Temporal and spatial climate changes in the mid-Baltic region in the Late Glacial and the Holocene: Pollen-based reconstructions

This study investigates vegetation patterns and presents quantitative pollen-based climate reconstructions in the Baltic region spanning the Late Glacial and Holocene periods, addressing knowledge gaps regarding the climate history and its impact on ecosystems. We prepared climate reconstruction from fossil pollen samples using the Modern Analog Technique (MAT). The MAT reconstructions were validated by comparing them to outputs from an ensemble of complementary reconstruction methods. Reconstructions were based on pollen data from the Dūkštelis palaeolake in southeastern Lithuania and three previously studied sites, providing a broad geographical and temporal range in Lithuania. The analysis of the Dūkštelis palaeolake reveals divergent trends between mean winter and summer temperatures (MWT and MST) observed at about 14.0, 12.8, 9.7, 3.2, 2.7, 2.4, and 1.4 kyr, with varying degrees of deviation from modern levels across seasons and locations. MWT increases are mostly linked to higher precipitation. Tripartite reversals with a notable temperature increase were observed during the second part of the Greenland Stadial- 1 event, with colder MST in the western Lithuania. Gradual summer warming, likely influenced by solar irradiance, was seen during the Early Holocene; the most prominent change, however, is observable in MWT, particularly in the western region, with modern values reached at about 10.4 kyr. MWT during the Holocene Thermal Maximum is estimated to be approximately 3 °C higher in eastern Lithuania and 5–6 °C higher in the western part than present levels. Uncertainties arise in temperature reconstructions from approximately 3.3 kyr due to anthropogenic landscape changes.