Sea level in the Bay of Bengal is not just rising - it’s responding dynamically to climate modes like El Niño/La Niña and the Indian Ocean Dipole (IOD)

Sea level in the Bay of Bengal is influenced not only by global warming but also by regional climate modes like El Niño, La Niña, and the Indian Ocean Dipole (IOD). In our recent study published in the recent issue of Defense Science Journal on “Influence of Climatic Events on Sea Level Variability over the Bay of Bengal: Insights from EOF Representation”, we explored how these climate modes affect the interannual sea level anomalies (SLA) using satellite altimeter observations and Empirical Orthogonal Function (EOF) analysis.

The study reveals that:

• The Bay shows strong annual and interannual sea level variability.

• The total sea level is rising at 4.28 mm/yr, higher than the global average.

• El Niño-Positive IOD (or pure PIOD) years cause higher sea levels in the western Bay and lower levels in the eastern Bay, while La Niña–Negative IOD (or pure NIOD) years show exactly the opposite pattern.

• Strong IOD events exert a greater influence on sea level variability than El Nino Southern Oscillation alone.

These findings highlight the complex interplay between ocean-atmosphere processes and regional sea level and highlight how wind forcing and coastal Kelvin waves modulate sea level across the Bay, creating spatial contrasts that have implications for coastal vulnerability and adaptation planning. Understanding these dynamics is vital for predicting sea level changes and preparing for their impacts on the densely populated coastal regions of the Bay of Bengal.

Research team: Mr. Ullas M. Pillai, Dr. Ajith Joseph K (NERCI), Dr.Roshin P. Raj (NERSC, Norway), and Prof. Ola M. Johannessen (Nansen Scientific Society, Norway).

Time series of monthly mean sea level anomalies (SLA) from satellite altimeter data for 1993–2021 over Bay of Bengal (black), Western Bay of Bengal (blue), Eastern Bay of Bengal (red)

The full study can be accessed here: https://publications.drdo.gov.in/ojs/index.php/dsj/article/view/21347

For more information, please contact: Dr. Ajith Joseph K

[ ajith_jk@nerci.in ]