Global Impacts of Sea Level Rise

11/17/20224 min read

The physical changes arising from rising sea levels include the permanent submergence of land by higher mean sea levels or mean high tides (Oppenheimer et al 2019), and more frequent or intense coastal flooding (Oppenheimer et al 2019). Increased annual coastal flood damage is estimated to increase by at least 2 orders of magnitude by 2100 (IPCC 2019). Other physical changes include enhanced coastal erosion, loss and change of coastal ecosystems, and impeded drainage (Oppenheimer et al 2019).

The rise in sea levels also has negative influences on water resources in the form of the displacement of coastal wetlands, alteration of shorelines, loss of habitat (EPA), and the destruction of most coastal ecosystems at 110cm SLR, if adaptation does not increase (Oppenheimer et al 2019). We can also expect the increased salinisation of soils, ground and surface water, reaching inland in extreme years (Oppenheimer et al 2019). “New York City, Philadelphia and much of California’s Central Valley obtain some of their water from portions of rivers that are slightly upstream from the point where water is salty during droughts. If sea level rise pushes salty water upstream, the existing water intakes might draw on salty water during dry periods” (EPA). As for the contamination of aquifers, “[in] southeastern Florida, saltwater driven by sea level rise is increasingly intruding into the porous limestone of the Biscayne Aquifer, which supplies drinking water to about 6 million people” (Hurdle 2020).

Sea level rise (“SLR”) has impacts on extreme climate events. SLR leads to the increased occurrence of extreme sea level events, especially in tropical regions (IPCC 2019), and on an annual basis for low-lying and small island communities by 2050 (RCP2.6) (IPCC 2019). It also contributes to an increase in extreme significant wave height over the Southern Ocean (Oppenheimer et al 2019), and higher average intensities of tropical cyclones, more frequent Category 4 and 5 cyclones compared to lower categories, and related rainfall rates (IPCC 2019).

Population distributions will shift as a result of SLR, as communities migrate by reason of loss of land and freshwater (Asuncion and Lee 2017). In Asia, we will see human migration to high islands and continental sites, by reason of threats caused by flooding to public health infrastructure and general safety (Asuncion and Lee 2017). Specifically in China, SLR will influence migration from developed coastal cities to other developing inland regions, by reason of SLR-related increased unemployment in developed coastal regions (Cui et al 2018).

The economic effects of SLR include loss of gross domestic product (“GDP”) and disruption of socioeconomic activities (Asuncion and Lee 2017). Coupled with sudden-onset extreme storm surges, researchers project a 11.06% coastal GDP loss in China in 2050, translating to national GDP loss by around 0.96%–1.16% (Cui et al 2018). In Kiribati, there is a projected increase in causeways destroyed, damaged coral reefs, and shoreline erosion (Asuncion and Lee 2017).

Coastal megacities, urban atoll islands, population-dense deltas, and Arctic communities have been identified as the primary coastal communities vulnerable to SLR-impacts.

Coastal megacities are vulnerable because of their high and increasing density of population and population in general, sharp concentrations of income and assets within small areas, “high exposure of monetary value to coastal hazards,” vulnerability of below-ground space due to development, and limited protection of proximal natural ecosystems due to exploitation or damage or destruction, all resulting in uneven coastal adaptation (Oppenheimer et al 2019).

Urban atoll islands experience SLR-related vulnerability by reason of their low elevation, “composition of reef-derived unconsolidated material”, highly dense population, “concentration of critical infrastructure and settlements in naturally low-lying flood-prone areas”, and extant coastal flooding and erosion and salinisation of groundwater lenses (Oppenheimer et al 2019).

As for population-dense deltas, their vulnerability derives from them being large, low-lying, primarily agricultural, possessing high population density, experiencing high exposure to flooding and erosion and salinisation due to “removal of natural vegetation buffers”, with partial degradation of wetlands and extant riverine flooding, coastal and riverbank erosion, and salinity of water and soil resources (Oppenheimer et al 2019).

The increased vulnerability of Arctic coastal communities can be traced to their location on “exposed coasts composed of unlithified ice-rich sediments in permafrost" with seasonal ice and slow to moderate SLR, heavy dependence on marine species, low-lying location “remote from regions of glacio-isostatic adjustment”, situation of infrastructure in nearshore areas, extant major coastal erosion and high risk of flooding, accelerating permafrost thaw, and decrease in Arctic seasonal sea ice (Oppenheimer et al 2019).

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