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

Abstract

The seasonal occurrences of three water types on the 27.20 and 26.80 σ_t, surfaces on a section east of Port Hacking, 153-160º E., and at certain stations north of this line are discussed.

On the 27.20 σ_t, surface it is shown that the Pacific Equatorial Intermediate is found in maximum intensity during September-October at longitude 158-160º E. Subsequently it moves west and during April-June it occurs at longitude 153-157º E.

The South-West Pacific Intermediate appears at maximum intensity during March-July at 158-160º E. but in September-February it moves west to longitude 152-154º 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 (152-154º E.) during March-April.

On the 26.80 σ_t, 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.