Publication Date:
2022-05-25
Description:
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September, 1976
Description:
The temporal and spatial variability of low frequency
moored temperature and velocity observations, obtained as
part of the Mid-Ocean Dynamics Experiment (MODE), are
analyzed to study the kinematics and energetics of mesoscale
eddies in the ocean.
The temporal variability of the low frequency motions
is characterized by three regimes: very low frequencies
with periods greater than 200 days, an eddy energy containing
band of 80 to 120 day periods, and high frequencies
wìth periods less than 30 days. At very low frequencies,
the zonal kinetic energy exceeds the meridional at all
depths. In the thermocline, the very low frequency zonal
flow dominates the total kinetic energy. The greatest
contribution to the kinetic and potential energy in the
MODE region, except for the thermocline zonal flow, is
from an eddy energy containing band of 80 to 120 day
periods. Eddy scale kinetic energy spatial variations
are confined to this band. At high frequencies, the
kinetic and potential energy scale with frequency as ω-2.5
and with depth in the WKB sense. Energy at high frequencies
is partitioned evenly between zonal kinetic, meridional
kinetic and potential energy and is homogeneous over 100
km.
Using the technique of empirical orthogonal expansion,
the vertical structure of the energetically dominant eddies
is described by a few modes. The displacement is dominated
by a mode with a thermocline maximum and in phase displacements
with depth, while the kinetic energy is dominated by
an equivalent barotropic mode. A smaller portion of the
kinetic and potential energy is associated with out of
phase thermocline and deep water currents and displacements.
The dynamics of the mesoscale eddies are very nonlinear.
Using the vertical veering of the current at
MODE Center, the estimated horizontal advection of heat
contributes significantly to the low frequency thermal
balance. The observed very low frequency anisotropic
flow is consistent with the nonlinear eddy spindown
models, dominated by cascades of vorticity and energy.
At high frequencies, the spectral similarity is consistent
with advected geostrophic turbulence.
Description:
The National Science Foundation
supported the work through grants GX29034 and IDO-75-03998 and a graduate fellowship.
Keywords:
Ocean currents
;
Ocean circulation
;
Ocean temperature
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
7112504 bytes
Format:
application/pdf
Permalink
