Southern Portugal hydroclimate of the last millennium from near‐annually resolved speleothem records

Abstract

Hydroclimate in Portugal is influenced by the North Atlantic subtropical high‐pressure system (the Azores High) and by internal climate modes, most prominently the North Atlantic Oscillation, which may shift in position and/or intensity due to anthropogenic climate change. The development of high‐resolution paleoclimate records from sites in Portugal is critical for providing baseline climate estimates, including hydroclimate variability, for better constraining climate model predictions under future warming scenarios. Here, we present a near‐annually resolved composite stable carbon isotope (δ 13 C) and oxygen isotope (δ 18 O) time series from three stalagmites from two proximally located caves in the Algarve region of southern Portugal. U/Th dating indicates that our record spans the last millennium, with a short hiatus at ~1450 CE. During the last millennium, the stalagmite record shows coherence with regional sea surface temperature, Northern Hemisphere air temperature, and the North Atlantic Oscillation, demonstrating that the stalagmite proxies broadly reflect hydroclimate. Hydroclimate during the Medieval Climate Anomaly was relatively dry/warm and generally more variable than modern conditions and transitioned to an overall wetter/cooler early Little Ice Age with similar hydroclimate variability. From ~1650 to 1700 CE, conditions in southern Portugal became increasingly dry/warm, with hydroclimate remaining fairly stable from 1700 CE to the present.