Poleward boundary current off Western Australia

1983 ◽  
Vol 34 (1) ◽  
pp. 173 ◽  
Author(s):  
RORY Thompson ◽  
G Veronis
Keyword(s):  
Indian Ocean ◽  
Reverse Direction ◽  
Western Coast ◽  
Kelvin Wave ◽  
Boundary Current ◽  
North West ◽  
Leeuwin Current ◽  
The North ◽  
Great Australian Bight ◽  
A Current

The southern Indian Ocean is modelled here as a body of homogeneous water with a shelf and slope region on the eastern side. A 'Leeuwin Current' is found to be the poleward extension of a boundary current generated on the north-west slope of Australia by winter winds. Simple, approximate balances demonstrate that a current forced in one region can propagate in the direction that a Kelvin wave travels but not in the reverse direction. Thus, the Leeuwin Current can be induced by winds acting north of Cape Leeuwin but not by winds in the Great Australian Bight. This study also predicts the existence of a southward current off the western coast of Tasmania.

scholarly journals Effect of tropical cyclones on the Stratosphere-Troposphere Exchange observed using satellite observations over north Indian Ocean

2016 ◽  
Author(s):  
M. Venkat Ratnam ◽  
S. Ravindra Babu ◽  
S. S. Das ◽  
Ghouse Basha ◽  
B. V. Krishnamurthy ◽  
...  
Keyword(s):  
Water Vapor ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
Lower Stratosphere ◽  
North Indian Ocean ◽  
Satellite Observations ◽  
Upper Troposphere ◽  
North West ◽  
The North ◽  
The Impact

Abstract. Tropical cyclones play an important role in modifying the tropopause structure and dynamics as well as stratosphere-troposphere exchange (STE) process in the Upper Troposphere and Lower Stratosphere (UTLS) region. In the present study, the impact of cyclones that occurred over the North Indian Ocean during 2007–2013 on the STE process is quantified using satellite observations. Tropopause characteristics during cyclones are obtained from the Global Positioning System (GPS) Radio Occultation (RO) measurements and ozone and water vapor concentrations in UTLS region are obtained from Aura-Microwave Limb Sounder (MLS) satellite observations. The effect of cyclones on the tropopause parameters is observed to be more prominent within 500 km from the centre of cyclone. In our earlier study we have observed decrease (increase) in the tropopause altitude (temperature) up to 0.6 km (3 K) and the convective outflow level increased up to 2 km. This change leads to a total increase in the tropical tropopause layer (TTL) thickness of 3 km within the 500 km from the centre of cyclone. Interestingly, an enhancement in the ozone mixing ratio in the upper troposphere is clearly noticed within 500 km from cyclone centre whereas the enhancement in the water vapor in the lower stratosphere is more significant on south-east side extending from 500–1000 km away from the cyclone centre. We estimated the cross-tropopause mass flux for different intensities of cyclones and found that the mean flux from stratosphere to troposphere for cyclonic stroms is 0.05 ± 0.29 × 10−3 kg m−2 and for very severe cyclonic stroms it is 0.5 ± 1.07 × 10−3 kg m−2. More downward flux is noticed in the north-west and south-west side of the cyclone centre. These results indicate that the cyclones have significant impact in effecting the tropopause structure, ozone and water vapour budget and consequentially the STE in the UTLS region.

Non-linear model of the tides in the Gulf of Carpentaria

1981 ◽  
Vol 32 (5) ◽  
pp. 685 ◽  
Author(s):  
JA Church ◽  
AMG Fobes
Keyword(s):  
Open Boundary ◽  
Open Boundary Conditions ◽  
Kelvin Wave ◽  
Rapid Phase ◽  
North West ◽  
The North ◽  
Northern Half ◽  
Non Linear ◽  
Amphidromic Point ◽  
Phase Variations

A non-linear barotropic model was used to evaluate the tidal regime in the Gulf of Carpentaria. The model was forced by open boundary conditions specified on a line joining Wessel Islands to False Cape and a volume flow through Torres Strait estimated from tidal constants on each side of the Strait. The model gives results in agreement with the available observations and in particular predicts mixed tides in the northern half of the Gulf and diurnal tides in the south-east corner of the Gulf. The diurnal tide consists of a Kelvin wave entering the Gulf in the north-west and propagating clockwise around the Gulf with one amphidromic point. The higher frequencies of the semidiurnal tides allow the generation of a first-mqde Poincare wave and the trapping of energy in the northern half of the Gulf. Amphidromes near Mornington Island and Groote Eylandt are also predicted, as is a region of low amplitude and rapid phase variations in the centre of the Gulf.

