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

这项研究有助于了解海洋中一个生物学上高度相关的区域，即北大西洋亚极地，它是大气碳的持久汇。它评估了亚中尺度过程的生物学重要性，这些过程在全球碳循环模式中没有表现出来。混合层涡旋，以及由海气通量引起的湍流，调节了浮游植物生产力的光和营养。本研究探讨了混合层涡旋在年周期的冬、春、夏三个不同阶段对亚极地环流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，该研究将深入了解它们的耦合如何影响斜斜和混合层之间的垂直交换。该项目将资助一名马萨诸塞大学达特茅斯分校的博士后科学家和一名麻省理工学院/伍兹霍尔海洋研究所联合项目的博士生，为期四年。调查人员将通过新贝德福德海港海洋探索馆的海洋学院，通过数字和桌面实验演示海洋动力学，为外联工作做出贡献，包括教师培训和海洋扫盲讲习班。这项研究将是第一个包括垂直和横向过程（即湍流混合和1-10公里尺度的混合层涡流）的研究，以了解上层海洋在短时间尺度（小时-天）上对时间变化的海气通量的响应。通过研究深层冬季混合层形成分层的机制，研究人员将评估在光照不足限制光合作用（冬季和早春）时，涡流和海气通量对浮游植物初级生产力的影响。通过研究受间歇海气通量影响的地下中尺度涡旋与地面亚中尺度场之间的耦合，研究强表层分层期（夏季）的平流垂直营养物供应。这些过程研究将有助于解决以下关于亚极地海洋浮游植物生产力的重要问题：(i)浮游植物种子种群如何在冬季维持？春季分层的机制，无论是涡旋还是热效应，是否与整个季节的净初级生产力有关？（三）夏季分层强烈时，营养物是如何供给表层的？这项研究将扩展目前对混合层涡旋的理解，这是基于对理想混合层环境的研究，通过考虑它们与下方斜斜中尺度涡旋的相互作用，以及与响应时间波动的海气通量的地表湍流的相互作用。

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.