H. Mercier et al., AN INVERSE MODEL OF THE NORTH-ATLANTIC GENERAL-CIRCULATION USING LAGRANGIAN FLOAT DATA, Journal of physical oceanography, 23(4), 1993, pp. 689-715
A nonlinear finite-difference inverse model is used for estimating the
North Atlantic general circulation between 20-degrees and 50-degrees-
N. The inverse model with grid spacing 2-degrees latitude and 2.5-degr
ees longitude is based on hydrography and is in geostrophic and hydros
tatic balances. The constraints of the inverse model are surface and s
ubsurface float mean velocities; Ekman pumping derived from wind data;
conservations of mass, heat, and salt; and the planetary vorticity eq
uation at the reference level. The mass, heat, and salt conservations
are applied in a vertically integrated form. The model does not have e
xplicit mixing or air-sea flux terms. Vertical velocities result from
the nondivergence of the 3D velocity field. After inversion, float vel
ocities, hydrographic data, and dynamical constraints are generally co
mpatible within error bounds. A few float velocities are, however, rej
ected by the model mainly due to inadequate time or space sampling of
the 2-degrees latitude by 5-degrees longitude boxes for which mean flo
at velocities are computed. The resulting circulation shows a maximum
Gulf Stream transport close to 130 X 10(6) m3 s-1 at 64-degrees-W. Res
iduals of the vertically integrated heat and salt conservation constra
ints may be interpreted as air-sea fluxes and are of the right order o
f magnitude as compared to in situ measurements. The float database us
ed is already important particularly at the surface. However, its addi
tion to the inversion does not change substantially the estimation by
the model of integrated quantities, such as Gulf Stream transports, as
compared to an inversion using hydrography and dynamical constraints
alone. But floats significantly affect the estimation of the deep circ
ulation increasing, for instance, the estimated velocity amplitude for
the deep western boundary current flowing westward south of the Grand
Banks.