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The study of paleoclimates enables us to improve and better constrain climate models in order to forecast future climate variations. Marine Isotope Stage 11 (MIS11), which began around 425,000 yr BP and lasted about 65,000 yr, is a warm isotope stage of paramount importance, because the astronomical configuration was similar to the one characterizing the Holocene. Therefore, this warm isotope stage is the most appropriate analog to present-day climate known to date. This study aims to provide new data on sea-surface temperatures (SSTs) inferred from the carbon and oxygen isotope compositions of skeletal carbonates of marine invertebrates preserved in two marine deposits of the Canary Islands located at Piedra Alta, Lanzarote, and Arucas, Gran Canaria. According to published isotopic fractionation equations the marine deposit from Arucas recorded SSTs of 15.9 ± 2.2°C on average, while the tsunamite from Piedra Alta recorded SSTs of 21.2 ± 1.9°C on average. Absolute dating, mollusc assemblages, and calculated marine temperatures suggest that the Arucas marine deposit corresponds to the beginning of MIS11, while the Piedra Alta tsunamite was formed during MIS11c. These results show that low latitudes also experienced sizable SST changes during interglacial stages. [ABSTRACT FROM AUTHOR]

The Canary Islands, east of the North Atlantic Ocean (27°N-29°N), are under the influence of the Canary Current, the descending branch of the North Atlantic Gyre, which is modulated by coastal upwelling off North-West Africa. They constitute strategic sites for palaeoclimatic reconstructions, especially for the Last Interglacial (LIG, 129 to 116 ky BP) estimated to be warmer than present. Seventy-four carbon and oxygen isotope bulk analyses and time series measurements were performed on 32 aragonitic mollusc shells from the LIG marine deposits on Lanzarote and Fuerteventura islands during a period of sea-level highstand that we estimated to occur between ≈125 and 119-116 ky BP. Our SST calculations, inferred from shell δ18O values using available isotopic fractionation equations, provide a seasonal SST amplitude ranging from 3.5 °C to 6.0 °C, in agreement with the modern seasonal amplitude, along with a mean SST comprised between 20.4 ± 1.3 °C and 22.2 ± 1.2 °C. With respect to the pre-industrial times, we deduce a positive SST anomaly in the range of +1.0 ± 1.4 °C to +2.8 ± 1.3 °C, consistent with the presence of the species Persististrombus latus , typical of warm SSTs. Although this finding does not match with the zonal negative anomaly of a reconstructed SST at low latitudes of the North Atlantic, it is nevertheless corroborated by other climate reconstructions in the northeastern tropical Atlantic region. We attribute this trend to an excess of summer insolation during the LIG which warmed the Canary Current, enhanced by a weakening of the North African upwelling. The entire North Atlantic Gyre was probably warmer during the LIG. • Isotopes in mollusc shells from Canary Islands reveal seawater warming at MIS5e. • Shells were deposited during sea-level highstand in the second part of LIG. • Seasonal SST amplitude at MIS5e in Canary Islands is similar to that of modern times. • Northeast tropical Atlantic warmed at LIG by insolation and weakening of upwelling. [ABSTRACT FROM AUTHOR]

Fossiliferous bioclastic calcarenites of fluvial-aeolian origin were deposited between 4.3 ± 0.7 Ma and 3.78 ± 0.71 Ma in Lanzarote, Canary Archipelago. Climate was characterized by warm and steppic conditions. The fossil assemblage contains land snail shells that recrystallized into calcite as revealed by Raman spectroscopy. Carbon and oxygen isotope measurements were performed to understand whether or not these isotopic compositions may still reflect some climatic conditions contemporaneous with shell fossilisation and burial. Interpretations have been performed assuming two working hypotheses 1) isotopic compositions still record climatic conditions at the time of snails were living despite diagenesis and 2) isotopic compositions reflect both δ18O and δ13C of soil water as well as soil temperature. Positive correlations are observed between δ18O and δ13C of fossil land snail shells, which are not observed within populations of modern aragonitic land snail shells. This pattern could reflect shell CaCO 3 recrystallisation from a CO 2 -rich aqueous solution that suffered varying rates of evaporation. For the present investigated case, we propose that stable isotope compositions of these diagenetic land snail shells mimic those expected for unaltered snail shells that would still record original climatic conditions. Indeed, δ13C values could result from soil plant decay, which were not significantly different from the δ13C of snail diet mainly based on fresh leaves, even though a bias may result from diet preferences while soil organic matter averages the composition of the vegetation. Oxygen isotope ratios of shells result from a combination of evaporated soil water inherited from meteoric waters and soil temperatures that are closely related to mean air temperatures. • Stable isotopes were measured on Zanclean snail shells from Lanzarote, Canary Islands. • Recrystallisation of snail shells into calcite was revealed by Raman spectroscopy. • δ13C values (VPDB) of land snail shells result from C3–C4-CAM plant decay in soils. • Shells recrystallized with soil water having δ18O comprised between −4 and +2 (VSMOW). • Correlated δ13C and δ18O values suggest varying rates of soil water evaporation. [ABSTRACT FROM AUTHOR]