Origin and circulation of water types of the 25.00 sigma-t surface of the South-west Pacific

1969 ◽  
Vol 20 (2) ◽  
pp. 105 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Continental Margin ◽  
High Salinity ◽  
Vertical Mixing ◽  
Water Type ◽  
Subtropical Water ◽  
Water Types ◽  
Low Salinity ◽  
Tropical Water ◽  
South West ◽  
Mixed Transition

The salinity and oxygen of 25.00 sigma-t waters of the Tasman and Coral Seas have been averaged within 5� squares. From these average values four water types were identified by their salinity-oxygen relations. These were: a tropical high salinity (mean salinity 36.00‰, mean oxygen 3.50 ml/l.), a tropical low salinity (mean salinity 35.25‰, mean oxygen 3.10 ml/l.), a subtropical high salinity (mean salinity 35.75‰, mean oxygen 5.15 ml/l.), and a subtropical low salinity (mean salinity 35.46‰, mean oxygen 5.15 ml/l.). Waters north of 15�S. were all mixtures of the two tropical water types, and those south of 35� S. were all mixtures of the two subtropical water types. Topography of the 25.00 sigma-t surface showed easterly flow at around 15� S. and, as far as could be interpreted, easterly flow at 35� S. Between these two zones of tropical and subtropical water types there occurred a region of mixed transition waters in which large meridional gradients of oxygen but small gradients of salinity were found. This transition region occupied a much larger area off east Australia than elsewhere, mainly because there was greater meridional exchange of the tropical and subtropical water types off east Australia. North of 20� S. the high salinity subtropical water type spreads northward in the central Tasman and Coral Seas in summer and the low salinity tropical water type spreads southward along the Queensland continental margin in winter. South of 20� S. it was impossible to separate changes due to circulation from those caused by vertical mixing and winter formation of 25.00 sigma-t water at the surface.

The Intermediate Depth Waters of the Tasman and Coral Seas. III. Succession of Water Types East of Port Hacking in 1957-1959

1962 ◽  
Vol 13 (1) ◽  
pp. 61 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Seasonal Cycle ◽  
Vertical Mixing ◽  
Maximum Intensity ◽  
Water Type ◽  
Intermediate Depth ◽  
Water Types ◽  
South West ◽  
The Pacific ◽  
Actual Movement ◽  
The Antarctic

The seasonal occurrences of three water types on the 27.20 and 26.80 σt, surfaces on a section east of Port Hacking, 153-160� E., and at certain stations north of this line are discussed. On the 27.20 σt, surface it is shown that the Pacific Equatorial Intermediate is found in maximum intensity during September-October at longitude 158-160� E. Subsequently it moves west and during April-June it occurs at longitude 153-157� E. The South-West Pacific Intermediate appears at maximum intensity during March-July at 158-160� E. but in September-February it moves west to longitude 152-154� E. The Antarctic Intermediate is only about 30% of the water type mixture and occurs at the eastern end of the section during December to April and at the western end (152-154� E.) during March-April. On the 26.80 σt, surface the Subtropical formed between 30 and 75% of the water type mixture and was the principal water type, though it was not possible to distinguish between the part formed by local vertical mixing and that formed by actual movement from the Subtropical Convergence. No seasonal cycle could be determined for the Upper Antarctic Intermediate which varied between 0 and 55% of the water type mixture. The Upper Equatorial Intermediate varied from 5 to 45% of the mixture and showed no seasonal cycle.

Seasonal changes in the hydrological and biological environments off Port Hacking, Sydney

1966 ◽  
Vol 17 (1) ◽  
pp. 77 ◽  
Author(s):  
BS Newell
Keyword(s):  
Seasonal Changes ◽  
Algal Blooms ◽  
High Salinity ◽  
Vertical Mixing ◽  
Hydrological Regime ◽  
Offshore Water ◽  
Subtropical Water ◽  
Tropical Water ◽  
Land Drainage ◽  
The Western Pacific

Data obtained over 10 yr at the Port Hacking 100-m station show an annual cycle in some properties. In May the continental shelf is dominated by high salinity subtropical water from the western Pacific. From June to August, cooling and vertical mixing decrease temperatures and salinities at all depths. From September, tropical water of northern origin penetrates southwards, increasing temperatures and decreasing salinity at 10 and 50 m. This tropical water exerts its maximum influence in March. From September to March other offshore water from deeper than 100 m rises onto the shelf, decreasing temperature, salinity, and oxygen, but increasing nitrate. In addition there is probably a continual land drainage influence on the hydrological regime. Algal blooms occur from August to April, in association with the penetration of nitrate-rich water onto the shelf.

