The coupled surfzone and inner-shelf heat budget: The effect of albedo, surface gravity, and internal waves

近岸水域具有重要的经济和生态意义。各种各样的物种，包括无脊椎动物（蛤蜊、螃蟹、软体动物）、鱼类和鸟类在这一地区定居和觅食。海岸也是旅游和娱乐中心，促进了经济活动。众所周知，这里的水温在空间和时间上变化很大，在近岸生态系统的许多组成部分中起着至关重要的作用。在大陆架较深的水域（深度12-100 m），热收支已经得到了广泛的研究，并对跨大陆架的热量输出进行了量化。然而，在较浅的水域中，尚未对表层（浅深度导致波浪破碎）和近海内大陆架的耦合热收支进行研究。因此，驱动近岸温度变化的过程知之甚少，影响该地区的独特物理过程？没有考虑到美国的热量预算。该项目将使用一项为期9个月的新现场实验的数据，该实验解决了从海岸线到6米水深的热结构，以表征驱动近岸温度变化的关键过程，如离岸流的传热、破碎内波的混合、重力波能量耗散时的局部热生成，以及破碎波引起的泡沫和气泡对太阳能的反射。对这些独特数据的分析将提高对控制温度（热）演化的物理过程的理解，这些物理过程可以应用于广泛的经济和生态重要的近岸地区。这一工作将应用于非线性内波变换及相关混频。近岸温度演变和跨岸通量与该地区细菌病原体、硅藻、幼虫和无脊椎动物的生态密切相关。地表反照率升高可以解释地表有害病原体的持久性，并对人类健康产生影响。这项工作也将对内波驱动的幼虫进入和穿过近岸产生影响。各级学术研究和教育将相结合。该项目将培养一名全面参与实地工作的博士生。将与服务水平较低的科尔尼科学高中（Kearny Science High School）的AP环境科学班开展外展合作，开发课程材料，教授讲座，并举办实地考察。本科生将通过SIO REU项目参与。虽然非线性内波驱动的近岸温度变化以前已经在单个地点观察到，但耦合的表面带和内大陆架的完整跨岸、垂直和时间变化尚未表征。一个试点的表层热收支表明，完全耦合的表层大陆架内部热收支是可行的，表面重力波能量通量加热表层的速度平均为太阳辐射的四分之一，表明它对热量收支的重要性。在斯克里普斯海洋研究所（SIO）码头上进行的一项为期9个月的新现场实验刚刚完成，该实验旨在关闭耦合的表层/内部大陆架热量收支。该实验由三年级研究生Greg Sinnett执行，在几乎一个完整的季节周期内，高度解决了从海岸线到6米水深的温度时空结构。此外，还部署了3台ADCP流速仪来测量对流热通量，部署了一个码头部署的4路辐射计来测量表层和内大陆架反照率。这些广泛的新现场观测结果将被分析，以关闭一个耦合的表层和大陆架内部热收支，并量化热收支项的大小和变异性。特别是，该地区具有影响热收支的独特过程，这些过程尚未被考虑或适当量化。海面反照率（由于泡沫或白水）可能明显高于开阔的海洋反照率，从而减少了海面的太阳加热。然而，地表反照率尚未量化，影响反照率的因素也不清楚。本研究将量化地表反照率，确定其在减少地表入射太阳辐射中的重要性，并发展地表反照率参数化。试点的地表热收支发现，在夏季，当波浪小而白天长时，地表重力波加热相对于太阳辐射是重要的。这一分析将量化夏末到早春期间波浪加热的相对重要性。在初步研究中，推断（未测量）平流热通量驱动显著的温度变化，并平均冷却地表。驱动热通量的两种物理机制是非线性内波和离岸流。观测结果将用于量化横跨近岸的平流热通量，其大小和时间尺度，并研究驱动它的机制，以及入射波或正压潮的潜在反馈。因此，该项目将提供对控制近岸温度变化过程的详细了解，并将允许对其中一些过程进行参数化。

Nearshore waters are of critical economic and ecological importance. A wide variety of species including invertebrates (clams, crabs, mollusks), fish, and birds make their home and forage in this region. Coasts are also centers of tourism and recreation, fueling economic activity. Water temperature is known to be highly variable here in space and over time, playing a critical role in many components of nearshore ecosystems. In the deeper water of the continental-shelf (depths 12-100 m) heat budget has been extensively studied and the cross-shelf export of heat has been quantified. However, in shallower water, the coupled heat budget of the surfzone (where the shallow depth causes wave breaking) and the inner-shelf just offshore has not been studied. Thus, the processes that drive nearshore temperature variability are poorly understood and unique physical processes that affect this region?s heat budget have not been considered. This project will use data from a new 9-month field experiment that resolved the thermal structure from the shoreline to 6m water depth to characterize key processes that drive temperature variability in the nearshore such as heat transfer by rip currents, mixing by breaking internal waves, local heat generation upon the dissipation of gravity wave energy, and the reflection of solar energy by foam and bubbles due to breaking waves. Analysis of these unique data will improve understanding of the physical processes governing temperature (heat) evolution that can be applied to the broad range of economically and ecologically important nearshore regions. This work will have application to nonlinear internal wave transformation and related mixing. Nearshore temperature evolution and cross-shore fluxes are tightly linked to the ecology of bacterial pathogens, diatoms, larvae, and