Date of Award

2017

Document Type

Open Access Thesis

Department

Marine Science

Sub-Department

College of Arts and Sciences

First Advisor

Subrahmanyam Bulusu

Abstract

The Southwest Tropical Indian Ocean (SWTIO) features a unique, seasonal upward lift of the thermocline, which is known as the Seychelles-Chagos Thermocline Ridge (SCTR; 55°E-65°E, 5°S-12°S). It is known that a high correlation exists between the depth of the thermocline and sea surface temperature (SST; a key ingredient for tropical cyclogenesis). With a particular focus on 2012/2013, this study reveals the dynamic properties of the SCTR that play an important role in the modulation of tropical cyclones in the SWTIO. Phenomena including Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO) are also well correlated to cyclogenesis through changes in the thermocline of the SCTR. More tropical cyclones form over the SWTIO when the thermocline is deeper, which has a positive relation to the arrival of downwelling Rossby waves originating in the southeast tropical Indian Ocean due to the anomalous effects of IOD.

In addition to influencing cyclogeneis over the SCTR region, remote processes such as IOD and ENSO are also the primary drivers of the SCTR interannual variability with respect to both ocean temperature and salinity. Thus, this study also explores how temperature and salinity with depth, as well as at the surface, in the SCTR change with the climatic events in a given year. Although ENSO is known to have a stronger impact on SST south of the SCTR (10°S-15°S), this study reveals the stronger impact of ENSO on sea surface salinity (SSS) in the SCTR.

Rights

© 2017, Jessica Maureen Burns

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