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

• Published in: Geoscientific Model Development
• Main Authors: Y. Sasaki, H. Kobayashi, A. Oka
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: Geology; QE1-996.5; Southern Ocean
• Online Access: https://doi.org/10.5194/gmd-15-2013-2022; https://doaj.org/article/933793b5ceee41668f67b0672df777b2

Sedimentary <math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi/><mn mathvariant="normal">231</mn></msup><mi mathvariant="normal">Pa</mi><msup><mo>/</mo><mn mathvariant="normal">230</mn></msup><mi mathvariant="normal">Th</mi></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="62pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="b118a40effcf5fa5b508e16481bf10eb"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gmd-15-2013-2022-ie00003.svg" width="62pt" height="15pt" src="gmd-15-2013-2022-ie00003.png"/></svg:svg> 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 <math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" ...