invertebrates in this region. Elevated surfzone albedo may explain surfzone persistence of harmful pathogens, with human health implications. This work will also have implications for internal wave driven larval transport into and across the nearshore. Research and education will be integrated at all academic levels. This project will train a PhD student who was involved in all aspects of the field work. An outreach collaboration will be developed with an AP Environmental Science class at the underserved Kearny Science High School, developing curriculum materials, teaching lectures, and hosting a field trip. Undergraduate students will be engaged through the SIO REU program.Although nonlinear internal-wave driven nearshore temperature variability has previously been observed at a single location, the full cross-shore, vertical, and temporal variability of the coupled surfzone and inner-shelf has yet to be characterized. A pilot surfzone heat budget showed that a full coupled surfzone inner-shelf heat budget was feasible and that surface gravity wave energy flux heated the surfzone at a rate on average a quarter of the solar radiation, indicating its importance to the heat budget. A new 9-month long field experiment on the Scripps Institution of Oceanography (SIO) pier, designed to close the coupled surfzone/inner-shelf heat budget, has just been completed. The experiment, executed by 3rd year graduate student Greg Sinnett, highly resolved the spatio-temporal structure of temperature from the shoreline to 6-m water depth over almost a full seasonal cycle. In addition, 3 ADCP current meters were deployed to measure advective heat fluxes and a pier-deployed 4-way radiometer was deployed to measure surfzone and inner-shelf albedo. These extensive new field observations will be analyzed to close a coupled surfzone and inner-shelf heat budget and quantify the magnitude and variability of the heat budget terms. In particular, this region has unique processes influencing the heat budget that have yet to be considered or properly quantified. The surfzone albedo (due to foam or whitewater) may be significantly elevated over open ocean albedo, thereby reducing surfzone solar heating. However, surfzone albedo has not been quantified and the factors influencing it are not understood. This study will quantify surfzone albedo, determine its importance in reducing surfzone incident solar radiation, and develop albedo parameterizations. The pilot surfzone heat budget found that surface gravity wave heating was important relative to solar radiation during summer when waves are small and days long. This analysis will quantify the relative importance of wave heating from late summer to early spring. In the pilot study, advective heat flux was inferred (not measured) to drive significant temperature variability and on average cool the surfzone. Two physical mechanisms driving heat fluxes are nonlinear internal waves and rip currents. The observations will be used to quantify the advective heat flux across the nearshore, its magnitude and time-scales, and examine the mechanisms driving it, and potential feedbacks with incident waves or barotropic tides. Thus, the project will provide a detailed understanding of the processes governing nearshore temperature variation and will allow for the parameterization of some of these processes.