Eddy Tracking From In Situ and Satellite Observations Journal of Geophysical Research: Oceans

Mesoscale eddies are a dominant source of spatial variability in the surface ocean and play a major role in the biological marine carbon cycle. Satellite altimetry is often used to locate and track eddies, but this approach is rarely validated against in situ observations. Here we compare measurements of a small (under 25 km radius) mode water anticyclonic eddy over the Porcupine Abyssal Plain in the northeastern Atlantic Ocean using CTD and Acoustic Doppler Current Profiler (ADCP) measurements from three ships, two gliders, two profiling floats, and one Lagrangian float with those derived from sea level anomaly (SLA). In situ estimates of the eddy center were estimated from maps of the thickness of its central isopycnal layer, from ADCP velocities at a reference depth, and from the trajectory of the Lagrangian float. These were compared to three methods using altimetric SLA: one based on maximizing geostrophic rotation, one based on a constant SLA contour, and one which maximizes geostrophic velocity speed along the eddy boundary. All algorithms were used to select CTD profiles that were within the eddy. The in‐situ metrics agreed to 97%. The altimetry metrics showed only a small loss of accuracy, giving >90% agreement with the in situ results. This suggests that current satellite altimetry is adequate for understanding the spatial representation of even relatively small mesoscale eddies.

中尺度涡旋（Mesoscale eddies）是海洋表层空间变异性的主导来源，在海洋生物碳循环中发挥着关键作用。卫星测高（Satellite altimetry）常被用于定位和追踪涡旋，但该方法鲜少通过原位观测（in situ observations）进行验证。本研究依托三艘科考船、两架水下滑翔机、两台剖面浮标及一台拉格朗日浮标（Lagrangian float）获取的温盐深剖面仪（CTD）与声学多普勒流速剖面仪（ADCP）实测数据，对比了东北大西洋豪猪深海平原（Porcupine Abyssal Plain）海域内一个半径小于25 km的小型模态水反气旋涡旋（mode water anticyclonic eddy）的原位观测结果与基于海平面异常（SLA）的推导结果。研究人员分别从涡旋核心等密度层厚度分布图、参考深度处的ADCP流速数据以及拉格朗日浮标的运动轨迹中估算得到原位涡旋中心位置，并将其与三种基于卫星测高海平面异常的算法结果进行对比：第一种算法基于最大化地转旋转量，第二种基于恒定海平面异常等值线，第三种基于最大化涡旋边界处的地转流速率。所有算法均用于筛选处于涡旋覆盖范围内的CTD剖面数据。各原位估算指标间的一致性达97%，卫星测高算法仅存在小幅精度损耗，与原位观测结果的一致性超过90%，这表明当前的卫星测高技术足以支撑对即便相对小型的中尺度涡旋的空间表征研究。