Subinertial variability across and around the Greenland-Scotland Ridge and its impacts on the ocean circulation

该项目将研究格陵兰-苏格兰海岭（GSR）环流，该环流是向北流动的暖流和咸水表面流与向南流动的密集溢出流和北极流出流汇合的地方，与一系列高分辨率现实数值模型模拟的时间平均流量相比，量化亚惯性变率（以天到几十天为周期）的相对重要性。该工作将量化亚惯性变率对以下方面的影响：(1)GSR两侧深海盆地的跨脊体积输送；(2)横额水团交换；(3)浅层大陆架内外的跨架破碎体搬运。将提供沿山脊（格陵兰、冰岛、法罗和苏格兰大陆架）横跨大陆架断裂带的第一个gsr范围内的体积、热量和盐通量估计，包括它们的空间和时间变化。项目成果将提供对GSR变率的性质和重要性的基本理解，GSR变率在全球气候系统中起着关键作用，并为潜在的观测策略提供信息。更广泛的影响包括支持一名早期职业女性PI，并培训一名本科生获得实际研究经验。假设亚惯性变动性超过季节性和超惯性变动性的渠道，沿着GSR，冰岛和法罗群岛周围（除了靠近海岸边缘的潮汐），并且它可能主导GSR上一些地方的时间平均流量，将通过解决几个目标来验证。这包括表征亚惯性流、海面高度和等平位移变异性；量化这种变异性如何影响脊间体积输送；表征与高输运事件相关的空间结构和尺度，以及水的质量性质如何因锋面热通量和盐通量而改变；并量化亚惯性变率如何影响跨架破碎体积运输。基于这些发现，将推荐一种观测策略来捕捉对平均流量很重要的亚惯性变率。将使用的工具包括麻省理工学院环流模型（MITgcm）现有的三个为期一年的区域海洋-海冰配置流体静力模拟，这些模拟已被证明能够真实地代表区域海洋的特性和动力学。将使用一个用于拉格朗日分析的离线粒子跟踪工具（由pi开发），该工具采用带有预测-校正方案的梯形求解器，并使用完整的四维速度场来计算粒子轨迹。公开可用的数据集将用于模型数据比较。目标是量化数值模拟的真实性和估计偏差，并阐明稀疏，间歇性观测和不准确模拟中的互补信息。使用的产品包括水文剖面、系泊时间序列、滑翔机数据集、网格化和沿轨道测高数据产品。如果计划中的地表水和海洋地形（SWOT）任务的高质量控制高分辨率卫星测高数据在本项目期间发布，它们也将被利用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will examine Greenland-Scotland Ridge (GSR) circulation, where northward-flowing warm and saline surface currents meet southward-flowing dense overflows and Arctic outflows, to quantify the relative importance of subinertial variability (with periods of days to tens of days) compared to the time-average flow in a series of high-resolution realistic numerical model simulations. The work will quantify the impact of subinertial variability on (1) cross-ridge volume transports to and from the deep ocean basins on either side of the GSR; (2) cross-frontal water mass exchange; and (3) cross-shelfbreak volume transport on and off the shallow continental shelves. The first GSR-wide estimates of volume, heat, and salt fluxes across continental shelfbreaks along the ridge (the Greenland, Iceland, Faroe, and Scottish shelves) will be provided, including their spatial and temporal variability. Project outcomes will provide fundamental understanding of the nature and importance of GSR variability, which plays a key role in the global climate system and inform potential observing strategies. Further broader impacts include support of an early-career female PI and train an undergraduate student to gain practical research experience. Hypotheses that subinertial variability exceeds seasonal and superinertial variability in channels, along the GSR, and around the Iceland and the Faroes (excepting tides close to coastal margins) and that it may dominate the time-mean flow in some places on the GSR will be tested by addressing several objectives. These include characterizing subinertial current, sea surface height and isopycnal displacement variability; quantifying how such variability impacts the cross-ridge volume transport; characterizing the spatial structures and scales associated with high-transport events, and how water mass properties are modified due to cross-frontal heat and salt fluxes; and quantifying how subinertial variability impacts the cross-shelfbreak volume transport. Based on these findings, an observational strategy will be recommended to capture the subinertial variability where it is important to the mean flow. Tools to be used include three existing one-year-long hydrostatic simulations from regional ocean-sea ice configurations of the Massachusetts Institute of Technology general circulation model (MITgcm), which have been shown to realistically represent the regional ocean properties and dynamics. An offline particle tracking tool for Lagrangian analyses (developed by the PIs) will be used, which employs a trapezoidal solver with a predictor-corrector scheme, and uses the full four-dimensional velocity fields to calculate particle trajectories. Publicly-available data sets will be used for a model-data comparison. Goals are to quantify the realism of the numerical simulations and estimate bias, and to elucidate the complementary information in sparse, intermittent observations and inaccurate simulations. Products to be used include hydrographic profiles, mooring timeseries, glider datasets , and gridded and along-track altimetry data products. If quality-controlled high resolution satellite altimetry from the planned Surface Water and Ocean Topography (SWOT) mission are released within the duration of this project, they will also be utilized.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.