THE PACIFIC OCEAN 



113 



the surface and 100 meters to 0.8 - 3 cm/sec at 700 me- 

 ters. 



The westerly current in the Gulf of Alaska has a ve- 

 locity of 7 cm/sec at the surface, but at 400 meters it 

 has practically disappeared. The southerly current along 

 the coast of California shows a velocity of 17 cm/sec at 

 the surface. This velocity also decreases downward, but 

 below 400 meters the decrease appears to be very small 

 because at the levels 400 and 700 meters the computed 

 velocities are 4.3 and 4.2 cm/sec respectively. 



The numerical values which are shown in the figures 

 and briefly treated here give, no doubt, a fairly correct 

 idea of the intensity of the circulation in the Pacific, 

 especially in the North Pacific, down to a depth of 700 

 meters, but the picture will probably be much modified 

 in details when more observations become available. 



Flow of the Deep Water 



Since high temperatures are found in the equatorial 

 regions, it is probable that a slow descending motion 

 takes place here and that the circulation is to some ex- 

 tent, therefore, as suggested by Wtist (1930). The de- 

 scending water, however, cannot contribute directly to 

 the formation of the typical deep water because of its 

 high temperature and low salinity, but must spread to the 

 north and the south above the deep water. 



In the North Pacific the bottom water and the deep 

 water must come from the south because it cannot be 

 formed anywhere in the area of the North Pacific. The 

 inflow probably takes place near the bottom because 

 there the highest oxygen values are found. The low tem- 

 peratures in the northern part of the North Pacific at the 

 levels below 2000 meters suggest an ascending motion of 

 the deep water in this region. If this is correct, we must 

 assume that the deep water returns to the south at a 



level between 2000 and 1000 meters, and on this journey 

 it is being mixed with water from the intermediate cur- 

 rent. 



The deep water of the South Pacific must also come 

 from the south and the greater part probably enters the 

 Pacific to the south of New Zealand. Part of the deep 

 water flowing into the South Pacific continues to the 

 North Pacific, but another part probably ascends when 

 approaching the equator and returns to the south at 

 levels above 2000 meters. The distribution of oxygen 

 leads to this suggestion. 



It has already been indicated that at levels above 

 2000 to 1000 meters the water of the North Pacific prob- 

 ably moves to the south and thus flows into the South 

 Pacific. At levels below 1000 meters the oxygen con- 

 tent, however, is much higher in the South Pacific than 

 in the North Pacific, and this could not be the case if 

 the water at these levels came from the North Pacific 

 only. Therefore, in the South Pacific the return current 

 above 2000 meters must carry water which mainly has 

 been circulating in the South Pacific only, and with 

 which some water from the North Pacific has been 

 mixed. 



It must be emphasized, however, that at any level the 

 flow in an east-west direction is considerably stronger 

 than the flow in a north-south direction. Because of 

 this circumstance and of the obvious differences in the 

 currents of the eastern and western parts of the ocean, 

 no attempt has been made to give a schematic represen- 

 tation of the meridianal circulation in the Pacific Ocean. 

 Such a representation would contain too many hypotheti- 

 cal elements, because at present it is not possible to 

 arrive at any definite conclusions as to the flow of the 

 deep water. Some possibilities have been suggested but 

 these and others cannot be examined more closely be- 

 fore a greater number of observations are at hand. 



