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Of the major ports in India, Diamond Harbour in West Bengal located at the mouth of river Hooghly has recorded the maximum sea level increase, according to latest data.
THE RISING TREND:
- While recent studies reveal that sea level rise in the country has been estimated to be 1.3 mm/year along India’s coasts during the last 40-50 years, at Diamond Harbour the rise was almost five times higher at 5.16 mm per year. This is followed by:
- Kandla port in Gujarat where the sea level rise was 3.18 (1950 to 2005)
- Haldia in West Bengal, which recorded a sea level rise of 2.89 mm a year (1972 to 2005)
- Port Blair, which recorded a sea level rise of 2.20 mm per year (1916-1964)
- Going by the data from the Ministry of Earth Sciences, four ports, Diamond Harbour, Kandla, Haldia, and Port Blair, recorded a higher sea level rise than the global average.
- Chennai and Mumbai recorded a sea level rise far below the global and the national averages at 0.33 mm per year (1916-2005) and 0.74 mm (1878-2005) respectively.
- Studies over Indian region have shown a warming trend of 0.6°C on all India average basis, mainly contributed by maximum temperatures.
REASONS BEHIND THE REGIONAL DIFFERENCES IN SEA-LEVEL RISE:
- Temperatures are rising faster in almost every part of the world’s oceans but the level varies.
- There are some natural factors, which are major reasons for regional differences in sea-level rise:
- Heat Transportation by ocean currents
- Periodic climatic phenomena such as El Nino
WHY SEA LEVELS ARE RISING MUCH FASTER ALONG THE WEST BENGAL COASTLINE?
- The sea level rise is higher in West Bengal, particularly in the Sunderbans delta, because of the deltaic sediment deposition as a result of the mixing of freshwater and saline water.
- Contours of river deltas are naturally dynamic being shaped by sediment deposition by the vast amounts of soft, fertile silt transported by the rivers constituting them.
- Land accretes by sedimentation but is lost by silt compactification and coastal erosion.
- Sediment transport into the Sundarbans has been severely affected by upstream damming, especially the Farakka dam in West Bengal built on the Ganga in 1975. Dams trap sediment and greatly reduce downstream transport.
- As a result, subsidence has outpaced accretion on average in the Indian part of the Sundarbans and the Delta is sinking.
- The combined effect of an already high rate of sea-level rise in the Bay of Bengal and land subsidence has been an effective sea-level rise in the Sundarbans.
KOLKATA, THE MOST FLOOD-PRONE COASTAL CITIES:
- Recently, a study was conducted by researchers from the Netherlands and the United Kingdom, to calculate the flood vulnerability of cities.
- Located on the banks of the Hooghly River, Kolkata has been found to be one of the world’s most flood-prone coastal cities.
- Kolkata’s growing population and exposure to storms make it vulnerable.
HOW GLOBAL WARMING IS IMPACTING SEA LEVELS?
- In all the world’s oceans, sea levels have been rising for the past century and there are various natural reasons why sea levels change, but only two major ways in which human-induced global warming is impacting sea levels today.
- For one, with rising temperatures, trillions of tonnes of ice have melted in the past century from glaciers and ice sheets because of global warming, adding vast quantities of water to the oceans. The global warming not only causes melting of ice and glaciers but also leads to internal expansion of water in oceans and thus a rise in the sea level.
- For another, water expands as it warms causing the same quantity of water to occupy more space. Also, heavy rainfall and temperature extremes like heat waves and shifts in semi-arid regions were some may have linkages with climate change and global warming.
The combined effect of all these processes is leading to a rise in global sea levels.
WHAT NEEDS TO BE DONE?
- Recognition of Severity of Impact: There is a need for much higher recognition of the unequivocal scientific evidence of impacts on key marine and coastal organisms, ecosystems, and services even under the low emissions scenario.
- Concerted joined-up Global Policy Action for Ocean Protection: There is a need to join up the action across global conventions concerning climate change and environmental protection.
- Comprehensive Protection and Management: There is a need to ensure that we rapidly fill gaps in protective regimes, such as protecting the High Seas.
- Updated Risk Assessments: A re-evaluation is needed on the risks that impacts from ocean warming and other stressors pose to humanity, to the viability of the very species and ecosystems involved, and to the provisioning of goods and services we derive from the environment.
- Substantial cuts in Greenhouse Gases: By adopting a comprehensive protection plan for achieving rapid and substantial cuts in greenhouse gases. Greenhouse gas mitigation at the global scale appears to be the overarching solution.
Global climatic change along with rising sea levels are issues particularly relevant to Sundarbans. In the current scenario, sea-level rise mainly due to climate change is the greatest threat and challenge for sustainable adaptation within such area. The issues of climate change, therefore, constitute the major serious challenges of the 21st century and call for an integrated approach to issues of environmental preservation and sustainable development.