Sea Level Rise and Its Impact

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    A recent study, projecting different greenhouse gas scenarios, stated that Climate change will increase sea level in Lakshadweep Islands and it will affect airports and residential areas.

     

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    • Sea-levels will rise around the Lakshadweep Islands in the range between 0.4 mm/year to 0.9 mm/year.
    • The study highlights that the worst possible inundation (flooding) scenarios projected for Lakshadweep Islands are almost similar under different emission scenarios projected and all the islands in the archipelago would be vulnerable to impact from sea-level rise.
    • For the first time, climate model projections were used to assess the potential areas of inundation.
    • Smaller islands Chetlat and Amini are expected to have major land-loss.
    • The present work highlights that larger islands Minicoy and the capital Kavaratti are also vulnerable to sea-level rise, and expected to experience land-loss along 60% of the existing shoreline. 
    • Sea-level rise effects are seen to have the least impact on Androth Island under all emission scenarios.

     

    (Image Courtesy : Researchgate)

    • Average sea levels have swelled over 8 inches (about 23cm) since 1880, with about three of those inches gained in the last 25 years. 

     

    Three Primary Factors For Sea Level Rise

    • The change in sea levels is linked to three primary factors, all induced by ongoing global climate change:
    • Thermal expansion: 
      • When water heats up, it expands. About half of the sea-level rise over the past 25 years is attributable to warmer oceans simply occupying more space.
    • Melting glaciers: 
      • Large ice formations such as mountain glaciers naturally melt a bit each summer. 
      • In the winter, snows, primarily from evaporated sea water, are generally sufficient to balance out the melting. 
      • Recently, though, persistently higher temperatures caused by global warming have led to greater than average summer melting as well as diminished snowfall due to later winters and earlier springs. 
      • That creates an imbalance between runoff and ocean evaporation, causing sea levels to rise.
    • Loss of Greenland and Antarctica’s ice sheets: 
      • As with mountain glaciers, increased heat is causing the massive ice sheets that cover 
      • Greenland and Antarctica to melt more quickly. 
      • Scientists also believe that meltwater from above and seawater from below is seeping beneath Greenland’s ice sheets, effectively lubricating ice streams and causing them to move more quickly into the sea. 
      • While melting in West Antarctica has drawn considerable focus from scientists, especially with the 2017 break in the Larsen C ice shelf, glaciers in East Antarctica are also showing signs of destabilizing.

     

    Threats

    • Projected inundation due to sea-level rise can impact the islanders as residential areas are quite close to the present coastline. 
    • Airport and residential areas will be severely affected
      • The only airport in the archipelago is located at the southern tip of Agatti Island, and has a high likelihood of damage due to inundation from sea-level rise.
    • Devastating effect on coastal areas:
      • Destructive erosion
      • Wetland flooding
      • Aquifer and agricultural soil contamination with salt, and 
      • lost habitat for fish, birds, and plants.
    • Higher sea levels are coinciding with more dangerous hurricanes and typhoons that move more slowly and drop more rain, contributing to more powerful storm surges that can strip away everything in their path.
    • Forced migration of people due to flooding
    • The prospect of higher coastal water levels threatens basic services like internet access, since much of the underlying communications infrastructure lies in the path of rising seas.
    • A higher sea level causes heavy rains and strong winds, unleashes severe storms and other big atmospheric phenomena that can be a real threat to places that might be on its way.
    • If all the ice that currently exists on Earth in glaciers and sheets melted it would raise sea level by 216 feet. That could cause entire states and even some countries to disappear under the waves, from Florida to Bangladesh.

     

    Adapting to the threat

    • As a result of these risks, many coastal cities are already planning adaptation measures to cope with the long-term prospects of higher sea levels, often at considerable cost. 
    • Building seawalls, rethinking roads, and planting mangroves or other vegetation to absorb water are all being undertaken.
    • The communities vulnerable to rising seas can only go so far in holding back the tide. 

     

    Way Forward

    • In the Marshall Islands, where rising sea levels are forcing a choice between relocating or building up the land, residents will need help from other nations if they decide to undertake the expensive latter option.
    • The Coastal cities can implement following measures to address sea level rise
      • Using Beaches As Barriers 
      • Building Seawalls 
      • Raising Roads 
      • Building Stormwater Pumps 
      • Upgrading Sewage Systems 
      • Creating Natural Infrastructure
      • Slowing Land Sinkage

    Best Practices:

    • In Jakarta, a $40 billion project will aim to protect the city with an 80-foot-high seawall. 
    • Rotterdam, home to the global Center on Adaptation, has offered a model to other cities seeking to combat flooding and land loss. The Dutch city has built barriers, drainage, and innovative architectural features such as Water Square with temporary ponds.

     

    GoI’s Implementation Plan

    • Assess the factors attributable to the sea level changes through a comprehensive studies 
      • associated with the change in volume of the Indian Ocean basin in terms of sea water density (steric), salinity (halosteric), temperature (thermosteric) and change in mass due to glacier/ice melting (Eustatic)
      • associated with the changes to the shape of the Indian Ocean geometry due to vertical displacement of land (tectonic) and deltaic subsidence
    • Classify coastal environments based on tidal oscillations and using relative wave/tide energy, fluvial discharge in a temporal framework including transgression and progradation.
    • Studying changes in sea level and its impact on shoreline migration.Carbon dating and age determination based on bore hole samples and identifying sediment depositional trends – deriving brief overview of the Indian coastal zone based on sediment supply and geologic heritage (antecedent geology) such as Quaternary sea level history.
    • Beach profile measurements to study the changes in beach volume in the event of erosion caused by rise in sea level and predict the extent of loss of beaches – Sediment transport and associated models to assess the fate of lost sediments
    • The proposed programme is an integrated approach based on utilization of expertise from physical, chemical, biological and geological scientists together with scientists working in remote sensing and will be implemented by NCCR (National Centre for Coastal Research)

    Sources: PIB