MIDHOLOCENE PRECEDENT FOR A FUTURE RISE IN SEA-LEVEL ALONG THE ATLANTIC COAST OF NORTH-AMERICA

Sea level oscillated between 5500 and 3500 years ago at Murrells Inlet, South Carolina (33 degrees 33'N, 79 degrees 02'W). The oscillation is well constrained by marsh foraminiferal zonations. For the same time interval, data from Nova Scotia indicate an acceleration in sea-level rise and a report from the Gull of St. Lawrence suggests an oscillation of sea level at the same time. The implications are: (1) there was a eustatic sealevel oscillation of about 2 m in the mid-Holocene on the east coast of North America that is not detectable in present geophysical models of relative sea-level change; (2) if an anthropogenically derived global warming of 4 degrees C takes place, sea level may rise as much as 2 m in 500 yr along the east coast of North America. It appears that the initial rapid rise is recorded all along the eastern seaboard of North America, but detection of the subsequent fall is dependent on existing glacio-isostatic effects (either subsidence or rebound) that are independent of eustatic sea level.