Seasonal Climate Records Preserved In Limpet Shells (Patella vulgata) from Bronze Age, Neolithic, and Viking Shell Middens, Scotland, UK

Climate archives contained in shells of the European limpet, Patella vulgata, from archaeological shell middens can potentially provide much needed information about seasonality in mid-latitude coastal areas prior to the complicating effects of industrialization. P. vulgata shells are common in the Bronze Age/Neolithic and Viking middens accumulated in cave deposits on the Isle of Mull and in coastal deposits in the Orkney Islands, Scotland (respectively). Radiocarbon dates and artifacts place the cave deposit between 3300 BC and 500 AD and the Viking middens between 800 and 1200 AD. The latter interval coincides with the Medieval Warm Period. The earlier cold interval (the Vandal Minimum: 500-800 AD) is not represented in either deposit.

Previous investigation determined that oxygen isotope ratios in P. vulgata shells record seasonal growth temperature, and therefore can be used as a proxy for sea surface temperature. Isotopic analysis of shells dating to the 9th/10th century reveals similar winter and summer temperature relative to today. Based on a published oxygen isotope record from a speleothem in southwestern Ireland, we predict that shells from the Bronze Age and Neolithic cave deposit will reflect an early transition from cool conditions to a brief interval of warming followed by an extended cool interval from ~4500-3000 BP and ending with a warm interval that coincides with the Roman Warm Period.