Climate variability in the western Mediterranean basin since the last interglacial from growth rate speleothem data

Wednesday, 17 December 2014
Oana-Alexandra Dumitru1, Bogdan P Onac1, Victor J Polyak2, Yemane Asmerom2 and Joan J Fornos3, (1)University of South Florida Tampa, School of Geosciences, Tampa, FL, United States, (2)University of New Mexico Main Campus, Earth and Planetary sciences, Albuquerque, NM, United States, (3)Universitat de les Illes Balears, Department de Ciencies de la Terra, Palma de Mallorca, Spain
Speleothem growth is a sensitive indicator of both temperature and rainfall, and independent changes in either one or both of these can cause periods of enhanced or reduced growth. Our attempt to relate growth rates to past change in regional climate is based on results from an aragonite stalagmite (CAM; 22.5 cm tall) collected near the far end of Coves de Campanet, from a well-decorated and poorly ventilated chamber. The mean annual cave temperature and relative humidity are 21ºC and >95%, respectively. Twenty-five U-Th ages constrain the stalagmite growth from 120,143 to 4,656 (±0.3) yr BP, with a large range in growth rates, from 0.76 to 7.6 µm/yr, but no apparent hiatuses. We note a significant difference between growth rates during glacial, stadial, and interglacial periods, with maximum rates occurring during MIS 5e and 5a (7.6 and 5.1 µm/yr, respectively), periods that are coincident with maximum summer insolation recorded at ~125 and 82 ka, Similar growth rates were reported from two other caves in Mallorca (Tancada and Cala Falcó). Significant drop in growth rate occurs at the beginning of stadial MIS 5d (1.5 µm/yr) and remained low during MIS 5c and b, likely in response to a decrease in the amount of precipitation. The growth rate dramatically decreased during the shift towards colder and drier conditions at the start of MIS 4, from 5.1 to 0.76 µm/yr. In contrast to most other stalagmites from NW Iberian Peninsula which show episodic growth during MIS 4 and 3, CAM maintained low but stable growth rate, of 0.76 to 0.88 µm/yr beginning at ~52 ka. Cala Falcó stalagmite ceased its growth ~45 ka, during Greenland Stadial 5. Our CAM growth rate data suggest dropping SSTs as a cause of reduced transport of moisture to the Mediterranean region. Combining these growth rates with high resolution stable isotope analyses (in progress) will allow deciphering in great detail the climate shifts in the western Mediterranean region since the Last Interglacial.