Isotopic constraints on global marine iron cycling, ocean productivity and deoxygenation

同位素对全球海洋铁循环、海洋生产力和脱氧的限制

• 批准号: 523177429
• 负责人: Dr. Christopher Somes, Ph.D.
• 金额: --
• 依托单位: College of Marine Science
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/523177429?language=en
• 关键词: Isotopic; constraints; global; marine; iron

Dissolved iron is a key micronutrient limiting ocean primary productivity. The major source fluxes in the global oceanic iron budget are atmospheric deposition, sedimentary release, and hydrothermal input. They determine the amount of iron in the ocean but are nonetheless poorly constrained. A new emerging dataset of iron isotopes in the ocean provides additional constraints on the key iron sources since information on their source end-member signatures is known. In this project, we will implement iron isotope tracers in our global ocean biogeochemical model to provide an additional quantitative constraint on these source iron fluxes. In particular, we will develop a new module for ocean-sedimentary iron exchange, which currently represents the largest uncertainty in the marine iron budget. This new sedimentary iron flux component will explicitly account for both the organic matter driven reductive flux and the non-reductive seafloor dissolution flux. The reductive flux will be sensitive to bottom water oxygen concentrations according to a global observational dataset indicating enhanced sedimentary reductive iron fluxes as oxygen decreases. Our global ocean biogeochemical model will estimate how much the combination of increasing atmospheric iron pollution and warming-induced deoxygenation enhance iron fluxes to the surface ocean that fuels additional primary productivity, causing an amplifying feedback that drives additional deoxygenation. We hypothesize this enhanced source iron flux-deoxygenation amplifying feedback is a key missing feature causing global Earth System Climate models that provide projections for the Intergovernmental Panel on Climate Change to significantly underestimate the current rate of ocean deoxygenation.

溶解铁是限制海洋初级生产力的关键微量营养素。全球海洋铁收支的主要来源是大气沉降、沉积物释放和热液输入。它们决定了海洋中的铁含量，但却没有受到很好的约束。一个新出现的海洋铁同位素数据集提供了对关键铁源的额外限制，因为它们的源端元特征信息是已知的。在本项目中，我们将在全球海洋生物地球化学模型中实施铁同位素示踪剂，以对这些源铁通量提供额外的定量约束。特别是，我们将开发一个新的海洋沉积铁交换模块，这是目前海洋铁预算中最大的不确定性。这一新的沉积铁通量分量将明确说明有机质驱动的还原通量和非还原性海底溶解通量。根据全球观测数据集，还原通量将对底层水氧浓度敏感，表明随着氧的减少，沉积物还原铁通量增加。我们的全球海洋生物地球化学模型将估计大气铁污染增加和变暖引起的脱氧作用的结合在多大程度上增强了铁向海洋表面的通量，从而促进了额外的初级生产力，从而导致了一种放大的反馈，从而推动了额外的脱氧作用。我们假设这种增强的源铁通量脱氧放大反馈是一个关键的缺失特征，导致全球地球系统气候模型为政府间气候变化专门委员会提供预测，大大低估了目前的海洋脱氧速率。