Climate changes in interior semi-arid Spain from the last interglacial to the late Holocene

Abstract. The El Cañizar de Villarquemado sequence provides a palaeoenvironmental record from the western Mediterranean Basin spanning the interval from the last part of MIS6 to the late Holocene. The pollen and sedimentological records provide qualitative information about changes in temperature seasonality and moisture conditions. We use Weighted Averaging Partial Least-Squares (WA-PLS) regression to derive quantitative reconstructions of winter and summer temperature regimes from the pollen data, expressed in terms of the mean temperature of the coldest month (MTCO) and growing degree days above a baseline of 0 °C (GDD0) respectively. We also reconstruct a moisture index (MI), the ratio of annual precipitation to annual potential evapotranspiration, taking account of the effect of low CO₂ on water use efficiency. We find a rapid summer warming at the transition to MIS5. Summers were cold during MIS4 and MIS2, but some intervals in MIS3 were characterized by summers as warm as the warmest phases of MIS5 or the Holocene. However, MIS3 was not significantly warmer in winter than other intervals, and there was a gradual decline in winter temperature from MIS4 through MIS3 to MIS2. The pronounced changes in temperature seasonality during MIS5 and MIS1 are consistent with changes in summer insolation. The ecophysiological effects of changing CO₂ concentration through the glacial cycle has a significant impact on reconstructed MI. Conditions became progressively more humid during MIS5 and MIS4 was also relatively humid, while MIS3 was more arid. High MI values are reconstructed during the deglaciation and there was a pronounced increase in aridity during the Holocene. Changes in MI are anti-correlated with changes in GDD₀, with increased MI during intervals of summer warming indicating a strong influence of temperature on evapotranspiration. Although our main focus here is on longterm changes in climate, the Villarquemado record also shows millennial-scale changes corresponding to Dansgaard-Oeschger cycles.