Collaborative Research: Relating Topographic Complexity and Circulation Patterns on Coral Reefs from Colony-Scale to Reef-Scale

许多重要的沿海海洋系统要么生长在复杂的地形上，要么形成在广泛的空间尺度上不断变化的复杂地形。例如，在珊瑚礁上，地形从树枝(厘米)到斑块(10-100米)到珊瑚礁(几公里)不等。在沿海海洋中，水面波、潮汐和缓慢变化的水流迫使水在大范围的时间尺度上通过地形。了解这些水流如何与复杂的多尺度地形相互作用，对于预测珊瑚礁等浅海系统的环流模式至关重要。目前，这些相互作用的物理学没有明确地包括在观测工作或建模研究中，对珊瑚礁等沿海系统中的环流进行预测建模的最大挑战之一是缺乏根据地形空间统计对阻力和混合参数进行先验估计的方法。该项目将为沿海复杂地形上的流动提供一个理论和概念框架，其中包括水流和波浪与多尺度地形相互作用的物理。将开发用于海洋环流模型的复杂地形上流动的新参数，以提高它们在珊瑚礁等重要海岸系统中的预测能力。因此，改进对珊瑚礁环流的预测应能更好地估计跨礁营养物质和污染物的交换和运输，并更好地描述幼虫的滞留、扩散和连通性。这项实地研究将在NSF支持的Moorea珊瑚礁长期生态研究(MCR-LTER)地点进行，该地点聚集了许多珊瑚礁科学领域的领先者。通过与MCR-LTER和法国/塔希提亚研究人员的有计划的互动，成果将直接接触到多学科的国际受众。博士生将接受物理海洋野外工作、建模和理论方面的培训，并通过与MCR-LTER的互动获得跨学科和国际经验。至少9名本科生将进行独立研究并撰写与该项目相关的荣誉论文。在该项目中，将为海流和海浪与多尺度地形的相互作用建立一个理论和概念框架。一组新的现场测量和模拟将研究不同时间尺度的流动如何与以不同障碍大小、间距和斑块为特征的地形相互作用。地形空间统计将通过高分辨率卫星水深测量和3D扫描声纳测量来计算。在0.2-500米的尺度上，珊瑚礁上洋流的空间变异性将使用嵌套采样阵列进行量化。在构建的几何图形上的现场测量将调查在一系列时间尺度上变化的自然水流如何与不同长度尺度的海底地形相互作用。在理想化的礁石几何形状和真实的礁石分段上的定常和非定常流动的数值模拟将检查在现场的流、波和地形长度尺度范围内的流-地形相互作用的动力学。

Many important coastal marine systems either grow on or form complex topography that varies continuously over a wide range of spatial scales. For example, on coral reefs, topography varies from branch (centimeter) to patch (10-100 meters) to reef (several kilometers) scales. In the coastal ocean, water motion is forced past topography at a wide range of time scales by surface waves, tides and slowly varying currents. Understanding how these flows interact with complex multi-scale topography is critical for predicting circulation patterns in shallow coastal systems like reefs. At present, the physics of these interactions is not included explicitly in observational efforts or modeling studies and one of the biggest challenges for predictive modeling of circulation in coastal systems like reefs is a lack of methods for a priori estimation of drag and mixing parameters from topography spatial statistics. This project will provide a theoretical and conceptual framework for flow over complex topography in the coastal ocean that includes the physics of interactions of currents and waves with multi-scale topography. New parameterizations for flow over complex topography will be developed for use in ocean circulation models to improve their predictive ability in important coastal systems like coral reefs. Improved predictions of circulation over reefs should then lead to better estimates of cross-reef exchange and transport of nutrients and contaminants, as well as a better description of larval retention, dispersion and connectivity. The field study will be conducted at the NSF-supported Moorea Coral Reef Long Term Ecological Research (MCR-LTER) site which brings together many leaders in coral reef science. Through planned interactions with MCR-LTER and French/Tahitian researchers the results will directly reach a multi-disciplinary international audience. A PhD student will be trained in physical oceanographic field work, modeling, and theory, and gain interdisciplinary and international experience by interacting with the MCR-LTER. At least nine undergraduate students will conduct independent studies and write honors theses related to the project.In this project, a theoretical and conceptual framework will be developed for the interaction of currents and waves with multi-scale topography. A set of novel field measurements and simulations will examine how flow with different time scales interacts with topography characterized by different obstacle size, spacing, and patchiness. Topography spatial statistics will be computed from high-resolution satellite bathymetry and 3D scanning sonar measurements. Spatial variability in currents on the reef at scales from 0.2-500 meters will be quantified using a nested sampling array. Field measurements over constructed geometries will investigate how natural flow that varies at a range of time scales interacts with bottom topography with different length scales. Numerical modeling of steady and unsteady flow over idealized reef geometries and real reef segments will examine dynamics of flow-topography interactions across the range of currents, waves, and topography length scales at the field site.