Sea level rise refers to the increase in the average global sea level due to two main processes related to global warming:
- Thermal expansion: As oceans warm, water expands.
- Melting of glaciers and ice sheets: Particularly in Greenland and Antarctica.
Since the late 19th century, sea levels have risen by over 20 cm globally, and the rate is accelerating. According to the IPCC Sixth Assessment Report (2021), global mean sea levels could rise between 0.28 and 1.01 meters by 2100, depending on emission scenarios.
Why is Sea Level Rise Difficult to Predict?
- Complex Ice Sheet Dynamics: Predicting how quickly ice sheets will melt involves complex and poorly understood processes like ice cliff instability and basal melting.
- Regional Variations: Sea level rise is not uniform. Ocean currents, tectonic activity, and gravitational effects from ice mass loss cause regional disparities.
- Emission Uncertainty: Future greenhouse gas emissions and their mitigation determine warming levels, which influence sea level projections.
- Feedback Mechanisms: Climate feedback loops (e.g., albedo changes, methane release) may accelerate or decelerate warming unpredictably.
Impacts of Sea Level Rise:
- Coastal Flooding: Low-lying areas and islands (e.g., Maldives, Sundarbans) face frequent and intense flooding.
- Saltwater Intrusion: Infiltration into freshwater aquifers affects agriculture and drinking water.
- Erosion and Habitat Loss: Coastal ecosystems such as mangroves, estuaries, and wetlands face degradation, affecting biodiversity.
- Displacement of People: ‘Climate refugees’ may emerge as people are forced to relocate. Bangladesh, for instance, is extremely vulnerable.
- Economic Losses: Infrastructure, tourism, fisheries, and agriculture face threats from submersion and storm surges.
In summary, sea level rise is a slow-onset but potentially catastrophic impact of climate change, requiring urgent mitigation and adaptive planning.
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