SEA LEVEL CHANGE AT BARN ISLAND SALT MARSH, CONNECTICUT

Records of peat accumulation at Barn Island Marsh, in Stonington, Connecticut and tide gauge data from nearby New London, Connecticut indicate an average local sea level rise of 2.5 ± 0.5 mm/y since the 1950s.  Using marsh cores from Barn Island, we determine a chronology for local peat accumulation from several methods.  Cesium-137, which is absorbed on marsh sediment after fall-out from atmospheric nuclear tests that spiked in 1963, is used as an impulse tracer, and Lead-210, a naturally occurring radionuclide supplied to the marsh from the atmosphere, is used as a steady-state tracer to find an age-depth profile for the last ~100 years. Storm deposits from several major hurricanes are located and measured based on radiometrically-derived peat accumulation rates.  Marsh grass succession is determined by rhizome analysis of four dominant species: Spartina alterniflora, Spartina patens, Distichlis spicata, and Juncus gerardi in transects of cores across the marsh. Mirroring the distribution of grasses from high to low marsh, the cores record a shift from a J. gerardi and D. spicata regime deeper in the core to a Spartina-dominated environment in recent decades. In agreement with other regional and global studies, the techniques we combine indicate that marsh accretion at Barn Island and relative sea level rise in the adjacent waters appear to be accelerating in recent decades.