North Atlantic Ocean–Atmosphere Dynamics Controlled the Hydroclimate in Western Iberia During the Holocene

Abstract

Hydroclimate variability in western Iberia during the Holocene remains insufficiently resolved despite the high sensitivity of this region to the North Atlantic atmosphere and ocean dynamics. Here, we present the first source‐resolved reconstruction of centennial‐ to millennial‐scale moisture variability over the last 11,000 years using sediments from Lake Peixão (Portugal) based on compound‐specific hydrogen and carbon isotopes of plant wax n ‐alkanes, supported by bulk organic geochemistry and continuous X‐ray fluorescence elemental data. Terrestrial source‐resolved isotope series, obtained using non‐negative matrix factorization, primarily reflect precipitation isotopic composition and plant water use efficiency. The record indicates a wet early Holocene, a progressive mid‐Holocene drying trend that culminated in maximum aridity at approximately 4,000 calibrated years before present, and a transition to generally wetter but more variable late Holocene conditions, partly overprinted by anthropogenic land‐use change. These trends are interpreted as reflecting orbitally driven changes in Northern Hemisphere insolation that modified the latitudinal temperature gradient (LTG) and, in turn, influenced the North Atlantic storm track position and intensity. Enhanced early Holocene moisture reflects a higher LTG and southward‐displaced storm tracks, whereas mid‐Holocene aridity corresponds to a reduced LTG and northward‐shifted westerlies. The late Holocene recovery of wetter conditions agrees with a higher LTG and increased storm‐track influence over Iberia. Superimposed centennial‐scale variability likely reflects changes in North Atlantic Oscillation phases, the position of the Azores Front, and the intensity of the subpolar gyre. These results demonstrate the dominant roles of the LTG and coupled ocean–atmosphere dynamics in shaping the western Iberian hydroclimate throughout the Holocene.