Uranium Isotope Constraints on the Pre-Deposition Time of Asian Dust to the North Pacific Ocean: Implications for Provenance and Iron Supply

Asian dust delivers highly reactive iron (FeHR) to the Pacific Ocean, affecting marine biogeochemical cycles and Earth's climate. Tracing the source of dust deposited in the Pacific is vital for assessing global nutrient cycles but poses challenges. This work applies the (234U/238U) activity ratio to determine the pre-deposition time and provenance of dust in North Pacific Ocean sediments (Ocean Drilling Program site 1209B). Results indicate a consistent dust pre-deposition time (134 +/- 10 ka) over the past 300,000 years, except during Marine Isotope Stage 7 when volcanic ash input shortened it to 31 +/- 19 ka. Comparing the dust pre-deposition times to those of the potential source deserts, we identify the dust transported to the North Pacific Ocean was primarily from the Taklamakan Desert, which contains higher FeHR content than other deserts. This finding enhances our understanding of soluble Fe supplied to the oceans, especially in dust circulation models. Unraveling the provenance of aeolian dust deposited in the oceans is critical for understanding marine biogeochemical cycles, past climate changes, and dust transport mechanisms. Here we measured the (234U/238U) activity ratio of marine sediments in the North Pacific Ocean to understand the source and pre-deposition time of dust deposited in the Pacific. The source of dust in the Pacific has remained debated because of the non-unique geochemical signatures of possible source regions and the complexity introduced by the volcanic ash. The (234U/238U) of the dust fraction in marine sediments informs the source-to-sink transport time for dust particles, providing a new source tracer. We compared the (234U/238U)-derived pre-deposition time, Nd isotopes, grain size, magnetic susceptibility and aeolian dust flux of the North Pacific marine sediments to those of potential dust source regions, and identify the Taklamakan Desert as a major source delivering dust to the North Pacific. Our work highlights the (234U/238U) and associated particle pre-deposition time as a promising tool for tracing sources of dust in marine sediments, holding profound implications for our understanding of global dust-nutrient cycles. Uranium isotope-based pre-deposition time serves as a novel tool to trace the provenance of Asian dust transported to the North Pacific Ocean Dust pre-deposition time at site 1209B remains relativity stable (134 +/- 10 ka), but decreases during MIS 7 due to volcanic ash input Taklimakan Desert is the major source of dust delivered to the North Pacific Ocean, supplying dust with highly reactive iron