Unexpected wet and warm conditions during glacial periods in the Central North Atlantic as recorded by paleosols from Flores Island (Western Azores)

Rapid climate change is increasingly expected to trigger major disturbances of regional temperatures and precipitation, but the atmospheric effects of globally colder climatic episodes remain poorly documented, especially in oceanic areas. In the Central North Atlantic, the Azores Archipelago lies under the influence of major regional climatic drivers and comprises groups of volcanic islands that recorded successive paleoclimatic conditions during most of the Pleistocene. We reconstructed the Mean Annual Precipitation and Air Temperature of Flores Island, in the westernmost extreme of the archipelago, through paleoclimatic proxies based on paleosols geochemistry. K Ar geochronology of volcanic units “bracketing” paleosols revealed two episodes of significant weathering during glacial periods (~550 ka and 630–670 ka), contrasting with the Central and Eastern Azores where paleosols formed during interglacial peaks. Mild/wet conditions prevailed in Flores (21.5 °C; 1340 mm yr −1 ), hotter/drier than current conditions (17 °C; 1716 mm yr −1 ), and wetter/warmer than those reached in other Azores islands. This is consistent with modern regional climatic gradients (wetter/hotter to the west). Ages between Flores and other Azores islands do not overlap, suggesting (1) persistent warm/wet conditions in Flores due to its northern position, closer to the westerlies' trend; or (2) unexpected regional warm/wet conditions around 550 ka and 650 ka, i.e., even during two globally-cold main glacial periods. Further studies in the Azores and at broader scales (e.g., the Canary Islands) are needed to improve regional paleoclimatic reconstructions, and to shed light on the interactions between global climatic forcing and their impacts in the Atlantic throughout the Quaternary. • K Ar dating of volcanic units in Flores (Western Azores) constrains paleosol ages. • Paleoclimatic conditions were reconstructed based on paleosol geochemistry. • Significant weathering during glacial stages contrasts with other Azores Islands. • Despite global glacial conditions, Flores was hotter/drier at ~650 ka and 550 ka. • A trend of wetter/hotter conditions to the WNW is inferred at the regional scale.