Back up mandate Research Council (Rebecca Doyle): HYDRONIC: HYDrological RecOnstructions using N-alkanes, speleothem Inclusions and Clumped isotope analysis

Hydroclimate is rapidly changing in western Europe due to anthropogenic climate warming (ACW). Reliable hydroclimate models are needed to prepare for floods, as occurred in eastern Belgium in the summer of 2021. Yet, many existing models rely on tree ring data that struggles to distinguish between variations in temperature and moisture. HYDRONIC presents temperature- controlled, dual isotope hydroclimate reconstructions from lakes in Spain and Ireland. These locations represent endmembers of hydroclimate in western Europe. Temperature control is achieved using clumped isotope analysis, a cutting-edge method of determining the temperature of carbonate formation in the lacustrine
water column. Hydrogen isotope analysis of n-alkanes extracted from lake sediments, and fluid inclusions in speleothems from the same region, reveal changes in hydroclimate. Lakes and speleothems from Spain and Ireland respond oppositely to the North Atlantic Oscillation (NAO). Comparing hydroclimate trends from both areas produces an NAO reconstruction during the Late Pleistocene and Holocene. Such long-term NAO reconstructions are useful for assessing if and how
the NAO has changed due to ACW. Changes to the NAO could alter hydroclimate across Europe, contributing to major precipitation or drought events in western Europe.