Cooling and Rainfall Isotope Composition During the Last Glacial Maximum in the Low-Latitude Eastern Canary Islands: Insights from Carbonate Clumped Isotopes in Land Snails

Abstract. Compilations of proxy data suggest that global temperatures during the Last Glacial Maximum (LGM; ~21,000 years ago) were 3–6 °C cooler than present. However, large-scale proxy syntheses and assimilation products largely focus on the mid- and high-latitude northern hemisphere and marine environments with limited data from low latitudes or terrestrial island settings. Here, we report modern and LGM land snail proxy data from endemic land snails of the Canary Islands (Monilearia monilifera, Theba geminata, and Theba sp.), in the subtropical Atlantic off the coast of Northwest Africa and compare results to LGM paleoclimate model simulations. We apply carbonate clumped paleothermometry, a thermodynamically based environmental tracer, to terrestrial snail shells to constrain mean annual surface air temperature and compare results to climate model simulations from the Paleoclimate Modeling Intercomparison Project (PMIP3 and PMIP4) and from the Hadley Center (HadCM3). Proxy data indicate that LGM mean annual air temperatures ~8.4 °C ± 2.8 °C cooler than estimates from modern land snails, which is cooler than most paleoclimate model estimates. We applied a snail-based proxy system model to reconstruct the oxygen isotope composition of rainfall and show that data are consistent with winter-dominated rainfall with no major changes in water source with respect to present. Our work indicates major glacial cooling in a terrestrial low-latitude ocean island setting that contradicts broader LGM terrestrial temperature reconstructions and simulations.