Alan D. Wanamaker
Lydia M. Staisch
David J. Reynolds
Karine L. Holmes
Bryan A. Black
David C. Edge
2022
<div class="abstract-content"><div class="abstract" data-abstract-type="normal"><p>Quantifying the marine radiocarbon reservoir effect, offsets (ΔR), and ΔR variability over time is critical to improving dating estimates of marine samples while also providing a proxy of water mass dynamics. In the northeastern Pacific, where no high-resolution time series of ΔR has yet been established, we sampled radiocarbon (<span class="sup">14</span>C) from exactly dated growth increments in a multicentennial chronology of the long-lived bivalve, Pacific geoduck (<span class="italic">Paneopea generosa</span>) at the Tree Nob site, coastal British Columbia, Canada. Samples were taken at approximately decadal time intervals from 1725 CE to 1920 CE and indicate average ΔR values of 256 ± 22 years (1σ) consistent with existing discrete estimates. Temporal variability in ΔR is small relative to analogous Atlantic records except for an unusually old-water event, 1802–1812. The correlation between ΔR and sea surface temperature (SST) reconstructed from geoduck increment width is weakly significant (r<span class="sup">2</span><span> </span>= .29, p = .03), indicating warm water is generally old, when the 1802–1812 interval is excluded. This interval contains the oldest (–2.1σ) anomaly, and that is coincident with the coldest (–2.7σ) anomalies of the temperature reconstruction. An additional 32<span> </span><span class="sup">14</span>C values spanning 1952–1980 were detrended using a northeastern Pacific bomb pulse curve. Significant positive correlations were identified between the detrended<span> </span><span class="sup">14</span>C data and annual El Niño Southern Oscillation (ENSO) and summer SST such that cooler conditions are associated with older water. Thus,<span> </span><span class="sup">14</span>C is generally relatively stable with weak, potentially inconsistent associations to climate variables, but capable of infrequent excursions as illustrated by the unusually cold, old-water 1802–1812 interval.</p></div></div>
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10.1017/RDC.2022.83
en
Cambridge University Press
A modern multicentennial record of radiocarbon variability from an exactly dated bivalve chronology at the Tree Nob site (Alaska Coastal Current)
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