Mixing Trajectories of Intermediate Depth Waters of the South-East Indian Ocean as Determined by a Salinity Frequency Method

1963 ◽  
Vol 14 (1) ◽  
pp. 1 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Indian Ocean ◽  
Water Masses ◽  
Intermediate Water ◽  
The South ◽  
Intermediate Depth ◽  
East Indian ◽  
The Core ◽  
Deep Mixing ◽  
Core Method ◽  
East Indian Ocean

A new method for the detection of water masses and for the tracing of their mixing paths is described. Histograms of the salinity frequency distribution on 0.10 σt intervals from σt 26.90 to 27.70 contain modes which indicate the salinity characteristics of the intermediate water masses of the south-east Indian Ocean. These salinity characteristics are used to trace the extent of spreading of the water masses on these σt intervals and to determine trajectories of shallow and deep mixing. Comparison is made of the results obtained by the new method with those by the core method for the water masses and circulation in intermediate depth of the south-east Indian Ocean. The core method in this region has not been able to show the large extent of deep mixing associated with the spreading of the Banda and Antarctic Intermediate water masses. The core method has also failed to show the widespread distribution of patches of Banda water at about 400-500 m throughout the whole south-east Indian Ocean.

Hydrology of the Indian Ocean. I. The Water Masses in Intermediate Depths of the South-East Indian Ocean

1961 ◽  
Vol 12 (2) ◽  
pp. 129 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Indian Ocean ◽  
West Indian ◽  
Water Masses ◽  
The South ◽  
North West ◽  
East Indian ◽  
The North ◽  
The Indian Ocean ◽  
The Antarctic ◽  
East Indian Ocean

Three water masses have been identified from maxima and minima in temperature-salinity diagrams for intermediate depths of the south-east Indian Ocean. (1) The Antarctic Intermediate occurred as a salinity minimum within the density range of 7.00-27.28 σt. (2) The North-West Indian Intermediate was found as a salinity maximum within the σt range 27.20-27.50. (3) The Banda Intermediate, lying below the North-West Indian Intermediate, had the characteristic of a salinity minimum within the σt range of 27.28-27.59. Preformed phosphate has been found useful as a third conservative property for the identification of major paths of spreading. The distribution and paths of spreading of the three water masses are shown in charts of the Indian Ocean east of 90�E.

Seasonal variations in the Indian Ocean along 110°E. I. Hydrological structure of the upper 500 m

1969 ◽  
Vol 20 (1) ◽  
pp. 1 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Indian Ocean ◽  
Surface Waters ◽  
Water Masses ◽  
Surface Currents ◽  
Temperature Changes ◽  
East Indian ◽  
Hydrological Structure ◽  
The Indian Ocean ◽  
The Tropics ◽  
East Indian Ocean

Tropical and subtropical water masses at surface and subsurface depths were separated by their salinity, temperature, oxygen, and nutrient characteristics. The annual mean depths and latitudinal extent of these water masses were determined. Annual changes in the upper 50 m were generally so small relative to those found in other oceans that advection and mixing must have been less important in their genesis than local climatic changes. There was a barely significant seasonal rhythm in surface phosphate and nitrate, with peak occurrences of each some 6 months apart. At each latitude the permanent thermal discontinuity centred around a particular isotherm varied little in intensity during the year, but rose and fell in accordance with surface currents. The thermocline south of c. 18�S. varied little in depth but greatly in intensity during the summer. The depth of the mixed layer was much less in summer and at all times shallower in the tropics. The depth of this layer was governed more by the accumulation of surface waters by zonal currents and eddies, than by wind stress or convective overturn. Therefore there was little difference from south to north, or month to month, in average nutrient values of this mixed column. The movement of the various surface waters, deduced from salinity and temperature changes during the year, usually agrees with geostrophic currents across 110�E, and ships' observations of surface currents in the south-east Indian Ocean.

Hydrology of the Indian Ocean. III. Water masses of the upper 500 metres of the South-east Indian Ocean

1964 ◽  
Vol 15 (1) ◽  
pp. 25 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Indian Ocean ◽  
Persian Gulf ◽  
Water Mass ◽  
Sea Water ◽  
Core Layer ◽  
Water Masses ◽  
Intermediate Water ◽  
Surface Currents ◽  
North West ◽  
East Indian

The following seven water masses have been identified, and their distribution traced during several seasons of the year: Red Sea mass, with the same distribution and properties in 1962 as the north-west Indian Intermediate described in 1959-60; Persian Gulf mass, which is confined to the region south of Indonesia and is limited in extent of easterly flow by the opposing flow of Banda Intermediate water; upper salinity minimum mass, entering via Lombok Strait and moving zonally in the direction of the prevailing surface currents, a secondary movement of this water mass towards north-west Australia is limited by the northern boundary of a south-east Indian high salinity water mass. This latter water mass occurs as three separate core layers north of 22-23� S. The deep core layer mixes with waters of the oxygen maximum below it, the mid-depth core layer mixes with Persian Gulf and upper salinity minimum water masses, and the upper core layer mixes with the Arabian Sea water mass. The latter water mass spreads eastwards to about 120� E. and southwards to north-west Australia, in conformity with surface currents. A sixth water mass enters with the counter-current and is found as a salinity maximum within the thermocline to about 20� S. A seventh water mass characterized by a salinity maximum around temperatures of 28-29�C has a limited distribution and an unknown origin. Both of these water masses move in the direction of surface currents.

scholarly journals Atmospheric microplastic over the South China Sea and East Indian Ocean: abundance, distribution and source

