BARRIER ISLAND AND ESTUARY CO-EVOLUTION IN RESPONSE TO HOLOCENE CLIMATE AND SEA-LEVEL CHANGE: EXAMPLES FROM THE NORTH CAROLINA OUTER BANKS - PAMLICO SOUND COASTAL SYSTEM

Barrier islands and associated back-barrier estuaries and lagoons interact via hydrodynamic and sedimentary processes, affecting the evolution of both systems. Understanding changes to one system can inform us on changes that may occur (or have occurred) to the other system. Understanding these coupled dynamic processes is vital to forecasts of future coastal morphologic and hydrodynamic changes in response to such factors as sea-level rise and storm patterns. This investigation addresses the co-evolution of Pamlico Sound and the Outer Banks barrier islands of North Carolina, USA. A variety of data are used to characterize the geology and dynamic nature of the system, including geophysical, sedimentological, microfossil, and geochemical proxies. These new data are used for paleoenvironmental and geomorphic reconstructions to determine boundary conditions for hydrodynamic models. Models are corroborated by geological data and provide an understanding of tidal water level, currents, and salinity variations within the estuaries as a function of barrier island evolution. The barrier island evolution is largely a function of climate conditions and the characteristics of the flooded paleotopography as it interacts with rising sea level. The new data and models illustrate the highly sensitive nature of responses in this system to rapid, but minor, decadal to century time-scale climate changes (e.g. the Medieval Climate Anomaly – MCA, and the Little Ice Age), and the response to storm wind events for the present-day geomorphology. As an example, the data show that during the Medieval Climate Anomaly, conditions were characterized by extreme barrier island segmentation and enhanced tidal and wave energy in Pamlico Sound, resulting from increased hurricane activity. The MCA coastal condition represents a likely analogue for the near future.