Novel and skilful ocean-based predictors for European hydro-meteorological extremes

With anticipated changes in future hydrological extremes over Europe, it is important to better understand their underlying drivers for ultimately improving their forecasting. Previous studies have demonstrated a significant influence of the North Atlantic Ocean on European climate. Building on this, we identify novel North Atlantic Sea surface temperature (SST) indicators that are linked to meteorological and hydrological extremes across various European catchments at long lead times. We evaluate predictor-predictand relationships by assessing the concurrent and lagged statistical links between European hydro-climate variables (e.g., precipitation, evaporation, temperature, streamflow and groundwater levels) with North Atlantic SST indicators. These SST indicators are associated with events that increase freshwater input into the ocean, leading to subsequent shifts in key ocean currents. Combining observations and theory, we trace the associated teleconnection pathways from North Atlantic Ocean changes to atmospheric dynamics influencing the North Atlantic Jet Stream, ultimately impacting the European hydroclimate that can account for the statistical links. Our findings reveal that these North Atlantic SST patterns exert varying influences on the Scandinavian regions, central western Europe and Iberian Peninsula at one-to-two years lead time. Our research therefore has significant potential in practical applications for advancing forecasting of extremes and early warning systems through the identification of novel and skilful predictors, which can contribute to the mitigation of risks associated with hydro-meteorological extremes.