Collaborative Research: Role of mixed layer eddies on phytoplankton productivity in seasonally variable regimes

这项研究有助于理解海洋中一个与生物高度相关的区域--亚极地北大西洋，它充当着大气碳的持久汇。它评估了次中尺度过程的生物学重要性，这些过程没有在全球碳循环模型中得到体现。混合层涡旋，以及由海-气通量引起的湍流，对浮游植物生产力的光和营养物质都进行了调制。本研究探讨了亚极地环流中混合层涡旋在冬季、春季和夏季三个不同的年度周期阶段对浮游植物生产力的影响。通过模拟混合层涡旋与中尺度涡旋的相互作用，这项研究将深入了解它们的耦合如何影响跃层和混合层之间的垂直交换。该项目将为马萨诸塞大学达特茅斯分校的一名博士后科学家和麻省理工学院/伍兹霍尔海洋研究所联合项目的一名博士生提供四年的支持。研究人员将通过海洋学院在新贝德福德海港的海洋探索中心通过使用数值和桌面实验演示海洋动力学，为包括教师培训和海洋扫盲在内的外联工作做出贡献。这项研究将是第一批包括垂直和横向过程(即湍流混合和1-10公里尺度混合层涡流)的研究之一，以了解上层海洋对短时间尺度(小时-日)上时间变化的海-气通量的响应。通过研究深冬混合层分层的产生机制，研究人员将评估在光能稀缺限制光合作用的时期(冬季和初春)，涡旋和海气通量对浮游植物初级生产力的影响。通过研究次表层中尺度涡旋与受海-气间歇性通量影响的地表次中尺度场之间的耦合，他们将研究在地表强烈层化期间(夏季)的平流垂直营养物质供应。这些过程研究将有助于解决关于亚极地海洋浮游植物生产力的下列重要问题：(I)种子浮游植物种群如何维持过冬？(2)春季分层的机制，无论是涡旋或热效应，是否与季节的净初级生产力有关？(Iii)在夏季强烈层结期间，营养物质如何供应给表层？这项研究将扩展目前对混合层涡旋的理解，这是基于在理想化混合层环境中的研究，通过考虑它们与下面的跃层中的中尺度涡旋的相互作用，以及与响应时间脉动的海-气通量的地面湍流的相互作用。

This study contributes to the understanding of a biologically highly relevant region of the ocean, the subpolar North Atlantic, which acts as a persistent sink for atmospheric carbon. It assesses the biological importance of submesoscale processes, which are not represented in global carbon cycle models. Mixed layer eddies, along with the turbulence induced by air-sea fluxes, modulate both light and nutrients for phytoplankton productivity. This study explores the role of mixed layer eddies on phytoplankton productivity in the subpolar gyres during three distinct phases of the annual cycle - winter, spring, and summer. By modeling the interaction of mixed layer eddies with mesoscale eddies, the study will provide insight on how their coupling affects vertical exchange between the pycnocline and the mixed layer. The project will support a postdoctoral scientist at University of Massachusetts Dartmouth and a Ph.D. student in the Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program for four years. The investigators will contribute to outreach efforts including teacher training, and ocean literacy workshops through the Ocean Academy at the Ocean Explorium at New Bedford Seaport by demonstrating ocean dynamics using numerical and tabletop experiments. This study will be amongst the first to include vertical and lateral processes (namely turbulent mixing and 1-10 km scale mixed layer eddies) in understanding the upper ocean's response to temporally varying air-sea fluxes on short time scales (hours-days). By studying the mechanisms generating stratification of deep winter mixed layers, the researchers will assess the effect of eddies and air-sea fluxes on phytoplankton primary productivity during times when a scarcity of light limits photosynthesis (in winter and early spring). By studying the coupling between subsurface mesoscale eddies and the surface submesoscale field subject to intermittent air-sea fluxes, they will examine the advective vertical nutrient supply during periods of strong surface stratification (summer). These process studies will help to address the following important questions about phytoplankton productivity in the subpolar oceans: (i) How is a seed phytoplankton population sustained over the winter? (ii) Is the mechanism for spring stratification, be it eddies or thermal effects, relevant to the net primary productivity over the season? (iii) How are nutrients supplied to the surface layer during times of strong stratification in the summer? This investigation will extend current understanding of mixed layer eddies, which is based on studies in idealized mixed layer settings, by considering their interaction with mesoscale eddies in the pycnocline beneath, and with surface turbulence in response to temporally fluctuating air-sea fluxes.