Insights into Quaternary iron fertilization dynamics in the western equatorial Pacific: Proxy archives offshore of northern Papua New Guinea

The equatorial Pacific is a key oceanographic region for unraveling Earth's climate system dynamics, where nutrient availability (e.g., iron, nitrogen, and phosphorus) plays a crucial role, at least partially, in governing the biologic pump and sea-air carbon exchange. Despite this, provenance, routing, and depositional processes, together with fertilization effects of nutrient supply to the western equatorial Pacific during the Quaternary, with Papua New Guinea potentially acting as a major iron contributor, remain elusive. Here, we present a comprehensive analysis of proxy archives for island erosion and weathering, terrestrial matter supply, surface ocean productivity, downward export of biogenic material, and bottom-water redox, all closely linked to orbital variations of iron fertilization, along the continental slope offshore of northern Papua New Guinea since 275 kyr. Our findings reveal a prominent precession cycle across these integrated records, aligning with changes in January–March insolation at 5°S. The observed temporal coupling indicates that heightened precipitation and erosion in northern Papua New Guinea stimulated nutrient input, thereby enhancing surface ocean fertilization, biologic production, and particulate carbon burial in the western equatorial Pacific during periods of high January–March insolation at 5°S. This caused the area to be a significant atmospheric CO₂ sink during La Niña-like conditions. We propose that enhanced erosion in northern Papua New Guinea led to increased iron fertilization in the western equatorial Pacific. Ongoing iron fertilization may significantly mitigate anthropogenic global warming by enhancing atmospheric CO₂ sequestration associated with increased occurrences of future consecutive La Niña events, as predicted by model simulations.