The North Atlantic marine reservoir effect in the Early Holocene: Implications for defining and understanding MRE values

The marine reservoir effect (MRE) is a 14C age offset between the oceanic and atmospheric carbon reservoirs. The MRE is neither spatially nor temporally constant and values may deviate significantly from the global model average provided by the Marine04 curve. Such a deviation is calculated as a ΔR value and modern (pre-bomb) values show considerable spatial variations. There is also considerable evidence for temporal variability linked to paleoenvironmental changes identified in paleoclimatic proxy records. Seven new ΔR values are presented for the North Atlantic, relating to the period c. 8430–3890 cal. BP (c. 6480–1940 BC). These were obtained from 14C analysis of multiple samples of terrestrial and marine material derived from seven individual archaeological deposits from Mainland Scotland, the Outer Hebrides and the Orkney Isles. The ΔR values vary between 143 ± 20 14C yr and −100 ± 15 14C yr with the positive values all occurring in the earlier period (8430–5060 cal. BP), and the negative values all coming from later deposits (4820–3890 cal. BP). The nature of MRE values and the potential for spatial and temporal variation in values is the subject of current research interest and these data are placed in the context of (i) other estimates for UK coastal waters and (ii) important questions concerning current approaches to quantifying the MRE.