SEA-LEVEL CHANGES ALONG THE ATLANTIC COAST OF THE UNITED STATES: IMPLICATIONS FOR GLACIAL ISOSTATIC ADJUSTMENT MODELS AND CURRENT RATES OF SEA-LEVEL CHANGE

We have begun to establish a relative sea-level (RSL) database from the Atlantic Coast of the USA. These data are being used to validate and refine Glacial Isostatic Adjustment (GIA) models. There is need for a re-assessment of the quality of the observational evidence of former sea levels from the Atlantic Coast of the USA, as well as concepts inherent in the interpretation of the data. Furthermore, other factors such as sediment compaction and tidal range changes are rarely taken into account. Such deficiencies in RSL histories represent a significant gap in our understanding of Late Quaternary RSL, its driving mechanisms and spatially variable expression.

Rates of RSL rise since the LGM provide the fundamental basis for comparison with historical and present-day changes. They provide an essential benchmark against which the RSL rise that has occurred over the last 100-150 years is compared. Moreover, high quality RSL data reveal spatial and temporal variations in crustal movements since the LGM. Thus, sites from North America (the Atlantic Coast of the USA and Canada, and the USA Gulf Coast) and the Caribbean constitute a vital constraint upon the dynamical models of the GIA process. There is an urgent need for a sufficiently accurate model of the GIA process to inform the global data set currently being produced by the Gravity Recovery and Climate Experiment (GRACE). There exists a systematic misfit of the existing GIA filter for GRACE to sea-level observations along the Atlantic coast of the USA greater than a few thousand years. It is presently unknown whether these misfits derive from a fundamental flaw in the models of the GIA process or in the interpretation of former RSL measurements from this critical region.

The specific objectives of this presentation are: 1) critical re-assessment of (un)published RSL data since the LGM from the Atlantic Coast of the USA; 2) combine the USA Atlantic Coast data with sea-level reconstructions from Atlantic Canada, the Caribbean and the USA Gulf Coast; 3) isolate the effects of tidal regime change and sediment consolidation from differential crustal movements; 4) validate and refine GIA models; and 5) determine rates of RSL change and differential crustal movements along the Atlantic Coast of the USA and Canada, as well as the Gulf Coast and Caribbean.