Sediment provenance changes in the southwestern Okhotsk Sea since MIS 5 and their implications for sediment transport dynamics

The Okhotsk Sea, located between the Asian continent and the western Pacific, is a natural laboratory for investigating sediments source -to -sink influenced by atmosphere-ocean-land-sea ice interactions. However, despite their paleoenvironmental significance, changes in sediment provenance within the Okhotsk Sea are still debated due to the diversity of sediment sources and transport processes. Here, we investigate Sr and Nd isotope compositions in surface sediment samples from regions across the Okhotsk Sea, as well as Sr and Nd isotope compositions and elemental abundances in the sediments of core LV55-40-1, collected from the southwestern Okhotsk Sea. Our results reveal an increasing trend of epsilon Nd values over the past -110 kyr, with an abrupt increase during the transition into the last deglacial/early Holocene (MIS 1). We also observed minor variations characterized by less radiogenic epsilon Nd during the glacial/stadial (G/S) periods (MIS 5d, MIS 5b, MIS 4, MIS 2), and more radiogenic epsilon Nd during the interglacial/interstadial (I/I) periods (MIS 5c, MIS 5a, MIS 3). The major terrigenous sediment sources in the northwestern Okhotsk Sea are via the Amur River and from Sakhalin Island (-60-80%), with a minor volcanic contribution (-20-40%) from the Okhotsk-Chukotka volcanic belt and the southern Kuril Islands/Hokkaido. Provenance variations are primarily controlled by the interplay of sea -ice drifting and ocean circulation, reflecting a dominant transport mode shift from sea ice to surface current dominance since the early Holocene. During the G/S periods with severe sea -ice condition, terrigenous materials from the Amur River and Sakhalin Island were transported to the study site, due to the southeastward drift of sea ice driven by the prevailing northwesterly winds and enhanced Okhotsk Sea Intermediate Water circulation. In contrast, during the I/I periods with moderate sea -ice conditions, an increased contribution from the OkhotskChukotka volcanic belt was caused by sea -ice drifting southwestwards under the prevailing northerly and northeasterly winds, supplemented by surface currents. This study provides the first Sr-Nd isotopes record spanning the last glacial cycle in the Okhotsk Sea and it offers new insights into the relationship between sediment provenance and the interplay of sea ice and ocean currents in this region.