Continental-shelf-scale model of the Leeuwin Current

1987 ◽  
Vol 45 (4) ◽  
pp. 813-827 ◽  
Author(s):  
R. O. R. Y. Thompson
Keyword(s):  
Continental Shelf ◽  
Scale Model ◽  
Leeuwin Current

Dynamics of the Ningaloo Current off Point Cloates, Western Australia

2006 ◽  
Vol 57 (3) ◽  
pp. 291 ◽  
Author(s):  
Mun Woo ◽  
Charitha Pattiaratchi ◽  
William Schroeder
Keyword(s):  
Numerical Model ◽  
Continental Shelf ◽  
Western Australia ◽  
Bottom Topography ◽  
Volume Transport ◽  
Relative Strength ◽  
Cross Sectional ◽  
Leeuwin Current ◽  
The North ◽  
Tropical Water

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.

Dipole vortices in the Great Australian Bight

2015 ◽  
Vol 66 (2) ◽  
pp. 135 ◽  
Author(s):  
George R. Cresswell ◽  
Lars C. Lund-Hansen ◽  
Morten Holtegaard Nielsen
Keyword(s):  
Surface Temperature ◽  
Continental Shelf ◽  
Sea Surface Temperature ◽  
Sea Surface ◽  
The South ◽  
Leeuwin Current ◽  
A Chain ◽  
Salinity Difference ◽  
Great Australian Bight

Shipboard measurements from late 2006 made by the Danish Galathea 3 Expedition and satellite sea surface temperature images revealed a chain of cool and warm ‘mushroom’ dipole vortices that mixed warm, salty, oxygen-poor waters on and near the continental shelf of the Great Australian Bight (GAB) with cooler, fresher, oxygen-rich waters offshore. The alternating ‘jets’ flowing into the mushrooms were directed mainly northwards and southwards and differed in temperature by only 1.5°C; however, the salinity difference was as much as 0.5, and therefore quite large. The GAB waters were slightly denser than the cooler offshore waters. The field of dipoles evolved and distorted, but appeared to drift westwards at 5km day–1 over two weeks, and one new mushroom carried GAB water southwards at 7km day–1. Other features encountered between Cape Leeuwin and Tasmania included the Leeuwin Current, the South Australian Current, the Flinders Current and the waters of Bass Strait.

scholarly journals Seasonal and inter-annual variability of water column properties along the Rottnest continental shelf, south-west Australia

Ocean Science ◽  
2019 ◽  
Vol 15 (2) ◽  
pp. 333-348 ◽  
Author(s):  
Miaoju Chen ◽  
Charitha B. Pattiaratchi ◽  
Anas Ghadouani ◽  
Christine Hanson
Keyword(s):  
Chlorophyll Fluorescence ◽  
Continental Shelf ◽  
Water Column ◽  
Inner Shelf ◽  
Leeuwin Current ◽  
Enso Events ◽  
Annual Variability ◽  
South West ◽  
Basin Scale ◽  
Autumn And Winter

Abstract. A multi-year ocean glider dataset, obtained along a representative cross-shelf transect along the Rottnest continental shelf, south-west Australia, was used to characterise the seasonal and inter-annual variability of water column properties (temperature, salinity, and chlorophyll fluorescence distribution). All three variables showed distinct seasonal and inter-annual variations that were related to local and basin-scale ocean atmosphere processes. Controlling influences for the variability were attributed to forcing from two spatial scales: (1) the local scale (due to Leeuwin Current and dense shelf water cascades, DSWC) and (2) the basin scale (El Niño–Southern Oscillation, ENSO, events). In spring and summer, inner-shelf waters were well mixed due to strong wind mixing, and deeper waters (>50 m) were vertically stratified in temperature that contributed to the presence of a subsurface chlorophyll maximum (SCM). On the inner shelf, chlorophyll fluorescence concentrations were highest in autumn and winter. DSWCs were also the main physical feature during autumn and winter. Chlorophyll fluorescence concentration was higher closer to the seabed than at the surface in spring, summer, and autumn. The seasonal patterns coincided with changes in the wind field (weaker winds in autumn) and air–sea fluxes (winter cooling and summer evaporation). Inter-annual variation was associated with ENSO events. Lower temperatures, higher salinity, and higher chlorophyll fluorescence (>1 mg m−3) were associated with the El Niño event in 2010. During the strong La Niña event in 2011, temperatures increased and salinity and chlorophyll fluorescence decreased (<1 mg m−3). It is concluded that the observed seasonal and inter-annual variabilities in chlorophyll fluorescence concentrations were related to the changes in physical forcing (wind forcing, Leeuwin Current, and air–sea heat and moisture fluxes).

