Oxygen isotopes as tracers of Mediterranean climate variability: An introduction

Oxygen isotopes provide one of the best tracers of the Mediterranean hydrological cycle from source areas in the oceans, through precipitation, to ground- and surface freshwaters. The ratio of oxygen isotopes preserved in sedimentary carbonates also provides a key indicator of natural climatic variability over timescales beyond those based on direct monitoring or historical observations. This set of papers, originally deriving from an ESF MedClivar workshop meeting in Pisa, Italy, critically considers how δ18O data can be used to provide records of Mediterranean climate variability over a hierarchy of timescales. They focus on five main themes, namely 1) water isotopes as tracers for monitoring and modelling patterns of precipitation, 2) lakes and surface waters, and their sedimentary records, 3) groundwaters and cave systems as preserved in speleothems, 4) marine systems, such as deep-sea sediments and surface corals, and 5) intercomparison of different archives and regional-scale data: model comparisons using isotope data bases. Future priorities include improved calibration of proxy-climate data via monitoring of contemporary systems and mass balance modelling, and a focus on synthesising high-resolution climate reconstructions during the last 2000 years.