GEOLOGICAL FRAMEWORK OF THE GREAT AUSTRALIAN BIGHT

1969 ◽  
Vol 9 (1) ◽  
pp. 60
Author(s):  
R. Smith ◽  
P. Kamerling
Keyword(s):  
Middle Eocene ◽  
Early Stage ◽  
Upper Jurassic ◽  
The South ◽  
The West ◽  
Offshore Area ◽  
North West ◽  
Carbonate Sedimentation ◽  
The North ◽  
Great Australian Bight

Geophysical exploration carried out in the Great Australian Bight since 1966, combined with geological fieldwork in the adjacent land areas, has made it possible to outline the broad geological framework of the area.The "basement" consists of two major units, an offshore extension of the locally metamorphic Cambrian Kanmantoo Group in the south-east and the extension of the West Australian Archaean shield in the north-west. The boundary is thought to follow a trend extending westerly from the Cygnet-Snelling fault zone on Kangaroo Island.In two areas the basement has been downfaulted, thus creating depositional areas for thick sequences of sediments, namely the Elliston trough to the west of Eyre Peninsula and the Duntroon basin, south of Eyre Peninsula and west of Kangaroo Island.The geological setting of the Duntroon basin appears to be comparable with the Otway basin and a Jurassic- Cretaceous age is assumed for the folded sequence of sediments overlying the basement and underlying the Tertiary with angular unconformity. The basin was possibly partially and temporarily closed to the south and open to marine influences from the west.In the Elliston trough the lower part of the section which has low to medium velocity seismic character, is probably Mesozoic, as is evidenced by the Upper Jurassic encountered in its onshore extension. Proterozoic-Cambrian sediments may overlie the basement in the eastern part of the trough. Deformation of the Mesozoic is limited to the mouth of the trough where there is indication of a base- Tertiary unconformity. This trough was probably also open to marine influences to the west.Along the continental margin between the basins and also south of the Eucla basin a thin Mesozoic section, conformably underlying the Tertiary, is probably present, gradually thickening towards the continental slope.In the onshore area Tertiary sedimentation started with local deposition of clastics during the Middle Eocene, which also may have been the case off the Eucla basin, in the Elliston trough and in the Duntroon basin. Carbonate sedimentation took place from the Middle-Upper Eocene onwards, to reach its widest areal extent during the Lower Miocene. A hiatus during the Oligocene may have occurred in the western part of the Bight as is the case in the Eucla basin.Only weak deformation of the Tertiary in the offshore area has been observed. This generally occurs over Mesozoic structures in the Duntroon basin and as draping over topographic basement highs at the mouth of the Elliston trough.No significant hydrocarbon indications are known from the surrounding land areas, but the well-documented bitumen strandings along the coast point to offshore seepages indicating generation of hydrocarbons in the general area.At this stage prospects must be regarded as speculative.although a folded probable Mesozoic sequence forms an objective in the Duntroon basin while prospective Mesozoic-Tertiary section appears to be present in the Elliston trough, where structural evaluation is still at a relatively early stage.

scholarly journals The dynamic connection of the Indonesian Throughflow, South Indian Ocean Countercurrent and the Leeuwin Current

2015 ◽  
Vol 12 (5) ◽  
pp. 2231-2256
Author(s):  
E. Lambert ◽  
D. Le Bars ◽  
W. P. M. de Ruijter
Keyword(s):  
Indian Ocean ◽  
General Circulation ◽  
Circulation Model ◽  
Coastal Current ◽  
Indonesian Throughflow ◽  
Boundary Current ◽  
South Indian Ocean ◽  
Leeuwin Current ◽  
South Indian ◽  
The Indian Ocean

Abstract. East of Madagascar, wind and surface buoyancy fluxes reinforce each other, leading to frontogenesis, outcrop and an eastward along-front flow: the South Indian Ocean Countercurrent (SICC). In the east the Leeuwin Current (LC) is a unique eastern boundary current which flows poleward along Australia. It is often described as a regional coastal current forced by an off-shore meridional density gradient or a sea surface slope, yet little is known of the forcing and dynamics that control these open ocean meridional gadients. To complete this understanding, we make use of both an ocean general circulation model and a conceptual two-layer model. The SICC impinges on west Australia and adds to a sea level slope and a southward geostrophic coastal jet: the Leeuwin Current. The SICC and the LC are thus dynamically connected. An observed transport maximum of the LC around 22° S is directly related to this impingement of the SICC. The circulation of the Indonesian Throughflow (ITF) through the Indian Ocean appears to be partly trapped in the upper layer north of the outcrop line and is redirected along this outcrop line to join the eastward flow of the SICC. Shutdown of the ITF in both models strongly decreases the Leeuwin Current transport and breaks the connection between the LC and SICC. In this case, most of the SICC was found to reconnect to the internal gyre circulation in the Indian Ocean. The Indonesian Throughflow, South Indian Ocean Countercurrent and the Leeuwin Current are thus dynamically coupled.

