The Ningaloo Current (NC) is a wind-driven, northward-flowing current present during the summer months along the continental shelf between the latitudes of 22° and 24°S off the coastline of Western Australia. The southward flowing Leeuwin Current is located further offshore and flows along the continental shelf break and slope, transporting warm, relatively fresh, tropical water poleward. A recurrent feature, frequently observed in satellite images (both thermal and ocean colour), is an anti-clockwise circulation located offshore Point Cloates. Here, the seaward extension of the coastal promontory blocks off the broad, gradual southern shelf, leaving only a narrow, extremely steep shelf to the north. The reduction in the cross-sectional area, from the coast to the 50 m contour, between southward and northward of the promontory is ~80%. Here, a numerical model study is undertaken to simulate processes leading to the development of the recirculation feature offshore Point Cloates. The numerical model output reproduced the recirculation feature and indicated that a combination of southerly winds, and coastal and bottom topography, off Point Cloates is responsible for the recirculation. The results also demonstrated that stronger southerly winds generated a higher volume transport in the NC and that the recirculation feature was dependent on the wind speed, with stronger winds decreasing the relative strength of the recirculation.
Hydrological data from a repeated cross‐shore transect obtained using Teledyne Webb Research Slocum Electric gliders offshore Two Rocks in south‐western Australia over 13 months are presented. The data revealed that formation of dense water inshore and its transport across the shelf as a near bed gravity current (defined as Dense Shelf Water Cascade, DSWC) was a regular occurrence, particularly during autumn and winter months. In autumn, the dense water is mainly formed through changes in salinity resulting from evaporation, whilst in winter; temperature change through surface cooling was the dominant factor. The mean wind speeds also decrease during the transition during autumn. The speed of the DSWC was estimated to be 0.01–0.02 m s−1, and similar to that measured in other selected regions globally. The offshore transport from the shelf is a significant component of the alongshore wind‐driven transport.
Currently, pilots maximise the performance of Seaglider underwater gliders by manually selecting their set-up parameters. Building on existing procedures based on the assumption of steady-state motions, a recommender system for the trim and flight parameters has been developed to aid trainee pilots and enable round-the-clock operations. The system has been validated with data from 12 missions run in waters off the United Kingdom and Australia, representative of a range of oceanographic conditions. The recommended trim parameters present a maximum difference of 14% from the values selected by the pilots, whereas pilots are found not to change the flight parameters. Additionally, suggestions are made to improve operational practices to further improve the accuracy of the recommender system. As a result, the developed system is expected to greatly help trainee pilots achieve expertise in a much smaller time frame than standard practice. Additionally, thanks to its high precision, the recommender system can be used to autonomously select the trim and flight parameters of Seagliders for night operations in the future.
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