Global simulation of dissolved ²³¹Pa and ²³⁰Th in the ocean and the sedimentary ²³¹Pa∕²³⁰Th ratios with the ocean general circulation model COCO ver4.0

Abstract 231 Pa/230 Th ratios provide clues to estimate the strength of past ocean circulation. For its estimation, understanding the processes controlling the distributions of 231 Pa and 230 Th in the ocean is important. However, simulations of dissolved and particulate 231 Pa and 230 Th in the modern ocean, recently obtained from the GEOTRACES project, remain challenging. Here we report a model simulation of 231 Pa and 230 Th in the global ocean with COCO ver4.0. Starting from the basic water-column reversible scavenging model, we also introduced the bottom scavenging and the dependence of scavenging efficiency on particle concentration. As demonstrated in a previous study, the incorporation of bottom scavenging improves the simulated distribution of dissolved 231 Pa and 230 Th in the deep ocean, which has been overestimated in models not considering the bottom scavenging. We further demonstrate that introducing the dependence of scavenging efficiency on particle concentration results in a high concentration of dissolved 230 Th in the Southern Ocean as observed in the GEOTRACES data. Our best simulation can well reproduce not only the oceanic distribution of 231 Pa and 230 Th but also the sedimentary 231 Pa/230 Th ratios. Sensitivity analysis reveals that oceanic advection of 231 Pa primarily determines sedimentary 231 Pa/230 Th ratios. On the other hand, 230 Th advection and bottom scavenging have an opposite effect to 231 Pa advection on the sedimentary 231 Pa/230 Th ratios, reducing their latitudinal contrast. Our best simulation shows the realistic residence times of 231 Pa and 230 Th, but simulation without bottom scavenging and dependence of scavenging efficiency on particle concentration significantly overestimates the residence times for both 231 Pa and 230 Th in spite of similar distribution of sedimentary 231 Pa/230 Th ratios to our best simulation.

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch

References and Relationships

• Bibliographic citation: Global simulation of dissolved ²³¹Pa and ²³⁰Th in the ocean and the sedimentary ²³¹Pa∕²³⁰Th ratios with the ocean general circulation model COCO ver4.0 ; volume:15 ; number:5 ; year:2022 ; pages:2013-2033 ; extent:21 ; Geoscientific model development ; 15, Heft 5 (2022), 2013-2033 (gesamt 21)

Contributors, Places and Time

• Creator: Sasaki, Yusuke ; Kobayashi, Hidetaka ; Oka, Akira

Further information

• DOI: 10.5194/gmd-15-2013-2022
• URN: urn:nbn:de:101:1-2022031704322519482560
• Rights: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 15.08.2025, 7:20 AM CEST