Observations of warming on the Western Australian continental shelf

2007 ◽  
Vol 58 (10) ◽  
pp. 914 ◽  
Author(s):  
Alan Pearce ◽  
Ming Feng
Keyword(s):  
Indian Ocean ◽  
Continental Shelf ◽  
Southern Oscillation ◽  
Warming Trend ◽  
Eastern Indian Ocean ◽  
The South ◽  
Leeuwin Current ◽  
South Eastern ◽  
The Past ◽  
Western Australian

Global temperature datasets indicate a warming trend in the south-eastern Indian Ocean of ~0.02°C year–1. This is supported by in situ temperature measurements at a coastal monitoring station on the Western Australian continental shelf that have shown a mean temperature rise of 0.013°C year–1 since 1951, corresponding to ~0.6°C over the past 5 decades. Measurements from three other shallow stations between 1985 and 2004 indicated warming trends of 0.026–0.034°C year–1. It is suggested that enhanced air–sea heat flux into the south-eastern Indian Ocean may be a key factor in the rising temperature trend. There has also been a steady rise in salinity over the past half-century. At interannual scales, coherent temperature variability at the various stations indicates that larger-scale processes are influencing the shelf waters and are linked with El Niño/Southern Oscillation (ENSO)-related events in coastal sea level and hence the Leeuwin Current.

scholarly journals Some features of modeling of massive ice-resistant supports of continental shelf structures

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Sergey Pilyaev
Keyword(s):  
Continental Shelf ◽  
Scaling Laws ◽  
Oil And Gas ◽  
Experimental Studies ◽  
Physical And Mechanical Properties ◽  
Scale Model ◽  
Inertia Force ◽  
Natural Material ◽  
Model Studies ◽  
The Impact

Development of new oil and gas waters of the continental shelf of the Far North due to the need to create a unique ice-resistant oil country waterworks. To assess the impact of the power of ice on such constructions are carried out theoretical and experimental research. One of the main issues are the issues of modeling with experimental studies. Ice, as a natural material belongs to the class of solids which is characterized by both physical and mechanical properties, but the ice consists of the same basic elements as that of ordinary water, i.e., from hydrogen and oxygen molecules. In this connection, ice scaling laws can obtain an extension of standard hydraulic methods. Phenomena called similar characteristics when one of them may be prepared by conversion of other characteristics of this phenomenon using permanent relationship, similar to the transition from one unit to another system. To ensure the similarity phenomena under the influence of ice is necessary that a hydraulic or mechanical model is completely consistent nature subject to geometrical, kinematic and dynamic similarity. The article notes that the dynamic similitude ratio Fн = Fм ∙ λF is sufficient to determine all other scale model. If all the forces manifest themselves in the same ratio for the corresponding points and points in time, the mechanical equilibrium equation will be the same on the model and in nature. This simplifies the preparation of other scales of values. Article is relevant due to insufficient knowledge of the issues of modeling of ice in model studies. Finally it is noted that complete similarity to ice model that takes into account the force of gravity for the water and ice, the inertia force and friction of water ice is thus similar in Froude.

