle fluxes to a level of three times higher than that during the normal period