Circulation in the Great Barrier Reef Lagoon using numerical tracers and in situ data

Luick, John L., Mason, Luciano, Hardy, Thomas, and Furnas, Miles J. (2007) Circulation in the Great Barrier Reef Lagoon using numerical tracers and in situ data. Continental Shelf Research, 27 (6). pp. 757-778.

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Abstract

Numerical hydrodynamic models of the northeastern Queensland shelf, forced by regional winds and modelled boundary currents in the northern Coral Sea, are used to provide improved estimates of general flow trajectories and water residence times within the Great Barrier Reef (GBR) shelf system. Model performance was checked against a limited set of current metre records obtained at Lark Reef (16°S) and the Ribbon Reefs (15.5°S). Estimates of water parcel trajectories are derived from a series of numerical tracer experiments, with daily releases of neutrally buoyant, un-reactive particles at 320 sites along the coast between Cape York (10.7°S) and Hervey Bay (25°S). Flow trajectories and residence times for tracer particles introduced to the GBR lagoon in the southern—ca. 22°S, central—19°S, and northern reef—14°S are emphasised. For purposes of the analysis, the year was divided into two seasons based on mean alongshore current direction. Most coastal sourced tracers entering the central GBR lagoon between 16° and 20°S during the northward-current season (January–August) primarily encounter the outer-shelf reef matrix after exiting the lagoon at its northern “head” (nominally 16°S), after 50–150 days. Up to 70% of tracer particles entering in the southward-current season (August–December) eventually crossed the lagoon to the outer-shelf reef matrix, with median crossing times between 20 and 330 days. During favourable wind conditions, tracers introduced at the coast may move rapidly across the lagoon into the reef matrix. The tracer experiments indicate that most coastal-sourced tracers entering the GBR lagoon remain near the coast for extended periods of time, moving north and south in a coastal band. Residence times for conservative tracer particles (and implied residence times for water-borne materials) within the GBR shelf system ranged from ca. 1 month to 1 year—time frames that are very long relative to development times of planktonic larvae and cycling times for nutrient materials in the water column, implying they are transformed long before reaching the outer reef matrix.

Item ID: 2727
Item Type: Article (Refereed Research - C1)
Keywords: Great Barrier Reef lagoon; circulation; numerical tracers; in situ data
ISSN: 1873-6955
Date Deposited: 31 Aug 2009 07:49
FoR Codes: 04 EARTH SCIENCES > 0405 Oceanography > 040501 Biological Oceanography @ 50%
04 EARTH SCIENCES > 0405 Oceanography > 040503 Physical Oceanography @ 50%
SEO Codes: 96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961104 Physical and Chemical Conditions of Water in Marine Environments @ 100%
Citation Count from Web of Science Web of Science 36
Downloads: Total: 2
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