12-- 



T III 



34.4 



-) 1 1 (- 



1967 



28-- 



24-. 



20- 



16 ■■ 



12-- 



C 0, 



J , /oc 



1969 



34.8 



-i 1 1 1 1- 



34.4 



34.8 



H 1 1 1 1- 



1970 



.-'".K7 



34.4 



348 



-I 1 1 1 1 1 I 



344 34.8 



28- 



24.. 



20- 



16- 



12-- 



28- ■ 



24- 



20 ■■ 



16-- 



12- 



1968 



H 1 1— —I 1- 



34.4 



34.8 



1971 



-1 1 1 1 1- 



34 4 



34.8 



Figure 13.— Monthly mean surface temperature-salinity relationships at Ocean Weather Station V, 1966-71, connected by dashed lines. Arabic 

 numerals represent months. Solid line connects 6-yr mean values. Roman numerals on the 1966 plot give months for the mean values. 



well-developed cells as in June to August 1968, August 

 1969, and November 1971. 



The baroclinicity of the area is reflected by the depth 

 of cr, levels. Time variability penetrates to the a, level. 

 The depth of a, 26, the level below the seasonal 

 temperature and salinity variability, ranges from about 

 200 to 400 m. These depth changes are not seasonal but 

 show longer term variations. For example, during much 

 of 1966 a, 26 was deeper than 300 m; during 1970 it 

 remained near 200 m. Superimposed on these variations 

 are perturbations of several months duration as in July 

 to September 1969. Amplitudes of the harmonic series, 

 C„ = (Ai + B;)"- , of the depth of the ff, 26 level for the 

 entire 6-yr record (Fig. 15) show that the greatest por- 

 tion of the variance, C„ >30 m; occurs on the interan- 

 nual time scale. Beyond the 39th harmonic (56 day 

 period) the absolute magnitudes of the amplitudes re- 

 main <10 m. Thus, changes in the depth of the pycno- 

 cline, as reflected by the a, 26 level, are climate-scale 

 phenomena. 



In terms of the oceanographic setting of OWS-V, the 

 depth variations reflect north-south shifts of the 

 Kuroshio Extension and/or passage of baroclinic eddies. 

 The salinity variability above the a, 26 level permits 

 qualitative interpretation of the observed depth 

 changes. Whenever the depth of a, 26 increases to >300 

 m (see dashed lines in salinity sections. Fig. 14) there is 

 a concurrent increase in the salinity of the shallow max- 

 imum, and during the winter, an increase in the surface 

 salinity. Increases in depths began in February and June 

 1966, May 1968, April and July 1969, March and 

 November 1971. A shallow salinity maximum is charac- 

 teristic of Kuroshio water (Fig. 12). Thus, the coinci- 

 dent increases in salinity in the shallow maximum, or at 

 the surface during the winter with increasing depths of 

 a, 26 indicate a northward meander of the Kuroshio Ex- 

 tension. 



In 1970, when a, 26 shoaled to <300 m, the salinity in 

 the shallow maximum during spring, summer, and fall 

 was relatively high in contrast to that in 1967 when the 



17 



