OCE-PRF Track 1 (Broadening Participation): Internal wave-generated turbulent mixing and vertical nitrate flux during spring and neap tides along the Mid-Atlantic Bight shelf break

海洋生物碳泵将二氧化碳转化为有机碳，并将其从表层海洋输送到深渊。海洋的生物生产力取决于深水营养物质向上混合到表层海洋的速度。潮汐被认为是沿海海洋中这种混合的原因，但我们不知道它们对生物碳泵的影响程度。在这个项目中，这位研究员将解决一个基本问题：潮汐是否通过增加基本营养物质进入阳光照耀的表层海洋的速度，显著影响沿海海洋的生物生产和有机碳出口？此外，该研究员将通过领导实践教育活动，向巴尔的摩市公立学校的学生教授机器人入门知识；在Horn Point实验室开放参观期间向当地社区展示研究结果，包括马里兰州公立学校系统的学生；以及与马里兰大学的路易斯·斯托克斯少数群体参与计划合作，指导一名本科生研究人员，从而扩大未被充分代表的群体在海洋科学领域的参与。海洋生物碳泵是降低大气二氧化碳浓度的关键过程，是在初级生产和随后从表层海洋向深渊输送二氧化碳的过程中将二氧化碳固定到有机物质(COG)中。在大陆架上，出口的Corg总量的比例远远大于公海，因此即使是大陆架上生物生产力的微小波动也会对全球碳预算产生很大影响。在许多表层海洋中，生物生产力受到营养物质可获得性的限制，营养物质的垂直输送受到湍流混合的控制。在与陆架/斜坡地形相互作用的过程中，一部分潮汐能量在转化为内波的过程中被湍流所损失，而内波在向岸上移动时又被湍流所损失。这种机制可能会增加大陆架上垂直营养物质通量和生物生产力的速率。鉴于世界各地潮汐的普遍存在和频率(几小时到几个月)，由潮汐-陆架内部破裂相互作用引起的混合可能是向表层海洋生态系统提供营养的一种全球重要机制。这项研究的目的是量化内波对垂直营养物质通量的影响。利用推进的自主水下航行器(AUV)，该研究员将在新英格兰南部大陆架大潮和小潮期间的两个半日潮汐周期内，同时现场测量垂直湍流混合率和硝酸盐浓度分布。这些测量将被用来估计在前所未有的时间和空间尺度上的垂直硝酸盐通量的变化。他们验证了这样的假设，即与大陆架边缘相互作用引起的潮汐能量耗散将增加大西洋中部真光层底部附近的垂直湍流混合速率，从而增加垂直营养盐通量。

The marine biological carbon pump transforms carbon dioxide into organic carbon and transports it from the surface ocean to the abyss. Biological productivity in the oceans is dependent on the rate at which deep water nutrients mix upward into the surface ocean. Tides are believed to contribute to this mixing in the coastal ocean, but we do not know the extent to which they influence the biological carbon pump. In this project, the fellow will address the fundamental question: Do tides significantly impact biological production and organic carbon export in the coastal ocean by increasing the rate at which essential nutrients enter the sunlit surface ocean? In addition, the fellow will broaden participation of underrepresented groups in the ocean sciences by leading hands-on educational activities teaching introductory robotics to students of Baltimore City public schools; presenting findings to the local community during the an open house at Horn Point Laboratories, including students in the Maryland public school system; and collaborating with the University of Maryland's Louis Stokes Alliance for Minorities Participation program to mentor an undergraduate researcher. The marine biological carbon pump, a critical process in reducing atmospheric carbon dioxide concentration, is the fixation of carbon dioxide into organic material (Corg) during primary production and subsequent transport from the surface ocean into the abyss. Over the continental shelves, the proportion of total Corg that is exported is much greater than that in the open ocean, so even small fluctuations in biological productivity over the shelves can have a large impact on the global carbon budget. In much of the surface ocean, biological productivity is limited by nutrient availability and the vertical transport of nutrients is controlled by turbulent mixing. During interaction with the shelf/slope topography, a portion of tidal energy is lost to turbulence during conversion into internal waves, which lose further energy to turbulence as they move onshore. This mechanism likely increases the rate vertical nutrient flux and biological productivity over the continental shelves. Given the ubiquity and frequency (hours to months) of tides worldwide, mixing caused by internal tide-shelf break interaction may be a globally important mechanism of nutrient supply to surface ocean ecosystems. The goal of this study is to quantify the effect of internal waves on vertical nutrient flux. Using a propelled Autonomous Underwater Vehicle (AUV), the fellow will make simultaneous in-situ measurements of vertical turbulent mixing rate and nitrate concentration profiles over two semidiurnal tidal cycles during both a spring and neap tide over the southern New England shelf. These measurements will be used to estimate the change in vertical nitrate flux on unprecedented temporal and spatial scales. The fellow test the hypothesis that tidal energy dissipation caused by the interaction with the continental shelf edge will increase the rate of vertical turbulent mixing, and thus vertical nutrient flux, near the base of the euphotic zone in the Mid-Atlantic Bight.