Directional wave climate and power variability along the Southeast Australian shelf

Thomas R. Mortlock*, Ian D. Goodwin

*Corresponding author for this work

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

Variability in the modal wave climate is a key process driving large-scale coastal behaviour on moderate- to high-energy sandy coastlines, and is strongly related to variability in synoptic climate drivers. On sub-tropical coasts, shifts in the sub-tropical ridge (STR) modulate the seasonal occurrence of different wave types. However, in semi-enclosed seas, isolating directional wave climates and synoptic drivers is hindered by a complex mixed sea-swell environment. Here we present a directional wave climate typology for the Tasman Sea based on a combined statistical-synoptic approach using mid-shelf wave buoy observations along the Southeast Australian Shelf (SEAS). Five synoptic-scale wave climates exist during winter, and six during summer. These can be clustered into easterly (Tradewind), south-easterly (Tasman Sea) and southerly (Southern Ocean) wave types, each with distinct wave power signatures. We show that a southerly shift in the STR and trade-wind zone, consistent with an observed poleward expansion of the tropics, forces a n increase in the total wave energy flux in winter for the central New South Wales shelf of 1.9GJm-1 wave-crest-length for 1° southerly shift in the STR, and a reduction of similar magnitude (approximately 1.8GJm-1) during summer. In both seasons there is an anti-clockwise rotation of wave power towards the east and south-east at the expense of southerly waves. Reduced obliquity of constructive wave power would promote a general disruption to northward alongshore sediment transport, with the cross-shore component becoming increasingly prevalent. Results are of global relevance to sub-tropical east coasts where the modal wave climate is influenced by the position of the zonal STR.

Original languageEnglish
Pages (from-to)36-53
Number of pages18
JournalContinental Shelf Research
Volume98
DOIs
Publication statusPublished - 15 Apr 2015

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