MAINLAND COSMOPOLITANISM AND THE RISE OF PERSONAL PRESTIGE: NEW EVIDENCE FROM THE COASTAL EARLY HELLADIC TOWN OF HELIKE, NORTH-WEST PELOPONNESE, GREECE

2017 ◽  
Vol 112 ◽  
pp. 1-32
Author(s):  
Dora Katsonopoulou ◽  
Stella Katsarou
Keyword(s):  
Aegean Sea ◽  
Western Coast ◽  
North West ◽  
The North ◽  
Gulf Of Corinth ◽  
The Social ◽  
The Status ◽  
Architectural Transformation ◽  
New Evidence ◽  
Material Evidence

Excavations carried out by The Helike Project in the Helike plain on the south-western coast of the Gulf of Corinth, north-west Peloponnese, since 2000, have brought to light the well-preserved remains of a coastal Early Helladic (EH) II–III settlement. The site developed as a densely organised settlement during the EH II period and underwent a major architectural transformation at the beginning of the following EH III. In addition to a reorganisation of the settlement on a rectangular town grid, the outstanding feature among the buildings discovered is that of a monumental Corridor House. The newly organised building plan of the settlement was most probably associated with the rise of a new socio-economic structure at the time, including advanced technological specialisation, and possibly the establishment of administrative control within the town supporting communal interests, together with a new emphasis on the status of the private individual.Considering EH Helike in its broader geographical context, the site's prosperity marks an exception to the widespread decline attested in the mainland settlements of the time, and links it rather with centres across the Aegean Sea and further east. In addition to similarities at the level of settlement organisation, such overseas links and contacts are conspicuously evidenced at Helike through the presence of an array of exotic, prestigious items and commodities including an outstanding depas cup of Trojan/Anatolian type, ornaments of precious metal from the east or the north and Melian obsidian tools, and by the adoption of ‘international’ fashions of life such as the ‘serve and drink’ culture and ‘potter's marks’. In this paper, we present the range of material evidence from the EH III town of Helike illustrating its various spheres of foreign contact, and discuss possible insights into the social and economic conditions that generated the town's floruit and cosmopolitanism in EH III.

The Day the Earth Shook: The Sumatra–Andaman Earthquake 2004

2013 ◽  
Author(s):  
Mike Searle
Keyword(s):  
Indian Ocean ◽  
Plate Boundary ◽  
Chandler Wobble ◽  
North West ◽  
North East ◽  
The North ◽  
Tilted Surface ◽  
The Earth ◽  
The Indian Ocean ◽  
Length Of The Day

At 00.58 GMT (7.58 local time) on Sunday, 26 December 2004 a massive earthquake occurred off the north-west coast of Sumatra. The earthquake measured between magnitude 9.0 and 9.3 on the Richter scale with its epicentre at 3.32oN, 95.85oE, and occurred at a depth of approximately 30 kilometres. It was the second largest earthquake recorded since instrumental records began and was the deadliest natural disaster in recorded history. The earthquake and the resulting tsunami are estimated to have killed at least 228,000 people across fifteen countries bordering the Indian Ocean. The worst affected countries were Indonesia, Sri Lanka, India, Thailand, Burma, the Maldives, and Somalia. The earthquake occurred on the subduction zone interface between the down-going Indian Ocean plate and the overriding Burma–Andaman–Sumatra plate. It ruptured approximately 1600 kilometres’ length of the plate boundary from Sumatra all the way north to the Burmese coast, travelling at 2–3 kilometres per second. Aftershocks continued unrelentingly for over four months after the earthquake, several reaching magnitude 7.5 as far north as the northern Andaman Islands. The seismic waves indicated a thrust fault earthquake that tilted the surface up to the south-west and down to the north-east. The ground surface was elevated as much as 11 metres at the epicentre, with the tilted surface sinking up to one metre further to the north-east, offshore Sumatra. During the rupture, the Burma plate slipped as much as 15 metres horizontally as the Indian Ocean plate slipped beneath. The force of the quake perceptibly shifted the Earth’s axis, raised sea level globally and speeded Earth’s rotation. It has been suggested that the earthquake shortened the length of the day by 2.68 microseconds, because of the decrease in oblateness of the Earth. The earthquake caused the Earth to wobble on its axis by up to 2.5 cm in the direction of 145o east longitude. The natural ‘Chandler wobble’, a small motion in the Earth’s axis of rotation (the motion that occurs when the spinning object is not a perfect sphere) can be up to 9 metres over 433 days, so this eventually offsets the comparatively minor wobble produced by the earthquake.

scholarly journals Trends in strandings and by-catch of marine mammals in north-west Spain during the 1990s

