Timing and magnitude of accelerated relative sea-level rise in North Carolina
Abstract
We present a 1000 year, high resolution record of relative sea-level rise (RSLR) from foraminifera preserved in salt-marsh sediments at four sites in North Carolina. Reconstructions of sea level across the region enable us to identify regional trends and spatial variation in the timing and magnitude of RSLR. In the absence of long-term instrumental records in this region, geologically derived estimates of former sea level are necessary to detect changes in the rate of RSLR. Using a foraminifera-based transfer function we show that RSLR increased at the start of the 19th Century from a background rate of 0.8mm/yr ± 0.04mm to 1.5mm/yr ± 0.16mm. We identified a second acceleration around 1900AD to ~4mm/yr. This current rate of RSLR has been reconciled with the available tide gauge data and validates our approach. Contemporary foraminifera were collected from 11 salt marshes in North Carolina representing a wide range of physiographic settings. The strong relationship between foraminifera and elevation in the modern environment was used to develop a regional scale transfer function. We reconstructed RSL by applying this transfer function to assemblages of foraminifera in four cores of salt-marsh peat recovered from sites across the Albemarle - Pamlico Estuarine system. The timing of RSL changes is constrained by age models developed from composite chronologies of conventional, high precision and bomb spike radiocarbon, 210Pb, 137Cs dating and a pollen chrono-horizon (Ambrosia). Recent geological investigations of historic RSL in North America (e.g., Maine and Connecticut) have identified accelerated rates of sea-level rise beginning in the late 19th and early 20th Centuries. Our study suggests that in North Carolina the onset of rapid RSL change began earlier (around the beginning of the 19th Century) and is comprised of two distinct accelerations. High resolution studies of RSL change and accurate dating of accelerations may be able to provide new information pertaining to the mechanisms behind historic RSL rise.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMGC33A0760K
- Keywords:
-
- 1105 Quaternary geochronology;
- 1641 Sea level change (1222;
- 1225;
- 4556);
- 4217 Coastal processes