Eustatic variations à mean sea level/measure of the height of the ocean surface, caused by:
Thermal expansion:
-As water heats (due to increased atm. temp.) it expands, occupies a larger volume à causes SLR. -IPCC 3rd report – contribute 110-430m between 1990-2100 (70-75% total rise).
Glacial melt:
-Leads to changes in volume of ocean water. -Ice sheets floating on the surface of ocean do not cause change in ocean volume à have already displaced water. -But it is ice situated above sea level/on land that causes the problem and increases the volume of water. -IPCC 3rd report – contribute 10-230mm between 1990-2100.
Glacio-Isostatic Adjustments:
-Post-glacial rebound- rising land that was previously compressed by the weight of glacier (some can be 3km thick). -Viscoelastic mantle displaced underneath. -Around edges of former glacier- bulging of land masses à land now sinking (subsidence) à experiencing elevated SLR than other areas.
Ocean circulation changes:
-Regional rather than global effects. -Circulation caused by differences in density, temperature and salinity of ocean water. -E.g. weakening/shut down of Atlantic over-turning circulation à 1m increase in SL. -Compared to other factors à contribute more rapidly. -Ocean isn’t flat (series of hills and depressions due to Coriolis force and geostrophic flows) à Atlantic associated with a particularly low level of water. Circulation weakened = depression could rise rapidly.
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