also feed into source regions of the THC. Changes in any of these fluxes could contribute to THC changes. The result from Cuffey and Marshall (2000) that modest warming above recent conditions during the previous interglacial led to major shrinkage of the Greenland ice sheet suggests that large changes in Greenland are likely in the future. Changes in river and groundwater discharge are similarly important.
Arctic sea-ice volume appears to have shrunk dramatically in recent decades (Vinnikov et al., 1999; Johannessen et al., 1999; Rothrock et al., 1999). The influence of that decline on the freshwater budget of the Atlantic THC is unknown but could be critical. It is crucial to know the net freshwater flux from the Arctic Ocean to the Nordic Seas, in the form of both sea ice and low-salinity surface water. The sea ice emerging from Fram Strait is thought to influence convection in the Greenland Sea and, after being transported through the Denmark Strait in the East Greenland Current, in the Labrador Sea. Indeed, sea ice from the Arctic could be the origin of such events as the Great Salinity Anomaly that have been documented in the North Atlantic (Dickson et al., 1988; Häkkinen, 1993). Given the importance of freshwater forcing for the stability of the THC, such events might presage change in the circulation. However, even if melting Arctic sea ice does not markedly influence the THC, sea-ice disappearance is likely to have radical consequences for Arctic ecosystems and possibly regional climate. It is not now possible to quantify such possibilities.