The Onset of Summer Drought on the Iberian Peninsula Following Pliocene Global Cooling

The highly biodiverse Iberian Peninsula has winter‐dominated precipitation and summer drought. The onset of this modern climate regime, termed a Mediterranean‐Type Climate, began during the Late Pliocene–Early Pleistocene, concurrent with global cooling. To advance our understanding of regional hydroclimate changes in relation to past global changes, we present a stable oxygen isotope record measured on paleosol carbonates (δ 18 O c ) from Teruel, Spain spanning 4.1–2.4 Ma, when the regional ecosystems shifted from subtropical requiring high humidity to dominantly drought‐tolerant. The δ 18 O c values show a negative excursion during Marine Isotope Stage M2 (∼3.3 Ma) and a subsequent decrease during the onset and intensification of the Northern Hemisphere Glaciation (iNHG: ∼2.73 Ma). While the δ 18 O c decrease during global cooling could have resulted from less high‐δ 18 O summer rainfall and/or intensified low‐δ 18 O winter rainfall, comparison with previously published proxy records point toward drying in the Mediterranean Basin during the Late Pliocene. We therefore propose that global cooling at this time resulted in lower Atlantic and Mediterranean sea surface temperatures during the iNHG which decreased moisture availability to the Mediterranean Basin, and together with enhanced and equatorward shifted Hadley circulation, reduced summer rainfall in the Mediterranean Basin when compared to the conditions of the Early Pliocene.