Stability of some New Zealand coastal inlets

The relation of tidal compartments to entrance cross‐sectional areas is examined for 20 coastal inlets. Sixteen inlets conform to a linear relationship, which is consistent with stable entrances the sizes of which are determined by the ability of the tidal flow to transport sediment. Based on this criterion deposition should be taking place at the entrances of the other four inlets: Wellington, Lyttelton, and Akaroa harbours, and Paterson Inlet. Available data confirm this for Wellington and Lyttelton Harbours.     

Phase distribution of tidal constituents around New Zealand

The phase distributions of the M₂, S₂, K₁, and O₁ tidal constituents around New Zealand are plotted from existing harmonic analyses of tidal heights. Both semidiurnal constituents exhibit a complete 360° range of phase around New Zealand, with complex areas of rapid phase change through or near the strait separating the two main islands. The K₁ amphidrome and that for O₁, which previously were thought to be centred on New Zealand, are shown to be located cast of New Zealand. The distributions plotted highlight areas where tidal observations are lacking.     

Recoveries of drift cards released from: Oil rigs around New Zealand, 1975–76 (note)

Drift cards were released in batches of 50 every 2 d at drilling sites off the north and south Taranaki coast (May‐October 1975), Banks Peninsula (July‐August 1975), and in Tasman (January‐March 1976) and Hawke Bays (November 1975‐January 1976). The shortest distance “despatch to recovery” trajectories indicate that only in the South Taranaki Bight are the trajectories predominantly unidirectional, the surface drift being southwards on the west coast of the North Island south of Cape Egmont. The trajectories of cards despatched in both Tasman and Hawke Bays highlight the variable nature of the surface drift in these bays.     

Circulation and hydrology of Manukau Harbour

Abstract

Current meter and current drogue measurements made over tidal periods show that the circulation in Manukau Harbour is mainly tidal, with strongest flows within the inner harbour in the four main channels. In the entrance channel, peak tidal speeds reach 2.25 m.s^?1 at the surface, and 0.6 m.s^?1 near the bottom. Salinity and temperature observations show that the water is nearly homogeneous with depth in summer. A residence time of 22 d is calculated, assuming the small horizontal salinity contrast is maintained by freshwater inflow and evaporation.     

Semi‐diurnal tides in Cook Strait

The phases and amplitudes of the M₂ and S₂ constituents of tidal elevation in Coiok Strait may be adequately described as an open mouth reflection of tidal waves advancing from the east and west coasts of New Zealand and reflecting near the latitudes of Titahi Bay and Cape Campbell (a distance of approximately 60 km). Other reflection conditions give amplitude and phase distributions different from those observed. Best fits to the observed phases and amplitudes for the M₂ tide elevation arise from non‐rotational one‐dimensional solutions which allow for the bathymetry. If rotation is introduced in the form of Kelvin Wave solutions, the result is a two‐dimensional phase‐distribution pattern qualitatively similar to that observed, with the change in phase more rapid and the tidal amplitude smaller on the eastern than on the western side of Cook Strait.

The solution for the S₂ tide also fits closest to the observed tidal elevations for the non‐rotational one dimensional solution, but the introduction of rotation leads to a two‐dimensional phase‐distribution pattern qualitatively similar to that observed. The ratio of the amplitude of the wave (£) advancing from the northwest into Cook Strait to that (A) advancing from the southeast is substantially greater for the S₂ (B/A = 11) than for the M₂ (B/A = 2) tidal constituent and leads to the region of most rapid phase change for S₂ being shifted further to the south than that for M₂.     

Physical oceanographic observations in Marlborough Sounds

Results of temperature and salinity observations with depth, current drogue measurements in Pelorus and Queen Charlotte Sounds, and a current meter record from Pelorus Sound are discussed. The circulation in both Sounds is mainly tidal. Salinities in Pelorus Sound were found to be lower than in Queen Charlotte Sound; there was a rapid decrease in salinity near the head of Pelorus Sound where the Pelorus and Kaituna rivers enter it. Residence time of water in Pelorus Sound was estimated to be about 21 days.