Volcanic sourced input enhances biological export in the Kuroshio Extension

The Kuroshio Extension lies at the confluence of the North Pacific subtropical and subarctic gyres and receives particulate inputs from Asian dust and volcanic arcs. Constraining the provenance and burial fluxes of these materials is key to understanding how external nutrient supply regulates oceanic productivity. Here we quantify mass fluxes and sediment source contributions across a north–south transect of five sediment cores, using a combined approach of 230 Th profile dating and 230 Th normalization. Mass flux shows a pronounced north-to-south gradient, decreasing from 2.7 g cm −2 ka −1 in the north to 0.38 g cm −2 ka −1 in the south. Aeolian dust provides a regionally uniform lithogenic flux (0.18–0.25 g cm −2 ka −1 ), whereas volcanic inputs are more localized but more potent, with fluxes ranging from 0.06 to 1.72 g cm −2 ka −1 . Volcanic flux co-varies spatially with biogenic–authigenic burial flux ( r = 0.78), and elevated volcanic inputs in the northern cores are accompanied by enhanced burial of biogenic and authigenic materials (0.07–0.75 g cm −2 ka −1 ) This pattern suggests that volcanic iron fertilization may enhance biological export and promote the co-sequestration of trace metals such as rare earth elements. Our findings show that aeolian dust supplies a background level of trace metals, while volcanic inputs drive localized hotspots of biological productivity and metal burial. This framework highlights the interconnected roles of lithogenic sources in regulating the biological pump, although direct constraints on iron bioavailability await further investigation.