Sea Level Variability on the West Coast of New Zealand

Abstract

Variations in coastal sea level in the weather band (periods 5?20 days) on the west coat of New Zealand can largely be explained in terms of wind-forced coastal-trapped waves. Long-wave theory was applied to the North Island shelf with some success in hindcasting sea level at New Plymouth. On the southern South Island shelf, the sea level signal was found to propagate like a mode-one coastal-trapped wave, but the complex topographic variations made application of simple long-wave theory impossible. The sea level signal in the south of the region was highly correlated with alongshore wind stress over the shelf region to the north, suggesting that alongshore wind stress is the major forcing mechanism. In contrast, the generation of coastal-trapped waves by a coastal flux through Taranaki Bight/Cook Strait appears to be the dominant mechanism over the northern and central South Island shelf, from the present and previous studies.