Effects of Climate Change and Sea Level Rise on Coastal Water Resources

Abstract

A better understanding of the relevant climate-change drivers for coastal areas has been realized in the past few years. A significant increase in atmospheric CO2 concentration is predicted to virtually occur and as a result, more CO2 is absorbed by surface waters, decreasing seawater pH and carbonate saturation. Sea surface temperatures are also essentially certain to rise significantly, although less than the global mean temperature rise. Globally, SLR derived from thermal expansion due to warming of oceans and the melting of ice caps, glaciers, and ice sheets (i.e., Greenland and Antarctica) act together as major factors contributing to RSLR. The rise will not be spatially uniform, with possible intensification of ENSO and time variability which suggests greater change in extremes with important implications for coral reefs. In most cases there will be significant regional variations in the changes, and any impacts will be the result of the interaction between climate change drivers (i.e., CO2 concentrations, SST, SLR, storm intensity, frequency, and track, wave conditions and runoff) and other drivers of change, leading to diverse effects and vulnerabilities. The direct influences of sea level rise (SLR) on coastal water resources are associated with seawater encroachment into surface waters and coastal aquifers. Inundation as a result of increases in mean sea level will have devastating impacts on unprotected low-lying areas, especially as a result of storm events which are expected to intensify. Seawater intrusion caused by natural and human-derived factors will be exacerbated by SLR. However, some coastal areas, especially on some arid coasts, receiving more precipitation may be less impacted by seawater intrusion as a result of increased aquifer recharge. Climate change adverse impacts on freshwater supplies at a global scale are most likely to be more visible in developing countries with large extents of coastal lowland, small island states, semi-arid and arid coasts, and large coastal cities particularly in the Asia-Pacific region, reflecting both natural and socio-economic aspects that increase the risk levels. Thus, it is difficult to identify future coastal areas with stressed freshwater resources, particularly where there is a seasonal water demand stress and poor management. Assessments of RSLR-related coastal impacts, adaptation, and mitigation, require information related to climate-induced GMSLR, regional variations, and non-climate-related sea level changes and freshwater stressors.