Collaborative Research: A Study of Submesoscale Mixed-Layer Dynamics at a Mid-Latitude Oceanic Front: Isolating the Sub- and Super-Inertial Response to Atmospheric Forcing

合作研究：中纬度海洋锋的亚尺度混合层动力学研究：分离对大气强迫的亚惯性和超惯性响应

• 批准号: 1536359
• 负责人: John Farrar
• 金额: $ 35.47万
• 依托单位: Woods Hole Oceanographic Institution
• 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: 2015-10-01 至 2020-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1536359&HistoricalAwards=false
• 关键词: Collaborative; Research; Study; Submesoscale; Mixed

The ocean mixed-layer is both conduit and barrier for exchange of momentum, heat and gases between the atmosphere and ocean. Recent modeling has revealed a host of competing submesoscale mixed-layer processes which can either promote or inhibit air-sea exchange. These processes are an observational challenge because of the need for unaliased temporal and lateral resolution, as well as sufficient duration to establish persistent mechanisms. This study plans to dramatically improve understanding of 1-10 km scale lateral processes in three-dimensional mixed-layer dynamics with a 28-day experiment in the North Pacific Subtropical Front, a region of above-average atmospheric forcing, typical mid-ocean mesoscale advection and straining, and typical submesoscale activity, maximizing the likelihood of finding significant signals. The results of this observational program will improve the physical basis of mixed-layer parameterizations, leading to better model predictions for air-sea fluxes, gas transfer and biological productivity. The project will train one graduate student and provide research experiences to undergraduate students. A cruise blog and experiment website will make the results of the project available to the wider scientific community and general publicMultiple ship surveys, profiling float array deployments (16-20 floats measuring temperature, salinity, horizontal velocity and microstructure) and a drifting air-sea flux platform will sample the upper-ocean's response to winter storm forcing in the presence of the mixed-layer fronts that characterize the central ocean gyres. The arrays will profile in sync every 30-40 minutes to eliminate space-time aliasing, cycling between the surface and 100-150 m depth (below the transition layer). During and between deployments, the region will be surveyed repeatedly with (i) a tow-yo body and a shipboard Acoustic Doppler Current Profiler to provide larger-scale context and (ii) a multi-depth flow-through temperature and salinity system to resolve smaller horizontal scales in the upper 2-5 m. Submesoscale variability in the surface mixed-layer leads to dynamical processes which do not readily satisfy the quasigeostrophic or 1-D surface layer approximations in common use. Although these processes have been examined in isolation or idealized conditions, observational evidence to date is insufficient to clarify whether these subinertial processes are able to operate in the presence of high-frequency atmospheric forcing and strong internal-wave shears. The planned 5-7 array deployments of 3-5 days each will be of sufficient duration to separate the evolution of low-frequency dynamics from near-inertial shear that dominates short timescales, allowing evaluation of mixed-layer restratification and destratification rates by mixed-layer eddies, wind-forcing and vertical processes.

海洋混合层既是通道和障碍物，用于交换大气和海洋之间的动量，热量和气体。最近的建模揭示了许多相互竞争的子尺度混合层过程，这些过程可以促进或抑制空气交换。这些过程是一个观察性的挑战，因为需要非偏见的时间和横向分辨率，以及足够的持续时间才能建立持久机制。这项研究计划在三维混合层动力学中通过在北太平洋亚热带阵线进行28天的实验，以极大地提高对1-10公里尺度横向过程的理解，这是一个高于平均水平的大气强迫，典型的中ecean中尺度尺度上的区域对流和紧张，以及典型的集合活动，最大程度地发现了查找重要信号的可能性。该观察计划的结果将改善混合层参数化的物理基础，从而更好地对空气通量，气体转移和生物生产力进行更好的模型预测。该项目将培训一名研究生，并为本科生提供研究经验。 邮轮博客和实验网站将使该项目的结果提供给更广泛的科学界和通用公有船舶调查，分析浮点阵列的部署（16-20浮子，测量温度，盐度，水平速度和微观结构）以及漂流的空气气味通量平台将在具有特征的中央海洋循环的混合层阵线的情况下对上海洋对冬季风暴强迫的反应进行采样。阵列将每30-40分钟进行一次同步，以消除时空混叠，在表面和100-150 m深度之间循环（在过渡层以下）。在部署期间和之间，将与（i）（i）拖曳的身体和船舶声型多普勒电流剖面厂反复进行调查，以提供更大的环境，（ii）多深度的流通温度和盐度系统来解决上部2-5 m的水平尺度较小。 表面混合层中的子尺度变异性会导致动态过程，这些过程不容易满足普通使用中的准真神经或1-D表面层的近似。尽管这些过程已经在孤立或理想化的条件下进行了检查，但迄今为止的观察证据不足以阐明这些次允许过程是否能够在存在高频大气强迫和强大的内波剪切的情况下进行操作。计划的5-7个阵列部署3-5天将有足够的持续时间，可以将低频动力学的演变与近惯性剪切的演变分开，该剪切占用了短时间，可以通过混合混合的混合限制和破坏率进行评估。层涡流，风能和垂直过程。