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

耦合的表面区和内陆架热收支：反照率、表面重力和内波的影响

• 批准号: 1558695
• 负责人: Falk Feddersen
• 金额: $ 29.16万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2021-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1558695&HistoricalAwards=false
• 关键词: coupled; surfzone; inner; shelf; heat

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.

近岸沃茨在经济和生态方面具有重要意义。各种各样的物种，包括无脊椎动物（蛤蜊，螃蟹，软体动物），鱼类和鸟类在这个地区安家和觅食。海岸也是旅游和娱乐的中心，推动经济活动。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发挥着关键作用。在大陆架较深的水域（12-100米深），热量收支已得到广泛研究，跨大陆架的热量输出也已量化。然而，在浅水区，耦合的surfzone（浅的深度导致波浪破碎）和内大陆架只是离岸的热收支还没有研究。因此，驱动近岸温度变化的过程是知之甚少，独特的物理过程，影响这一地区？的热量预算没有考虑。该项目将使用新的9个月现场实验的数据，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，例如离岸流的热传递，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温度（热）演变的物理过程的理解，这些物理过程可应用于广泛的经济和生态重要的近岸区域。这项工作将应用于非线性内波变换和相关的混合。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。升高的冲浪区温度可能解释了有害病原体在冲浪区的持续存在，并对人类健康产生影响。这项工作也将有影响的内波驱动的幼虫运输进入和穿越近岸。研究和教育将在所有学术层面上结合起来。该项目将培养一名博士生，他参与了实地工作的各个方面。将与服务不足的Kearny科学高中的AP环境科学班开展外联合作，开发课程材料，教学讲座，并举办实地考察。本科生将通过SIO REU programme.Although非线性内波驱动的近岸温度变率先前已被观察到在一个单一的位置，耦合surfzone和内架的完整的跨岸，垂直和时间的变化尚未被表征。一个试点冲浪区热预算表明，一个完整的耦合冲浪区内架热预算是可行的，表面重力波能量通量加热冲浪区的速度平均四分之一的太阳辐射，表明其重要性的热预算。在斯克里普斯海洋学研究所（SIO）码头进行的一项为期9个月的新的实地实验刚刚完成，该实验旨在关闭耦合的冲浪区/内大陆架热收支。 该实验由三年级研究生Greg Sinnett执行，高度解析了从海岸线到6米水深的温度时空结构，几乎是一个完整的季节周期。此外，还部署了3个ADCP海流计来测量对流热通量，部署了一个码头部署的4路辐射计来测量冲浪带和内大陆架对流。这些广泛的新的现场观测将进行分析，以关闭一个耦合的surfzone和内大陆架热预算和量化的幅度和变化的热预算条款。特别是，该地区有独特的影响热预算的过程，尚未考虑或适当量化。冲浪区的温度（由于泡沫或白水）可能会显着升高，从而减少了冲浪区的太阳能加热。然而，冲浪带的破坏性还没有量化，影响它的因素也不清楚。这项研究将量化冲浪带的反射，确定其在减少冲浪带入射太阳辐射的重要性，并开发反射参数化。试点surfzone热收支发现，表面重力波加热是重要的，相对于太阳辐射在夏季时，波小，天长。这项分析将量化从夏末到早春波浪加热的相对重要性。在试点研究中，对流热通量推断（未测量）驱动显着的温度变化和平均冷却冲浪区。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近岸的平流热通量，其大小和时间尺度，并检查驱动它的机制，以及入射波或正压潮汐的潜在反馈。因此，该项目将提供对控制近岸温度变化的过程的详细了解，并将允许对其中一些过程进行参数化。