NOAA/WDS Paleoclimatology - North Atlantic 2000 Year Relative Sea Level Data

STUDY NOTES: North Atlantic relative sea level data points from the east coast of the United States, in North Carolina (Sand Point and Tump Point) and at Wood Island, Massachusetts. In North Carolina, a modern dataset of 193 surface samples collected from 10 salt marshes was used to develop transfer functions to quantify the relationship between foraminifera and elevation. We used these transfer functions to estimate paleomarsh elevation (PME) at Sand Point and Tump Point, North Carolina. PME is the elevation at which a sample formed with respect to its contemporary sea level. Foraminifera preserved in 1 cm thick samples from the Sand Point and Tump Point cores provided the basis for estimating PME. To reconstruct relative sea level (RSL), estimated PME was subtracted from the measured altitude of each sample. At Wood Island (Massachusetts), salt-marsh plants were used as sea-level indicators. The modern mean elevation of Juncus geradii (Jg), Spartina patens (Sp), and Distichlis spicata (Ds) was estimated by measuring stands at the Wood Island site. Multiple, stratigraphically ordered, samples were recovered along the boundary between a gently sloping granite erratic and overlying salt-marsh sediments. Identifiable remains of Jg, Sp, and Ds were used to provide an estimate of PME.
ABSTRACT SUPPLIED BY ORIGINATOR: We present new sea-level reconstructions for the past 2100 y based on salt-marsh sedimentary sequences from the US Atlantic coast. The data from North Carolina reveal four phases of persistent sea-level change after correction for glacial isostatic adjustment. Sea level was stable from at least BC 100 until AD 950. Sea level then increased for 400 y at a rate of 0.6 mm/y, followed by a further period of stable, or slightly falling, sea level that persisted until the late 19th century. Since then, sea level has risen at an average rate of 2.1 mm/y, representing the steepest century-scale increase of the past two millennia. This rate was initiated between AD 1865 and 1892. Using an extended semiempirical modeling approach, we show that these sea-level changes are consistent with global temperature for at least the past millennium.