Tree‐Ring Stable Isotopes Reveal a Hydroclimate Shift in Eastern England Around 4.2 ka Ago

Abstract

Abstract Tree ring‐based climate reconstructions are fundamental for high‐resolution paleoclimatology, but only a few of them extend back into the mid‐Holocene (8,200–4,200 years BP). Here, we present annually‐resolved tree‐ring stable carbon and oxygen isotopes (δ 13 C and δ 18 O) from subfossil yew ( Taxus baccata ) wood excavated in the Fenland region of eastern England. We develop an eco‐physiological model to reconstruct hydroclimate variability from 5,224 to 4,813 ± 4 and 4,612–4,195 ± 6 cal. years BP. Our findings suggest that a relative sea‐level rise in the North Sea, riverine flooding, and a prolonged negative phase of the North Atlantic Oscillation caused unusually wet conditions around 4,200 years ago when yew woodlands in eastern England disappeared. We expect our study to stimulate high‐resolution stable isotope measurements in relict wood and encourage the integration of terrestrial and marine proxy archives to reconstruct the causes and consequences of large‐scale climate variations around the still debated 4.2 ka event. Plain Language Summary Understanding how the Earth's climate system has varied in the past is essential to predict future climate changes. In this study, we measured thousands of annually‐resolved tree‐ring widths and tree‐ring stable isotopes in hundreds of subfossil yew trees excavated by generations of farmers in the Fenland region of eastern England. The exceptionally well‐preserved wood archive, together with an innovative methodological approach allowed mid‐Holocene hydroclimate variability to be reconstructed from circa 5,200–4,200 years ago. Our new paleoclimate record reveals unusually wet conditions around 4,200 years ago when yew woodlands in eastern England disappeared. Likely driven by a sea‐level rise, riverine flooding, and a prolonged negative phase of the North Atlantic Oscillation, the observed environmental shift adds new insights into the period around the enigmatic 4.2 ka event. Our study also emphasizes the potential of stable isotopes in relict wood to reconstruct Holocene climate at high spatiotemporal resolution. Key Points Combining tree‐ring widths (TRW) and tree‐ring stable isotopes (TRSI) allows us to develop floating climate reconstructions A shift toward unusually wet conditions in eastern England coincided with the disappearance of yew woodlands around 4,200 years ago Hydroclimate variability over the North Atlantic provides new insights into the nature of the enigmatic 4.2 ka event