Interannual Sea Level Variability Amplifies Coastal Wetland Loss

Accelerating rates of global sea level rise (SLR) are a primary land loss driver today for coastal wetlands. Predictive models to anticipate rates and locations of land loss typically incorporate smoothed SLR projections that lack interannual variability. Here we utilize a biophysical numerical model to examine the impact of randomly generated sea-level variability derived from tide gauge observations on projections of wetland loss timing and magnitude to 2100 for a deltaic subbasin (Barataria Basin) of the Mississippi River Delta in Louisiana, USA. We demonstrate that periods of enhanced SLR rate that have been observed as a SLR hotspot on the US Atlantic and Gulf Coasts in recent decades can irreversibly accelerate land loss by several decades relative to state-of-the-art smooth SLR projections. These trends are even more negative when marsh edge erosion induced by storms is included in model projections. Our projections also demonstrate a limited or no ability of marsh ecotypes to backstep to accommodate these regional interannual accelerations. Our results emphasize the importance of (1) identifying other oceanographically linked regional hotspots in SLR, and (2) modifying SLR projections to accommodate this variability in coastal protection and restoration planning.