Coastal wetland dynamics in response to sea-level rise: Transgression and erosion

Much research has been devoted to understanding the processes and dynamics active in coastal wetlands. Yet, very little of this work has been undertaken explicitly to study the landward migration (transgression) of coastal wetland systems in response to sea-level rise. This dissertation identifies those processes that are important to understanding wetland transgression, clarifies the usage of terms from the literature, develops a new classification scheme for coastal marshes based on the relationship between accretionary balance and marsh edge movement, and suggests a framework within which future wetland transgression research should be carried out.; In addition, a new model for marsh transgression is developed based on a detailed, 2000 year record of marsh edge movement from eastern North Carolina. The marsh front advances in pulses termed transgression events. Events occur on the order of every 300-350 years. The transgression events are asynchronous between sites and therefore upturns in the rate of sea-level rise cannot explain the jumps. Rather, the transgression events are a result of upland disturbance allowing landward expansion of the marsh. The upland vegetation has an ability to delay the advance of the marsh margin, even as sea level continues to rise, until there is a disturbance. At this point a transgression event is initiated, and the marsh margin jumps landward striving for a new equilibrium with the temporal position of sea level. Disturbances are most likely generated by large storms. The results provide important new evidence for how biological systems can influence geological change.; Finally, this study incorporates new carbon accumulation data from two estuarine marsh sites with additional carbon data collected from the literature to estimate the annual, erosion-induced flux of carbon from wetlands in the Albemarle-Pamlico-Currituck Sound system in eastern North Carolina. Final results indicate that the annual loss of carbon through shoreline erosion {dollar}(9.3 times 10sp{lcub}10{rcub}{dollar} g yr{dollar}sp{lcub}-1{rcub}){dollar} is roughly equal to that accumulating at the surface of estuarine wetlands in the Albemarle-Pamlico-Currituck Sound system {dollar}(7.2 times 10sp{lcub}10{rcub}{dollar} g yr{dollar}sp{lcub}-1{rcub}).{dollar} If sea-level rise rates, and thus erosion rates, increase over the next century as predicted, carbon loss through erosion will overwhelm accumulation in estuarine wetlands.