This study presents the first high-resolution speleothem-based hydrological reconstruction for much of the last 2.7 kyr in the central-western Mediterranean. The paleohydrological information comes from a combination of five U-Th dated stalagmites from two Mallorca island caves. Interpretations are based on high-resolution records of δ18O, δ13C and trace element analyses combined with information from mineralogical X-ray diffraction, fabrics and morphological features, and cave monitoring data. None of the studied stalagmites cover the whole 2.7 kyr period but they provide sufficient overlap to replicate most of the discussed climatic intervals with the exception of the Medieval Climate Anomaly (MCA), which is represented by a hiatus. Taking into account the results of five years farmed calcite collected in glass plates and cave environmental parameters, we argue that main patterns in the stalagmite geochemical records are mostly controlled by changing rates of prior calcite precipitation (PCP) that respond to hydrological changes in the region. We apply a principal component analysis to the stalagmite geochemical data set and a composite δ18O record to obtain a robust regional hydrological record. This record supports wet conditions for the early Roman Period (RP), the first half of the Early Middle Ages (EMA) and the Little Ice Age (LIA), and drier conditions for the late RP, the late EMA and the entire MCA. These results are discussed in the context of other climatic and oceanographic records from the region including paleo North Atlantic Oscillation (NAO) records. This ocean-atmosphere approach suggests complex non-stationary climate patterns for the last 2.7 kyr, including the occurrence of both wet-warm and wet-cold intervals and underlying the complex interaction of factors controlling climate evolution in the region. Overall, positive (negative) NAO phases appear coincident with drier (wetter) conditions for all the examined period at decadal time-scales.
Bibliographical noteFunding Information:
We thank financial support from ERC-Consolider Grant TIMED ( 683237 ); OPERA ( CTM2013-48639-C2-1-R ); PLIOKAR ( CGL2013-48441-P ); CHIMERA ( CTM2016-75411-R ); PLIOKAR-II ( CGL2016-79246-P , AEI-FEDER, EU); SPYRIT ( CGL2016-77479-R ) and Generalitat de Catalunya, Grups de Recerca Consolidats ( 2017 SGR 315 ) to GRC Geociències Marines. We are grateful to M. Guart and A. Gallardo (Dept. de Dinàmica de la Terra i de l’Oceà, Universitat de Barcelona), J. Perona, T. Bullich, M. Aulet and À. San Martín for their collaboration in the laboratory tasks, and A. Pilares for his collaboration in the fieldwork. M. Cisneros benefited from a fellowship of the UB. IC thanks ICREA Academia programme from the Generalitat de Catalunya.
The hydroclimate variability interpreted in base to the ?18O composite record produced in this study is compared with previously published reconstructions derived from marine sediments from the same area and for the same period: (i) SST based on Mg/Ca analysed on the planktonic foraminifera Globigerina bulloides (Cisneros et al., 2016); and (ii) Deep Water Formation (DWF) variability in the Gulf of Lions based on the grain-size parameter UP10, which corresponds to the fraction coarser than 10 ?m and can be used as a proxy of deep-current variability (Cisneros et al., 2019). This comparison shows that dry conditions in Mallorca, represented by heavier ?18O values in the Mallorca composite record, occurred during both warm and cold periods indicated by SST variations (Fig. 7). This complex relationship is well illustrated when RP and EMA periods are compared. During RP climate conditions evolved from cold and wet to warm and dry while during the EMA, climate migrated from warmer/wetter conditions to colder/drier conditions (Fig. 7). These observations highlight the complexity in the climatic response of the region and also suggest the RP and EMA transition as a period of breakdown in the operation mode of the regional climate variability (Cisneros et al., 2019). Regarding the relationship of the ?18O composite with the proxy of DWF, deep convection was mostly enhanced during the rather dry periods as part of the TP, part of the RP and EMA supporting previous hypothesis that linked events of reinforced DWF to enhanced evaporation-precipitation balance (Cisneros et al., 2019). However, a perfect match between high ?18O values and high UP10 is not always evident, since this connection in compromised by the uncertainties in the marine chronologies, its lower resolution and the speleothem hiatus during the MCA and LIAa.We thank financial support from ERC-Consolider Grant TIMED (683237); OPERA (CTM2013-48639-C2-1-R); PLIOKAR (CGL2013-48441-P); CHIMERA (CTM2016-75411-R); PLIOKAR-II (CGL2016-79246-P, AEI-FEDER, EU); SPYRIT (CGL2016-77479-R) and Generalitat de Catalunya, Grups de Recerca Consolidats (2017 SGR 315) to GRC Geoci?ncies Marines. We are grateful to M. Guart and A. Gallardo (Dept. de Din?mica de la Terra i de l'Oce?, Universitat de Barcelona), J. Perona, T. Bullich, M. Aulet and ?. San Mart?n for their collaboration in the laboratory tasks, and A. Pilares for his collaboration in the fieldwork. M. Cisneros benefited from a fellowship of the UB. IC thanks ICREA Academia programme from the Generalitat de Catalunya.
© 2021 The Authors
- Central-western Mediterranean
- Hydroclimate variability
- Late Holocene
- Muti-proxy records