Some dilution effects are observable from the Olenek and Yana 

 Rivers, but, generally speaking, station coverage was not adequate 

 to develop the fluvial plume from either river. No attempt is made 

 here to distinguish between effects of the Olenek River and the combined 

 Khatanga and Anabar Rivers . 



In addition to the oceanographic features noted, dissolved oxygen 

 measurements indicated frequent oxygen supersaturation in both types 

 of water discussed. 



a. The Lena River Fluvial Plume . Definition of the Lena 

 River plume using isotherms and isohalines is somewhat subjective, 

 depending upon temperature and salinity values chosen. Surface temperatures 

 in the plume ranged from S.TS'C near the river delta to -l.OO'C where 

 definition became poor. Similarly, surface salinities ranged from 

 2.56%o near the river mouth to over 20'yn(, where the plume was less 

 clearly defined. The 0° and -O.S'C isotherms and the 15 and 20'^no Isohalines 

 have been used here to overcome some of the subjectivity inherent 

 in using a single temperature and salinity value for plume description. 



(1) Temperature Distribution . Observed temperatures 

 indicate a roughly wedge-shaped distribution of Lena River water 

 in the Laptev Sea during the 1963 survey. Both the 0° and -0.5'C 

 isotherms suggest a northerly distribution of considerable areal 

 extent at the surface and 5 meters, but the isotherms at 10 meters 

 suggest a more localized, easterly distribution. 



Figure 9 illustrates the relative locations of the CC 

 isotherm at the surface, 5 meters, and 10 meters. The -O.S^C isotherm 

 is shown for comparative purposes. 



The surface 0°C isotherm encloses two regions of relatively 

 high temperature water. The larger region, probably attributable 

 primarily to the Lena River, occurred north and east of the Lena 

 River Delta and in Borkhaya Bay. The smaller, probably a result 

 of Olenek River outflow, occurred west of 123**E and north of the 

 Olenek River mouth. 



The same general regions of lesser areal extent and slightly 

 lower temperatures are defined at 5 meters as sho\<m in figure 9. 

 At a depth of 10 meters, the O'C isotherm defines a small region 

 east of the Lena River Delta, the northern portion of Borkhaya Bay, 

 and Yanski Bay. Below 10 meters this isotherm does not serve to 

 describe the Lena River plume. 



Surface and 5-meter definition, using the -0.5''C isotherm, 

 approximates that obtained using the O'C isotherm. At 10 meters, 

 however, the -0.5°C isotherm describes a considerably larger region 



13 



