Ocean turbulence is responsible for stirring and spreading ocean tracers, and contributes to the mean circulation as eddy bolus
fluxes. The influence of the eddies on the mean circulation becomes particularly important in regions where mean geostrophic flows are
weak, such as the meridional flow across the Antarctic Circumpolar Current. However, high resolution observations of eddies and their
influence on the circulation are generally lacking, particularly in the deep ocean that cannot be observed via satellites. The Diapycnal
and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) was designed to observe the transport and stirring associated with the
eddies in the Southern Ocean, using RAFOS floats and a passive tracer. In the first half of the thesis, the imprint of the eddies on the
large scale circulation ([greater than] 100 km) is assumed to be diffusive, and the corresponding eddy diffusivities are quantified using
the long term behavior of the RAFOS floats. The eddy diffusivities are found to be suppressed in the presence of mean flows. These eddy
diffusivity estimates from DIMES, along with estimates from a couple of other diffusivity studies, are then used to quantify the eddy
bolus fluxes in the Southern Ocean, which were found to vary in response to the bottom bathymetry. The second part of this work, addresses
the flow at the length scales of the submesoscale and mesoscale ([less than] 100 km). Here, in addition to the DIMES RAFOS floats, we also
used surface drifter observations from an experiment, Grand Lagrangian Deployment (GLAD), conducted in the Gulf of Mexico. The goal was to
observe the kinematic stirring properties at these smaller scales, and also to characterize the dynamics of the turbulence that is active
by investigating the energy spectrum. At the surface ocean in the Gulf of Mexico, we characterized the scale dependent energy distribution
over 5 orders of length scales (10 m - 1000 km) using second order velocity structure functions. Divergent motions were found to be
dominant, over non-divergent motions, at length scales smaller than 5km, where the Rossby number was greater than one and the third order
velocity structure functions indicated the presence of a forward energy cascade. These methods were also used to explain subsurface
turbulence in the Southern Ocean with DIMES RAFOS floats. The RAFOS floats showed that divergent flows are also present in the deep ocean
at length scales smaller than 30 km, and become comparable in magnitude to the non-divergent flows near 5 km. The observed dispersion of
the floats was used to address the question - is the mixing at small scales due mainly to large scale shear (non-local) or small scale
eddies (local)? The associated stirring was found to be local at depth. / A Dissertation submitted to the Geophysical Fluid Dynamics Institute in partial fulfillment of the
requirements for the degree of Doctor of Philosophy. / Fall Semester 2016. / November 10, 2016. / Eddy diffusivity, Lagrangian Observations, Meridional overturning circulation, Ocean Turbulence, Relative
Dispersion, Structure Functions / Includes bibliographical references. / Kevin Speer, Professor Directing Dissertation; William Landing, University Representative;
William Dewar, Committee Member; Phillip Sura, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_405546 |
| Contributors | Balwada, Dhruv (authoraut), Speer, Kevin G. (Kevin George) (professor directing dissertation), Landing, William M. (university representative), Dewar, William K. (committee member), Sura, Phillip (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Program in Geophysical Fluid Dynamics (degree granting departmentdgg) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource (159 pages), computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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