Collaborative Research: Dynamics of Cross-shore Thermally Driven Exchange

合作研究：跨境热驱动交换的动态

• 批准号: 1436522
• 负责人: Eugene Pawlak
• 金额: $ 20.19万
• 依托单位: University of California-San Diego
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1436522&HistoricalAwards=false
• 关键词: Collaborative; Research; Dynamics; Cross; shore

In contrast to well-studied continental shelves, relatively little is known about cross-shelf circulation on island coastlines typically characterized by steep bathymetry and narrow shelves. Cross-shelf circulation results in the exchange of water masses and controls the distribution of heat, salt, nutrients, contaminants, sediment, and planktonic organisms like larvae or phytoplankton in the coastal ocean. In addition, in the case of coral reefs, the horizontal redistribution of heat by cross-shelf circulation moderates the daily variations in temperature experienced by coral polyps, thus potentially reducing thermal stress. This study will use existing data sets from two locations and high resolution numerical modeling to study the thermally driven exchange flows and how they vary with cross-shore distance and are modulated by swell energy, shelf slope, nearshore morphology, wind regimes and seasonal changesObservations at two reefs at Eilat, Israel and Oahu, Hawaii have highlighted the role of thermally forced baroclinic exchange in cross-shore transport. At each site, daytime conditions were characterized by offshore flow at the surface in response to increased temperatures in shallower water nearshore. Nighttime cooling resulted in offshore flow near the bottom. Significant differences in flow response at the two sites indicate distinct dynamic regimes, however. Time series data from Oahu further indicates that the exchange provides a first order contribution to the overall cross-shore exchange. This study will examine the dynamical structure of thermally driven flows and establish the extent of their influence and generality for tropical coasts by leveraging existing data sets in a comprehensive historical analysis coupled with high-resolution numerical modeling spanning a wide parameter space ranging from a relatively simple wedge case with generally two-dimensional bathymetry (similar to Eilat) to a complex (more typical) forereef-lagoon environment with significant wave forcing (Kilo Nalu Observatory, Oahu). It will provide fundamental understanding of cross-shore transport processes in reef environments and should reveal the extent to which thermally driven baroclinic exchange contributes to cross-shore circulation for tropical coastlines in general. Improved understanding should lead to the construction of models capable of making accurate predictions of these flows. The results of the proposed research will have particular applicability to ecologically rich and economically important coral reefs and other steep, tropical, coastal environments, such as understanding how reef ecosystems will respond to environmental changes like ocean acidification or rising ocean temperatures, as well as to efforts to protect them like the establishment of marine reserves.

与已得到充分研究的大陆架相比，人们对岛屿海岸线上的跨大陆架环流知之甚少，而岛屿海岸线的特点是水深陡峭，大陆架狭窄。 跨大陆架环流导致水团的交换，并控制着热量、盐、营养物质、污染物、沉积物和浮游生物（如幼虫或浮游植物）在沿海海洋中的分布。此外，就珊瑚礁而言，跨大陆架环流造成的热量水平再分布缓和了珊瑚虫每天经历的温度变化，从而有可能减少热应力。这项研究将使用现有的数据集从两个位置和高分辨率数值模拟研究热驱动的交换流，以及它们如何随越岸距离变化，并调制的涌浪能量，陆棚坡度，近岸形态，风制度和季节性变化观测在两个珊瑚礁在以色列埃拉特和夏威夷强调了热强迫斜压交换在越岸运输的作用。在每个站点，白天条件的特点是离岸流在表面上的温度升高，在浅水近岸。夜间冷却导致海底附近的离岸流。在两个网站的流量响应显着差异表明不同的动态制度，但是。来自Oscillation的时间序列数据进一步表明，交换对整个跨海岸交换提供了一阶贡献。本研究将检查热驱动流的动力学结构，并通过利用全面历史分析中的现有数据集，结合跨越广泛参数空间的高分辨率数值模拟，确定其对热带海岸的影响程度和普遍性，（类似于埃拉特）到复杂（更典型）的前礁-泻湖环境，具有显著的波浪强迫（基洛纳鲁天文台，俄勒冈州）。它将提供在珊瑚礁环境中的跨海岸运输过程的基本理解，并应揭示在何种程度上热驱动的斜压交换有助于跨海岸环流的热带海岸线一般。 加深了解应有助于建立能够对这些流动作出准确预测的模型。拟议研究的结果将特别适用于生态丰富和经济重要的珊瑚礁和其他陡峭的热带沿海环境，例如了解珊瑚礁生态系统如何应对海洋酸化或海洋温度上升等环境变化，以及建立海洋保护区等保护它们的努力。