Seasonal temperature and moisture changes in interior semi‐arid Spain from the last interglacial to the Late Holocene

Dongyang Wei,Graciela Gil-Romera,Penélope González-Sampériz,I Colin Prentice,Sandy P Harrison

doi:10.1017/qua.2020.108

Abstract

Abstract The El Cañizar de Villarquemado pollen record covers the last part of MIS 6 to the Late Holocene. We use Tolerance-Weighted Averaging Partial Least Squares (TWA-PLS) to reconstruct mean temperature of the coldest month (MTCO) and growing degree days above 0°C (GDD0) and the ratio of annual precipitation to annual potential evapotranspiration (MI), accounting for the ecophysiological effect of changing CO2 on water-use efficiency. Rapid summer warming occurred during the Zeifen-Kattegat Oscillation at the transition to MIS 5. Summers were cold during MIS 4 and MIS 2, but some intervals of MIS 3 had summers as warm as the warmest phases of MIS 5 or the Holocene. Winter temperatures declined from MIS 4 to MIS 2. Changes in temperature seasonality within MIS 5 and MIS 1 are consistent with insolation seasonality changes. Conditions became progressively more humid during MIS 5, and MIS 4 was also humid, although MIS 3 was more arid. Changes in MI and GDD0 are anti-correlated, with increased MI during summer warming intervals. Comparison with other records shows glacial-interglacial changes were not unform across the circum-Mediterranean region, but available quantitative reconstructions are insufficient to determine if east-west differences reflect the circulation-driven precipitation dipole seen in recent decades.

Highlights

The modern climate of the Mediterranean region is influenced by high-pressure systems in summer and westerly storm tracks in winter, giving rise to a highly seasonal climate with dry summers, relatively wet winters, and strong seasonal temperature contrasts
We present a quantitative reconstruction of three bioclimatic variables: winter temperature, growing-season warmth, and a moisture index using the pollen record from El Cañizar de Villarquemado and Tolerance-Weighted Averaging Partial Least Squares regression (TWA-PLS) (Liu et al, 2020) that are calibrated using modern pollen (Harrison, 2019) and climate (Harrison, 2020) datasets for Europe and northern Eurasia
For ToleranceWeighted Averaging Partial Least Squares (TWA-PLS) regression based on the full complement of 195 taxa, we used results from component 2 for MTCO and moisture index (MI) and component 1 for growing degree days above 0°C (GDD0) because these are the significant results (95% confidence level) with the lowest RMSE and highest R2

Summary

Introduction

The modern climate of the Mediterranean region is influenced by high-pressure systems in summer and westerly storm tracks in winter, giving rise to a highly seasonal climate with dry summers, relatively wet winters, and strong seasonal temperature contrasts. The climate of the region is not homogeneous and the pattern of climate changes across the region is complex (Lionello, 2012). Seasonal temperature and moisture changes in interior semi‐arid Spain from the last interglacial to the Late Holocene. This east-west dipole is characteristic of rainfall trends over the twentieth century (Zittis, 2018) and during the Holocene (Peyron et al, 2017). It is highly likely that climate changes on longer timescales, orbital timescales in response to change in insolation, and on glacial-interglacial timescales in response to changes in icesheet volume (Magri and Tzedakis, 2000; Rohling et al, 2013), are complex

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Conclusion