SEA LEVEL

Sea level data used in this discussion was provided by the UH Sea Level Center http://uhslc.soest.hawaii.edu. “Normal” sea level at each island is defined as the average sea level for that location from 1993 – 2001.

For the third quarter (July-September), the sea level continued to be below normal in western Micronesia (Palau, western FSM, CNMI and Guam) and slightly above normal in the east (eastern FSM, RMI). In June 2004, the sea level was below normal in a large region from Guam extending westward to Yap State and Palau —(the sea level anomaly was lowest in the vicinity of Yap Island, where the sea level for June was lower than normal by approximately 10 inches). During July and August these negative anomalies decreased. By September 2004, the sea level remained slightly (~2 inches) below normal from Palau eastward to Guam and the CNMI. Throughout the rest of Micronesia, the sea level was slightly higher than normal, with highest positive deviation of sea level height of 10 cm (4 inches) along the equator to the south of Pohnpei, Kosrae and the RMI. During July and August the positive anomalies remained near the equator. The sea level was higher than normal from Kapingamarangi eastward through the southern Marshalls and at Tarawa. The largest positive anomaly was at Tarawa, where the sea level was approximately 4 inches above normal. In the South Pacific, American Samoa was consistently above normal (3-4 inches) throughout the third quarter.

The deviations of sea level are relatively small at the present time, but are consistent with a weak El Niño pattern. With weak El Niño conditions, the sea level distribution in Micronesia for the rest of 2004 through the first few months of 2005 should be a few inches below normal for Palau, Yap, Guam, the CNMI, the Caroline Islands north of 5° N, and the northern and central islands of the RMI. The sea level should remain a few inches above normal at islands located near the equator from Kapingamarangi eastward into Kiribati. During major El Niño events, substantial falls of sea level on the order of 1 foot below normal occur throughout much of Micronesia. PEAC researcher, Dr. Rashed Chowdhury, is studying the connection between the ENSO cycle and sea level variations. For more information read SPECIAL SECTION: ENSO and Sea-Level Variability.