Marine Radiocarbon Reservoir Ages in Scottish Coastal and Fjordic Waters

Abstract

High freshwater inputs into Scottish sea lochs (fjords) combined with the restricted exchange between sea loch basin water and coastal Atlantic water masses are likely to result in reduced regional marine radiocarbon reservoir ages (R[t]) in these environments. To test this hypothesis, historical, museum-archived shells, collected live on known dates prior to AD 1950 from coastal locations in NW Scotland, were 14C dated to provide a means of determining R(t) and hence the regional deviation (ΔR) from the modeled global surface ocean reservoir age (R). The sea loch data, when combined with 14C dates from the Scottish west coast (Harkness 1983), yield a regional ΔR value of −26 ± 14 yr. The ΔR of sea loch (fjordic) and coastal waters of NW Scotland are statistically different (at a confidence level >95%) from the ΔR value of 17 ± 14 yr reported for UK coastal waters (Reimer 2005; data after Harkness 1983) and are in good agreement with the coastal ΔR value of −33 ± 93 yr reported by Reimer et al. (2002). Therefore, it is recommended that a regional ΔR correction of −26 ± 14 yr should be applied to modern (i.e. pre-bomb but not prehistoric) marine 14C dates from the NW coast of Scotland.