Short-term submesoscale eddy variations observed in SWOT KaRIn SLA fields

In this study, we present a series of typical submesoscale eddy short-term variations revealed by one-day repeat SWOT KaRIn sea level anomaly (SLA) fields. First, several representative cases demonstrate SWOT’s capacity to continuously track submesoscale signals (<80 km diameter) over multiple days. By comparing with eddies detected based on traditional merged SLA fields with 0.25 spatial resolution, it is observed that SWOT can resolve eddy signals several days earlier. This early detection proves essential for investigating the processes involved in eddy generation. Second, the study validates the effectiveness of SWOT in resolving complex eddy-eddy interactions of merging and splitting which are often ambiguous in data merged from multiple altimeters, especially in high latitudes. Third, the vertical structures of SWOT-derived submesoscale eddies are revealed by combining with Argo observations. Results indicate that these submesoscale eddies can induce strong temperature and salinity anomalies, and also exhibit vertical biochemical signatures (e.g., chlorophyll, backscattering coefficient of particles). A BGC-Argo float was trapped by an anticyclonic eddy for nearly 2 months in the Northwest Pacific, revealing that the vertical temperature anomaly of the eddy had a double-core structure with a warm (cold) core in the upper (lower) layer during its generation phase. In addition, the submesoscale features observed by SWOT are accompanied by significant chlorophyll and SST signatures, further confirming the ability of SWOT to detect submesoscale features. This study not only integrates diverse observations to underscore the resolving ability of SWOT at the submesoscale, but also emphasizes the unique advantage of the one-day repeat product in capturing rapidly changing signals. Such insights are of great significance for an in-depth understanding of submesoscale dynamical processes and facilitate further statistical analyses of submesoscale eddies using the global coverage by SWOT in its 21-day revisit cycle.