Within-region replication of late Holocene relative sea-level change: An example from southern New England, United States

Tide-gauge measurements in the western North Atlantic Ocean show coherent, multi-decadal relative sea-level (RSL) trends across multiple spatial scales. Proxy reconstructions developed from salt-marsh sediment can extend this instrumental record. However, the degree of coherence in proxy re-constructions is underexamined through within-region replication. To explore within-region replication, we developed a new RSL reconstruction from Fox Hill Marsh, Rhode Island to complement similar re-cords at nearby sites. We established the elevation of former sea level from assemblages of foraminifera and bulk-sediment d13C values using a Bayesian transfer function. We employed radiocarbon dating and recognition of pollution horizons to construct a core chronology. Since-1200 BCE, RSL rose by-3.7 m at Fox Hill Marsh. After correction for glacial isostatic adjustment, application of a statistical model intended to quantify (multi-) century-scale trends showed that the fastest rate of rise in at least the past 3000 years was 1.71 +/- 0.84 mm/yr (95% credible interval) in 2020 CE. This result replicates regional tide -gauge measurements and other proxy reconstructions. Using an alternative statistical model constructed to identify sub-centennial sea-level changes, we examined if there was a hotspot of 18th century rise in the northeastern United States and found no spatially-coherent trend (i.e., occurring at all or most sites). This lack of replication indicates that accelerated rise during the 18th century is likely local (site-specific) in scale, or an artifact of individual reconstructions. Continued efforts to replicate RSL reconstructions will increase confidence in the accuracy of records and their subsequent interpretation. (c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Tide-gauge measurements in the western North Atlantic Ocean reveal consistent multi-decadal relative sea-level trends across various scales. Proxy reconstructions from salt-marsh sediments can extend this record, but the coherence of these reconstructions within a region is not well-investigated. In this study, a new relative sea-level reconstruction from Fox Hill Marsh, Rhode Island is developed to complement existing records at nearby sites, using a Bayesian transfer function and radiocarbon dating. The findings replicate regional tide-gauge measurements and other proxy reconstructions, highlighting the importance of continued replication efforts to enhance confidence in sea-level records.