COMMON ERA SEA-LEVEL BUDGETS ALONG THE U.S. ATLANTIC COAST INFORMED BY ROBUST FORAMINIFERAL-BASED RECONSTRUCTIONS (Invited Presentation)

Foraminifera from salt-marsh environments have been used extensively to produce continuous high-resolution records of relative sea-level (RSL) change due to their strong relationship with tidal level. A detailed understanding of the variability of foraminifera assemblages in the modern environment is essential for their use as a proxy to reconstruct RSL. We conducted a monitoring study of foraminifera from four high marsh monitoring stations along a salinity gradient in New Jersey over three years to evaluate small-scale spatial and temporal variability of live, dead, and total (live + dead) foraminifera assemblages. Using the results from this study, for the first time we formally incorporated information about the temporal and spatial variability of modern foraminiferal distributions into a Bayesian transfer function through informative foraminifera variability priors to include in RSL reconstructions. Importantly, we found that even when accounting for modern foraminifera variability, foraminiferal-based RSL reconstructions from high marsh environments remain robust and reproducible.

We incorporated the informative foraminifera variability priors into a RSL reconstruction from northern New Jersey and combined it with previously published foraminiferal-based RSL reconstructions to use with a spatiotemporal model to analyze magnitudes and rates of RSL change. Using these numerous high-resolution reconstructions, we produced Common Era sea-level budgets for sites along the U.S. Atlantic coast to further elucidate variability of driving processes of sea-level changes in the past and present, and which will shape such changes in the future. Each budget is dominated by regional-scale, temporally linear processes driven by glacial isostatic adjustment until at least the mid-19th century. Non-linear regional and local-scale processes, such as ocean/atmosphere dynamics and groundwater withdrawal, are smaller in magnitude and vary temporally and spatially. The most significant change to the budgets is the increasing influence of the global signal due to ice melt and thermal expansion since ~1800 CE, which reaches a 20th century rate of 1.3 ± 0.1 mm/year, accounting for 43-65% of each budget.