2002 ◽  
Vol 82 (3) ◽  
pp. 513-521 ◽  
Author(s):  
A. López ◽  
M.B. Santos ◽  
G.J. Pierce ◽  
A.F. González ◽  
X. Valeiras ◽  
...  
Keyword(s):  
Marine Mammals ◽  
Atlantic Coast ◽  
Western Coast ◽  
Common Dolphin ◽  
North West ◽  
The North ◽  
By Catch ◽  
Average Size ◽  
Autumn And Winter ◽  
Common Dolphins

Strandings of marine mammals on the north-western Spanish coast (Galicia) have been systematically recorded since 1990. A total of 1433 marine mammals belonging to 15 species was recorded from 1990 to 1999. The most frequently recorded species stranded were common dolphin (47%), bottlenose dolphin (11%) and harbour porpoise (7%). The number of strandings recorded increased annually over the study period, probably reflecting an increased observer effort. During 1996–1999, an average of 1·65 animals were stranded annually for each 10 km of coastline, the highest density of strandings recorded on the Atlantic coast of the Iberian Peninsula. More than 80% of the strandings were located on the western coast of Galicia, mainly in autumn and winter. During the study period, 42 proven incidental catches were recorded, although signs of by-catch were seen in a further 198 animals. The average size of stranded common dolphins and the proportion of males both increased towards the end of the calendar year.

Distribution and transport pathways of Panulirus ornatus (Fabricius, 1776) and Panulirus spp. larvae in the Coral Sea, Australia

2001 ◽  
Vol 52 (8) ◽  
pp. 1175 ◽  
Author(s):  
Darren M. Dennis ◽  
C. Roland Pitcher ◽  
Timothy D. Skewes
Keyword(s):  
Ocean Currents ◽  
Boundary Current ◽  
Transport Pathways ◽  
North West ◽  
The North ◽  
Coral Sea ◽  
Breeding Grounds ◽  
Equatorial Current ◽  
Torres Strait ◽  
Phyllosoma Larvae

Distribution of phyllosoma larvae and pueruli of the rock lobster Panulirus ornatus and other Panulirus species was surveyed in the north-west Coral Sea in May 1997 and compared to ocean currents. Distribution of P. ornatus larvae revealed the sources of recruits to the Torres Strait lobster fishery. Phyllosomas and pueruli of P. ornatus dominated the Panulirus spp. plankton-trawl catch. Surviving pueruli were transferred to an aquarium to await confirmation of their identity. Pregilled P. ornatus phyllosomas were most abundant approximately 300 km east of the northern Great Barrier Reef (GBR) and near the confluence of the South Equatorial Current and Coral Sea Gyre. Gilled phyllosomas were also common there but most numerous adjacent to the GBR. Pueruli were most abundant adjacent to the GBR well south of Torres Strait. The distribution of P. ornatus phyllosomas and pueruli in relation to the ocean currents supported the hypothesis that phyllosomas are transported from the Gulf of Papua breeding grounds by the Hiri boundary current into the Coral Sea Gyre and then by surface onshore currents onto the Queensland coast and into Torres Strait. Distributions of larvae of other Panulirus species and the synaxid Palinurellus wieneckii differed from those of P. ornatus.

scholarly journals PREDICTION METHOD FOR THE WAVE HEIGHT DISTRIBUTION OEF THE WESTERN COAST OE TAIWAN

1984 ◽  
Vol 1 (19) ◽  
pp. 31 ◽  
Author(s):  
Frederick L.W. Tang ◽  
Jea-Tzyy Juang
Keyword(s):  
Wave Height ◽  
Prediction Method ◽  
Distribution Model ◽  
Western Coast ◽  
Height Distribution ◽  
North West ◽  
The North ◽  
Wave Height Distribution ◽  
Wave Heights ◽  
The Western Pacific

Taiwan Strait locates on the continental shelf of the western Pacific Ocean. The water depth is less than 100 meters. Furthermore, the bathemetry of the eastern side namely the offing of western coast of Taiwan shoals gradually. In consequence, in case of the wind "blows from the north to south, waves in the deeper part of the strait refract to he north west direction while they are approaching the shore and local waves directly generated by the wind still keep the same direction of the wind. The situation is shown in Figure 1. Erom September to April of the next year, anticyclones come from Mongolia causes monsoon in this area. The wind velocity in the monsoon sometimes exceeds 20 meters per second, but it is arround 10 meters per second in general. Howerer, the duration of winds over 5 meters per second has been recorded more than 50 days. Engineering works such as towing caissons for building breakwater as well as dredging offshore have to be done in these days. Furthermore, navigation operations should not be stopped unless the wind is too strong. Of course, waves are forecast every day, however, more precise information about the probability of the occurrence of certain wave height is of great significance. In last conference, the authors submitted a probability density function of wave heights in this area. This distribution model is to be remended by considering energy loss in this paper, and concrete forecasting procedure is submitted for engineering and navigation practice.

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