Distribution and timing of spawning by the Australian pilchard (Sardinops sagax neopilchardus) off Albany, Western Australia

1992 ◽  
Vol 43 (6) ◽  
pp. 1437 ◽  
Author(s):  
WJ Fletcher ◽  
RJ Tregonning
Keyword(s):  
Continental Shelf ◽  
Western Australia ◽  
Outer Shelf ◽  
Spawning Activity ◽  
Leeuwin Current ◽  
Sardinops Sagax ◽  
Marine Embayment ◽  
Eggs And Larvae ◽  
Main Influence ◽  
Timing Of Spawning

The pattern of abundance of eggs and larvae of the Australian pilchard, Sardinops sagax neopilchardus, collected by plankton tows in the region off Albany, Western Australia, was investigated. In 1989, surface tows were undertaken at five localities extending from the marine embayment of Princess Royal Harbour to the continental shelf just outside King George Sound. In 1990, oblique tows were undertaken at six localities extending from just inside King George Sound to beyond the edge of the continental shelf. Eggs and larvae of pilchards were found in many months, but peaks in egg numbers were found in July and December of both 1989 and 1990. There was, however, only one peak in larva abundance, during December. Most eggs and larvae were found in the region 2-8 km offshore from the entrance to King George Sound. Few were found either well inside King George Sound and Princess Royal Harbour or in outer-shelf localities. Spawning in the Albany region therefore occurred inshore of the main influence of the eastward-flowing tropical waters of the Leeuwin Current. The implications of this spawning activity in relation to the fishery for this species and the potential for stock separation along this coast are discussed.

scholarly journals A continental shelf scale examination of the Leeuwin Current off Western Australia during the austral autumn–winter

2011 ◽  
Vol 31 (17) ◽  
pp. 1858-1868 ◽  
Author(s):  
Evan Weller ◽  
David Holliday ◽  
Ming Feng ◽  
Lynnath Beckley ◽  
Peter Thompson
Keyword(s):  
Continental Shelf ◽  
Western Australia ◽  
Leeuwin Current ◽  
Austral Autumn

Continental shelf currents near the Abrolhos Islands, Western Australia

1989 ◽  
Vol 40 (2) ◽  
pp. 113 ◽  
Author(s):  
GR Cresswell ◽  
FM Boland ◽  
JL Peterson ◽  
GS Wells
Keyword(s):  
Continental Shelf ◽  
Sea Level ◽  
Strongly Correlated ◽  
Mean Flow ◽  
Southerly Wind ◽  
Leeuwin Current ◽  
Current Pulses ◽  
The Mean ◽  
Wind Events ◽  
Alongshore Wind

Recording current meters were used to identify features of the circulation of the continental shelf near the Abrolhos Islands and Rottnest Island in 1973-75. In summer, from November to March, there was a mean northward drift of 0.1 m s-1; in winter, from April to August, the mean flow was southward at 0.2 m s-1, possibly due to the spread of the Leeuwin Current onto the shelf. In all seasons, the current records had superimposed upon them a variability with period from days to weeks. The several- day period variability in the along shore currents had peaks of up to 0.5 m s-1 and was strongly correlated with sea level and with phase-lagged alongshore wind at the nearby port of Geraldton. In summer, strong southerly wind events associated with the eastward passage of highs produced sea-level troughs and northward current pulses. In winter, northwesterly storms from lows passing over Cape Leeuwin produced sea-level crests and southward current pulses. Satellite drifter tracks confirmed the summer and winter behaviour revealed by the current meter records and, further, showed that the winter behaviour extended north of the Abrolhos Islands to 26�S.

Modeling Within-Person Variance in Reaction Time Data of Older Adults

GeroPsych ◽  
2011 ◽  
Vol 24 (4) ◽  
pp. 169-176 ◽  
Author(s):  
Philippe Rast ◽  
Daniel Zimprich
Keyword(s):  
Reaction Time ◽  
Cognitive Aging ◽  
Reaction Times ◽  
Reaction Time Task ◽  
Reaction Time Data ◽  
Scale Model ◽  
Time Data ◽  
Time Task ◽  
The Mean ◽  
Second Wave

In order to model within-person (WP) variance in a reaction time task, we applied a mixed location scale model using 335 participants from the second wave of the Zurich Longitudinal Study on Cognitive Aging. The age of the respondents and the performance in another reaction time task were used to explain individual differences in the WP variance. To account for larger variances due to slower reaction times, we also used the average of the predicted individual reaction time (RT) as a predictor for the WP variability. Here, the WP variability was a function of the mean. At the same time, older participants were more variable and those with better performance in another RT task were more consistent in their responses.

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