Discipline: Ecology Environmental and Earth Sciences
Subcategory: Geosciences and Earth Sciences
Room: Park Tower 8212
Nimal de Lanerolle - Suffolk County Community College, Selden, NY
Ocean stratification occurs when water masses with different properties – salinity, oxygenation, density, temperature form layers that act as barriers to water mixing. These layers are arranged according to density with the least dense water masses sitting above the more dense layers. The colder denser water forms the lower layer and is richer in dissolved oxygen. Oceanographic data collected from moorings off the coast of North Carolina were analyzed in order to observe stratification with seasonal changes. The analysis showed that winter to summer changes did not trend with expected stratification principles, specifically with respect to dissolved oxygen (DO), with higher DO measured in the upper least dense layer in winter. Time series analysis of normalized parametric data (DO, wind speed, temperature, salinity and density) confirmed this behavior. The expected stratification with the seasons can be upset if turbulence with vertical mixing exists. Wavelet Power Spectra showed the existence of small waves (internal tides) with periods similar to that of tidal waves. Bathymetric profiles suggest a discontinuity in the shelf topography which can which can disrupt the ocean wave form and contribute to turbulence and internal tides. The turbulence resulting from interaction with the discontinuity in the shelf topography, enhanced by wind energy which is higher in winter, causes mixing of the water column, which can extend to the surface water layer. The vertical mixing of the water column breaks down stratification, resulting higher dissolved oxygen (DO) in shallower waters during winter. We attribute the observed seasonal stratification anomaly to increased turbulent mixing over areas of rough bottom ocean topography associated with internal waves. References: Trujillo, A.P., Thurman, H.V.: ‘Ocean Circulation’, in Essentials of Oceanography, 12th Ed., Pearson, 2017, 236. Garrett, C: Internal Tides and Ocean Mixing, Science, 301(5641), 1858-1959. Open University Course Team: Waves, Tides, and Shallow-Water Processes, 2nd Ed, Butterworth Heinemann, 199-201.
Funder Acknowledgement(s): Funder Acknowledgement: I thank Stony Brook University for providing the NSF funded GEOPATH Internship during which this research was performed. Professor K. Lwiza for his guidance in this research.
Faculty Advisor: Dr. Marianne McNamara, firstname.lastname@example.org
Role: The entire research was done by myself.