No abstract

Sea surface temperature (SST) observations from 16 coastal sites around New Zealand are analysed along with some corresponding air temperatures. Day-to-day variations in SST show weak periodicity over an 8-16 day range. Air temperatures are generally cooler and short-term fluctuations have 3-4 times the standard deviation of the SSTs. Seasonal SST variations are described and coastal SSTs are compared with offshore SST data. At Farewell Spit the coastal SSTs were always cooler than offshore SSTs which supports the view that upwelling is persistent in the Cape Farewell region. Inter-annual variations in SST are found to be correlated with Southern Oscillation atmospheric pressure anomalies. In particular we find that the El Nino phenomenon which is accompanied by warm SSTs in the central and eastern tropical Pacific is also accompanied by lowered SSTs throughout New Zealand's coastal waters.

[1] Surface to deep-ocean coupling was investigated in subtropical (STW) and subantarctic (SAW) waters off eastern New Zealand. Moorings, comprising a near-surface fluorometer, temperature loggers, current meters, and sediment trap at 1500 m depth, were deployed at 41°and 46°40 0 S along 178°30 0 E between October 2000 and October 2001. Locally validated, remotely sensed data provided areal estimates of surface chlorophyll that were representative of 1997-2004 annual cycles. In STW, early spring chlorophyll peaks were coupled with deposition of labile (molar C:N$7-8), bio-siliceous organic matter. Low winter chlorophyll concentrations were associated with high particulate organic carbon (POC) fluxes of moderately refractory material (C:N$9-10). This indicates that winter flux was affected by heterotrophic recycling processes (zooplankton exuviae, fecal pellets) and/or slowly sinking particles from the preceding autumn. Deep-ocean POC fluxes off New Zealand were similar to global estimates and Tasman Sea (0.8 cf. 1.0 g C m À2 yr À1). Elevated biogenic silica and lithogenic fluxes probably reflect processes within a warm-core eddy near an eroding landmass, rather than STW in general. In SAW, POC and biogenic silica flux peaks occurred in spring with moderate surface chlorophyll concentrations. Decoupling between high chlorophyll and low flux in summer may reflect near-surface organic matter recycling by the microbial-dominated ecosystem. In spring, moderate chlorophyll levels in SAW, high POC and silica flux, and high C:N ratios (9-13) indicate some coupling with upper water column processes. SAW, east of New Zealand, was characterized by low POC (0.2 g C m À2 yr À1 ), high biogenic silica, and low carbonate fluxes, unlike other subantarctic sites, which are dominated by carbonate deposition with fivefold higher POC flux.

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.

Data were analysed from two current meters moored 100 and 300 m off the seabed in the Mernoo Saddle from June to November 1988. The flow was dominated by the lunar semidiurnal constituent M 2 with an amplitude of 15.1 cm s -1 at the upper level and 15.8 cm s -1 at the lower level. The major axes of the tidal ellipses for the semidiurnal constituents were aligned more or less alongshore whereas those of the two largest diurnal constituents, Oj and Ki, were aligned across-shore. Peak tidal period flows of 28 cm s -1 (upper) and 33 cm s -1 (lower) were recorded. Over the entire record, net flow was to the north at an average speed of 3.1 cm s -1 but there were periods of up to 5 weeks during which net flow was to the south. Strong southward flow events lasting 10-12 days were recorded on three occasions and the maximum current speed recorded was 67 cm s -1 to the south. Satellite imagery was used to show that these southward flow events coincide with the influx of warm water at the surface within 5 km of the coast near Kaikoura, and we suggest that the southward flows are caused by this influx of warm water which is carried by eddies from the south of the Wairarapa eddy to the area immediately north of the Mernoo Saddle. There is some indication that internal tides may be significant in this area but inertial currents were found to be weak. M91039