Ekman Pumping and Mixed Layer Depth Variability over the Indo-Pacific Oceans during the El Nino and IOD Events

Abstract

The following study addresses the variability of Mixed Layer Depth (MLD) and Ekman pumping (W EK ) during the extreme El Nino and Indian Ocean Dipole (IOD) over the Indo-Pacific regions. Monthly anomalies considering the climatology of the period of 1980 through 2011 show that during the El Nino years, Ekman suction (positive Ekman pumping) is replaced with Ekman pumping (negative Ekman pumping) in the tropical eastern Pacific Ocean (88˚W-90˚W and 13˚S-15˚S) resulting in positive MLD anomalies, and the strong Ekman pumping may be the source for the deepened thermocline during El Nino. In the La Nina events shallow MLD exits in the tropical eastern Pacific Ocean, due to positive Ekman pumping. During the positive IOD (PIOD) events in the south eastern Indian Ocean (97˚E-100˚E and 2˚S-5˚S) MLD becomes shallow and positive Ekman pumping anomalies occur. During the negative IOD (NIOD) years opposite signs take place. Composite events of El Nino are compared with those of IOD, showing more Ekman pumping anomalies during IOD events as against less deviation in SST.