ECOMORPHODYNAMIC FEEDBACKS AND COUPLINGS BETWEEN BARRIER AND BACK-BARRIER ENVIRONMENTS INFLUENCE HOLISTIC SYSTEM RESPONSE TO CHANGING CLIMATE

As dynamic, low-lying landforms, barrier islands and their associated back-barrier environments are especially sensitive to shifting environmental conditions. Whether or not barrier island systems persist in the future depends on the degree to which they can maintain elevation above sea level while also responding to changes in forcing by migrating landward to maintain equilibrium with evolving conditions. We are increasingly learning that ecomorphodynamic interactions (i.e., interactions between ecological and morphodynamic processes) as well as couplings between island and back-barrier marsh environments play a critical role in determining how barrier island systems will evolve as sea level rises, storm intensity increases and the species composition of coastal vegetation changes in the future. The integration of field observations and model experiments is central to developing a better understanding of these ecomorphodynamic feedbacks and landscape couplings. We present an overview and synthesis of recent and new model experiments and observations that illustrate the importance of feedbacks between vegetative and sediment transport processes, and couplings between landscape units, in influencing 1) the rate of formation, maximum height and morphology of coastal dunes, 2) overall island state (high vs. low) and the potential for rapid transitions in state to occur in response to gradually changing forcing; and 3) the persistence of back-barrier marshes, and thus the influence of back-barrier marshes on the rate of migration of barrier island-marsh systems overall.