The vertical propagation of inertial waves in the ocean
Citable URI
https://hdl.handle.net/1912/1353Location
Atlantic OceanBermuda
DOI
10.1575/1912/1353Keyword
Ocean currents; Internal waves; MeasurementAbstract
A set of vertical profiles of horizontal ocean currents, obtained
by electro-magnetic profilers in the Atlantic Ocean southwest
of Bermuda in the spring of 1973, has been analyzed in order to study
the vertical structure and temporal behavior of internal waves, particularly
those with periods near the local inertial period. An important
feature of the observed structure is the polarization of horizontal
velocity components in the vertical. This polarization, along
with temporal changes of the vertical wave structure seen in a time
series of profiles made at one location, has been related to the direction
of vertical energy flux due to the observed waves. Whereas
the observed vertical phase propagation can be affected by horizontal
advection of waves past the point of observation, the use of wave polarization
to infer the direction of vertical energy propagation has
the advantage that it is not influenced by horizontal advection. The
result shows that at a location where profiles were obtained over
smooth topography, the net energy flux was downward, indicating that
the energy sources for these waves were located at or near the sea
surface. An estimate of the net, downward energy flux (~ .2 - .3
erg/cm2/sec) has been obtained. Calculations have been made which
show that a frictional bottom boundary layer can be an important energy
sink for near-inertial waves. A rough estimate suggests that
the observed, net, downward energy flux coul d be accounted for by
energy losses in this frictional boundary layer. A reflection
coefficient for the observed waves as they reflect off the bottom
has been estimated.
In contrast, some profiles made over a region of rough topography
indicate that the rough bottom may also be acting to generate
near-inertial waves which propagate energy upward.
Ca1culations of vertical flux of horizontal kinetic energy,
using an empirical form for the energy spectrum of internal waves,
show that this vertical flux reaches a maximum for frequencies 10% -
20% greater than the local inertial frequency. Comparison with profiler
velocity data and frequency spectra supports the conclusion
that the dominant waves had frequencies 10% - 20% greater than the
inertial frequency. The fact that the waves were propagating energy
in the vertical is proposed as the reason for the observed frequency
shift.
Finally, energy spectra in vertical wave number have been
calculated from the profiles in order to compare the data with an
empirical model of the energy density spectrum for internal waves
proposed by C. Garrett and W. Munk (1975). The result shows that
although the general shape and magnitude of the observed spectrum
compares well with the empirica1 model, the two-sided spectrum is
not symmetric in vertical wave number. This asymmetry has been
used to infer that more energy was propagating downward than upward.
These calculations have also been used to obtain the coherence between
profiles made at the same location, but separated in time
(the so-called dropped, lagged, rotary coherence). This coherence
is compared with the aforementioned empirical model. The coherence
results show that the contribution of the semidiurnal tide to the
energy of the profiles is restricted to long vertical wave lengths.
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 June, 1975
Collections
Suggested Citation
Thesis: Leaman, Kevin Douglas, "The vertical propagation of inertial waves in the ocean", 1975-06, DOI:10.1575/1912/1353, https://hdl.handle.net/1912/1353Related items
Showing items related by title, author, creator and subject.
-
Understanding the ocean carbon and sulfur cycles in the context of a variable ocean : a study of anthropogenic carbon storage and dimethylsulfide production in the Atlantic Ocean
Levine, Naomi M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2010-02)Anthropogenic activity is rapidly changing the global climate through the emission of carbon dioxide. Ocean carbon and sulfur cycles have the potential to impact global climate directly and through feedback loops. Numerical ... -
Oceanic lithosphere magnetization : marine magnetic investigations of crustal accretion and tectonic processes in mid-ocean ridge environments
Williams, Clare M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2007-09)The origin of symmetric alternating magnetic polarity stripes on the seafloor is investigated in two marine environments; along the ridge axis of the fast spreading East Pacific Rise (EPR) (9º 25’-9º 55’N) and at Kane ... -
A study of ocean wave statistical properties using nonlinear, directional, phase-resolved ocean wave-field simulations
Henry, Legena Albertha (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2010-02)In the present work, we study the statistics of wavefields obtained from non-linear phase-resolved simulations. The numerical model used to generate the waves models wave-wave interactions based on the fully non-linear ...