Sea Level & Climate: Their Present State Cook Islands

Executive Summary

• A SEAFRAME gauge was installed in Rarotonga, Cook Islands, in February 1993. It records sea level, air and water temperature, atmospheric pressure, wind speed and direction. It is one of an array designed to monitor changes in sea level and climate in the Pacific.
• This report summarises the findings to date, and places them in a regional and historical context.
• The sea level trend to date is +4.8 mm/year but the magnitude of the trend continues to vary widely from month to month as the data set grows. Accounting for the precise levelling results and inverted barometric pressure effect, the trend is +4.9 mm/year. Nearby gauges, with longer records but less precision and datum control, show trends of +4.34 and +1.69 mm/year.
• Variations in monthly mean sea level include a moderate seasonal cycle and were affected by the 1997/1998 El Niño.
• Variations in monthly mean air and water temperature include more pronounced seasonal cycles and were likewise affected by the 1997/1998 El Niño.
• In October-November 1997 Tropical Cyclone Martin devastated the northern Cook Islands. In December 1997 Tropical Cyclone Pam passed Rarotonga as a category 2 cyclone and caused high sea levels and flooding.
• The SEAFRAME at Rarotonga, Cook Islands has recorded 12 separate tsunami events since its installation. The largest tsunami signal was recorded after an earthquake of magnitude Mw8.3 that occurred near the Kuril Islands on 15 November 2006. The trough-to-peak tsunami height was 40cm for the 1-minute sea level data, or 17cm for 6-minute sea level data.