A hydrodynamic model of Chatham Rise, New Zealand

Abstract

A three-dimensional hydrodynamic ocean model, the Regional Ocean Modelling System (ROMS), was applied to a region encompassing the Chatham Rise, New Zealand and forced by surface fluxes from an atmospheric reanalysis data set. The model outputs fields were validated against a number of observation-based data sets, including the CSIRO Atlas of Regional Seas 2000 (CARS 2000) climatology of sub-surface temperature and salinity, a sea surface temperature (SST) climatology from the NIWA SST Archive (NSA), and sea surface height (SSH) from the Archiving, Validation and Interpretation of Satellite data in Oceanography (AVISO) Mapped Sea Level Anomalies (MSLA) data set. The model reproduced the flow around Chatham Rise well and had a realistic seasonal cycle in the upper ocean. Its biggest deficiency was that the Wairarapa Eddy was too steady and pushed warm water too far south towards the head of Hikurangi Trough. This exercise confirms the need to validate a model against multiple data sets and shows the value of SST data for revealing underlying oceanographic features.

A study of tides and currents in Cook Strait, New Zealand

“…The deep canyon is filled with subtropical water from the East Cape Current (Heath 1971). In this paper, we use a modelled climatology of water temperature and salinity (Hadfield et al 2007) to investigate the mean circulation driven by spatial variations in water density through the strait.…”

“…In order to examine this issue in greater detail, a diagnostic calculation was made using a density field derived from climatology. The density field was derived from model results of Hadfield et al (2007) which describe the mean state of GCS (Fig. 9).…”

“…The amplitudes and phases of the tidal constituents were derived from a regional scale tidal model (Walters et al 2001). The amplitude for Z 0 was obtained from another model for the regional ocean climatology (Hadfield et al 2007). …”

“…In addition, temperature and salinity that characterise the mean state of GCS were obtained from another model (Hadfield et al 2007). From these variables, density was calculated and used in diagnostic calculations to evaluate the influence of density forcing on the residual currents.…”

The population genetic structure of the waratah anemone (Actinia tenebrosa) around New Zealand

“…Along with this, the geological history and coastline have been dynamic and changing (Fleming 1979). New Zealand straddles the subtropical convergence and the marine climate follows a steep gradient from the subtropical north to the sub-Antarctic south (Laing & Chiswell 2003;Hadfield et al 2007). A combination of these present day environmental and oceanographic factors along with historical changes have led to regional variation in the distribution and abundance of fauna and flora.…”