An update on how sea level rise is happening worldwide
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How is global Sea Level rise moving - Ocean State Report 5
- The story: The global ocean, which covers 71 per cent of the Earth’s surface and regulates the Earth’s climate and sustains life, is undergoing severe changes from natural variations, over-exploitation and anthropogenic influences, a new report has flagged. These changes caused the sea level to rise by 3.1 millimeters each year on an average from January 1993 through May 2020, according to the report The Ocean State Report 5 by the Copernicus Marine Environmental Monitoring Service.
- Warming ocean waters have caused many marine species to move towards cooler waters, leading to introduction of non-native and invasive species to different marine ecosystems. According to the report, between January 1993 and May 2020:
- The warming of the world’s oceans and melting land ice caused sea levels to rise by 2.5 mm per year in the Mediterranean; 4.5 mm per year in Baltic Sea; 4.2 mm per year in western Pacific Islands; 1.7 mm per year in the Black Sea; 3.6 mm per year in the Iberian Biscay Ireland Seas; 2.9 mm per year in the North West Shelf; 3.5 mm per year Central Pacific Islands and 3.4 mm per year in Pacific Islands (total area).
- The report showed that warming ocean waters have caused many marine species to move towards cooler waters; this migration has led to the introduction of non-native and invasive species to different marine ecosystems.
- Increasing temperatures in the eastern Mediterranean basin saw the lionfish (Pterois miles) entering the Mediterranean Sea from the Suez Canal to the Ionian Sea.
- Recent changes: A series of unprecedented and strong Acqua Alta (high water) events occurred in Venice in 2019, which contributed by an unusually high mean sea level, a high spring tide and extreme local and regional weather conditions. Water levels rose to 1.89 metres, the highest recorded level since 1966, flooding 50 per cent of the city between November 11 and 18, 2019. In the Arctic, sea ice is steadily decreasing; in September 2019, sea ice followed a decreasing trend of -12.89 per cent per decade — a record low in sea ice extent in the last two years.
- Oxygen: Around 50 per cent of Earth’s oxygen production takes place in the ocean, sustaining marine life cycles. This is threatened by growing human activities leading to climate change and eutrophication. This deoxygenates the oceans and seas and has adverse consequences on the marine life.
- New tools, technologies to monitor warming ocean: Ocean temperature is increasing, influencing catches and marine species migration. Human pollution and overexploitation are affecting seawater quality, creating the need for a new indicator to measure seawater conditions.
- The report suggested new tools for monitoring ocean changes: Forecast alert systems in Malta, prediction models for jellyfish blooms in the Mediterranean Sea and real-time monitoring programmes for tailored sea ice data.
- These tools can help scientists and policy-makers adapt to a changing ocean on a local, regional and global scale.
- Learn from Malta: The new Maltese tracking system provides alerts and near-real-time evolution of potentially extreme ocean and weather conditions. In 2019, it helped local authorities improve land and marine protection, providing guidance for safe ocean navigation and relaying critical information to emergency units during severe ocean and weather events.
- Summary: Coastal communities worldwide, including in India, are threatened by the rising sea levels. Only a drastic reversal in global warming may stop this. Mitigation efforts, and adaptation, must happen in parallel.
- Knowledge Centre:
- Sea level rise and water expansion due to heat - The warming of Earth is primarily due to accumulation of heat-trapping greenhouse gases, and more than 90 percent of this trapped heat is absorbed by the oceans. As this heat is absorbed, ocean temperatures rise and water expands. This thermal expansion contributes to an increase in global sea level. Temperature measurements of the sea surface, taken by ships, satellites and drifting sensors, along with subsurface measurements and observations of global sea-level rise, have shown that the warming of the upper ocean caused sea level to rise due to thermal expansion in the 20th century.
- Anomalous expansion of water - The above should not be confused with the behaviour of water between 0° and 4°C. The anomalous expansion of water is an abnormal property of water where it expands - instead of contracting - when the temperature goes from 4°C down to 0°C, and it becomes less dense. The density is maximum at 4 degree centigrade and decreases below that. So, water does not expand between 0°C to 4°C instead it contracts. It expands above 4°C.
- EXAM QUESTIONS: (1) Explain the impact of sea level rise, on coastal communities worldwide. (2) What is the "anomalous expansion of water"? Explain.
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