153 Paleoclimatology/Paleoceanography I: Proxy Evaluations

Tuesday, 24 October 2006
1:30 PM - 5:30 PM

CONTROLS ON SHELL d18O OF THE EUROPEAN LIMPET, PATELLA VULGATA : A NEW ARCHIVE FOR LATE HOLOCENE CLIMATE CHANGE

Paper number: 153-5
Program: Technical Sessions
Time: 2:30 PM – 2:45 PM

Authors

Abstract

Climate archives contained in shells of the European or common limpet, Patella vulgata, from Viking archaeological deposits can potentially provide much needed information about Late Holocene environmental change in coastal areas. Moreover, sites from northern Europe and the United Kingdom are particularly critical locations because they are under the influence of the North Atlantic Oscillation, a prominent component of the climate system in that region. Before reconstructing climate information preserved in these zooarchaeological records, we developed a temperature proxy using oxygen isotope ratios (d18O) contained in modern shells of P. vulgata. This was achieved by comparing measured shell values to expected values calculated using temperature measurements recorded over the life of live-collected individuals.

Three specimens were collected alive from St. Mary's lighthouse, Whitley Bay, northeastern England in 2001. We completed a sclerochronologic analysis to identify annual growth lines, which defined the microsampling protocol. We sampled the shells at 0.05 to 0.1 mm intervals for d18O analysis to achieve submonthly to subweekly resolution. d18OSHELL values ranged from +0.64 to +3.44‰ (VPDB).

We constructed expected d18OSHELL using observed sea surface temperature (SST) records, assuming d18OWATER is +0.10‰ (VSMOW), and assuming equilibrium fractionation. Expected d18O ranged from -0.77‰ to +2.02‰ (VPDB). Comparison of d18OSHELL with expected values revealed that d18OSHELL values were higher than expected by +1.51±0.21‰. Consequently, SST estimates calculated from d18OSHELL were 6.50±2.45°C lower than observed SSTs. However, because of the relatively uniform offset between observed and expected d18O, an adjustment can be made to account for this predictable vital effect. Thus, past climate can be reliably reconstructed using sclerochronology and variation in d18OSHELL of P. vulgata once the predictable offset is taken into account.