Origin and circulation of water types on the 26.00 sigma-t surface of the south-west Pacific

1968 ◽  
Vol 19 (2) ◽  
pp. 107 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Oxygen Content ◽  
Water Type ◽  
The South ◽  
West Pacific ◽  
Water Types ◽  
South West ◽  
Tasman Sea ◽  
Type 3

CSIRO hydrological data from the south-west Pacific (0-45�S., 140°E.-160� W.) during 1960-67 have been used to calculate annual means of salinity and oxygen, within 5� squares, on the 26.00 sigma-t surface. In addition, for some squares it was possible to calculate mean summer (December-February) and mean winter (July- September) values of salinity and oxygen. From the annual means the salinity-oxygen relations were used to characterize four water types. Water type 1 of tropical origin had a salinity of 35.03‰ and an oxygen content of 3.20 ml/l. Water type 2, also of tropical origin, had a salinity of 35.23‰ and an oxygen content of 2.30 ml/l. Water type 3 of subtropical origin had a salinity of 35 +66‰ and an oxygen content of 5.45 ml/l. Water type 4 of Subantarctic origin had a salinity of 34.80‰ and an oxygen content of 6.00 ml/l. The ultimate origins of water types 1 and 2 are thought to be at considerable distances from the south-west Pacific region. Water type 1 is suggested as a mixture of waters of the North Equatorial Pacific, to the west of about 160°W., and waters of type 3 originating in the south Tasman Sea and other regions of the south Pacific. Water type 2 forms at around 16O°W., by mixing of eastern tropical Pacific waters and water type 3. It is thought that water types 1 and 2 form at different times of the year depending upon the extent of meridional or zonal flow in the central Equatorial region. Water types 3 and 4, however, are formed by southward spreading and winter cooling at the surface of subtropical waters, and by northward spreading and summer warming at the surface of Subantarctic waters, respectively. These two water types are therefore of south-west Pacific origin. Generally in the Tasman Sea (south of 25�S.), the concentration of water type 1 is very low (less than 10%); of water type 2 only a little higher (20-30%), but that of water type 3 is high (around 60-75%). The concentration of water type 4 was much greater (40%) off the west coast of South Island, New Zealand, than off the east coast of Tasmania (15 %). Seasonal pulses in the concentrations of water types 1 and 2 along 170�E., between 0 and 15�S., are in phase with seasonal changes in the concentration of these two water types in the Tasman and Coral Seas, if these water types spread southward at about 10 cm/sec. Summer increases in the concentration of water type 3 in the Tasman Sea off New Caledonia have been explained by the northward spreading of the previous winter's accumulation of this water type in the central Tasman Sea.

scholarly journals The distribution of Recent Radiolaria in surficial sediments of the continental margin off northern Namibia

1983 ◽  
Vol 2 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Simon Robson
Keyword(s):  
Continental Margin ◽  
High Salinity ◽  
Cold Water ◽  
Distribution Patterns ◽  
Abundant Species ◽  
High Salinity Water ◽  
Low Salinity ◽  
Apparent Correlation ◽  
Benguela Current ◽  
Salinity Water

Abstract. 47 Species of radiolaria have been identified from 30 surface sediment samples collected along transects across the continental margin of northern Namibia between the Kunene River and Walvis Bay. From the distribution patterns of the 24 most abundant species, it was possible to identify a warm water, high salinity population and a cold water, low salinity population. The distribution patterns of each population shows a close correspondence with the known positions of the Angola Current (warm, high salinity water) and the Benguela Current (cold, low salinity water) respectively. Two other trends are apparent from the overall radiolaria distribution; dilution of the nearshore samples by terrigeneous input and a strong preference for open ocean conditions. There is no apparent correlation with upwelling.

scholarly journals The Leeuwin Current south of Western Australia

1993 ◽  
Vol 44 (2) ◽  
pp. 285 ◽  
Author(s):  
GR Cresswell ◽  
JL Peterson
Keyword(s):  
Wind Stress ◽  
Western Australia ◽  
Satellite Image ◽  
Subtropical Water ◽  
Tropical Waters ◽  
Leeuwin Current ◽  
Low Salinity ◽  
Tropical Water ◽  
Autumn And Winter

