The impacts of Tsushima Warm Current and sea-ice on hydrodynamics in the Sea of Japan during the last deglaciation

Abstract

The Sea of Japan (JS) is characterized by hydrodynamics that are highly sensitive to climate change. Current knowledge of JS hydrodynamics over geological timescales stems mainly from studies of sediment lithology, biomarkers and microfossils. However, the relationship between sedimentological proxies, such as Sortable Silt (SS), and hydrodynamics remains poorly understood. Here we analyzed SS parameters and elemental ratios from sediment cores collected at three distinct locations (southwestern, central, and northwestern JS) to investigate hydrodynamic changes during the last glaciation. Our results suggest hydrodynamics intensified in the southwestern JS around 18 ka, coinciding with the initial intrusion of the Tsushima Warm Current (TWC). Enhanced hydrodynamics occurred in the central JS around 16 ka, driven by sustained TWC's intrusion and northward shift of the subpolar front (SPF). Accompanied the northern shift of SPF, the convergence of northern cold and southern warm waters around the SPF caused surface water densification and sinking in the central JS, enhancing local hydrodynamics and sediment sorting at that time. In the northwestern JS, hydrodynamics is primarily influenced by brine rejection process induced by sea-ice activity. Our records show the TWC and sea-ice activity primarily drove site-specific hydrodynamics changes in the JS during the last deglaciation, providing valuable insights into JS paleoceanography from a hydrodynamic perspective.