Influence of the Current Field
Non-stationarity and the
Non-simultaneity of Hydrographic
Measurements on ADCP-based
Transport Estimates
R. Yu. Tarakanov
Introduction
The horizontal absolute geostrophic velocities in the entire water column are
determined by the following equations:
uðzÞ = −
g
f
dζ
dy
+
g
f ρ 0
Z 0
z
dρðzÞ
dy
dz,
ð1aÞ
vðzÞ =
g
f
dζ
dx
−
g
f ρ 0
Z 0
z
dρðzÞ
dx
dz;
ð1bÞ
here u, v are the zonal and meridional components of the current velocity, ζ is the
elevation of the ocean surface relative to the geopotential surface, ρ is the density
in situ, ρ 0 is the mean density of the ocean, g is the acceleration due to gravity, f is
the Coriolis parameter, the z-axis is directed upwards. The first term in (1a, 1b) is
the absolute geostrophic current velocity at the ocean surface. Hereinafter, we shall
consider this variable as the barotropic component of the absolute geostrophic
current. The second term in (1a, 1b) is depth-dependent (baroclinic) geostrophic
velocity profile with zero value at the ocean surface. The dependence of this profile
on the horizontal density gradient determines the simplicity of calculating the
baroclinic current component from the data of temperature, salinity (conductivity)
and pressure, and consequently water density at the stations of transoceanic
hydrographic sections or surveys. The barotropic components of the geostrophic
R. Yu.Tarakanov ( ✉ )
Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia
e-mail: rtarakanov@gmail.com
© Springer International Publishing AG, part of Springer Nature 2018
M. G. Velarde et al. (eds.), The Ocean in Motion, Springer Oceanography,
https://doi.org/10.1007/978-3-319-71934-4_23
361