Date of Award

1-1-2012

Document Type

Campus Access Thesis

Department

Marine Science

First Advisor

Subrahmanyam Bulusu

Abstract

Kelvin waves are internal ocean waves that balance the Earth's Coriolis force against a wave boundary such as a coastline or the equator. In the Indian Ocean, Kelvin waves originate from Wyrtki jets off the east African coast and propagate along the equatorial wave guide until reaching Sumatra, where they follow the coastal waveguide counter-clockwise around the perimeter of the Bay of Bengal (BoB). We observed these Kelvin waves using the sea surface height (SSH) anomalies derived from satellite altimeter observations for the 1993-2006 period, the Simple Ocean Data Assimilation (SODA) reanalysis, and the HYbrid Coordinate Ocean Model (HYCOM) simulations for the 2002-2006 period. Wavelet analyses of each time series of SSH data at five select locations revealed a dominant annual period in the equatorial Indian Ocean, progressing to a semiannual period off the Sumatra coast, and transitions into both annual and 120-day period around the perimeter of the BoB and along the east coast of India. The variability in the propagation of the Kelvin waves during the winter and summer monsoons (January-March and July-September) and the monsoon transitions (April-June and October-December) is observed, as well as the associated variability in the surface circulation in the study area from each data set. The winter transition downwelling Kelvin wave showed progressive propagation all along the equatorial region, coastal BoB and along the west coast of India to its northern edge, thus affecting India's coastal circulation.

The importance of Indian Ocean circulation dynamics to the regional and global climate has been increasingly recognized largely due to improved ocean observations in the last few decades. Recent observations indicate that the Indian Ocean directly influences large-scale climate variations, such as El Niño. A key component for better understanding the region is resolving the salt transport within a dynamic freshwater flux environment in contrast to a highly evaporative environment. The Indian Ocean shows significant variability in the distribution of sea surface salinity (SSS), especially in the BoB and the Arabian Sea (AS). The U.S/Argentinian Aquarius/SAC-D salinity mission successfully launched on June 10, 2011, provides global maps of surface salinity by measuring the ocean's brightness temperature. We used Aquarius and ESA's Soil Moisture-Ocean Salinity (SMOS) missions' salinity observations to estimate near-surface fresh and salt-water transports in order to understand the variability and distribution of salt in the Bay of Bengal. The role of Kelvin wave propagation in the Bay of Bengal will be used to determine pathways of fresh and salt-water transports throughout the Indian Ocean.

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