SEA-LEVEL RISE IN THE DELAWARE BAY (U.S. ATLANTIC COAST) DURING THE COMMON ERA

The study of sea levels during the Common Era (CE; last 2000 years) improves our understanding of the relation to known periods of climate variability, such as the Medieval Climate Anomaly and the Little Ice Age. Understanding natural variability in sea level is vital for model calibration and the improvement of predictions for future sea-level rise.

High-resolution records of sea level spanning the CE exist along the U.S. Atlantic coast from Connecticut, New Jersey, North Carolina and Northern Florida. Here, we present the first record from the Delaware Bay, a region with the highest rates of glacial isostatic subsidence along the U.S. Atlantic coast.

We collected a modern training set of 60 foraminiferal samples from Breakwater Harbor marsh, Delaware Bay. The assemblages are dominated by Trochammina inflata, Jadammina macrescens and Haplophragmoides spp. in the high marsh, and T. inflata, J. macrescens, Arenoparrella mexicana and Miliammina spp. in the low marsh. We developed a foraminifera-based transfer function to reconstruct the paleomarsh elevation from a ~2.6m long core of low and high marsh peat sediment.

Foraminifera-based reconstructions were placed into a temporal framework using a composite chronology composed of AMS radiocarbon, short-lived radionuclides (²¹⁰Pb and ¹³⁷Cs) and pollution histories. The reconstructed relative sea-level rise rate during the 20th century was assessed with the nearest Lewes (DE) tide gauge record, and then extended back over the CE.