Changes in precipitation and temperature patterns related to the state of the North Atlantic Ocean during the Medieval Climate Anomaly

Abstract. In a warmer climate, uncertainties persist regarding regional precipitation responses and a potential weakening of the Atlantic Meridional Overturning Circulation (AMOC). This study examines the Medieval Climate Anomaly (~800–1399 CE) warm period to uncover hydroclimate patterns and their links with the North Atlantic Ocean variability, including AMOC, Sea Surface Temperature (SST), and the Inter-Tropical Convergence Zone (ITCZ) at centennial (100-years) scales. Analyzing change-sensitive multi-proxy data reveals that North Atlantic Ocean conditions play a significant role in influencing hydroclimate variability across Europe and North America, potentially by regulating atmospheric heat and moisture transport. Specifically, we show that warm SST conditions correspond to warmer climates on both continents, while low SST periods are associated with a southward shift of the ITCZ, potentially initiating cooler climates and hydrological variations. However, the state of the AMOC remains unclear, despite indications of subtle weakening in some records. Exploring hydroclimate suggests that continental-scale precipitation variations are linked to temperature changes, but regional responses are uncertain. Notably, warmer/slightly warmer climates are primarily linked to more humid conditions, especially in mid-latitude regions. Conversely, slightly colder climates tend to result in more arid conditions. Comparing model assimilation with proxy data reveals significant discrepancies, suggesting that either the models fail to adequately capture key processes or the proxy data contain substantial uncertainties. While our findings provide valuable insights into regional hydroclimate changes and variability in the North Atlantic Ocean state under a warmer climate, they also emphasize the necessity for more in-depth research on regional precipitation variability and the identification of appropriate proxies for tracking AMOC signals.