Collaborative Research: Microstructure and Mixing Measurements During SPURS

全球海洋表面盐度的变化是由淡水通过蒸发、降水和径流与大气和陆地交换造成的。对水循环将随着全球变暖而加速的预期激发了人们对上层海洋盐度的兴趣；由于水循环主要是在海洋上进行的，所以海洋表面的盐度很可能是水循环变化的最好指标。在考虑这种海洋-大气相互作用时，地表盐度极值区域是特别有趣的。一个多机构的实地项目，盐度过程上层海洋区域研究（SPURS），开始了解控制上层海洋盐度的海洋过程，将于2012- 2013年执行。马刺集中在北大西洋东部的表面盐度最大值。上层海洋的盐度受地表淡水与大气的交换、来自下层的混合和夹带以及水平流的平均和涡旋平流控制，包括地转、埃克曼和较小尺度的运动。马刺计划的其他部分将对这些过程进行评估；在这里，我们建议把重点放在上层海洋混合上。剖面和滑动平台上的微结构传感器将用于量化在盐度最大区域内运行的混合过程。此外，模式模拟将阐明模式质量和对混合和上层海洋稳定结构重要的物理过程。智力优势：理解和预测上层海洋盐度场的演变取决于对亚网格尺度混合过程的准确描述和参数化，这些混合过程消散了地表水通量造成的盐度变化。微观结构测量将量化与总体马刺研究限制的温度和盐度预算相关的绝热通量项。将评估表面对流、内波过程和双扩散混合对这些通量的作用。由海气相互作用浮标数据提供的模式模拟将有助于确定湍流的来源。双重扩散的混合参数化将通过改变模型实现来评估，以利用从基于微观结构的估计中获得的扩散系数。微观结构测量和建模相结合的方法是提供信息的最有效途径，可以改进参数化。由于纳入整个热刺方案，将进行盆地、区域和中尺度的观测和模型，其协同效应将使影响倍增。更广泛的影响：提高对海洋混合过程的理解对于推进气候科学至关重要，因为大尺度模式中亚网格尺度过程的表示仍然是一个主要的未解决的问题。这个项目对盐度的关注与记录全球水循环的变化特别相关，这对社会有着巨大的影响。作为该项目的一部分，研究人员将维护在盐度最高区域运行的热刺和混合过程的网站。为了加强教育推广，调查人员将与位于伍兹霍尔的Zephyr教育基金会的创新海洋科学素养和教育计划合作。Zephyr基金会非常适合这一目的，并吸引了来自马萨诸塞州和罗德岛州的学校团体，包括来自波士顿和新贝德福德市中心项目的代表性不足和弱势学生。该项目还将涉及WHOI/MIT的全日制研究生的积极作用。此外，还将制作适合分布的建模和数据分析模块。

Surface salinity variations in the global ocean are caused by freshwater exchange with the atmosphere and land, via evaporation, precipitation and runoff. The expectation that the water cycle will accelerate with global warming has motivated an increased interest in upper-ocean salinity; since the water cycle is predominantly over the ocean, the sea-surface salinity may well be the very best indicator of changes in the water cycle. In considering such ocean-atmosphere interactions, areas of surface salinity extrema are of special interest. A multi-agency field program, the Salinity Processes Upper-ocean Regional Studies (SPURS), to begin to understand the oceanic processes that control upper ocean salinity will be executed in 2012-13. SPURS is focused on the surface salinity maximum in the eastern North Atlantic. The salinity of the upper ocean is controlled by surface freshwater exchange with the atmosphere, mixing and entrainment from below, and mean and eddy advection by horizontal currents, including those due to geostrophic, Ekman and smaller scales of motion. Other elements of SPURS will evaluate many of these processes; here we propose to focus on upper-ocean mixing. Microstructure sensors on profiling and gliding platforms will be used to quantify the mixing processes operating within the salinity maximum region. In addition, model simulations will elucidate both model quality and the physical processes important to the mixing and upper ocean stability structure. Intellectual Merit: Understanding and prediction of the evolution of the upper-ocean salinity field depends on accurate description and parameterization of the sub grid-scale mixing processes that dissipate the salinity variance created by surface water fluxes. Microstructure measurements will quantify the diabatic flux terms relevant to the temperature and salinity budgets being constrained by the overall SPURS study. The role of surface convection, internal wave processes, and double-diffusive mixing on these fluxes will be assessed. Model simulations, fed by the air-sea interaction buoy data, will help identify the source of the turbulence. Mixing parameterizations for double diffusion will be assessed through alteration of the model implementation to utilize diffusivities as taken from the microstructure based estimates. The combined approach of microstructure measurements and modeling is the most efficient route to provide information that could lead to improved parameterizations. The impact will be multiplied by the synergistic effects of being incorporated into the overall SPURS program, where observations and models of basin, regional and the mesoscale will be undertaken. Broader Impacts: Improved understanding of ocean mixing processes are essential for advancing climate science, as the representation of sub grid-scale processes in large-scale models continues to be a major unresolved issue. The focus of this project on the salinity is especially relevant to documenting change in the global water cycle, which has tremendous implications for society. As part of this project the investigators will maintain web sites on SPURS and the mixing processes operant in the salinity maximum region. To enhance educational outreach, the investigators will collaborate with The Zephyr Education Foundation's innovative marine science literacy and education program, located in Woods Hole. The Zephyr Foundation is ideally suited for this purpose and attracts school groups from Massachusetts and Rhode Island, including underrepresented and disadvantaged students from inner-city programs in Boston and New Bedford. This project will also involve active roles for full-time graduate students at WHOI/MIT. In addition, a modeling and data analysis module suitable for distribution will be produced.