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 station is defined as the average sea level for that location from 1985 – 2004.

The average sea level anomalies in most of the tide gauge stations in USAPI continued to be close to normal in the fourth quarter 2005 with monthly anomalies of less than 11 cm (< 5 inches) (Table 1). Since June 2004, the sea level was below normal in a large region from Guam extending westward to Yap State and Palau. During July, August, and September these negative anomalies decreased and remained slightly below normal (~ 2 inches) from Palau eastward to Guam and the CNMI. By October, November and December, these negative anomalies were confined to the area around Saipan and Guam. The sea level was slightly higher than normal from Kapingamarangi eastward through the southern Marshalls at Majuro. In the South Pacific, Pago Pago was slightly above normal (3 – 4 inches) in the third quarter and continues to be slightly above normal throughout the fourth quarter

The deviations of sea level are relatively small at the present, but are consistent with a weak El Niño pattern. With weak El Niño conditions, the sea level distribution in Guam, CNMI, Palau, and FSM for the first few months of 2005 is likely to be a few inches (one to three) below normal. The sea level is likely to start displaying negative anomalies in American Samoa beginning in 2005. However, as the El Niño condition is gradually weakening, the sea level variation may remain close to normal in this quarter too.

Table 1. Sea level anomalies (cm) at indicated islands for the fourth quarter (October, November, December) of 2004. - indicates negative anomaly (fall of sea level), + indicates positive anomaly (rise of sea level)

These forecasts are seasonal averages. Storm surges, typhoon strikes and hazardous surf can occur and cause large daily deviations in sea level. For more information on sea level read SPECIAL SECTION: ENSO and Sea-Level Variability.