Influence of Climatic Events on Sea Level Variability over the Bay of Bengal: Insights from EOF Representation

Abstract

Climate modes can contribute significantly to sea level variability over shorter time scales. The present study examines annual and inter annual Sea Level Anomalies (SLA) in the Bay of Bengal, emphasizing the influences of El Niño /La Niña and the Indian Ocean Dipole (IOD). An Empirical Orthogonal Function (EOF) analysis is employed to discern the spatiotemporal variability within SLA measurements obtained from the satellite altimeter data. The Oceanic Nino Index (ONI) and Dipole Mode Index (DMI) were used to identify the climatic events and to investigate their influence on the SLA variations over the Bay. Results show distinct seasonal SLA patterns in both Western and Eastern Bay, transitioning from positive to negative anomalies and vice versa within a year. The leading mode of EOF explains 25.5 % variance and indicates a contrasting SLA pattern in the Bay. Significant variations in the sea level are observed during the co-occurrences of Positive Indian Ocean Dipole (PIOD) and El Niño, as well as Negative Indian Ocean Dipole (NIOD) and La Niña. Specifically, the co-occurred El Niño and PIOD (La Niña and NIOD) or pure strong PIOD (pure strong NIOD) is associated with increased (decreased) SLA in the western Bay and decreased SLA in the eastern Bay. However, a detailed analysis of individual events reveals that strong IOD events exert a greater influence on the SLA of the Bay of Bengal.