Management Applications of the River Environment Classification System

Snelder, Ton H.; Slawecki, Theodore A.D.; Hickey, Christopher W.

doi:10.2175/193864704790896739

Cited by 2 publications

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“…The NZ River Environment Classification (NZ-REC, Biggs et al, 1990;Snelder et al, 2004) was used to identify the 17 biggest rivers that discharge into Greater Cook Strait. Interpolated annual-mean values of riverine freshwater input was used for each river to force the ROMS shelf model.…”

Section: Regional Modelingmentioning

confidence: 99%

Spatial Structure of Low Salinity Submesoscale Features and Their Interactions With a Coastal Current

et al. 2020

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Submesoscale features, characterized by a low salinity layer originating from river discharges, enhance water column stability in a New Zealand shelf sea. Using a combination of data from multiple ocean glider surveys and regional modeling, we show that low salinity submesoscale features (LSMFs) can cause increased stratification on the order of 10 −4 s −2 . Modeled oceanographic conditions compared well to observations, especially in austral spring. Stably stratified LSMFs can replace the previously well-mixed layer in the water column up to a distance of 100 km offshore before getting entrained by the regional barotropic current in Greater Cook Strait. LSMFs observed from glider surveys and reproduced from modeled results generate strong vertical and horizontal salinity differences of S ∼ 0.45 psu. These salinity differences define density fronts and stratification in the upper ∼ 30 m. Temperature differences of up to T ∼ 1.4 • C associated with LSMFs were not large enough to entirely cancel the density effect of salinity. The offshore advection reach of LSMFs is partly constrained by the variability of the barotropic d'Urville Current. Its presence and strong winds inhibit the propagation of LSMFs offshore in Greater Cook Strait, enhancing mixing and deepening the mixed layer depth. In contrast, moderate winds and weak current enable the propagation of LSMFs furthest offshore in Greater Cook Strait, where the water column becomes stably stratified. A stably stratified regime allows increased exposure of upper layers to light availability, encouraging phytoplankton growth, which may lead to enhanced primary production in the region.

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Section: Regional Modelingmentioning

confidence: 99%

Spatial Structure of Low Salinity Submesoscale Features and Their Interactions With a Coastal Current

et al. 2020

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A modelling synthesis of the volume flux through Cook Strait

Hadfield

Stevens²

2020

New Zealand Journal of Marine and Freshwater Research

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We present hindcasts of currents in Cook Strait from a baroclinic, tide-resolving ocean model. Three hindcasts are run, forced respectively at the lateral boundaries with data from the Bluelink Reanalysis (BRAN), the global Hybrid Coordinate Ocean Model (HYCOM) and a New Zealand Shelf Seas baroclinic hindcast (NZROMS). The hindcast forced by BRAN is evaluated against measured currents at locations in the Cook Strait Narrows and South Taranaki Bight. The model reproduces the observed tidal, subtidal and mean currents well. The three hindcasts produce a 3year-mean volume flux southward through the Narrows of 0.360, 0.734 and 0.230 Sv, respectively. When corrected for the observed discrepancies between model and measurements in the Narrows, the estimates are 0.430, 0.498 and 0.337 Sv. We conclude that true 3-year mean volume flux through Cook Strait is 0.42 ± 0.08 Sv. The tidal volume flux amplitude is 4.68 Sv (M2). The subtidal fluctuations in volume flux have a standard deviation of 0.62 Sv. The effect of wind is investigated with a wind-forced barotropic model, which produces volume flux fluctuations that are highly correlated (r = 0.93) with the subtidal fluctuations from the baroclinic model, implying that the latter are largely wind-generated.

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Management Applications of the River Environment Classification System

Cited by 2 publications

References 0 publications

Spatial Structure of Low Salinity Submesoscale Features and Their Interactions With a Coastal Current

Spatial Structure of Low Salinity Submesoscale Features and Their Interactions With a Coastal Current

A modelling synthesis of the volume flux through Cook Strait

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