Holocene Sea-Level Changes along the North Carolina Coastline: Implications for Glacial Isostatic Adjustment Models and Current Rates of Sea-Level Change

We have synthesized new and existing relative sea-level (RSL) data to produce a quality-controlled, spatially comprehensive database of Holocene RSL changes from the North Carolina coastline. The RSL database consists of 53 sea-level index points quantitatively related to an appropriate tide level together with an error estimate, and a further 37 data points that provide limits on the maximum and minimum elevation of RSL. The data illustrate RSL rapidly rising during the early and middle Holocene from an observed minimum of -35.71 ± 1.11 m NAVD88 at 11062 - 10576 cal a BP to -4.19 m ± 0.44 m NAVD88 at 4240 - 3592 cal a BP.

We subdivided the late Holocene RSL observations into two regions and compared these with predictions from the ICE-5G(VM2) glacial isostatic adjustment model. The observational data are only fully explicable when rotational feedback is included in the ICE-5G(VM2) model. Rotational feedback increases the rate of sea-level rise in Region 1 (Albemarle, Currituck, Roanoke, Croatan and northern Pamlico sounds), compared to Region 2 (southern Pamlico, Core and Bogue sounds and further south to Wilmington). The observations from Region 1 and 2 show late Holocene sea-level rising at 1.02 ± 0.04 mmyr-1 and 0.92 ± 0.05 mmyr-1, respectively. The ICE-5G(VM2) predictions capture the general temporal trend of the observations, although there is an apparent misfit for index points older than 2000 cal a BP. It is presently unknown whether these misfits derive from possible tectonic uplift associated with the mid-Carolina Platform High.

A comparison of local tide gauge data with the late-Holocene RSL trends imply an additional increase of mean sea-level of greater than 2 mmyr-1 during the latter half of the 20th century; this is in general agreement with historical tide gauge and satellite altimetry data.