Common Era sea-level budgets along the U.S. Atlantic coast

Abstract

Sea-level budgets account for the contributions of processes driving sea-level change, but are predominantly focused on global-mean sea level and limited to the 20th and 21st centuries. Here we estimate site-specific sea-level budgets along the U.S. Atlantic coast during the Common Era (0-2000 CE) by separating relative sea-level (RSL) records into process-related signals on different spatial scales. Regional-scale, temporally linear processes driven by glacial isostatic adjustment dominate RSL change and exhibit a spatial gradient, with fastest rates of rise in southern New Jersey (1.6 ± 0.02 mm yr^-1). Regional and local, temporally non-linear processes, such as ocean/atmosphere dynamics and groundwater withdrawal, contributed between -0.3 and 0.4 mm yr^-1 over centennial timescales. The most significant change in the budgets is the increasing influence of the common global signal due to ice melt and thermal expansion since 1800 CE, which became a dominant contributor to RSL with a 20th century rate of 1.3 ± 0.1 mm yr^-1.

Fig. 1. Location of relative sea-level (RSL) reconstructions on the U.S. Atlantic coast.

a The six sites used in analysis from north to south are: Connecticut, New York City, northern New Jersey (this study), southern New Jersey (Leeds Point (LP) and Cape May Courthouse (CMC)), and North Carolina. b Map of New Jersey with location of new northern New Jersey record and Sandy Hook tide gauge. c Salt-marsh study site at Cheesequake State Park in northern New Jersey off of Raritan Bay where the new RSL record was produced. Fossil core transect locations shown, including location of the sampled core for detailed analysis. d RSL record from northern New Jersey with spatiotemporal model predictions (mean with 1σ uncertainty) and decadal-average RSL measurements from the Sandy Hook tide gauge. Boxes represent the vertical RSL (1σ) and chronological (2σ) uncertainty for each data point.

Fig. 2. Common Era relative sea-level model predictions for U.S. Atlantic coast sites.

See Fig. 1a for site locations. Model predictions are the mean with 1σ uncertainty. LP Leeds Point. CMC Cape May Courthouse.

Fig. 3. Global sea-level contribution.

a Proxy sea-level records in the Common Era sea-level database, where new sites updated from Kemp et al. are shown in red. b Reconstructed global sea level from this study compared to the results from Kopp et al. and Kemp et al.. Model predictions are the mean with 1σ uncertainty.

Fig. 4. Common Era sea-level budgets.

Budgets are separated into global, linear, regional nonlinear, and local components for a northern New Jersey; b Connecticut; c New York; d southern New Jersey—Leeds Point (LP); e southern New Jersey—Cape May Courthouse (CMC); f North Carolina. Total rates for each site are indicated by dashed black line. Percentage contributions of each budget component are also shown for northern New Jersey for five 100-year time intervals through the Common Era.

Fig. 5. Sea-level budget compared with climate proxies over the Common Era.

a Global and regional nonlinear portion of the sea-level budget for northern New Jersey. RSL relative sea level. b PAGES2k global surface temperature anomaly from Neukom et al. and standardized Ocean2k synthesis of median global sea surface temperature (SST) anomaly from McGregor et al.. c Number of glacial advances by region from Solomina et al. and rate of Greenland ice-mass change from Briner et al.. d Atlantic Meridional Overturning Circulation (AMOC) proxy reconstructions from Rahmstorf et al. (blue) and Thornalley et al.  (green) and positive and negative North Atlantic Oscillation (NAO) reconstruction adapted from Baker et al.. Timing of Medieval Climate Anomaly (MCA) and Little Ice Age (LIA) from Neukom et al..