Dynamical and Material Connectivity Across Continental Shelves

在冲浪区内，水通常是很好地混合的，因为波浪作用主导了动力学，并产生了强烈的湍流。在更远的近海大陆架上，水按密度分层，环流主要由风和压力梯度驱动。这两个制度通常是分开研究的，因为变化的动态和尺度有很大的不同。然而，对于从幼虫运输到污染等一系列重要问题，表面-陆架过渡区(SSTZ)的交换过程是至关重要的。这项研究将开发和使用建模方法，既能优雅地处理动态和尺度，又能更好地理解这一重要的过渡区。主要的假设是：(1)SSTZ在风、潮和波浪强迫的气流之外具有很高的内在变异性；(2)海浪涡和次中尺度陆架涡具有间歇性的强相互作用；(3)涡旋在决定物质沿水深梯度以及通过跃层的垂直输送速率方面起主导作用。这项研究计划是解决SSTZ内许多重要的生物地球化学通量、生态通量、污染物通量和沉积通量的必要先导。方法是使用多重嵌套环流模式(区域海洋模式系统，ROMS)，其中包括波浪平均的Stokes漂移涡旋力以及物质平流和扩波混合过程，并与包括由海流引起的多普勒频移折射的表面重力波模式相耦合。它将用于一系列理想化的SSTZ过程研究，以评估以下因素的相互影响：水深形状；层结；表面波；盛行的近岸洋流及其不稳定；海浪涡流；大陆架涡流和沿岸困住的海浪；潮汐；以及暴雨水流入。此外，将在南加州的几个SSTZ地点进行长时间的真实ROMS模拟，包括完整的物理和积极的向下网格嵌套，现有的测量将提供模型验证测试。通过与日本和圣巴巴拉同事的无偿合作，现实的SSTZ建模和验证研究将扩展到其他地点。智力优势：海浪涡流和次中尺度陆架涡流都是相对未被探索的现象，拟议的对SSTZ中它们的性质、动力学和物质传输影响的全面理论和计算检查将导致新的现象学发现，未来用于验证的现场实验，以及对这一前线人-海界面中物质通量的重新评估。更广泛的影响：近岸地区是人类活动与海洋的主要交汇点，在理解和模拟其针对水流、污染物、生态系统、淹没和海滩地形的行为方面的进展将使其能够更好地管理和保护。所获得的知识将通过专业和公开讲座和出版物传播；咨询国家气象局海滩安全预报员和加利福尼亚州奥兰治县废水管理人员；并将其纳入加州大学洛杉矶分校的本科生和研究生海洋课程。它将为少数族裔STEM研究生提供研究培训。它的研究合作将加强与日本的国际科学合作，以及圣巴巴拉海峡巨型海藻森林生态系统长期生态研究计划的物理海洋学基础。

Inside the surf zone, the water is typically well mixed because wave action dominates dynamics and creates strong turbulence. Further offshore on the continental shelf, the water is stratified by density and circulation is primarily driven by wind and by pressure gradients. These two regimes are typically studied separately because of the drastic differences in the dynamics and scales of variability. However, exchange processes at the Surf-Shelf Transition Zone (SSTZ) are critical for a number of important concerns ranging from larval transport to pollution. This study will develop and use modeling approaches that handle both sets of dynamics and scales gracefully and lead to a better understanding of this important transition zone. The primary hypotheses are (1) the SSTZ has high intrinsic variability beyond the wind-, tide- and wave-forced flows; (2) surf eddies and submesoscale shelf eddies have intermittent strong interactions; and (3) the eddies play a dominant role in setting the rates of material transport across and along bathymetric gradients, as well as vertically through the pycnocline. This research program is a necessary precursor to addressing the many important fluxes of biogeochemical, ecological, pollutant, and sedimentary fluxes within the SSTZ. The approach is to use a multiply-nested circulation model (Regional Oceanic Modeling System, ROMS) that includes the wave-averaged Stokes drift vortex force and material advection and wave-augmented mixing processes, coupled to a surface gravity wave model that includes Doppler-shift refraction by the current. It will be used for a set of idealized SSTZ process studies to assess the competing influences of bathymetric shape; stratification; surface waves; prevailing alongshore currents and their instability; surf eddies; shelf eddies and coastally-trapped waves; tides; and storm-water inflows. In addition, realistic ROMS simulations, with full physics and aggressive down-scale grid nesting, will be made for extensive periods at several SSTZ sites in Southern California, and existing measurements will provide model validation tests. Realistic SSTZ modeling and validation studies will be extended to other sites through unpaid collaborations with Japanese and Santa Barbara colleagues.Intellectual Merit :Both surf eddies and submesoscale shelf eddies are relatively unexplored phenomena, and the proposed comprehensive theoretical and computational examination of their nature, dynamics, and material transport effects in the SSTZ will lead to new phenomenological discoveries, future field experiments for validation, and reassessments of the material fluxes in this front-line human-ocean interface.Broader Impacts :The nearshore region is the primary intersection of human activities with the ocean, and progress in understanding and modeling its behavior for currents, pollutants, ecosystems, inundation, and beach morphology will empower better management and protection. The knowledge gained will be disseminated through professional and public lectures and publications; by consultation with National Weather Service beach safety forecasters and Orange County, CA, wastewater managers; and by inclusion into the undergraduate and graduate ocean curriculum at UCLA. It will provide research training for a minority STEM graduate student. Its research collaborations will strengthen both an international scientific cooperation with Japan and the physical oceanographic underpinnings of the Long Term Ecological Research program on the giant kelp forest ecosystem in the Santa Barbara Channel.