Thermal Expansion or CO₂? Unveiling the Dominant Drivers of Sea Level Rise Along India’s Coasts Through Multivariate Analysis

Sea level rise (SLR) poses a major challenge for coastal regions of India, which host dense
populations, critical ecosystems, and vulnerable infrastructure. This study investigates the
spatial and temporal evolution of Sea Level Anomalies (SLA) along the eastern and western
coasts of India from 1995 to 2020 using satellite-derived gridded altimetry, along-track
measurements, and tide gauge data. SLA values show marked heterogeneity, with
consistently higher anomalies on the west coast (0.2 – 0.25 m) compared to the east coast
(0.1–0.15 m). Significant positive trends are observed across both coasts, ranging from
0.0075 to 0.01 m yr⁻¹, with a more uniform and accelerated rise after 2010.We used
multiple linear regression and Granger causality analysis to find the main causes of SLR.
Results indicate that CO₂ concentration (21.81 %) is the leading contributor to SLR on the
east coast, while sea surface temperature (21.36 %) exerts the strongest influence on the
west coast. Both methods reveal strong causal links from atmospheric warming, ocean heat
content, and cryospheric melt to regional sea level variability, which points to thermal
expansion as a key mechanism. Tide gauge observations similarly show rising sea levels at
most locations, with the west coast exhibiting a higher aggregated trend (6.78 ± 1.35 mm
yr⁻¹) than the east coast (1.91 ± 1.09 mm yr⁻¹).Future sea level projections using CMIP6
(CNRM-CM6-1HR) under SSP126, SSP245, and SSP585 scenarios suggest a substantial rise in
SLA by 2100, with larger increases along the east coast (0.4 – 0.55 m) compared to the west
coast (0.35 – 0.45 m). Although uncertainties in climate model performance remain, the
observed acceleration and consistent warming trends highlight significant risks for coastal
communities, ecosystems, and infrastructure. These findings point out the urgent need for
region-specific coastal adaptation and mitigation strategies.