Date of Award

1-1-2012

Document Type

Campus Access Thesis

Department

Earth and Ocean Sciences

Sub-Department

Geology

First Advisor

Subrahmanyam Bulusu

Abstract

The interactions of intraseasonal and interannual climate variability with surface ocean properties is an active area of research in the Indian Ocean region. Understanding how climate variations impact basin-wide salinity patterns is an important step in understanding how this variable impacts ocean circulation and feedbacks.

This study focuses on salinity patterns during the Indian Ocean Dipole (IOD), El Niño-Southern Oscillation (ENSO), and the Madden-Julian Oscillation (MJO). Simple Ocean Data Assimilation (SODA) reanalysis of Sea Surface Salinity (SSS) from 1871-2008 is used to study the salinity variations during numerous phases of IOD events. The dynamics associated with each phase are responsible for producing distinct patterns and strengthen the magnitude and extent of the SSS anomalies during co-occurring ENSO events.

The various stages of the MJO propagation across the Indian Ocean also force distinct SSS variations depending upon the atmospheric and surface ocean conditions. The variability of the MJO with season and ENSO phase create different SSS patterns due to changes in the strength and direction of the atmospheric component. The SSS anomalies are created through enhanced evaporation during the reduced cloud-cover period, which produces positive SSS anomalies while during the convective period, negative SSS anomalies are created through increased precipitation.

The air-sea coupling of the MJO is also studied using altimetric Sea Surface Height (SSH) to understand the interaction of Kelvin and Rossby waves with the MJO. It appears that propagations of the MJO force equatorial Kelvin waves in the Indian Ocean as shown by a lag between Outgoing Longwave Radiation (OLR) and SSH in wavelet analysis. Equatorial Rossby waves also interact with the atmospheric component of the MJO through changes in the mixed layer depth while the Rossby waves propagate westward.

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