Mid‐Holocene Iberian hydroclimate variability and paleoenvironmental change: molecular and isotopic insights from Praia Rei Cortiço, Portugal

ABSTRACT At Praia Rei Cortiço (PRC), coastal Portugal, we analyzed compound‐specific isotopes of plant wax‐derived n‐alkanes in combination with molecular distribution proxies and C/N ratios to reconstruct hydrologic and environmental change in a mid‐Holocene wetland. During this relatively brief segment of the Holocene (6.6–5.4k cal a BP), substantial shifts in the stable hydrogen isotope composition of terrestrially sourced C29 n‐alkanes (δDn‐C29) record significant multi‐decadal changes in precipitation origin and storm trajectory. Wetland formation at PRC occurred during a humid interval (6.6–6.5k cal a BP) with a dominantly tropical precipitation source, likely the result of a persistent negative phase of the North Atlantic Oscillation, which permitted the establishment and dominance of Sphagnum moss. A subsequent decrease in precipitation significantly reduced Sphagnum abundance at PRC, which is evidenced by decreased sedimentary C/N ratios and reduced mid‐chain n‐alkane abundances. From 5.9 to 5.4k cal a BP, relatively low δDn‐C29 values coincide with sand invasion along the Iberian coast and cooling in the North Atlantic. Strong correspondence between δDn‐C29 values and the occurrence of ice‐rafted debris recorded in deep sea sediment cores during this period illustrate a marked North Atlantic control on the trajectory of mid‐latitude storms and precipitation regimes in Iberia.