SHORT-TERM VARIATIONS IN SEA-LEVEL (2-15 DAYS) IN THE NEW-ZEALAND REGION

Sea level data from 15 tide gauges around New Zealand were analysed to assess the effect of meteorological forcing. Many of the data were of poor quality and special care was needed with the data processing to make the data usable. Analyses were carried out in both the time domain and the frequency domain in the frequency band from 1 to 9 degrees h(-1), resulting in the same general outcomes: that sites exposed to the prevailing westerly winds respond to changes in barometric pressure at greater than the conventional inverted barometer response, whereas eastern sites sheltered from the west respond at less than the inverted barometer. At northern sites, sea level generally changes in advance of changes in barometric pressure by 3 to 4 hours; however, for individual events, the reverse may be true. For other sites (from the mid-North Island southwards), sea level generally responds to barometric pressure changes after a few hours. For north-eastern sites, the percentage of the variation in sea level which can be explained by changes in barometric pressure is low and there appears to be no correlation between sea level and regional wind stress, leading to the conclusion that, to a large extent, variation in sea level is caused by waves propagating into the area.