The Leeuwin Current, eddies and sub-Antarctic waters off south-western Australia

2004 ◽  
Vol 55 (3) ◽  
pp. 267 ◽  
Author(s):  
G. R. Cresswell ◽  
D. A. Griffin
Keyword(s):  
Continental Slope ◽  
Western Australia ◽  
Anticyclonic Eddy ◽  
Satellite Observations ◽  
Leeuwin Current ◽  
Deep Mixing ◽  
Complex Interactions ◽  
Antarctic Waters ◽  
Anticyclonic Eddies ◽  
Great Australian Bight

Data from a research vessel cruise in late 1994 and several years of satellite observations revealed complex interactions of ocean features off south-western Australia. The ship measurements showed that the Leeuwin Current (LC) commonly ran at 0.5 m s–1 above the upper continental slope and extended down to approximately 250 m. South of the continent, a 200-km diameter anticyclonic eddy depressed the ocean structure in the upper 1000 m. The eddy showed influences of the LC, deep mixing in winter and summer heating. The sub-Antarctic water around the eddy was cooler, fresher and richer in nutrients and oxygen than both the eddy and the LC. Satellite thermal and topographic measurements showed that cyclonic eddies accelerated the LC along the southern upper continental slope, whereas anticyclonic eddies diverted it out to sea and then back again. The images suggested that weak eddies originating east of the Great Australian Bight migrate westward, first encountering the continental slope off the Recherche Archipelago. There, the anticyclonic eddies take on warm water from the LC and strengthen. Several anticyclonic eddies were followed westward beyond the archipelago for 18 months as they drifted at up to 5 km day–1 and interacted with the LC and with one another.

scholarly journals Condition of larvae of western rock lobster (Panulirus cygnus) in cyclonic and anticyclonic eddies of the Leeuwin Current off Western Australia

2015 ◽  
Vol 66 (12) ◽  
pp. 1158 ◽  
Author(s):  
Miao Wang ◽  
Richard O'Rorke ◽  
Anya M. Waite ◽  
Lynnath E. Beckley ◽  
Peter Thompson ◽  
...  
Keyword(s):  
Western Australia ◽  
Spiny Lobster ◽  
Dry Mass ◽  
Leeuwin Current ◽  
Dramatic Decline ◽  
Biochemical Analyses ◽  
Panulirus Cygnus ◽  
Anticyclonic Eddies ◽  
Western Australian ◽  
Stage Viii

Changes in the offshore oceanographic processes are suspected to be the cause of a recent dramatic decline in the settlement of post-larvae of the Western Australian spiny lobster (Panulirus cygnus), which has greatly reduced the productivity from the world’s second-largest spiny lobster fishery. The present study assessed whether there are differences in the nutritional condition of the larvae of P. cygnus sampled from two pairs of cyclonic eddies (CEs) and anticyclonic eddies (AEs). Morphometric and biochemical analyses were undertaken on the mid–late-stage larvae (VI, VII, VIII) sampled offshore from two pairs of adjacent counter-rotating mesoscale eddies in the Leeuwin Current off Western Australia. The results showed that larvae captured from CEs had greater average total dry mass (P<0.001) than those from AEs. Stage VIII larvae from CEs contained more protein (P<0.008) (38.5% ±5.4s.e.) and lipid (P<0.005) (67.2% ±12.1) than did those from AEs. The possible causes for these differences are uncertain but may be related to differences in water temperatures in CEs v. AEs influencing the ability of phyllosomas to accumulate nutritional reserves.

scholarly journals Observed Warm Filaments from the Kuroshio Associated with Mesoscale Eddies

2020 ◽  
Vol 12 (18) ◽  
pp. 3090
Author(s):  
Qian Shi ◽  
Guihua Wang
Keyword(s):  
High Frequency ◽  
Average Length ◽  
Mesoscale Eddies ◽  
Satellite Observations ◽  
Sea Surface ◽  
Large Temperature ◽  
Anticyclonic Eddies ◽  
The Kuroshio ◽  
Sst Gradient

Based on high resolution satellite observations of sea surface temperature (SST), warm filaments near the Kuroshio around the Luzon Strait were systematically identified. These filaments extend an average length of about 200 km from the Kuroshio. The occurrence and features of the warm filaments are highly associated with both mesoscale eddies and the intensity of the SST gradient of the Kuroshio. Warm filaments are formed by heat advection from the warm Kuroshio into the colder interior Pacific Ocean by anticyclonic eddies (∼58%), cyclonic eddies (∼10%), and the dipole eddies (∼16%). The large temperature gradient near the Batanes Islands may also contribute to the high frequency of warm filaments in their vicinity. This study will help elucidate the role of zonal heat transport associated with the Kuroshio–eddy interaction during filament formation.

