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-苏格兰海脊环流，在那里，向北流动的温暖和含盐表面流与向南流动的密集溢流和北极外流相遇，以量化亚惯性变化（周期为几天到几十天）与一系列高分辨率现实数值模型模拟中的时间平均流相比的相对重要性。这项工作将量化亚惯性变率对以下方面的影响：（1）海脊两侧深海盆地的跨海脊体积运输;（2）跨锋面水团交换;（3）浅大陆架内外的跨陆架断裂体积运输。第一个GSR范围内的体积，热量和盐通量的估计横跨大陆架断裂沿着脊（格陵兰，冰岛，法罗群岛和苏格兰大陆架）将提供，包括其空间和时间的变化。项目成果将使人们对海平面变化率的性质和重要性有基本的了解，海平面变化率在全球气候系统中起着关键作用，并为潜在的观测战略提供信息。更广泛的影响包括支持职业生涯早期的女性PI和培训本科生获得实际研究经验。将通过解决几个目标来检验以下假设：在海峡、沿着海平面SR以及冰岛和法罗群岛周围（靠近海岸边缘的潮汐除外），亚惯性变率超过季节性和超惯性变率，而且在海平面SR某些地方，亚惯性变率可能支配时间平均流量。这些包括表征亚惯性流，海面高度和等密度线位移的变化;量化这种变化如何影响跨脊体积运输;表征与高运输事件相关的空间结构和尺度，以及水质量特性如何由于跨锋面热通量和盐通量而被修改;以及量化亚惯性变化如何影响跨shelfbreak体积运输。根据这些研究结果，将建议一种观测策略，以捕捉亚惯性变化，这是重要的平均流量。将使用的工具包括现有的三个为期一年的流体静力学模拟，这些模拟是根据马萨诸塞州理工学院大气环流模型的区域海洋-海冰结构进行的，这些模型已被证明能够真实地反映区域海洋的特性和动态。将使用用于拉格朗日分析的离线粒子跟踪工具（由PI开发），该工具采用具有预测-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，间歇性的观察和不准确的模拟中的互补信息。将使用的产品包括水文剖面图、系泊时间序列、滑翔机数据集以及网格化和沿航迹测高数据产品。如果计划中的地表水和海洋地形（SWOT）使命的质量控制高分辨率卫星测高在本项目期间发布，它们也将被利用。该奖项反映了NSF的法定使命，并被认为值得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来支持。

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.