Accretion of a New England (U.S.A.) Salt Marsh in Response to Inlet Migration, Storms, and Sea-level Rise |
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| Authors: | CT Roman JA Peck JR Allen JW King PG Appleby |
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| Institution: | aU.S. Geological Survey, Biological Resources Division, Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, 02882, U.S.A.;bGraduate School of Oceanography, University of Rhode Island, Narragansett, RI, 02882, U.S.A.;cU.S. Geological Survey, Biological Resources Division, 15 State Street, Boston, MA, 02109, U.S.A.;dDepartment of Applied Mathematics and Theoretical Physics, University of Liverpool, Liverpool, L69 3BX, U.K. |
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| Abstract: | Sediment accumulation rates were determined at several sites throughout Nauset Marsh (Massachusetts, U.S.A.), a back-barrier lagoonal system, using feldspar marker horizons to evaluate short-term rates (1 to 2 year scales) and radiometric techniques to estimate rates over longer time scales (137Cs,210Pb,14C). The barrier spit fronting theSpartina-dominated study site has a complex geomorphic history of inlet migration and overwash events. This study evaluates sediment accumulation rates in relation to inlet migration, storm events and sea-level rise. The marker horizon technique displayed strong temporal and spatial variability in response to storm events and proximity to the inlet. Sediment accumulation rates of up to 24 mm year−1were recorded in the immediate vicinity of the inlet during a period that included several major coastal storms, while feldspar sites remote from the inlet had substantially lower rates (trace accumulation to 2·2 mm year−1). During storm-free periods, accumulation rates did not exceed 6·7 mm year−1, but remained quite variable among sites. Based on137Cs (3·8 to 4·5 mm year−1) and210Pb (2·6 to 4·2 mm year−1) radiometric techniques, integrating sediment accumulation over decadal time scales, the marsh appeared to be keeping pace with the relative rate of sea-level rise from 1921 to 1993 of 2·4 mm year−1. At one site, the210Pb-based sedimentation rate and rate of relative sea-level rise were nearly similar and peat rhizome analysis revealed thatDistichlis spicatarecently replaced this onceS. patenssite, suggesting that this portion of Nauset Marsh may be getting wetter, thus representing an initial response to wetland submergence. Horizon markers are useful in evaluating the role of short-term events, such as storms or inlet migration, influencing marsh sedimentation processes. However, sampling methods that integrate marsh sedimentation over decadal time scales are preferable when evaluating a systems response to sea-level rise. |
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| Keywords: | salt marsh sedimentation rates 210Pb 137Cs radiocarbon sea-level rise storms Massachusetts (U S A ) |
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