Interpreting palaeoclimate from oxygen isotopes in lake sediment biogenic silica

Oxygen isotope analysis of lake sediment biogenic silica (δ18OBiSi) is a rapidly expanding palaeoclimate tool, particularly where calcium carbonates are scarce. However, sedimentary δ18OBiSi values are often a complex function of multiple forces - essentially a cascade which begins with the climate controls over rainwater oxygen isotopes (δ18OP) and ends with the diagenetic processes during sedimentation. Such complexity means that it is often difficult to derive single, quantitative climate indices from δ18OBiSi. In an attempt to circumvent these issues, we discuss how each link of the cascade can be modelled, to varying degrees of accuracy, to enable the forward modelling of lake sediment δ18OBiSi, using the case study of Lochnagar, an upland lake in Scotland. Progress and potential future research in this respect are highlighted.