2020 ◽  
Vol 389 ◽  
pp. 121846 ◽  
Author(s):  
Xiaohui Wang ◽  
Changjun Li ◽  
Kai Liu ◽  
Lixin Zhu ◽  
Zhangyu Song ◽  
...  
Keyword(s):  
Indian Ocean ◽  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
Abundance Distribution ◽  
The South ◽  
China Sea ◽  
East Indian ◽  
East Indian Ocean

The bathythermograph as a tool in gathering synoptic thermohaline data

1976 ◽  
Vol 27 (3) ◽  
pp. 405 ◽  
Author(s):  
JC Andrews
Keyword(s):  
Indian Ocean ◽  
Historical Data ◽  
Density Field ◽  
Depth Interval ◽  
The South ◽  
Density Data ◽  
East Indian ◽  
The Mean ◽  
Oceanographic Data ◽  
East Indian Ocean

A method for converting synoptic bathythermal data to density data by inferring salinity is discussed. In the depth interval covered by the bathythermograph, the salinity is obtained from mean temperature -salinity curves; these may be calculated either from historical data or from reference hydrographic stations occupied during relevant cruises. Further, on the basis of analysis of oceanographic data previously gathered in an area, the regression of the mean density field at depths below those covered by a bathythermograph on functions based on data from the bathythermograph may be obtained. These methods are exemplified for the south-east Indian Ocean but should be generally applicable in other mid-latitude regions. The aim of this paper is to provide a means for obtaining synoptic data from rapid physical oceanographic surveys.

Hydrology of the Indian Ocean. II. The Surface Waters of the South-East Indian Ocean and Arafura Sea in the Spring and Summer

1962 ◽  
Vol 13 (3) ◽  
pp. 226 ◽  
Author(s):  
DJ Rochford
Keyword(s):  
Indian Ocean ◽  
High Salinity ◽  
Transitional Zone ◽  
The South ◽  
East Indian ◽  
Upwelled Water ◽  
P Content ◽  
Arafura Sea ◽  
East Indian Ocean ◽  
High Phosphate

The hydrological properties of five major surface zones in the south-east Indian Ocean are discussed. These are the Subantarctic, the Subtropical, the Tropical, and two transition zones separating them. Two regions of upwelled water are described. The Subantarctic Zone lies south of the 35.00‰ isohaline and has an inorganic phosphate P content hetween 0.30 and 0.60 μg-atom/l. The Subtropical Zone lies between the 35.80‰ isohaline in the south and the 35.50‰ isohaline in the north and has an inorganic phosphate P content between 0.10 and 0.15 μg-atom/l. For this zone waters with salinity greater than 36.00‰ in the south-east Indian Ocean and greater than 36.30‰ in the Great Australian Bight constitute the major source regions of high salinity water. Both of these, but particularly the latter, are very low in phosphate. The Tropical Zone lies between the south equatorial salinity minimum (34.26‰) and the Monsoon Current (salinity 34.10‰), at about 2°N. Four hydrological regions have been distinguished in this zone. From north to south these are (1) the Monsoon Current with low salinity (34.10‰), high temperature (28.9°C), and low phosphate P (0.12 μg-atom/l.); (2) the Equatorial Counter-Current with moderately high salinity (34.50‰), high temperature (28.7°C), and high phosphate (0.21 μg-atom/l.); (3) the South Equatorial Divergence with moderately high salinity (34.48-34.55‰), moderate temperature (26-27.5°C), and high phosphate (0.20-0.30 °g-atom/l.); (4) the South Equatorial Current with waters at its core of salinity 34.26-34.31‰, temperature 26-27°C, and phosphate 0.20-0.25 μg-atom/l. In the transitional zone between the Subantarctic and the Subtropical Zones salinity changes rapidly with latitude. The centre of the zone is marked by the position of the 35.40‰ isohaline. The centre of the transitional zone between the Subtropical and the Tropical Zones is marked by the position of the 34.90‰ isohaline. Two regions of upwelled water were found: (1) along the shelf and elope regions of north-west Australia south of Timor, distinguished by high phosphate P (0.20-0.30 μg-atom/l.) and a maximum upwelling occurring before September; (2) along the shelf and slope region of the eastern Arafura Sea, from the Aroe Islands to the Gulf of Carpentaria,, where the highest surface phosphate values in oceanic waters of Australia were found (0.66 μg-atom/l.), and a maximum upwelling probably occurring before August.

The concentration of chlorophylls a and c in the south-east Indian Ocean

1966 ◽  
Vol 17 (2) ◽  
pp. 135 ◽  
Author(s):  
GF Humphrey
Keyword(s):  
Indian Ocean ◽  
Water Column ◽  
Chlorophyll A ◽  
The South ◽  
Average Amount ◽  
East Indian ◽  
Similar Work ◽  
East Indian Ocean

Samples were collected in 1959-62, usually at 0, 25, 50, 75, 100, and 150 m, in the region between 90 and 140� E., and 10� N. and 50�S. At 0 m (and 150 m) the regional average for chlorophyll a was 0.08 (and 0.09) �p/l in summer and 0.12 (and 0.09) �p/l in winter; for chlorophyll c the values were 0.17 (and 0.21) �p/l in summer and 0.21 (and 0.21) �p/l in winter. Most samples had chlorophyll c/a ratios between 1 and 2. The average amount of chlorophyll a in the water column to 150 m was 15 mg/m² in summer and 23 in winter; for chlorophyll c the values were 29 mg/m² in both summer and winter. At most stations the maximum amounts of chlorophyll were at 75 m, often near density and temperature discontinuities. At 75 m the regional average for chlorophyll a was 0.14 �pll in summer and 0.19 in winter; for chlorophyll c the values were 0.35 and 0.24. The results of the present and similar work show that the amounts of the chlorophylls in the water column under 1 m² are similar for all oceans.

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