Estimates of the components of sea surface elevation contributing to the long-term variation of mean sea level around New Zealand

Abstract

The relative sizes of the factors contributing to the vanatIOns in mean sea level around New Zealand are examined. The oceanographic influence (specifically, changes in density and the oceanic circulation) appears to produce the largest variation, with ranges of the order of 10-20 em yr- •With an expected eustatic change of the order of 0.1-0.2 cm yr-1 long-term accurate sea-level records of at least 15-20 years are needed to allow accurate estimates of the eustatic and tectonic changes.

Oceanic circulation in the head of the Hikurangi trench, east coast, New Zealand

“…The temperature and salinity field in the Mernoo Gap is very similar to that found previously in September-October 1967 (Heath 1972a) Downloaded by [93.115.95.205] (m) from van der Linden (1968) and Krause & Cullen (1970). Arrows indicate the generalised surface circulation in the region.…”

“…These fluctuations appear to be produced by small eddies, shed off from the permanent anticyclonic eddy situated near 42° S, 177° E, which are guided by the bottom topography towards Kaikoura. Similar periodic fluctuations in mean sea level have been observed at Whangarei (Heath 1976), and this periodicity might be linked to a similar periodicity in the East Australian Current (Heath 1975a).…”

“…During southerly storms, oceanic water on the south Canterbury coast has been observed to cool: during the particularly severe storm of 10 April 1968 the temperature recorded at Kaikoura decreased by approximately 5°c in 24 h. Most of this change has been attributed to an increased flow in the Southland Current bringing cold water from the south (Heath 1970).…”

“…Over the past 15 years several studies of the geostrophic circulation immediately off the east coast of New Zealand (Sdubbundhit & Gilmour 1964, Garner 1967, Heath 1968, 1972a, 1973, 1975a) indicated a consistent broad circulation pattern ( Fig. 1, see, e.g., Heath 1972a) influenced by the bathymetric relief.…”

“…1, see, e.g., Heath 1972a) influenced by the bathymetric relief. The two major inflows into the Hikurangi Trench, the area of particular interest here, are a flow of Subtropical Water around East Cape forming the southwards-flowing East Cape Current, and a northwards inflow of less-saline, cooler water in the Southland Current on the continental shelf and through the Mernoo Gap at the latitude of the Chatham Rise (Fig.…”