MERGE SP: Proxy-based reconstructions and model simulations of seasonal climate variations during the Last Interglacial in the Baltic Sea

The climate during the Last Interglacial period (LIG, Marine Isotope Stage 5e, 130-115 thousand years before present, ka BP) is considered, on average, to have been warmer than the present, with a higher global sea level but also more unstable conditions. By comparing the different environmental conditions during the present and pre-industrial periods through observations and simulations, respectively, we may assess the mechanisms that caused the differences between interglacial periods and provide valuable analogs for future regional environmental changes. Today, the Baltic Sea interacts strongly with conditions in the North Atlantic region, and this interaction was likely even stronger during the Last Interglacial. The climate today in the Baltic Sea is sensitive to changes in the North Atlantic Oscillation (NAO), which strongly influences winter temperatures and precipitation in the North Atlantic and northern European regions (e.g., Hurrell, 1995; Lu & Greatbatch, 2002; Trigo et al., 2002). By applying climate model simulations will allow us to explain the influence of precipitation-evaporation and the North Atlantic Oscillation (NAO) on regional climate changes in the Baltic Sea and the North Sea during the LIG. We will employ a state-of-the-art general circulation model (EC-EARTH) for the climate simulations and combining it with existing foraminiferal-based reconstructions (Ni et al., 2021). We aim to investigate the impact of radiative forcing on regional climate changes, and responses of the atmospheric-oceanic interactions, oceanic variables such as seawater temperature and salinity. They can be linked to the changes of regional climate (i.e. sea-level pressure, NAO, precipitation) to the seasonal variations of western Baltic and North Sea water conditions. In specific, we plan to address: • modern hydrographic conditions within the Baltic Sea and North Sea area derived from SMHI database (Desired Outcomes, DO1); • the comparison of bottom water temperatures between benthic foraminifera geochemistry based reconstruction during LIG (~127 ka BP) and modern conditions (DO2); • simulations of LIG127 and PI climate using EC-EARTH focusing on the western Baltic Sea and North Sea region (DO3); • the environmental conditions anomalies of LIG127-PI (simulation) and LIG-modern (proxy-based) (DO4).