Dataset: Relative sea-level change and driving processes during the past ~4000 years in the Chesapeake Bay, U.S. Atlantic Coast

Late Holocene relative sea-level (RSL) histories from the mid-Atlantic coast of the US are largely driven by glacial isostatic adjustment, which are then superimposed by climatic driven alterations and local processes (e.g. sediment compaction). An understanding of past RSL changes and constraining future projections, is important to understand the vulnerability of low-lying regions. Here, we reconstruct RSL using proxy (foraminifera) and instrumental (tide gauge) records to understand how RSL has evolved, and the mechanisms driving RSL changes during the late Holocene in the Chesapeake Bay. Our proxy record utilizes a continuous sequence of salt-marsh peat that estimates the position of past RSL using a new modern foraminiferal training set comprising >130 samples from sites across the Chesapeake Bay. The training sets reveal the vertical zonation of foraminiferal assemblages and we use these to explore forcing mechanisms driving RSL changes derived from periodic changes in the biostratigraphy every ~1500 years. We constrained sedimentation rates using a Bayesian age model (Bchron) that incorporated 35 radiocarbon ages with event-based chronohorizons (e.g., pollen records of land clearance and pollution markers) and corrected sample elevations for sediment compaction using a geotechnical model calibrated by local sediment cores. We assessed changes in RSL using an Errors-In-Variables Integrated Gaussian Process model that integrates both proxy and instrumental records with full consideration of their uncertainties. We show a magnitude ~6 m RSL rise since ~2000 BCE is characterized by changes in RSL rate concurrent with climate alterations. Minimum RSL rates of 0.8 and 1.3 mm/yr are recorded at 700 BCE and 1450 CE, respectively, and coincide with widespread cooling phases of the late Holocene. Furthermore, we show the modern rate of RSL (rising at 3.6 mm/yr) is unprecedented in the last 4000 years, supporting other regional and global reconstructions that identify an anthropogenic influence on sea levels since the mid-19th century.