Sea Levels of the Past 2000 Years

Sea-level rise projected for the coming decades presents a hazard to intense concentrations of population, economic production, and static infrastructure along North American coasts. Modern sea-level rise lacks a fundamental paleo-perspective of the type already available for temperature changes. Common Era (last 2000 years) sea-level reconstructions capture multiple phases of climate and sea-level behavior for model calibration, provide a pre-anthropogenic background against which to compare recent trends, and characterize patterns of natural variability.

The Atlantic coast of North America provides a sedimentary record of Common Era sea levels with the resolution to identify the mechanisms that cause spatial variability in sea-level rise. We reveal three distinct patters in sea-level during the Common Era along the North American Atlantic coast, likely linked to wind-driven changes in the Gulf Stream: (1) Florida, sea level is essentially flat, with the record dominated by long-term geological processes;  (2) North Carolina, sea level falls to a minimum near the beginning of the second millennium, climbing to an early Little Ice Age maximum in the fifteenth century, and then declining through most of the nineteenth century; and (3) New Jersey, a sea-level maximum around 900 CE, a sea-level minimum around 1500 CE, and a long-term sea-level rise through the second half of the second millennium.

We combine the salt-marsh data from North American Atlantic coast with tide-gauge records and other high resolution proxies from the northern and southern hemispheres to estimate global sea level. We find that global sea level  varied by 16 cm over the pre-Industrial Common Era, with a notable decline over 1000–1400 CE that coincides with ∼0.2 °C of global cooling. The 20th century GSL rise was extremely likely faster than during any of the 26 previous centuries.