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.

Effect of the Leeuwin Current upon sea surface temperatures off south-western Australia

1984 ◽  
Vol 35 (4) ◽  
pp. 487 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Western Australia ◽  
Coastal Waters ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Leeuwin Current ◽  
South Eastern ◽  
Surface Temperatures ◽  
Autumn And Winter

Comparison of long-term mean monthly sea surface temperatures of coastal waters at comparable latitudes off south-eastern and south-westem Australia shows that, during the duration of the Leeuwin Current in autumn and winter, sea surface temperatures are 1-3�C higher off south-western Australia.

Comparison of the Semtner and Chervin eddy-resolving global ocean model with LUCIE and satellite observations in the Leeuwin Current region

1996 ◽  
Vol 47 (3) ◽  
pp. 509 ◽  
Author(s):  
CJC Reason ◽  
AF Pearce
Keyword(s):  
Western Australia ◽  
Satellite Data ◽  
General Circulation ◽  
Maximum Velocity ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Global Ocean ◽  
Western Coast ◽  
Model Output ◽  
Leeuwin Current

Output from the Semtner and Chervin eddy-resolving global ocean general circulation model is compared with observations from the Leeuwin Current Interdisciplinary Experiment (LUCIE) and satellite data for the coastal waters of Western Australia. The model output is a snapshot over the domain 9-43�S, 90-120�E for a day in mid July 1987, which is during the season that the Leeuwin Current is expected to be well established along the western and southern coasts of Western Australia. Maximum Leeuwin Current velocities in the model are of the order of 60 cm s-1 and are found in the southern part of the current on the western coast and around into the Great Australian Bight. At depths below about 200 m, and centred near 400 m, there is an equatorward-flowing undercurrent with maximum velocity of order 25 cm s-1. Comparison of temperature and salinity cross-sections with LUCIE observations reveals that the model output for this day exhibits many realistic features. In particular, the model fields display a number of prominent meanders and eddies on the Leeuwin Current as well as further offshore. Consistent with observations, mesoscale features associated with the Leeuwin Current are concentrated between 25�S and the Cape Mentelle region; the flow in the northern part of the Leeuwin Current and the North West Shelf may be too weak to induce eddy-generating instabilities. Prominent in the model output are two large meanders on the Leeuwin Current between 25�S and 29�S and two anticyclonic eddies further downstream; features similar to these are evident in satellite data during winter 1987.

Corrigenda - The Leeuwin Current south of Western Australia

1993 ◽  
Vol 44 (2) ◽  
pp. 285 ◽  
Author(s):  
GR Cresswell ◽  
JL Peterson
Keyword(s):  
Western Australia ◽  
Leeuwin Current

Ring structure in the poleward boundary current off Western Australia in Summer

1983 ◽  
Vol 34 (4) ◽  
pp. 547 ◽  
Author(s):  
JC Andrews
Keyword(s):  
Structure Function ◽  
Western Australia ◽  
Large Scale ◽  
Function Analysis ◽  
Ring Structure ◽  
Boundary Current ◽  
Length Scales ◽  
Leeuwin Current ◽  
Tropical Water ◽  
Geopotential Anomaly

Data from five summer cruises off Western Australia are examined objectively using structure functions to establish principal length scales and amplitudes of mesoscale fields. Previous estimates of length scales using geopotential anomaly and geomagnetic electrokinetograph vectors as inputs to structure- function analyses gave length scales that differed by a factor of two. The present analysis shows that there are two length scales, which dominate in different parts of the flow, and this reconciles the two previous estimates. The shorter scale is λs = 157�25 km and the longer is λL = 309�28 km. Regions of strong large-scale currents have warm- and cold-core rings and mesoscale waves associated with them that assume the Rossby deformation scale. These are the λS structures. The longer, λL structures are found in regions of weak large-scale currents. Geopotential anomaly amplitudes and currents in the rings are, respectively, about 0.7 m2 s-2 (geopotential relief = 1 4 m2 s-1) and 70 cm s-1. Data from one summer cruise with a station density of approximately 12 per degree square are analysed in detail subjectively and the structure-function analysis is shown to be quantitatively meaningful. This cruise was near the shelf and shows the advection of low-salinity tropical water poleward over the slope in a narrow baroclinic current. Seaward cyclonic rings were associated with the current. The baroclinic structure of the current and of the rings is compatible with the winter behaviour of Lagrangian drifters released into the Leeuwin Current.

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