Sea-Level Rise in the Indian Ocean : Early Warnings from Coral Microatolls

Context

A recent study based on coral microatolls in the Maldives has revealed that sea levels in the central Indian Ocean have been consistently rising since the late 1950s. This finding overturns the earlier belief that significant sea-level acceleration began only in the 1990s. Being low-lying islands, both Maldives and Lakshadweep are at the frontline of this crisis, facing ecological, social, and economic vulnerabilities.

Body

Data Highlights

Sea level rose by ~0.3 m (1930–2019), confirming long-term acceleration.
Decadal rise rates:
- 1–1.8 mm/yr (1930–59)
- 2.7–4.1 mm/yr (1960–92)
- 3.9–4.8 mm/yr (1990–2019)
Since 1959, the average rise has been 3.2 mm/yr, reaching ~4 mm/yr in the last 20–30 years.
Over the last 50 years, Maldives–Lakshadweep has seen a 30–40 cm rise in sea level.

Key Findings

Sea-level acceleration began in the 1950s, not the 1990s.
Coral growth bands and uranium dating gave precise long-term records.
Interruptions in coral growth linked to El Niño, Indian Ocean Dipole (IOD), and lunar tidal cycles.
The central Indian Ocean witnessed an earlier and sharper rise compared to coastal areas due to unique regional oceanographic factors.

Causes of Sea-Level Rise

Thermal expansion: Warmer oceans expand, raising global sea levels.
Glacial & ice-sheet melting: Melting from the Himalayas, Arctic, and Antarctica adds freshwater.
Indian Ocean warming: Above-average heating intensifies currents and circulation, causing higher local rise.
Climate variability: El Niño, IOD, and wind shifts amplify sea-level fluctuations.

Implications

Ecological: Coral bleaching, reduced sunlight, coastal erosion, and reef ecosystem disruption.
Social: Risk of forced migration and loss of homes in Maldives and Lakshadweep.
Economic: Threats to fisheries, tourism, and infrastructure—the backbone of island economies.
Geopolitical: Potential emergence of climate refugees, straining governance and regional security.

Way Forward

Monitoring: Integrate coral microatoll studies, tide gauges, and satellite data for long-term records.
Coastal resilience: Strengthen mangrove belts, seawalls, and climate-resilient infrastructure.
Regional cooperation: Indian Ocean Rim nations must share data and strategies collectively.
Global climate action: Urgently reduce emissions as per Paris Agreement targets.
For India: Prioritise Lakshadweep with ecosystem conservation, disaster preparedness, and adaptive infrastructure.

Conclusion

The Indian Ocean has experienced sea-level rise earlier and faster than widely assumed, posing existential risks to Maldives and Lakshadweep. Coral microatolls provide vital historical evidence that enhances scientific projections. Addressing this crisis demands urgent adaptation, regional collaboration, and global climate action to safeguard vulnerable island nations and coastal communities.