Satellite images as well as data collected in situ were used to follow the seasonal changes of the Leeuwin Current south of Western Australia (WA) in 1986-87. The current has two major sources: salty subtropical water from west of WA, and fresher tropical water from north of WA. In summer, the tropical waters are excluded by the strong equatorward wind stress. In autumn and winter, this wind stress is reduced and tropical waters flood southward to dominate the flow. Nevertheless, salty subtropical water is entrained en route, and so, whatever the season, the Leeuwin Current is more saline than the 'local' subantarctic waters off southern WA. From a research vessel, observations were made on the current and one of its offshoots in June 1987. The Leeuwin Current had a maximum surface speed of more than 1 m s-1 just beyond the shelf edge. Its warm, low-salinity surface core rode on a sheath of higher-salinity subtropical water that it had entrained upstream. The first survey of the offshoot showed it to be 50 km across and 130 m deep (for water warmer than 17�C), and it extended 200 km seaward (as deduced from a satellite image). Velocities in the offshoot ranged up to 1 m s-1 southward and 1 m s-1 north-eastward on the western and eastern sides, respectively. Richardson numbers were, in places, as low as 0.25. On a second survey two days later, the offshoot was found to have pinched off and the remnant bulge on the edge of the parent stream to have moved 30 km eastward. The flow around this bulge reached 1.6 m s-'. The offshoot/bulge was possibly first formed in April, and it kept its identity at least until August. During this time, it moved eastward at speeds between 2 and 15 km day-1. In June, the offshoot was estimated to contain water equivalent to five days' transport of the parent current.

Larval ecology of the Western Australian marine crayfish, with notes upon other panulirid larvae from the eastern Indian Ocean

1969 ◽  
Vol 20 (3) ◽  
pp. 199 ◽  
Author(s):  
RG Chittleborough ◽  
LR Thomas
Keyword(s):  
High Salinity ◽  
Surface Wind ◽  
Larval Ecology ◽  
Brood Stock ◽  
Wind Drift ◽  
Vertical Movements ◽  
Low Salinity ◽  
Tropical Water ◽  
Phyllosoma Larvae ◽  
Western Australian

The Western Australian marine crayfish is now regarded as Panulirus longipes cygnus (George). Larvae could not be distinguished morphologically from those of tropical subspecies. The identity of the various stages of phyllosoma and puerulus larvae of the species has been established, and an outline is given of the seasonal occurrence and growth of larvae. The eggs of P. longipes cygnus hatch during summer, larvae being released along the coast into water of relatively high salinity (generally exceeding 35.4‰). Offshore surface wind drift during summer is proposed as the means by which the newly hatched phyllosoma larvae are transported away from the coast. It is not clear how late-stage larvae return to the coast; there is some evidence that their behaviour might change with regard to depth of occurrence and also diurnal vertical movements. The timing of the larval cycle varies from year to year; final-stage larvae probably cannot return to settle on the coast until the disappearance of the low salinity tropical water which extends down the west coast of Australia each winter. The importance of larval surveys as a means of estimating the size of the brood stock and to forecast the strength of a year class is discussed. Other species represented in the plankton of this area as phyllosoma larvae are listed, and some information given on the morphology, distribution, and dispersal of phyllosoma larvae tentatively identified as P. penicillatus.

Carbon-Isotope, Diatom, and Pollen Evidence for Late Holocene Salinity Change in a Brackish Marsh in the San Francisco Estuary

2001 ◽  
Vol 55 (1) ◽  
pp. 66-76 ◽  
Author(s):  
Roger Byrne ◽  
B. Lynn Ingram ◽  
Scott Starratt ◽  
Frances Malamud-Roam ◽  
Joshua N. Collins ◽  
...  
Keyword(s):  
San Francisco ◽  
High Salinity ◽  
Carbon Isotopic Composition ◽  
Brackish Marsh ◽  
San Francisco Estuary ◽  
Freshwater Inflow ◽  
Water Diversion ◽  
Freshwater Flow ◽  
Low Salinity ◽  
Carbon Isotopic

AbstractAnalysis of diatoms, pollen, and the carbon-isotopic composition of a sediment core from a brackish marsh in the northern part of the San Francisco Estuary has provided a paleosalinity record that covers the past 3000 yr. Changes in marsh composition and diatom frequencies are assumed to represent variations in freshwater inflow to the estuary. Three periods of relatively high salinity (low freshwater inflow) are indicated, 3000 to 2500 cal yr B.P., 1700 to 730 cal yr B.P., and ca. A.D. 1930 to the present. The most recent period of high salinity is primarily due to upstream storage and water diversion within the Sacramento–San Joaquin watershed, although drought may also have been a factor. The two earlier high-salinity periods are likely the result of reduced precipitation. Low salinity (high freshwater flow) is indicated for the period 750 cal yr B.P. to A.D. 1930.

