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The CfA Space Geodesy Homepage Sea Level Hazards: Increased flood and storm damage Increased salinity of estuaries and aquifers This webpage was created by Stacey Archfield |
Increased salinity of estuaries and aquifers
Rising sea level would allow saltwater to penetrate farther inland and upstream [IPCC, 1998]. Higher salinity impairs both surface and groundwater supplies [IPCC, 1998]. This effect would impair water supplies, ecosystems, and coastal farmland [IPCC, 1998]. Saltwater intrusion would also harm aquatic plants and animals as well as threaten human water supply [IPCC, 1998]. Salinity intrusion has already been cited as the primary reason oyster harvests have been reduced in the Delaware and Chesapeake Bays [IPCC, 1998]. In Louisiana, cypress swamps are becoming open lakes due to increasing salinity [IPCC, 1998]. In humid equatorial climates, gradual sea level rise would cause a brackish-water zone to migrate inland [Gornitz, 1991].
The penetration of saltwater can be compared to what occurs during extreme droughts when river runoff is diminished, forcing a fallow period in agriculture [Gornitz, 1991]. As sea level rises, the tidal saltwater zone penetrates further upstream [Gornitz, 1991]. The zone then becomes unfit for tidal harvests such as swamp rice [Gornitz, 1991]. Salinity has also been found to decrease seed germination in a variety of wetland species and higher salinities may decrease recruitment of seed bank species [Balwin et al., 1996].
In addition to damage to ecosystems, sea level rise promotes saltwater intrusion into coastal aquifers [Gornitz, 1991]. A freshwater lens overlies saltwater along barrier coasts, and volcanic and coral islands [Gornitz, 1991]. This freshwater lens is 40 times thicker than the elevation of the water table above mean sea level [Gornitz, 1991]. Therefore each increment of sea level rise reduces the freshwater capacity of the lens by 40 times [Gornitz, 1991]. On low coral atolls, less permeable Holocene sediments overlie a highly permeable Pleistocene karstic subsurface through which seawater can infiltrate [Gornitz, 1991]. Coastal communities will be forced to find alternative sources of freshwater.