Collaborative Research: Biogeochemical and Physical Conditioning of Sub-Antarctic Mode Water in the Southern Ocean

合作研究：南大洋亚南极模式水的生物地球化学和物理调节

• 批准号: 1736375
• 负责人: Dennis McGillicuddy
• 金额: $ 86.09万
• 依托单位: Woods Hole Oceanographic Institution
• 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: 2017-08-01 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1736375&HistoricalAwards=false
• 关键词: Collaborative; Research; Biogeochemical; Physical; Conditioning

Cold surface water in the southern Indian Ocean sinks to about 500 meters and travels in the dark for thousands of miles before it resurfaces some 40 years later near the equator in the other ocean basins. This major water mass is named the Sub-Antarctic Mode Water (SAMW). Nutrients it contains when it warms and rises into the sunlit subtropical and tropical waters are estimated to fuel up to 75% of the microscopic plant growth there. Before it sinks, the chemical properties of the SAMW are modified by the growth and distinct physiology of two common phytoplankton; diatoms with shells made of silica, and coccolithophores with carbonate shells. Local physical dynamics influence where and how fast these two phytoplankton classes grow. Consequently, differing nutrient and trace chemical fingerprints are established at the point of SAMW formation. This project is an exceptionally detailed field and modeling effort that will document and quantify the remarkable, interconnected processes that chemically connect two important oceanic ecosystems half a world apart. The scientists leading the project will study the complexity of the biological and chemical conditioning of the SAMW and thus provide critical data about the large-scale oceanic controls of the biological carbon pump that removes atmospheric carbon dioxide to the deep ocean over millennial timescales. Scientific impact from this project will stem from significant peer-reviewed publications and improved predictive models. Societal benefits will develop from training of a range of scholars, including high school, undergraduate, and graduate students, as well as technical and post-doctoral participants. A high school teacher and science communication specialist will go to sea with the project and share experiences from the ship with students on shore via social media and scheduled web interactions. To examine how SAMW formation and subduction controls the productivity of global waters well to the north, two January expeditions to the SE Indian Ocean will identify, track, and study the unique mesoscale eddies that serve as discrete water parcels supporting rich populations of either coccolithophores or diatoms plus their associated microbial communities. The eddies will be tracked with Lagrangian Argo drifters and observations will be made of exactly how SAMW is chemically conditioned (i.e. Si, N, P, Fe, and carbonate chemistry) over time scales of months. Using data obtained on the feedback between ecological processes and nutrient, trace metal, and carbonate chemistry in these eddies and on related transect cruises, the project will have three main goals: (1) determine the rates at which SAMW coccolithophores and diatoms condition the carbonate chemistry plus nutrient and trace metal concentrations, as well as assess taxonomic and physiological diversity in the study area with traditional methods plus next-generation sequence DNA/RNA profiling, (2) explore growth limitations by iron, silicate and/or nitrate in controlling algal assemblages and genetic diversity, and (3) combine these findings with the Ekman- and eddy-driven subduction of SAMW to examine biogeochemical impact on a basin scale, using both observations and global numerical models. A meridional survey from 30 to 60 degrees south latitude will be used to characterize the larger-scale variability of carbonate chemistry, nutrient distributions, productivity, genetics and biomass of various plankton groups as SAMW is subducted and proceeds northward.

印度洋南部的冷地表水沉入约500米，在黑暗中游览数千英里，然后在40年后重新浮出水面，附近其他海洋盆地的赤道。该主要水质量被命名为亚抗激模水（SAMW）。当它温暖并升入阳光亚热带和热带水域时，它含有的养分估计会为那里的显微镜植物生长的75％加油。在下沉之前，SAMW的化学特性会通过两个常见的浮游植物的生长和独特的生理来改变。用硅胶制成的壳和带有碳酸盐壳的壳硅。局部物理动态会影响这两个浮游植物类别的何处和速度。因此，在SAMW形成点建立了不同的营养和痕量化学指纹。该项目是一个非常详细的领域和建模工作，它将记录和量化相互联系的两个重要的海洋生态系统的杰出，相互联系的过程。领导该项目的科学家将研究SAMW的生物学和化学调节的复杂性，因此提供了有关生物碳泵的大规模海洋控制的关键数据，这些数据将大气中的二氧化碳移至千禧年时间尺度的深海。 该项目的科学影响将源于重大的同行评审出版物和改进的预测模型。社会福利将从培训一系列学者，包括高中，本科生和研究生以及技术和博士后参与者的培训。高中老师和科学传播专家将通过该项目出海，并通过社交媒体和预定的网络互动与岸上的学生分享这艘船的经验。为了研究SAMW的形成和俯冲如何控制北部全球水域的生产力，两次1月探险印度洋将识别，跟踪和研究独特的中尺度涡流，这些涡流是支持富裕人群的coccolithophophores或diotoms或diotoms的富裕水包裹。涡流将使用拉格朗日的Argo漂流者进行跟踪，并且将在几个月的时间尺度上对SAMW进行化学条件（即Si，N，P，Fe和碳酸盐化学）的方式进行观察。使用在这些涡流中以及相关的样带巡航中获得的生态过程和养分，微量金属和碳酸盐化学之间的反馈的数据，该项目将具有三个主要目标：（1）确定SAMW Coccocolithophotors和diatoms的速率，以及在碳酸盐化学以及在碳酸盐化学方面以及养分次数和痕量金属浓度，以及用于评估的分类学和物理学多样性，并在碳酸盐化学方面条件的速率，并确定碳酸盐磷酸化的速率，并确定碳酸盐液和物理学的多样性。 DNA/RNA分析，（2）在控制藻类组合和遗传多样性方面探索铁，硅酸盐和/或硝酸盐的生长限制，以及（3）将这些发现与Ekman-和Ekman-and-Eddy驱动的SAMW的俯冲相结合，以利用观察量和全球数字模型检查Basin量表的生物地球化学影响。从30到60度的子午调查将用于表征碳酸盐化学，营养分布，生产力，遗传学和生物量的较大尺度变异性，因为SAMW被俯冲并进行北部。

项目成果

Environmental Drivers of Coccolithophore Growth in the Pacific Sector of the Southern Ocean

• DOI: 10.1029/2023gb007751
• 发表时间: 2023-11
• 期刊: Global Biogeochemical Cycles
• 影响因子: 5.2
• 作者: H. Oliver;D. J. McGillicuddy;K. Krumhardt;M. Long;N. R. Bates;B. Bowler;D. Drapeau;W. Balch