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: 1536681
• 负责人: Eric Kunze
• 金额: $ 33.39万
• 依托单位: NorthWest Research Associates, Incorporated
• 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 2021-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1536681&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.

海洋混合层是大气和海洋之间动量、热量和气体交换的管道和屏障。最近的模拟揭示了一系列相互竞争的亚中尺度混合层过程，这些过程可以促进或抑制海气交换。这些过程是一项观测挑战，因为需要不间断的时间和横向分辨率，以及足够的持续时间来建立持久的机制。本研究计划通过在北太平洋副热带锋（一个高于平均水平的大气强迫区域，典型的海洋中中尺度平流和张力区域，以及典型的亚中尺度活动区域）进行为期28天的实验，极大地提高对三维混合层动力学中1-10公里尺度横向过程的理解，最大限度地提高发现重要信号的可能性。这一观测项目的结果将改善混合层参数化的物理基础，从而更好地预测海气通量、气体输送和生物生产力的模式。该项目将培养一名研究生，并为本科生提供研究经验。一个巡航博客和实验网站将把项目的结果提供给更广泛的科学界和公众。多艘船调查，分析浮子阵列部署（16-20个浮子测量温度、盐度、水平速度和微观结构）和一个漂流的海气通量平台将采样上层海洋对冬季风暴强迫的反应，这些冬季风暴强迫存在混合层锋，这是中央海洋环流的特征。这些阵列将每30-40分钟同步一次，以消除时空混叠，在地表和100-150米深度（低于过渡层）之间循环。在部署期间和部署之间，该区域将使用(i)拖缆体和船载声学多普勒电流分析器进行重复调查，以提供更大范围的背景；（ii）多深度的温度和盐度流动系统，以解决上部2-5米的较小水平尺度。地面混合层的亚中尺度变率导致动力过程不容易满足通常使用的准等转或1-D面层近似。虽然这些过程已经在孤立或理想化的条件下进行了研究，但迄今为止的观测证据还不足以阐明这些亚惯性过程是否能够在高频大气强迫和强内波切变存在的情况下运行。计划部署的5-7个阵列，每个部署3-5天，将足够的持续时间将低频动力学的演变与主导短时间尺度的近惯性切变分离开来，允许评估混合层涡旋、风强迫和垂直过程的混合层再气化和脱层速率。

项目成果

Destratification and Restratification of the Spring Surface Boundary Layer in a Subtropical Front

副热带锋面春季表面边界层的去层化和再层化

• DOI: 10.1175/jpo-d-21-0003.1
• 发表时间: 2021
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: Kunze, Eric;Mickett, John B.;Girton, James B.
• 通讯作者: Girton, James B.