Effect of barometric pressure on sea level variations in the Pacific region

Barometric pressure and sea level data sets from the South Pacific Sea Level and Climate Monitoring Project funded by AusAID were analysed for twelve Tropical Pacific island countries. During mid-1997 and 1998 pressure anomalies over the Pacific region were strongly positive and sea level dropped significantly. As a consequence, sea level trends in the Pacific region suddenly changed from positive to negative. It was believed that the delayed effect of the 1997 strong El Nino episode was directly linked to these positive pressure anomalies. The same observations were made in 2002 and 2003 during another El Nino episode which was however not as strong as the previous one. The La Nina episode which followed the 1997-98 El Nino in 1999 had opposite effects. The pressure anomalies were negative and the sea level anomalies were positive. While the thermal effect due to global warming is still the cause of sea level rise in the Pacific region, it is clearly evident that the barometric pressure effect on sea level is more abrupt and it can overshadow the other effects at least temporarily.