Submesoscale oceanic structures (<10-20 km) such as eddies and fronts are often difficult to describe given the influence of the mesoscale. In order to characterize the surface signatures of submesoscale structures, we utilize a custom spatial filtering function to separate the meso- and large-scale sea surface height (SSH) signal from the small scale SSH signal of 1/48° high resolution estimates provided by NASA’s Estimating the Circulation and Climate of the Oceans (ECCO) project. In this study, we use ECCO estimates from a 14-month global simulation between September 2011 and November 2012 with a 2 km horizontal grid spacing in the Gulf of Mexico. We then use an eddy detection and tracking algorithm to identify persistent circular features on both scales, giving rise to an atlas of submesoscale eddy-like variabilities (SEVs). We briefly investigate the geographic and temporal variability of SEVs as a whole before collocating SEVs inside mesoscale eddies, allowing us to evaluate the characteristics of internal SEVs and the impact of SEVs on mesoscale eddies. We find that SEVs, both anticyclonic and cyclonic, are ubiquitous inside mesoscale eddies with lifetimes longer than a week, accounting for an average of 10-20% of the spatial area and eddy kinetic energy of mesoscale eddies. We also show that internal SEVs are persistently associated with temperature and salinity anomalies in both eddy centers and edges of up to 0.1 °C and 0.05 psu, with anticyclonic internal SEVs being warmer and fresher while cyclonic internal SEVs are colder and saltier. Finally, we examine the life cycle of an anticyclonic Loop Current eddy, demonstrating that the number and intensity of internal SEVs within increases as the eddy approaches separation from the Loop Current until a maximum is obtained just after separation. In light of forthcoming submesoscale SSH observations from NASA’s Surface Water and Ocean Topography (SWOT) mission, our results showcase the variability of submesoscale eddy structures and their possible implications for biogeochemical cycling, the inverse energy cascade, and Loop Current prediction techniques.

中文翻译：

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根据 1/48° ECCO 估计的墨西哥湾中尺度涡旋内的亚尺度涡旋结构特征

考虑到中尺度的影响，涡流和锋面等亚尺度海洋结构（<10-20 公里）通常难以描述。为了表征亚尺度结构的表面特征，我们利用自定义空间滤波函数将中尺度和大尺度海面高度 (SSH) 信号与 1/48° 高分辨率估计提供的小尺度 SSH 信号分离NASA 的估计海洋环流和气候 (ECCO) 项目。在本研究中，我们使用 2011 年 9 月至 2012 年 11 月期间为期 14 个月的全球模拟的 ECCO 估计值，其中墨西哥湾的水平网格间距为 2 公里。然后，我们使用涡流检测和跟踪算法来识别两个尺度上的持续圆形特征，从而产生亚尺度涡流样变率 (SEV) 的图集。在将 SEV 置于中尺度涡流内部之前，我们简要调查了 SEV 作为一个整体的地理和时间变异性，从而使我们能够评估内部 SEV 的特征以及 SEV 对中尺度涡流的影响。我们发现，SEVs，包括反气旋式和气旋式，在中尺度涡旋中普遍存在，寿命超过一周，平均占中尺度涡旋空间面积和涡旋动能的10-20%。我们还表明，内部 SEV 与涡流中心和边缘的温度和盐度异常持续相关，最高可达 0.1 °C 和 0.05 psu，反气旋内部 SEV 更温暖、更新鲜，而气旋内部 SEV 更冷、更咸。最后，我们检查反气旋环流涡流的生命周期，表明内部 SEV 的数量和强度随着涡流接近与回路电流的分离而增加，直到在分离后立即获得最大值。鉴于 NASA 地表水和海洋地形 (SWOT) 任务即将进行的亚尺度 SSH 观测，我们的结果展示了亚尺度涡流结构的可变性及其对生物地球化学循环、逆能量级联和环流预测技术的可能影响。