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Percorrer por autor "Studer, Anja S."

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  • Reduced N2 fixation in the tropical Atlantic Ocean during the warm late Pliocene
    Publication . Yehudai, Maayan; Farmer, Jesse R.; Straub, Marietta; Ogretmen, Nazik; Studer, Anja S.; Oesch, Lukas; Creel, Roger C.; Schiebel, Ralf; Auderset, Alexandra; Lawrence, Kira; Haug, Gerald H.; Sigman, Daniel M.; Martínez-García, Alfredo
    Water column denitrification, a major oceanic nitrogen (N) sink, decreased under past warmer-than-present climates, but the response of N2 fixation, the main oceanic N source, remains unresolved. Here we address this gap using foraminifera-bound N isotope records from the tropical Atlantic spanning the warm late Pliocene, a geological analog for projected 21st century warming. Our records show that tropical North Atlantic N2 fixation was reduced during the late Pliocene and had increased markedly by the late Pleistocene, likely due to an increase in water column denitrification, a process that globally engenders N-poor, phosphorus (P)-bearing surface waters. After ~ 2.8 million years ago, as glaciations intensified, our records show that obliquity-paced variations in the intensity of N2 fixation emerged, likely reflecting sea-level controlled changes in continental shelf area and benthic denitrification in the western tropical Atlantic, again through the generation of N-poor, P-bearing surface waters. These findings show that N2 fixation responds to the ocean’s N loss processes both over millions of years and on orbital timescales, suggesting that the global marine fixed N budget may rebalance under warmer climates by reducing both water column denitrification and N2 fixation.
    2026-08-05Artigo científico Acesso aberto Ver mais
  • Reviews and syntheses: review of proxies for low-oxygen paleoceanographic reconstructions
    Publication . Hoogakker, Babette A.A.; Davis, Catherine; Wang, Yi; Kusch, Stephanie; Nilsson-Kerr, Katrina; Hardisty, Dalton S.; Jacobel, Allison; Macaya, Dharma Reyes; Glock, Nicolaas; Ni, Sha; Sepúlveda, Julio; Ren, Abby; Auderset, Alexandra; Hess, Anya V.; Meissner, Katrin J.; Cardich, Jorge; Anderson, Robert; Barras, Christine; Basak, Chandranath; Bradbury, Harold J.; Brinkmann, Inda; Castillo, Alexis; Cook, Madelyn; Costa, Kassandra; Choquel, Constance; Diz, Paula; Donnenfield, Jonas; Elling, Felix J.; Erdem, Zeynep; Filipsson, Helena L.; Garrido, Sebastián; Gottschalk, Julia; Menon, Anjaly Govindankutty; Groeneveld, Jeroen; Hallmann, Christian; Hendy, Ingrid; Hennekam, Rick; Lu, Wanyi; Lynch-Stieglitz, Jean; Matos, Lélia; Martínez-García, Alfredo; Silveira Molina, Giulia; Muñoz, Práxedes; Moretti, Simone; Morford, Jennifer; Nuber, Sophie; Radionovskaya, Svetlana; Raven, Morgan Reed; Somes, Christopher J.; Studer, Anja S.; Tachikawa, Kazuyo; Tapia, Raúl; Tetard, Martin; Vollmer, Tyler; Wang, Xingchen; Wu, Shuzhuang; Zhang, Yan; Zheng, Xin-Yuan; Zhou, Yuxin
    A growing body of observations has revealed rapid changes in both the total inventory and the distribution of marine oxygen over the latter half of the 20th century, leading to increased interest in extending oxygenation records into the past. The use of paleo-oxygen proxies has the potential to extend the spatial and temporal range of current records, constrain pre-anthropogenic baselines, provide datasets necessary to test climate models under different boundary conditions, and ultimately understand how ocean oxygenation responds beyond decadal-scale changes. This review seeks to summarize the current state of knowledge about proxies for reconstructing Cenozoic marine oxygen: sedimentary features, sedimentary redox-sensitive trace elements and isotopes, biomarkers, nitrogen isotopes, foraminiferal trace elements, foraminiferal assemblages, foraminiferal morphometrics, and benthic foraminiferal carbon isotope gradients. Taking stock of each proxy reveals some common limitations as the majority of proxies functions best at low-oxygen concentrations, and many reflect multiple environmental drivers. We also highlight recent breakthroughs in geochemistry and proxy approaches to constraining pelagic (in addition to benthic) oxygenation that are rapidly advancing the field. In light of both the emergence of new proxies and the persistent multiple driver problem, the need for multi-proxy approaches and data storage and sharing that adhere to the principles of findability, accessibility, interoperability, and reusability (FAIR) is emphasized. Continued refinements of proxy approaches and both proxy–proxy and proxy–model comparisons are likely to support the growing needs of both oceanographers and paleoceanographers interested in paleooxygenation records.
    2025-02-18Artigo científico Acesso aberto Ver mais