Mitigating errors in marine gravity recovery induced by sea level variability in SWOT observations

• Sea level variations in SWOT observations can bias gravity modeling. • Sea level variability correction reduces RMSE by ∼40 % (DOV), ∼9% (gravity anomaly) • Regions with sea level variability >15 cm should be corrected to ensure accuracy. The Surface Water and Ocean Topography (SWOT) mission has significantly advanced marine gravity recovery, yet its wide-swath measurements reveal the effects of strong sea level variability, emphasizing the need for effective correction methods. This study reveals that traditional correction strategies, such as stacking method, are insufficient for SWOT gravity recovery in high-variability environments, and quantifies the conditions under which more targeted correction approaches are necessary. Experimental results in the Kuroshio indicate that strong sea level variability directly affects SWOT observations, leading to gravity anomaly disturbances of approximately 2 mGal. To mitigate these disturbances, two strategies are implemented: stacking and sea level anomaly (SLA) model correction. Using SLA model correction, deflection of the vertical (DOV) accuracy improves by ∼40 % in regions of strong sea level variations, while gravity anomaly accuracy is enhanced by 0.25 mGal (∼9%). To determine the conditions under which correction becomes necessary, this study evaluates gravity anomaly accuracy across varying sea level variability levels, quantified by the standard deviation of sea level anomaly (STD-SLA). Results show that when STD-SLA is below 15 cm, gravity recovery remains largely unaffected. However, above this threshold, SLA-induced disturbances become non-negligible, and applying correction improves gravity anomaly accuracy by more than 0.1 mGal on average. Global analysis reveals these regions exceeding this threshold, where correction is essential, are predominantly located along major Western Boundary Currents and the Antarctic Circumpolar Current. These findings underscore the need to reassess standard correction approaches in SWOT-era gravity recovery, and provide quantitative guidance on where SLA-based correction should be applied.