EVIDENCE FOR RECENT ACCELERATION(S) IN THE RATE OF SEA-LEVEL RISE FROM THE ALBEMARLE – PAMLICO ESTUARINE SYSTEM, NORTH CAROLINA

We provide a high resolution relative sea-level (RSL) history for the last ~2000 years from the Albemarle - Pamlico estuarine system in North Carolina. The need for high resolution, late Holocene RSL reconstruction has increased with the recognition that sea-level rise is a potentially devastating consequence of climate change. This concern is acute for the Outer Banks and its back barrier estuary system which are considered to be very vulnerable to sea-level rise. In order to consider the potential impacts sea-level rise may have on the Outer Banks it is necessary to place them in an appropriate geological framework. Scenarios for future sea-level rise are concerned with decadal to centennial timescales; as such they must be viewed in light of geologically derived sea-level reconstructions at a comparable temporal resolution. Foraminifera based transfer functions are a quantitative approach which may be effective in establishing these records.

Contemporary foraminifera were collected from five back barrier marshes to create a regional scale modern training set. The use of multiple marshes from a region increases the ecological and environmental diversity included within the training set and reduces the probability of a no modern analogue outcome. To merge the five spatially distinct sites and to relate each to local tide levels we used the VDatum transformation tool. This method relates all samples to a common orthometric datum (NAVD88) and reduces error.

A transfer function was developed to reconstruct former sea-levels based upon the modern, observable relationship between foraminifera and elevation (m MSL). Foraminifera from a core of saltmarsh sediment from Sand Point (Roanoke Island), North Carolina were counted. An age-depth model was produced from composite chronologies of 210Pb, 14C and pollen chrono-horizons. We validated our approach by comparing historical sea level from geological based reconstructions and instrumental tide gauge records. Application of the transfer function to fossil foraminifera was used to produce a late Holocene RSL record. In the last ~2000 years sea level has risen at a background rate of ~1.1mm/yr. There is evidence for two recent accelerations in the rate of sea-level rise during the late 19th and 20th centuries to a current rate of ~4mm/yr.