Wind-driven and steric fluctuations of sea surface height in the southwest Pacific

Large fluctuations in sea surface height (SSH) occurred in the southwest Pacific between New Zealand and Fiji in the late 1990s. A model of SSH including steric heating and wind-driven Rossby waves explains more than 40% of the observed SSH variance in the region over the 12 years of satellite measurements. The modelled SSH also agrees with dynamic height calculated from subsurface temperatures measured along an expendable bathythermograph (XBT) line between New Zealand and Fiji. The model simulations show a large high in SSH was created by anomalous downward Ekman pumping during 1998 when the seasonal change to upwelling failed to occur. The 50-year wind record shows other downwelling events have occurred in the region predominantly during El Nino conditions.