Westerlies migrations and volcanic records over the past 4000 years from the Azores lacustrine sequences. Exploring correlations and impacts on Western Europe

Abstract

[Abstract] The Azores region plays a crucial role as a pathway for precipitation fronts traversing the North Atlantic from west to east, driven by the prevailing westerly winds. Variations in the strength of the Azores High affect the dynamics of the North Atlantic Oscillation (NAO), leading to latitudinal shifts in the trajectory of the westerlies and jet stream current over time. Throughout the Holocene and Late Pleistocene, the Azores islands experienced numerous highly explosive eruptions. Volcanic ash from these events was primarily dispersed to the east, carried by the North Atlantic Jet Stream, with cryptotephras being found across the British Isles and Northern-Central Europe. To investigate how NAO variations influenced the latitudinal position of the westerlies and in the ash dispersal towards Europe during the Late Holocene, we analysed the stratigraphy and sedimentology from 20 lake sediment sequences across five islands of Azores and revise highstand/lowstand periods in several lakes in Europe. Our facies analysis of Azorean lakes revelated three long-term phases highstand at 0–0.6, 2.6–1.5 and > 4.2–3.4 cal ka BP and two lowstand phases at 1.5–0.6 and 2.6–3.3 cal ka BP which are ultimately related to paleo-NAO intensity and signal variations. By modelling spatial and temporal climate variability between Azores and Europe, we tracked changes in the westerlies' latitudinal position over the last 4200 years. Additionally, we characterised tephra deposits in Azorean lakes, creating a preliminary database to support future tephrostratigraphic and tephrochronological research. This framework can also be useful for recognising distal cryptotephra layers in Europe and North Africa.