Maintenance of near-surface stratification in Doubtful Sound, a New Zealand fjord

Gibbs, Mark T., Bowman, M. J., & Dietrich, D. E. (2000) Maintenance of near-surface stratification in Doubtful Sound, a New Zealand fjord. Estuarine, Coastal and Shelf Science, 51(6), pp. 683-704.

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Abstract

The surface waters of Doubtful Sound, a glacially carved fjord in south-western New Zealand, feature a quasi-permanent low-salinity-layer (LSL). The LSL is maintained year round by the extreme precipitation in the catchment ( ∼ 7 m yr-1) and discharge from a hydroelectric power station ( ∼ 450 m3 s-1). The robust, stable LSL has been shown to play a major role in controlling intertidal and subtidal community structure. By contrast, little is known about the dynamics of the LSL itself. The work presented here elucidates the response of the LSL to perturbations in the wind stress and rainfall. Frequency-domain analysis of salinity data collected from an array of moored instruments revealed that the LSL responded to perturbations in both the winds and rainfall. However, the specific roles of the wind stress and rain could not be adequately resolved in these analyses. By contrast, simulations of the response of the LSL using a three-dimensional primitive equation model revealed that strong up-fjord directed wind events set up a storm surge at the head of the fjord. This surge significantly deepens the LSL at the head of the fjord and retards or reverses estuarine circulation. The subsequent relaxation of the surge after the abatement of the wind stress resulted in a redistribution of buoyancy throughout the fjord over a two-day period. It is shown that the development and relaxation of the storm surge is a major process controlling the maintenance of the near-surface stratification.

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ID Code: 97789
Item Type: Journal Article
Refereed: Yes
Keywords: Doubtful Sound, Fjord, Low salinity layer, New Zealand coast, Storm surge, precipitation (climatology), salinity, stratification, surface water, wind stress, New Zealand
DOI: 10.1006/ecss.2000.0716
ISSN: 0272-7714
Copyright Owner: 2000 Elsevier
Deposited On: 01 Aug 2016 02:25
Last Modified: 01 Aug 2016 02:25

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