Chapter 5. SPATIALLY-COHERENT STRUCTURES
Assuming that in the example shown in Figure 5-20, 0
h = 12 m, H = 71
m, 'U 0.54 kg m
-3 , 0
U 1024 kg m
-3 , and
1.2
Fr
the speed of the
gravity current due to the observed density anomaly within the mixed layer
is estimated as b
U | 0.30 m s
-1 . This is in fact a lower estimate, since the
effective thickness of the near-surface density anomaly layer driving the
gravity current is larger than 12 m. The effective thickness calculated as
0
h
1
0
( (0)
( ))
( )
( )
h
h
z
h d z
U
U
U
U
|
³
27 m results in b
U =0.44 m s
-1 ,
which is an upper estimate. (However, both estimates do not account for the
opposing wind stress.)
317
Figure 5-20. Vertical distribution of potential density (V 4 ) relative to the top of the thermocline
(bottom of nearly isothermal layer) and the impact of salinity (S) and potential temperature (4)
on stratification within the upper ocean from the CTD station indicated in Figure 5-19. Here, T
D
and S
E are the respective thermal expansion and salinity contraction coefficients; ' is the
difference operator (with respect to the bottom of the nearly isothermal layer). The depth of the
nearly isothermal layer, H = 71 m, is determined from criteria (1)
( )
T
T H
0.5
o C. Reproduced
from Soloviev et al. (2002) by permission from Elsevier.