Model Answer
0 min readIntroduction
Sea level change, a persistent feature of Earth’s history, refers to the rise or fall of the average sea level over time. While natural processes have always caused fluctuations, the current rate of sea level rise is significantly accelerated due to anthropogenic climate change. The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) confirms that global mean sea level increased by 0.20 [0.15 to 0.25] m between 1901 and 2018. Understanding the causes and consequences of these changes is vital for effective adaptation and mitigation strategies, particularly for vulnerable coastal communities and ecosystems.
Causes of Sea Level Changes
Sea level changes are broadly categorized into eustatic and isostatic movements.
Eustatic Changes
- Thermal Expansion: As ocean water warms, it expands, contributing significantly to sea level rise. This is a major component of current sea level rise due to global warming.
- Melting of Glaciers and Ice Sheets: The melting of land-based ice (glaciers, ice caps, and ice sheets – Greenland and Antarctica) adds water to the ocean, increasing its volume.
- Changes in Land Water Storage: Human activities like groundwater extraction, dam construction, and deforestation can alter the amount of water stored on land, impacting sea levels.
Isostatic Changes
- Post-Glacial Rebound: After the last glacial period, landmasses that were depressed by the weight of ice are slowly rising. This is known as post-glacial rebound and causes relative sea level fall in these areas (e.g., Scandinavia, Canada).
- Subsidence and Uplift: Tectonic activity, sediment compaction, and volcanic activity can cause localized land subsidence or uplift, affecting relative sea level.
- Sediment Loading: Large river deltas are subsiding due to the weight of accumulating sediments.
Consequences of Sea Level Changes
Coastal Erosion and Inundation
Rising sea levels exacerbate coastal erosion, leading to loss of land and infrastructure. Low-lying coastal areas, including island nations like the Maldives and densely populated deltas like the Ganges-Brahmaputra Delta, are particularly vulnerable to inundation.
Impact on Coastal Ecosystems
- Saltwater Intrusion: Sea level rise leads to saltwater intrusion into freshwater aquifers, contaminating drinking water supplies and impacting agriculture.
- Mangrove and Wetland Loss: Mangroves and coastal wetlands, crucial for biodiversity and coastal protection, are threatened by inundation and erosion.
- Coral Reef Degradation: Increased water depth and turbidity can stress coral reefs, leading to bleaching and decline.
Socio-Economic Impacts
- Displacement and Migration: Sea level rise can displace coastal communities, leading to climate-induced migration and potential social conflicts.
- Damage to Infrastructure: Coastal infrastructure (roads, ports, buildings) is vulnerable to damage from flooding and erosion, requiring costly repairs or relocation.
- Economic Losses: Loss of agricultural land, fisheries, and tourism revenue can have significant economic consequences.
Impact on Global Climate Patterns
Changes in ocean currents and salinity due to sea level rise can influence regional and global climate patterns. Alterations in thermohaline circulation, for example, could have far-reaching consequences for temperature and precipitation patterns.
| Consequence | Impacted Region/System |
|---|---|
| Coastal Erosion | East Africa, Bangladesh, Florida |
| Saltwater Intrusion | Ganges-Brahmaputra Delta, Mekong Delta |
| Mangrove Loss | Sundarbans, Indonesian Archipelago |
| Displacement | Pacific Island Nations (Tuvalu, Kiribati) |
Conclusion
Sea level changes, driven by both natural and anthropogenic factors, pose a significant threat to coastal regions and global ecosystems. The accelerating rate of sea level rise due to climate change demands urgent action to mitigate greenhouse gas emissions and implement adaptation strategies. These strategies include building coastal defenses, restoring coastal ecosystems, and developing climate-resilient infrastructure. International cooperation and sustainable coastal management practices are crucial to minimize the adverse consequences of sea level changes and ensure the long-term well-being of coastal communities.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.