NC CHaNGE Coastal Hydrodynamic and Natural Geological Evolution

Project title: A Multidisciplinary Investigation of Coastal System Response to Sea-Level Rise, Climate Dynamics, and Geomorphic Change. 01/09/2011-09/30/2014. $ 399,923.

Gaining a better understanding of the response of coastal systems to sea-level and climate change is vital to the future stability of the economies of communities, states and nations. This investigation will use observations and analyses of coastal stratigraphy and geomorphology, paleobathymetric models, geochemical proxies, and a physical oceanographic model (Delft3D) to understand past (Holocene) responses of a coastal system in North Carolina to changes in climate, geomorphology, and hydrodynamics. The modern estuarine system has a microtidal range of approximately 0.1 m, due in part to the existence of the Outer Banks barrier islands. We hypothesize that barrier island segmentation (similar to what is expected in the future) during two intervals of Holocene time resulted in an astronomical tidal component substantially in excess of the modern system, with associated changes in tidal currents, sediment transport, and salinity. To understand the hydrodynamic and morphodynamic response of the system to geomorphic changes brought on by climate and sea-level conditions, we propose to develop paleoenvironmental and paleobathymetric models of this system at specific time slices, and model the tidal effects (amplitude, currents, sediment transport, salinity) with Delft3D, using various representations of barrier island morphology, which are constrained by our geologic observations. Geochemical proxies will be used to understand the regional climate changes before, during, and following these two events. These data will facilitate a better understanding of the past coastal system response to climate conditions, and the potential for future changes. Intellectual Merit - This investigation will reveal, in great detail, the response of a coastal system to sealevel rise and climate change, by examining and modeling past responses to quantifiable paleoenvironmental, climate and sea-level conditions. The proposed work represents a synergistic relationship between observations and models, which will advance our understanding of the limitations of this approach for predictions of future change, and point us toward refinements in the methodology. By understanding the measured and modeled morphodynamic processes through time, these data will enable us to evaluate the potential for a threshold response (a rapid reorganization; i.e., a sudden change in tidal regime and sediment transport) of barriers and estuaries to future sea-level rise and storms. Results of this study will lay the foundation for additional continuing studies (geological, biological, hydrological) which depend upon a refined knowledge of hydrodynamic and geomorphic changes. Finally, a better understanding of the Holocene stratigraphy and evolution of this region advances the knowledge of the characteristics of paleoclimate events along the southeast U.S. margin (e.g., what is the record of the Little Ice Age or Medieval Warm Period within these sediments, and what does that indicate about climate during those time intervals).