584 KAPLAN AND RITTENBERG [CHAP. 23 



Four major types of basins can be defined on the basis of water circulation. 

 In submerged basins of the type found in southern Cahfornia and the East 

 Indies, the water and circulation characteristics are largely determined by sill 

 depth. In more protected basins, such as Kaoe Bay (Kuenen, 1943), Cariaco 

 Trench (Richards and Vaccaro, 1956), Norwegian (Strom, 1939) and New 

 Zealand fjords (Skerman, in lift.), Baffin Bay (Smith, Soule and Mosby, 1937) or 

 inland seas such as the Black Sea (Arkhangel'sky and Strakhov, 1938) and 

 Lake Maracaibo (Redfield, 1958), climatic conditions play the major role. 



An arid climate such as in the Mediterranean and Red Sea areas causes 

 evaporation and thus a sinking of heavy warm surface water and considerable 

 vertical mixing. A humid area like the Norwegian fjord region supplies a large 

 amount of low-density water which tends to overlay the heavier sea-water and 

 prevent vertical mixing across the halocline, thus aiding stagnation. The basins 

 close to the equator may belong to either type since both dry and wet seasons 

 exist. Run-off and evaporation being equal, it appears that basins in higher 

 latitudes are less prone to become stagnant than those in tropical waters 

 (Strom, 1939) because of overturn due to marked temperature differences in the 

 summer and winter. Where climatic conditions allow formation of sea-ice a 

 fourth basin type exists, for example Baffin Bay. The freezing process produces 

 a cold brine denser than the surface water that sinks and renews the basin water. 



Other forces influence water movement. Kuenen (1948) working on the 

 Moluccan deep-sea basins, and Redfield (1958) from studies on Lake Maracaibo 

 find evidence that both centrifugal and Coriolis forces have a dictatorial effect 

 on water movement despite their small magnitude relative to other areas of the 

 ocean. The centrifugal force may cause the accumulation of denser more saline 

 water in the center of a basin with a flat bottom. 



Little attention has been paid to the rate of renewal of water in basins. 

 Kuenen (1943) concluded that 200-300 years were required to renew the water 

 in the Moluccan basins, deriving his estimate from the horizontal velocities of the 

 currents. Calculations based on rate of oxidation of organic matter and on heat 

 flow from surface insolation gave a value of 111-160 years for the Cariaco 

 Trench (Richards and Vaccaro, 1956). Studies on regeneration in the sediments 

 and distribution of nutrients and oxygen in the water indicated that 2-20 

 years were required for water renewal in the basins off southern California 

 (Rittenberg, Emery and Orr, 1955). Emery (1956) has since shown that deep 

 standing internal waves having amplitudes of 130-200 m and causing bottom 

 currents of 18 cm/sec are perhaps the principal cause of vertical turbulent 

 mixing in these basins and are responsible for the rapid replacement of water. 

 It is quite probable, therefore, that shorter times than were previously thought 

 necessary are involved in water renewal. 



B. Nutrient Distribution in Basin Water 



The distribution of nutrients in basin waters depends mainly on sill depth 

 and circulation type. Where the sill is within the euphotic zone, j)hotosynthesis 

 removes nutrients from the upper layer which are in part released below this 



