Key Highlights from the News
Coral microatolls (a special form of coral reefs) have been used as a natural archive by scientists to discover new information about historical sea-level changes in the Indian Ocean.
Key Finding: A study in the Maldives indicates that sea levels in this region may have started rising decades earlier than previously thought, possibly as early as the late 1950s.
This poses a significant threat to low-lying islands like the Maldives, Lakshadweep, and the Chagos Archipelago.
The upper surface of a coral reef grows according to the height of the lowest tide in that area. Therefore, changes in sea level over time are precisely recorded in its annual growth bands.
This study was conducted using technologies such as Uranium-thorium dating.
The influence of climate phenomena like El Niño and Indian Ocean Dipole (IOD) has also been recorded in these corals, which helps in studying ancient climate.
Detailed Explanation: Key Concepts
Sea-Level Rise:
Main reasons for sea-level rise due to global warming:
Thermal expansion of seawater: Water expands when heated.
Melting of land-based ice: Melting glaciers and ice sheets in Greenland and Antarctica add water to the ocean.
Reports indicate that sea levels in the Indian Ocean are rising faster than the global average.
Coral Microatoll:
These are disc-shaped coral reefs.
Their upward growth is limited by the water level at the lowest tide. Therefore, their upper surface acts as a "natural tide gauge."
Their annual growth bands, like tree rings, provide accurate information about sea levels each year.
Dating Techniques:
Annual Growth Bands: Like tree rings, corals form new layers of calcium carbonate each year. Counting these layers provides a precise timeline.
Uranium-Thorium Dating: This is a radiometric method used to determine the age of calcium carbonate materials like corals.
Key Climatic Phenomena:
El Niño: A phenomenon where water temperatures in the eastern Pacific Ocean abnormally increase. It affects global climate and can cause coral bleaching.
Indian Ocean Dipole (IOD): Variation in temperatures between the western and eastern parts of the Indian Ocean. It influences the Indian Monsoon.
Lunar Nodal Cycle: An 18.6-year cyclical change in the Moon's orbit. It influences tides.
Mains Only Notes
The findings of this study have great significance for India.
Vulnerability of Islands: This study serves as a major warning to coral islands like Lakshadweep, which are low-lying like the Maldives.
Vulnerability of Mainland Coasts: India has a long and densely populated coastline. Historical information about sea-level rise is essential for planning coastal protection projects in cities like Kochi, Mumbai, and Chennai.
Monsoon and Climate: The Indian Ocean has a close connection with the Indian Monsoon. Long-term changes in the ocean recorded in coral reefs can help improve climate models and monsoon predictions.
Significance of Paleo-climatological Studies:
This is the study of ancient climate.
Pros:
Extends the Record: Records from instruments like tide gauges are only for the last 100-150 years. However, using corals, ice cores, and tree rings, we can go back thousands of years.
Provides Context: Helps understand whether current changes are part of natural cyclical variations or unprecedented.
Improves Future Models: Data on how the climate system responded in the past helps improve future climate predictions.
Balanced View / Way Forward: Modern instruments like satellites and tide gauges provide accurate information about changes in sea level.
However, this information is for a short period. The study of natural archives like coral microatolls provides a historical context for this modern data.
This is essential for understanding long-term trends in climate change.
For India, such studies are very important for protecting vulnerable island communities like Lakshadweep and planning coastal protection projects..
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