Spatial and seasonal variability of emergent aquatic insects and nearshore spiders in a subtropical estuary

2019 ◽  
Vol 70 (4) ◽  
pp. 541 ◽  
Author(s):  
Martha J. Zapata ◽  
S. Mažeika P. Sullivan
Keyword(s):  
Aquatic Insects ◽  
High Salinity ◽  
Aquatic Insect ◽  
Freshwater Ecosystems ◽  
Dispersal Ability ◽  
Insect Community ◽  
Insect Communities ◽  
Low Salinity ◽  
Subtropical Estuary ◽  
Adult Aquatic Insects

Variability in the density and distribution of adult aquatic insects is an important factor mediating aquatic-to-terrestrial nutritional subsidies in freshwater ecosystems, yet less is understood about insect-facilitated subsidy dynamics in estuaries. We surveyed emergent (i.e. adult) aquatic insects and nearshore orb-weaving spiders of the families Tetragnathidae and Araneidae in a subtropical estuary of Florida (USA). Emergent insect community composition varied seasonally and spatially; densities were lower at high- than low-salinity sites. At high-salinity sites, emergent insects exhibited lower dispersal ability and a higher prevalence of univoltinism than low- and mid-salinity assemblages. Orb-weaving spider density most strongly tracked emergent insect density rates at low- and mid-salinity sites. Tetragnatha body condition was 96% higher at high-salinity sites than at low-salinity sites. Our findings contribute to our understanding of aquatic insect communities in estuarine ecosystems and indicate that aquatic insects may provide important nutritional subsidies to riparian consumers despite their depressed abundance and diversity compared with freshwater ecosystems.

scholarly journals The Influence of Non-Engineered Municipal Landfills on Groundwater Chemistry and Quality in Bloemfontein, South Africa

Molecules ◽  
2020 ◽  
Vol 25 (23) ◽  
pp. 5599
Author(s):  
Rinae Makhadi ◽  
Saheed A. Oke ◽  
Olusola O. Ololade
Keyword(s):  
South Africa ◽  
Water Quality ◽  
Electrical Conductivity ◽  
High Salinity ◽  
Total Coliform ◽  
Landfill Site ◽  
Water Type ◽  
Permissible Limits ◽  
Salinity Hazard ◽  
Landfill Sites

This study assessed the groundwater quality around two municipal solid waste landfill sites, in the city of Bloemfontein, Free State Province, South Africa. The two landfill sites are located in two contrasting geological terrains, with both lacking some basic facilities found in a well-designed landfill. A total of eight groundwater samples were collected from pollution monitoring boreholes near the two landfill sites, with five samples representing the northern landfill site and three samples representing the southern landfill site. The samples were collected in the autumn and winter seasons to assess any possible seasonal variations. They were analysed for physicochemical (pH, electrical conductivity (EC), total dissolve solids (TDS), chemical oxygen demand (COD) and total organic carbon (TOC)) and microbiological parameters (Escherichia coli, total coliform). The results of the analysis showed that the waters from both landfills were generally dominated by Ca, Mg, SO4, and HCO3 ions. Some of the major anions and cations in the water samples were above the South African National Standard (SANS241:2015) and World Health Organisation (WHO) permissible limits for drinking water. Majority of the boreholes had total dissolved solids and electrical conductivity values exceeding the SANS 241:2015 and WHO permissible limits. Piper trilinear plots for the two landfill sites showed that Ca(Mg)HCO3 water type predominates, but Ca(Mg)SO4 and Ca(Mg)Cl were also found. These water types were further confirmed with expanded Durov diagrams, indicating that that the boreholes represented a water type that is seldom found which is undergoing ion exchange, typical of sulphate contamination. From the SAR diagrams, boreholes in the northern landfill site had a high salinity hazard with only one borehole in the southern landfill site having a high salinity hazard. The geology was found to play a significant role in the distribution of contaminants into the groundwater systems in the study area. The study concluded that the northern landfill site had a poorer water quality in comparison to the southern landfill site based on the analysed physicochemical parameters. However, the southern landfill site showed significant microbial contamination, due to the elevated amount of E. coli and total coliform concentrations. The high permeability of the weathered dolerites in the northern landfill site might have enabled the percolation of contaminants into the groundwater resulting in the poorer water quality.

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