Abstract
Local projections of future sea-level change are important for understanding climate change risks and informing coastal management decisions. Reliable and relevant coastal risk information is especially important in South Asia, where large populations live in low-lying areas and are at risk from coastal inundation. We present a new set of local sea-level projections for selected tide gauge locations in South Asia. The projections are used to explore the drivers of spatial variations in sea-level change for South Asia over the 21st century under the RCP2.6 and RCP8.5 scenarios. Global sea-level rise for 2081–2100 is projected to be 0.39 m (0.26–0.58 m) and 0.65 m (0.47 m–0.93m) for RCP2.6 and RCP8.5 respectively. Local sea-level rise projections for the same period vary spatially over the South Asia region, with local sea-level rise in excess of projected global sea-level rise in the equatorial Indian Ocean but less than projected global sea-level rise for the northern Arabian Sea and northern Bay of Bengal. Local sea-level rise for 2081–2100 is projected to be 0.44 m (0.29–0.67 m) and 0.72 m (0.51–1.06 m) at Gan II (Maldives) under RCP2.6 and RCP8.5 respectively, whereas for Diamond Harbour (West Bengal) the corresponding changes are 0.32 m (0.19–0.51 m) and 0.57 m (0.39–0.85m). We find that the sterodynamic contribution is generally the leading driver of change at any single location, with future groundwater extraction over the sub-continent landmass the main driver of spatial variations in sea-level across the region. The new localised projections quantify and enhance understanding of future sea-level rise in South Asia, with the potential to feed into decisions for coastal planning by local communities, government, and industry.
Highlights
Sea-level rise is of paramount concern in coastal regions of South Asia, where large populations are vulnerable and exposed to flooding from coastal inundation and surge events (Brecht et al 2012, Hijioka et al 2014)
We present new 21st century sea-level projections for South Asia tide gauge locations, developed using the outputs of Coupled Model Intercomparison Project Phase 5 (CMIP5) models and the methods applied in UK Climate Projections 2018 (UKCP18) (Palmer et al 2018, Palmer et al 2020)
We focus our discussion on projections for RCP2.6 and RCP8.5 to illustrate the commitment to sea-level rise for scenarios with contrasting trajectories for greenhouse gas emissions over the 21st century
Summary
Sea-level rise is of paramount concern in coastal regions of South Asia, where large populations are vulnerable and exposed to flooding from coastal inundation and surge events (Brecht et al 2012, Hijioka et al 2014). Reliable projections of sea-level change at spatial and temporal scales of relevance to climate change adaptation and investment decisions are required in order to ensure risks are understood and managed. Spatial variations in sea-level change can arise from differences in the relative contributions from local ocean dynamic processes (i.e. ocean circulation and density changes) as well as changes in Earth’s gravity, rotation, and viscoelastic solid-earth deformation that arise from the redistribution of mass from the continents to the oceans (e.g. through melting of ice sheets, glaciers and groundwater depletion) (Mitrovica et al 2001, Stammer et al 2013, Slangen et al 2014). Understanding and quantifying different contributions, or ‘fingerprints’, of regional and local sea-level change is essential for making more robust use of climate model datasets and providing projections at sub-global scales (Tamisiea and Mitrovica 2011)
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