Hydroclimate variability in southern Portugal during marine isotope stage 4

ABSTRACT While several marine and terrestrial sediment records provide the general climate boundary conditions for Iberia at a relatively low temporal resolution (often >100 years per sample) during the last several glacial cycles, few high‐resolution proxy records of continental climate have been developed from this region. Speleothems can provide millennia of seasonally to decadally resolved data on vegetation dynamics and hydroclimate variability. In this study we use stable carbon and oxygen isotopes and magnesium concentrations from a stalagmite collected from a cave in southern Portugal to better understand environmental variability during part of marine isotope stage (MIS) 4: ~69–64 ka. Stalagmite growth ceased as temperatures decreased just prior to the start of Heinrich stadial 6, an exceptionally cold period in the North Atlantic region, and growth did not resume after Heinrich event 6, suggesting dry and/or cold conditions in southern Portugal. Integration of these new data with previously published proxy records in western Europe reveals a complex and heterogenous spatial pattern of hydroclimate variability during MIS 4. For example, some regional stalagmite records, including those in Iberia, continued growing during Heinrich stadial 6, suggesting that a fine‐scale heterogeneity in precipitation patterns existed, or that infiltration pathways in these caves remained intact.