Understanding historical soil moisture (SM) variations and their relationship with temperature in high-latitude humid regions is essential for predicting hot droughts under widespread warming. This paper presents the first-ever annual-resolution summer surface SM reconstruction (1736-2006 CE) in Sweden, located in northern Europe (NE). The reconstruction utilizes the paleoclimate proxy, tree-ring delta O-18, which exhibits a strong correlation with reanalysis SM data during 1948-2007 CE (r = -0.67, p < 0.001). In contrast to an unprecedented trend suggested by previous studies, our reconstruction exhibits a wetting trend in NE since the 1960s falling within the historical spectrum of trends. Both reanalysis SM data and our reconstruction show significant negative correlations with temperature at interannual timescales. However, Coupled Model Intercomparison Project Phase 6 climate models failed to capture the significant SM-temperature relationship during the historical (1850-1947 CE) and observation periods (1948-2006 CE). This proxy-model comparison represents a critical step toward enhancing our understanding of SM dynamics and the reliability of SM projections in high-latitude humid regions.
