FRESHWATER HOSING DYNAMICS AND CLIMATE SHIFTS DURING HEINRICH STADIAL 1: A COMPREHENSIVE MODELING APPROACH

Heinrich Stadial 1 (HS1; 19–15 ka) was characterized by abrupt global climate perturbations in association with a weakening of the Atlantic Meridional Overturning Circulation (AMOC), which could be used as an analog to understand the Earth’s climate response to future AMOC weakening. However, paleoclimate records reveal a two-phase hydroclimate pattern across many regions, suggesting more complex global dynamics than previously understood. The roles of contemporaneous freshwater events during HS1, including Siku Event 1 (S1; 19-17 ka) in the North Pacific and Heinrich Event 1 (H1; 18-15 ka) in the North Atlantic, have not been systematically examined. In this study, we run freshwater hosing experiments by applying a freshwater flux in the North Pacific and North Atlantic to simulate the impacts of S1 and H1 on global climate systems. Results from these two experiments agree with the two-phase HS1 climate patterns observed in paleoclimate records, showing distinct responses over western North America, the Maritime Continent, East Asia, and South America. These findings indicate that the contemporaneous freshwater forcings in both regions, offset by only one thousand years, were responsible for large scale hydroclimate change. Distinguishing the impacts of North Atlantic versus North Pacific freshwater forcing during HS1 is essential for providing insights for future AMOC weakening.