Spatiotemporal Distribution of Submesoscale Eddies with Updated Interferometric Imaging Radar Altimeter Data

Submesoscale eddies (SEs) represent a potent force driving ocean vertical motion. However, the resolution limitations of conventional satellite data hinder the observation of smaller SEs. Advancements in satellite altimetry now enable the detection of SEs through sea level data. This study leverages 264 swaths of interferometric imaging radar altimeter (InIRA) data, spanning 10 orbits, to identify 7,348 SEs in the South China Sea (SCS) between 2016 September 22 and 2018 April 30 using a novel SE identification method. Notably, the counts of submesoscale cyclonic and anticyclonic eddies are nearly equivalent, contrasting previous findings. The average radius of cyclonic SEs is larger, reflecting a higher occurrence probability for SEs exceeding 2 km in radius. Another notable finding is the seasonal variation in SE occurrence, with the lowest probability in autumn and the highest in summer. We hypothesize that this pattern correlates with the weakening of the SCS front in autumn, as mesoscale eddies and sea surface temperature front edges are known to generate more SEs. This seasonal trend is also evident in surface drifting buoy temperature data. The average temperature fluctuation induced by multiple SEs can reach 0.2 °C, indicating a sub-mesoscale vertical heat flux surpassing that of mesoscale eddies across all oceanic regions. Consequently, vertical SE heat flux plays a pivotal role in the anomalous surface heat budget.