Nestled just south of the Indian subcontinent, the island nation of Sri Lanka plays an extraordinary, often unseen, role: it acts as a vital natural barrier, shielding India’s southeastern coast from the formidable, long-period swell waves originating deep within the Southern Ocean. This crucial function has been brought to light by insightful research conducted by scientists at the Indian National Centre for Ocean Information Services (INCOIS).
These powerful ocean swells are notorious for their ability to traverse vast distances across thousands of kilometers while losing very little of their destructive energy. Historically, they have frequently triggered significant coastal flooding and erosion, particularly along India’s southwestern shoreline, with Kerala bearing much of the brunt. However, remarkably, India’s eastern coast—especially regions like Tamil Nadu and southern Andhra Pradesh, situated north of Sri Lanka—has largely remained untouched by these hazards.
Despite these energetic swells actively propagating into the Bay of Bengal, their impact along India’s southeastern coast has been minimal. Intrigued by this disparity, researchers embarked on a detailed investigation. They utilized real-time data from specialized wave rider buoys stationed off Kollam on the west coast and Pondicherry on the east coast, complemented by sophisticated, high-resolution simulations using the advanced ‘WAVEWATCH III’ model.
The findings were conclusive and striking: over 96% of the significant long-period swell events recorded off Kollam simply did not reach Pondicherry. To underscore Sri Lanka’s protective role, the researchers conducted a hypothetical scenario within their model, digitally removing the Sri Lankan landmass. In this simulated absence, the very same destructive swells reached and impacted the eastern coast, a region previously safeguarded, unequivocally confirming the island’s indispensable function as a natural “swell shield.”
This groundbreaking study carries profound implications, particularly in an era grappling with global sea level rise and the escalating challenges of climate change. The scientists warn that even seemingly minor alterations in coastal geography, such as land submergence caused by rising sea levels, could dramatically reroute wave propagation paths, consequently exposing vulnerable new regions to unprecedented marine hazards.
Through their focused experiments, the research definitively demonstrated that the Sri Lankan Land Mass (SLLM), strategically positioned in the southeastern quadrant of the Indian peninsula, actively intercepts and blocks these powerful long-period swell waves from the Southern Ocean, preventing them from battering India’s southeast coast.
“Our comprehensive analysis clearly indicates that without the protective presence of the SLLM, destructive Southern Ocean swells would directly reach India’s southeast coast, affecting areas north of Sri Lanka all the way up to mid-Andhra Pradesh,” explained INCOIS director T.M. Balakrishnan Nair, who also served as a co-author of this pivotal study.
Mr. Nair further emphasized that these crucial findings underscore the imperative of recognizing and meticulously integrating natural geographic features like islands and large landmasses into our coastal hazard assessments and, critically, into our early warning systems, especially as our world continues to warm and sea levels continue to rise. This collaborative research also saw contributions from other scientists, including K.G. Sandhya, R. Harikumar, P.A. Francis, and Balaji Baduru, with additional support from the Department of Marine Geology at Mangalore University and the Indian Institute of Tropical Meteorology, Pune. Their detailed paper has been proudly published in the esteemed Journal of Earth System Science.