Predicting marsh vulnerability to sea-level rise using Holocene relative sea-level data
Benjamin P. Horton (Nanyang Technological University)
Ian Shennan (Durham University)
S.L. Bradley (TU Delft - Physical and Space Geodesy)
Niamh Cahill (University College Dublin)
Matthew Kirwan (Virginia Institute of Marine Science )
Robert E. Kopp (Rutgers University)
Timothy A. Shaw (Nanyang Technological University)
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Abstract
Tidal marshes rank among Earth's vulnerable ecosystems, which will retreat if future rates of relative sea-level rise (RSLR) exceed marshes' ability to accrete vertically. Here, we assess the limits to marsh vulnerability by analyzing >780 Holocene reconstructions of tidal marsh evolution in Great Britain. These reconstructions include both transgressive (tidal marsh retreat) and regressive (tidal marsh expansion) contacts. The probability of a marsh retreat was conditional upon Holocene rates of RSLR, which varied between -7.7 and 15.2 mm/yr. Holocene records indicate that marshes are nine times more likely to retreat than expand when RSLR rates are ≥7.1 mm/yr. Coupling estimated probabilities of marsh retreat with projections of future RSLR suggests a major risk of tidal marsh loss in the twenty-first century. All of Great Britain has a >80% probability of a marsh retreat under Representative Concentration Pathway (RCP) 8.5 by 2100, with areas of southern and eastern England achieving this probability by 2040.
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