A STALAGMITE COMPOSITE RECORD OF HYDROCLIMATE VARIABILITY FROM PORTUGAL DURING THE HOLOCENE

To better contextualize recent increases in aridity in Iberia, we present a multi-proxy composite record from six overlapping stalagmites from Buraca Gloriosa cave (BG), located in western Portugal. The BG record reveals that aridity in western Portugal increased from 9.0 ka BP to present, as evidenced by rising values of both stable carbon and oxygen isotope values. This trend tracks the decrease in Northern Hemisphere summer insolation and is coherent with Iberian margin sea surface temperatures. The increased aridity toward present day is consistent with changes in Hadley circulation and a southward migration of the intertropical convergence zone over the Holocene. To evaluate centennial-scale variability in hydroclimate, the long-term trend in the record was removed. This illustrated shifts in hydroclimate that were coincident with changes in total solar irradiance since ~4 ka BP. Several major drying events are apparent, the most prominent of which was centered around 4.2 ka BP, a feature also noted in other Iberian climate records and coinciding with well-documented regional cultural shifts. Substantially wetter conditions occurred in the detrended record from 0.8-0.15 ka BP. In the last 150 years, a trend toward increased aridity is present. Furthermore, Iberia is predicted to be increasingly impacted by drought under future warming scenarios, which may lead to increased fire activity and increased demand on water resources.