REPORT ON OCEANOGRAPHY 27 



BRITISH CONTRIBUTION TO THE OCEANOGRAPHY 

 OF THE PACIFIC OCEAN 



By G. E. R. Deacon 



The Royal Research Ship 'Discoverey II' worked two Hnes of sta- 

 tions across the East AustraHan Current in October, 1950, and another 

 line across the Tasman Sea to Wellington in the same month. In No- 

 vember she cruised southeast across the southern end of the Kermadec 

 Trench to the Chatham Island plateau and into deep water as far as 

 45°S 150°N. Observations were then made as far as the northern edge 

 of the pack-ice in 60° 46'S, before she turned westward along the ice- 

 edge to 63 °S 175°E and northward back to New Zealand. After more 

 observations between New Zealand, Macquarie Island and the ice-edge, 

 and several lines of stations in the southern Indian Ocean and south of 

 Australia, another line was worked across the southern part of the Tas- 

 man Sea. This was followed by observations across the South Pacific 

 Ocean, touching the ice-edge in 66°S 141°E and 64° S 78° W. 



The observations in the southwest Pacific Ocean give some support 

 to an earlier indication that the deep water east of New Zealand is 

 slightly more saline than the deep and bottom water south of the Tas- 

 man Sea, and revive the question of a possible weak source of highly sa- 

 line deep water north of New Zealand. It is particularly difficult to 

 draw conclusions about possible deep-water movements in this region 

 from the distribution of temperature and salinity because the salinity 

 differences below 2000 metres are very small. The same is true in the 

 deep water southwest of Cape Horn, where the data give a possible in- 

 dication that the eastward circumpolar drift may be offset to a small ex- 

 tent by a movement of deep water from the Atlantic Ocean. 



The similarities between the deep and bottom waters of the Tasman 

 Sea and those of the Southern Ocean indicate that there is no effective 

 barrier between them. Echo soundings between the New Zealand shelf 

 and Macquarie Island show a very rugged bottom at moderately great 

 depths, but give no evidence of a connecting ridge such as is drawn ten- 

 tatively on some maps. 



Vertical and oblique hauls were made down to 1500 metres at the 

 same time as the physical and chemical measurements, and records made 

 of the sighting of whales and birds. The primary object of the work 

 was to fill in the gaps of the oceanographic survey of the Southern Ocean 

 made by the Discovery Committee before the last war. The data are 

 being prepared for publication. 



H.M.S. 'Challenger', one of Her Majesty's surveying vessels, made 

 an extended cruise across the Pacific Ocean in 1950-51, taking echo 



