HIGH-RESOLUTION RECONSTRUCTION OF SEA-LEVEL CHANGE DURING THE PAST 300 YEARS

This study establishes three high-resolution sea-level records based on foraminiferal and chronological analyses of saltmarsh peat sequences with the aim to extend back in time observational records of sea-level change. We report on records from Wells and Machiasport (northern Gulf of Maine) and Chezzetcook (Atlantic coast of Nova Scotia). The relationship between distributions of foraminiferal species and elevation on the modern saltmarsh surface is quantified by regression analyses and applied to fossil foraminifera in cores to reconstruct former heights of the saltmarsh surface in relation to tide levels. The peat sequences are dated by ²¹⁰Pb, ¹³⁷Cs, ²⁰⁶Pb/²⁰⁷Pb and AMS¹⁴C. We also use pollen markers (primarily Ambrosia) and historical archives to date the onset of land clearing subsequent to European settlement in the late 18^th century. Our results indicate that, along the coast of Maine, sea level has risen by 30-40 cm since 1800 AD. A short-lived oscillation occurred in the 18^th century. The sea-level record from Chezzetcook provides the highest resolution. Here, sea level rose by about 10 cm in the second half of the 18^th century, but only by about 5 cm during the entire 19^th century. Since 1900 AD, sea level has risen by about 35 cm. The 19^th century slowdown of sea-level rise is also apparent in the Maine sea-level records albeit not as clearly pronounced when error margins are taken into account. The rates of 20^th century sea-level rise agree with tide-gauge records. These rates are unprecedented in the last millennium and correspond with hemispheric (and global) climatic warming.