Steric height contribution to intraseasonal sea surface height in the Southwestern Atlantic
Event: 2022 Ocean Surface Topography Science Team Meeting
Session: Science III: Mesoscale and sub-mesoscale oceanography
Presentation type: Type Forum only
Contribution: PDF file
The sea level varies at diverse spatial and temporal scales due to several physical processes. The main processes are the steric effect, changes in the density of sea water, and the mass changes (e.g. melting ice). In the Southwestern Atlantic, the sea level associated with the steric effect, known as steric height, dominates the seasonal variability and the spatial variation of sea level trends on the Confluence Brazil-Malvinas and adjacent area. The interannual variability, instead, is important on the mid-latitude of the South Atlantic and negligible over the Southwestern Atlantic continental shelf. Little, however, is known about the intraseasonal sea level variability. Thus, the objective of this work is the understanding of the physical drivers of the sea level variability in the Southwestern Atlantic at temporal scales shorter than seasonal using a combination of high resolution in situ data from CTD attached to elephant seals, altimetry data, and a 3D oceanic model. First, we did quality control of the in situ data and selected the best trajectories of 19 female elephant seals off-shore the continental shelf during spring and early summer of 2018 and 2019. The result shows that 14 trajectories out of 19 are reliable. Then, we compared the reanalysis and analysis forecast from Mercator with gridded altimetry data along the 14 trajectories. The comparison indicated that the performance of the reanalysis model sea level anomaly (SLA) is better than the analysis forecast, obtaining significant correlation coefficients higher than 0.54. With the selected model, the steric height (SHm) was estimated and validated with the in situ steric height (SH). For the SH estimation, we calculated the potential density in each vertical profile of the elephant seals and integrated the anomaly vertically. The preliminary results show that the reanalysis ocean model represents very well the steric height, obtaining 10 cases where the correlation with the SH is higher than 0.5. Finally, we discuss the role of the steric height in the altimetry SLA, finding that its contribution is important when the elephant seals cross an area with mesoscale activity.