values show the content of fine and coarse fractions in 

 particulates, the typification will differentiate waters by their 

 contents of possible volumes of coarse and fine particles. High 

 concentration of a certain fraction will be denoted by the letter 

 "H,"" medium by "M,"" low by "L." Combinations of these will 

 be denoted by two-letter codes, of which the first letter specifies 

 volumetric content of fine particles and the second letter that of 

 coarse particles. The numerical equivalent of the letters used 

 has been given in Table 1 . 



This typification is very helpful. Comparisons of waters 

 in the areas explored by us with typical ocean waters in 

 different stages of development can be made quickly. For 

 instance, from data of the same paper, type MM is typical of 

 open ocean waters; types LM (particularly, LL and ML) are 

 typical of deep-water horizons and types MH, HM, and HH 

 only of higher productivity regions. 



Chukchi Sea 



Investigation of Spatial-Temporal Variability of 

 Transmittance Field 



Fig. I, 



Zonal dislnhution of attenuation index {£ ) average for a certain layer 

 of water. 



It would probably be most reasonable to begin analyzing 

 the hydrooptic characteristics of spatial-temporal variability 

 by considering zonal distribution transmittance in northern 

 waters. The frontispiece shows that route of expedition with 

 numbers of stations. Numeration relates to the period of joint 

 Soviet-American research. 



Water transmittance T is dependent upon the attenuation 

 index (e ) according to the relation T = e*. In the literature, data 

 is presented for the attenuation index field. In order to make it 

 possible to compare our results with the data of other researchers, 

 we shall keep to this tradition (i.e., we shall imply, when 

 speaking of "transmittance" and "transmittance field," 

 corresponding values of distribution e) . 



Figure 1 shows zonal distribution of attenuation index ( e) 

 average for a certain layer of water. When interpreting the 

 results, it is useful to bear in mind that, according to Kopelevich 

 ( 1981 ), the suspended coarse fraction contributes 40-45*7^ to 

 light attenuation in the green portion of spectruin in oligotropHic 

 and mesotrophic waters and nearly 80% in littoral waters. It 

 seems quite justifiable to apply the latter assessment to 

 productive littoral waters of high latitudes. In this case, the 

 vertical structure e ,„, will depend mainly on the distribution of 

 suspended coarse fraction, while attenuation index (average 

 for the layer) will be dependent on average content of coarse 

 fraction. 



Maximum amounts of suspended matter are contained in 

 the Chukchi Sea waters (with absolute maximum found at the 

 area of Stations 55 and 60) and a minimum in the Gulf of 



Anadyr waters (with minimum found in its southeastern 

 periphery ) ( Fig. 1 ). When assessed in this way, the Bering Sea 

 waters will be in somewhat medium position. 



This zonal distribution reflects the main qualitative 

 transfomiation that the Pacific waters undergo as they are 

 transported to the Chukchi Sea, with an increase of suspended 

 matter with increasing latitude. 



Another parameter that is closely associated with average 

 attenuation, with wide application in oceanology, is 

 transmittancy, or maximum depth at which a reference white 

 disk (Secchi disk) is still seen. Such a depth is determined as 

 follows: the disk is gradually immersed deeper and deeper into 

 water, and the depth is noted at which the disk vanishes from 

 sight and then appears in sight again when being raised. The 

 average value H,, found froin the above-mentioned values is 

 termed as Secchi transmittance of water or transmittancy. 



These measurements are important because transmittancy 

 (associated with all primary hydrooptic characteristics and 

 illumination conditions), in practice, may accurately be 

 expressed in the form of a single uniparametric relationship 

 derived from average value of attenuation ( e ) „,, index in layer 

 O-H: 



- -A . (13) 



H., 



( f> 



Proportionality factor A depends on the rest of primary 

 optic properties of water (and, hence, on ocean region) and on 

 illumination conditions. This allows with known a priori 



138 



