492 Tides of the Oceans 



the diurnal tides. Comparing Chart II with Chart I there is quite a simplification 

 characterized by the smaller number of amphidromies. 



In the Atlantic Ocean there are two large amphidromies. One covering 

 the entire Northern Atlantic Ocean has its centre at approximately 30° N. lat., 

 and is symmetrical towards all sides, whereas the second one covers the 

 Southern Atlantic Ocean and seems to have a definite crowding of the co- 

 tidal lines in its western part. The distribution of the amplitudes of the K x 

 tide is very uniform in the entire Atlantic Ocean, except that in the extensive 

 shelves and in large bays it remains mostly below 10 cm. 



In the Indian Ocean we find an amphidromy in the form of two bundles 

 of crowded co-tidal lines, supported by the constants on the coast and Islands. 

 It's centre is located east of the Chagos Archipelago. The distribution of 

 the amplitudes support well the drawing of the co-tidal lines with a minimum 

 of 5-10 cm along a line extending from north-west Sumatra to southern 

 Ceylon, the Chagos Archipelago, the Mascarenes, and to South Madagascar. 

 In the antinode in the north-western part the tidal ranges exceed 20 cm on 

 the Seychelles and Laccedives, and more than 40 cm on the south coast 

 of Arabia. 



According to Dietrich there seems to be a small amphidromy rotating 

 to the right at the southern opening of the Mozambique channel. 



In the Pacific there are, similar to the Atlantic, two distinct regions with 

 regard to the distribution of the phase which lie opposite one another. In the 

 east the coasts of Peru and northern Chile have a minimum of about 30°; 

 from there on the phase increases to the north and to the south. In the west 

 there is a maximum with approximately 90° in the region of the Philippines 

 and Formosa and from this point the values decrease rapidly to the north 

 and to the south. Judging by the values in between, both regions lie on 

 a wide anti-node which extends across the entire Pacific Ocean. The values 

 north and north-west of this zone can be grouped into a large, unsymmetrical 

 amphidromy; its centre seems to be located between the South Sea Islands 

 in the south, the Hawaian Islands in the north and the Marshall Islands 

 in the west. According to the K x phases its location is probably south of 

 Fanning Island. 



In the Southern Pacific Ocean we have the remarkable case of an island 

 appearing as the centre of an amphidromy. All constants on New Zealand 

 point a complete rotation of 360° to the right around both islands, and at 

 the same time the K x amplitude decreases to below 3 cm. The observations 

 on distant islands and on the coast of Australia do support this amphidromy. 



The amplitudes of the K x wave are relatively small in the Pacific Region, 

 but they exceed 10 cm, at the coasts of this ocean (except in a small strip 

 along Equador). Around the Antarctic these amplitudes reach 30 cm and 

 more, while in the Gulf of Alaska they amount to 40 cm and above. In 

 general the diurnal tide in the Pacific, as well as in the Indian Ocean, is greater 



