Cryospheric contributions to sea-level rise and variability

Global mean sea level rose by ~1.8 mm/yr over the last 50 years, increasing to ~3.1 mm/yr during the 1990s (Church et al, 2004, Holgate and Woodworth, 2004, Cazenave and Nerem, 2004). Thermal expansion of ocean water is estimated to account for 0.4 mm/yr of sea level rise (SLR) for the past 4-5 decades rising to 1.5 mm/yr during the last decade (Levitus et al., 2005, Ishii et al., 2006, Willis et al., 2004, Lombard et al., 2006), Contributions from water on land are probably very small, with sequestration by dams more or less balanced by release of groundwater, but uncertainties are large (Cazenave et al., this Workshop). The most important source of the remainder is likely to be land ice which, if it were all to melt, would cause >60 meters SLR. Small glaciers and ice caps, including those around Greenland and Antarctica, represent ~ 1% of this, with 11% in Greenland, and 88% in Antarctica. Glaciers in most mountain regions are known to be retreating, and a recent assessment, using the spatially limited in-situ measurements and a statistical method of global area weighting of known ice masses, showed the contribution from ice caps and glaciers at 0.3-0.45 mm/yr SLR over the last 100 years rising to 0.8 mm/yr over the last decade (Dyurgerov and Meier, 2005).