About the Instructor

Dr. Donna Witter is a physical oceanographer who uses satellite data to study changes of ocean circulation. Dr. Witter joined the Kent State Department of Geology as a Senior Research Fellow in Fall of 2001.

Dr. Witter holds a B.S. in Physics and a B.A. in Geography from the University of California at Santa Barbara and a Ph.D. in Oceanography from Oregon State University. Dr. Witter's early career aspirations were to become a cartographer (age 12), a marine biologist (age 17), a meteorologist (age 20), and finally, an oceanographer (age 22). In retrospect, this circuitous path appears to have been a route of convergence.

In addition to teaching Oceanography, Dr. Witter is actively engaged in research projects that use satellite observations to study the oceans of the Southern Hemisphere.

The Instructor at the Mystic Seaport, Mystic CT. Photograph by Dr. Joseph Ortiz.

These projects currently include:

a) Agulhas-South Atlantic Thermohaline Transport Experiment (ASTTEX)

Figure 1. Sea level in the Parallel Ocean Program (POP) model, a numerical simulation of the ocean's circulation. Indian Ocean water (orange and red, indicating high sea level) enters the South Atlantic in filaments and rings south of Africa. These features migrate into the South Atlantic Ocean, where they alter the heat and salt of the surrounding water. Image courtesy of Dr. Julie McClean, Naval Postgraduate School, Monterey California. Click on the image for a larger view.

This project, funded by the National Science Foundation (NSF), aims at understanding the exchange of water between the Indian and Atlantic basins at their connection south of Africa (see Figure 1). This program combines analysis of data from in-water instruments deployed from ships with data from satellite altimeters.

Satellite altimeters detect small changes of sea level, which are associated with variations in the strengths and directions of currents near the surface of the oceans. For the ASTTEX project, satellite data will be collected by the TOPEX/POSEIDON and Jason-1 altimeters. The complementary in-water data will be collected over a two-year period, beginning with the deployment cruise in February of 2002.

The area south of Africa is particularly interesting to oceanographers. In this area, warm, fresh water from the Indian basin encounters the cooler, saltier water of the Atlantic. Rings and filaments of Indian Ocean water periodically enter the Atlantic via the Agulhas Current which flows to the southwest along the southeastern coast of southern Africa. The input of Indian Ocean water in to the South Atlantic may be important to ocean circulation and dynamics within the Atlantic basin, and to the circulation of saline water in the oceans as a whole.

b) Eddy-Mean Flow Interaction in the Antarctic Circumpolar Current

This project, funded by the National Aeronautics and Space Administration (NASA), aims at understanding the role of undersea topography in the changing ocean circulation of the Southern Ocean encircling Antarctica. This project combines the use of computer analysis of the mathematical equations governing theoretical fluid dynamics with observations of ocean currents from the TOPEX/POSEIDON satellite altimeter.

The primary target of this study is a flow known as the Antarctic Circumpolar Current (ACC). The ACC circles the Antarctic continent at latitudes varying from about 45S to about 65S (depending on longitude). In many regions, small-scale circulation features known as ocean eddies are associated with the current (see Figure 2). This study aims at understanding the effect of undersea topography on the process of eddy formation. A secondary objective is to understand how the geographic distribution of ocean eddies in this region affects the exchange of heat and momentum between the eddies and the ACC. Satellites and theoretical calculations are very important for understanding Southern Ocean eddies because of the cost and difficulty of obtaining ship-based observations in the harsh Circumpolar environment.

Figure 2.Sea level variations in the Southern Ocean around Antarctica from the TOPEX/POSEIDION satellite altimeter. (The South Pole is at the center of the map; Australia is at the lower right). Areas with more ocean eddies are shown in red; areas with fewer eddies are blue and light green. Bathymetry contours are shown in grey. This satellite data shows that eddies are not evenly distributed over the Southern Ocean. This has implications for the circulation in this region and for local exchanges of heat and salt. Click on the image for a larger view.