DataSheet_1_Using Argo Floats to Characterize Altimetry Products: A Study of Eddy-Induced Subsurface Oxygen Anomalies in the Black Sea.pdf

The identification of mesoscale eddies from remote sensing altimetry is often used as a first step for downstream analyses of surface or subsurface auxiliary data sets, in a so-called composite analysis framework. This framework aims at characterizing the mean perturbations induced by eddies on oceanic variables, by merging the local anomalies of multiple data instances according to their relative position to eddies. Here, we evaluate different altimetry data sets derived for the Black Sea and compare their adequacy to characterize subsurface oxygen and salinity signatures induced by cyclonic and anticyclonic eddies. In particular, we propose that the theoretical consistency and estimated error of the reconstructed mean anomaly may serve to qualify the accuracy of gridded altimetry products and that BGC-Argo data provide a strong asset in that regard. The most recent of these data sets, prepared with a coastal concern in the frame of the ESA EO4SIBS project, provides statistics of eddy properties that, in comparison with earlier products, are closer to model simulations, in particular for coastal anticyclones. More importantly, the subsurface signature of eddies reconstructed from BGC-Argo floats data is more consistent when the EO4SIBS data set is used to relocate the profiles into an eddy-centric coordinate system. Besides, we reveal intense subsurface oxygen anomalies which stress the importance of mesoscale contribution to Black Sea oxygen dynamics and support the hypothesis that this contribution extends beyond transport and involves net biogeochemical processes.

借助遥感测高数据（remote sensing altimetry）识别中尺度涡旋（mesoscale eddies），常作为地表或次表层辅助数据集后续分析的首要步骤，此即所谓的合成分析框架（composite analysis framework）。该框架通过依据涡旋的相对位置合并多组数据实例的局地异常，旨在表征涡旋对海洋变量引发的平均扰动。本研究针对黑海海域衍生的多款测高数据集开展评估，并对比其在表征气旋涡旋（cyclonic eddies）与反气旋涡旋（anticyclonic eddies）所诱导的次表层氧与盐度特征方面的适用性。具体而言，我们提出，重构得到的平均异常的理论一致性与估算误差可用于评估网格化测高产品（gridded altimetry products）的精度，而BGC-Argo浮标数据（BGC-Argo）在该方面具备显著优势。其中最新的数据集是在欧洲空间局（ESA）EO4SIBS项目框架下针对近岸场景研发的，相较于早期产品，其提供的涡旋特性统计结果更贴近模式模拟结果，尤其在近岸反气旋涡方面表现更佳。更重要的是，当使用EO4SIBS数据集将剖面数据重定位至以涡旋为中心的坐标系时，由BGC-Argo浮标数据重构得到的涡旋次表层特征一致性更强。此外，本研究揭示了强烈的次表层氧异常，这凸显了中尺度过程对黑海氧动力学的重要性，并支持了该贡献不仅限于输运过程，还涉及净生物地球化学过程的假说。