Salinity variability in shelf waters near Otago Peninsula, New Zealand, on a time scale of hours

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Abstract
A transect crossing the continental shelf adjacent to Otago Peninsula was occupied on six occasions each for c. 8 h. Substantial variability in both high‐salinity and low‐salinity waters was found. On five occasions, a clearly identifiable low‐salinity pulse, which took less than a tidal cycle to pass the transect, was observed. No correlation with any part of the tidal cycle was identified. These low‐salinity events are probably generated by ebb tide release of water from the Clutha River. The position and form of the surface salinity minimum across the continental shelf was highly variable on occasion. Movement up to 3 km cross‐shelf, splitting into two minima, and the combining of two minima were events observed within the timescale of the observations. The results allow prediction of salinity minimum off Otago Peninsula over a Clutha River flow range of 500–1000 m3 s−1 : S = ‐0.00201F + 35.53, where S = salinity minimum (psu) and F = mean daily Clutha River flow 4–12 days earlier (m3 s−1 ).