Collaborative Research: Refining foraminiferal I/Ca as a paleoceanographic oxygenation proxy for the glacial Atlantic Ocean

合作研究：提炼有孔虫 I/Ca 作为冰川大西洋的古海洋氧合代理

• 批准号: 1736771
• 负责人: Andrew Ridgwell
• 金额: $ 6.39万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-15 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1736771&HistoricalAwards=false
• 关键词: Collaborative; Research; Refining; foraminiferal; Ca

This collaborative project seeks to refine the use of I/Ca ratios in fossil foraminifera from marine sediments as a proxy for reconstructing past dissolved oxygen levels in the ocean, a fundamental variable because of the role oxygen plays in the biogeochemical cycle of carbon and in controlling the distribution of marine life. The present oceans because of warming and eutrophication are on a trajectory to lower oxygen contents and future expansion of marine "dead zones" - regions where waters have oxygen levels below the threshold necessary for life. Ocean-wide changes in dissolved oxygen levels that are projected to occur over the next century are expected to have magnitudes similar to those that occurred over the natural glacial-interglacial cycles of the last few millions of years. A better understanding of the ocean's oxygen history in the past, especially the geographic and bathymetric extent of oxygen depletion, can help improve future forecasts. While a number of geochemical proxies are available to reconstruct extreme oxygen changes that affected the whole or large parts of the global ocean in the distant geological past, proxies sensitive to the subtler oxygen fluctuations expected to occur in the near-future have been lacking. Measurements of foraminiferal I/Ca in preliminary studies have shown excellent potential to differentiate and reconstruct intermediate oxygen levels in the water column. This project will further evaluate and refine I/Ca as a quantitative proxy for reconstructing hypoxic and suboxic conditions, oxygen levels most relevant to future threats to marine ecosystems on a human time scale. Broader impacts of the project include the support of an early career scientist and two senior PIs, as well as two graduate students and several undergraduates. Public outreach will be through collaboration with the local Syracuse Science Museum and through the mainstream media. The project team will conduct I/Ca analyses of foraminifera from a large suite of core top samples from the west Africa margin to further develop empirical calibrations between iodine and subsurface oxygen levels. They will compare I/Ca data with two independent oxygen proxies (nitrogen isotope data and carbon isotope gradients in benthic foraminifera), targeting both the upper and deep oceans. The team will then apply I/Ca measurements to downcore planktic and benthic foraminifera from a variety of regions in the Atlantic and Southern Ocean to quantitatively reconstruct past variations in the distribution and intensity of the oxygen minimum zone (OMZ), with a focus on changes in the glacial ocean at different depths and in different parts of the Atlantic basin. In addition, a representation of the marine iodine cycle will be incorporated into a widely-used Earth System Model (cGENIE), enabling explicit data-model comparisons for the first time. Graduate and postgraduate training in earth system modeling will be provided through a two-day workshop to be held at Syracuse University. This project will lead to further develop of a promising proxy (I/Ca) for hypoxic and suboxic conditions, investigate the variability of ocean oxygenation with climate change, and advance the capacity for future integration between proxy oxygen data and earth system models.

该协作项目旨在完善从海洋沉积物中的化石有孔虫中使用I/CA比的使用，作为重建过去溶解的氧气水平的代理，这是一种基本变量，因为氧在碳的生物地球化学周期中的作用和控制海洋生物的分布中的作用。目前的海洋由于变暖和富营养化是在较低的氧气含量和海洋“死区”的未来膨胀的轨迹上 - 水域的氧气水平低于生命所需的阈值。预计下一世纪将发生的溶解氧气水平的海洋范围变化预计将具有与过去几百万年来自然冰川间冰期周期相似的幅度。对过去的海洋氧史，尤其是氧气耗竭的地理和测深程度，可以更好地了解海洋的氧历史，这可以帮助改善未来的预测。尽管许多地球化学代理可用于重建极端的氧气变化，这些变化影响了遥远的地质过去的整个全球海洋或大部分，但缺乏对微分氧气敏感的敏感的代理。初步研究中有孔虫I/CA的测量表明，在水柱中分化和重建中间氧气水平的巨大潜力。该项目将进一步评估和完善I/CA作为重建低氧和亚氧化条件的定量代理，氧气水平与未来对海洋生态系统的威胁最相关的氧气水平在人体时间范围内。该项目的更广泛影响包括早期职业科学家和两名高级PI，以及两名研究生和几名本科生。公众推广将通过与当地的锡拉丘兹科学博物馆合作以及主流媒体的合作。项目团队将对来自西非边缘的大量核心顶部样本进行I/CA分析，以进一步发展碘和地下氧气之间的经验校准。他们将将I/CA数据与两个独立的氧气代理（底栖有孔虫中的氮同位素数据和碳同位素梯度）进行比较，靶向上层和深海。然后，该团队将对来自大西洋和南大洋各个地区的板岩和底栖有孔虫进行下去浮游和底栖有孔虫的测量，以定量地重构氧最小区（OMZ）的分布和强度的过去变化，重点关注不同部分的冰川海洋和不同部分的冰川海洋的变化。此外，海洋碘循环的表示形式将被纳入广泛使用的地球系统模型（CGENIE），从而首次实现了明确的数据模型比较。将在锡拉丘兹大学举行的为期两天的研讨会提供地球系统建模的研究生和研究生培训。该项目将导致进一步发展有前途的代理（I/CA），用于低氧和亚氧化条件，研究随着气候变化的海洋氧合的变化，并提高了代理氧数据和地球系统模型之间未来整合的能力。

项目成果

Fundamentally different global marine nitrogen cycling in response to severe ocean deoxygenation

• DOI: 10.1073/pnas.1905553116
• 发表时间: 2019-11
• 期刊: Proceedings of the National Academy of Sciences
• 作者: B. Naafs;F. Monteiro;A. Pearson;M. B. Higgins;R. Pancost;A. Ridgwell;A. Ridgwell

The atmospheric bridge communicated the <i>δ</i>¹³C decline during the last deglaciation to the global upper ocean

大气桥将上次冰消期期间的 <i>δ</i>¹³C 下降传达给全球上层海洋

• DOI: 10.5194/cp-17-1507-2021
• 发表时间: 2021
• 期刊: Climate of the Past
• 影响因子: 4.3
• 作者: Shao, Jun;Stott, Lowell D.;Menviel, Laurie;Ridgwell, Andy;Ödalen, Malin;Mohtadi, Mayhar
• 通讯作者: Mohtadi, Mayhar

Late inception of a resiliently oxygenated upper ocean

• DOI: 10.1126/science.aar5372
• 发表时间: 2018-07-13
• 期刊: SCIENCE
• 影响因子: 56.9
• 作者: Lu, Wanyi;Ridgwell, Andy;Lu, Zunli
• 通讯作者: Lu, Zunli

Temperature controls carbon cycling and biological evolution in the ocean twilight zone

• DOI: 10.1126/science.abb6643
• 发表时间: 2021-03-12
• 期刊: SCIENCE
• 影响因子: 56.9
• 作者: Boscolo-Galazzo, Flavia;Crichton, Katherine A.;Pearson, Paul N.
• 通讯作者: Pearson, Paul N.

Regional patterns and temporal evolution of ocean iron fertilization and CO2 drawdown during the last glacial termination

• DOI: 10.1016/j.epsl.2020.116675
• 发表时间: 2021-01-15
• 期刊: EARTH AND PLANETARY SCIENCE LETTERS
• 影响因子: 5.3
• 作者: Lambert, Fabrice;Opazo, Natalia;Abe-Ouchi, Ayako
• 通讯作者: Abe-Ouchi, Ayako