Analysis of mean sea level data from New Zealand for the period 1899–1988

Abstract

Records from four New Zealand tide gauges were analyzed in order to determine the trends in mean sea level which have occurred in New Zealand since the beginning of this century. Although a substantial difference in the computed sea level trends between tide gauges was considered a possibility, due to the location of the gauges in relation to the boundary of the Australian and Pacific tectonic plates, the analyses did not show this to be the case. They indicated rising trends in sea level of 1.3, 1.7, 2.3, and 1.4 mm/yr for Auckland, Wellington, Lyttelton, and Dunedin, respectively, and together gave a mean trend of 1.7 mm/yr for the east coast of New Zealand as a whole. These figures not only add to the global picture of sea level change but also provide initial evidence suggesting little or no recent differential vertical motion across this portion of the Australian and Pacific tectonic plates. In addition, they provide conclusive evidence that the orthometric height datums established in New Zealand from tide gauge data collected in the early part of this century are in need of substantial revision.