Lagrangian analysis of fine-scale (1–100 km) ocean stirring: a preparatory study for the SWOT satellite mission
Event: 2022 Ocean Surface Topography Science Team Meeting
Session: Science III: Mesoscale and sub-mesoscale oceanography
Presentation type: Type Oral
Contribution: PDF file
Ocean fine scales (1–100 km, days to weeks) play a key role in pelagic ecosystems, the energy cascade, and biogeochemical cycles. Fine scales are largely studied with Lagrangian diagnostics derived from nadir altimetry data. However, these diagnostics are limited by the spatiotemporal resolution of nadir altimetry products. The new SWOT (Surface Water and Ocean Topography) satellite mission, planned for launch in the fall 2022, will enhance the spatial resolution of altimetry products by one order of magnitude. In this work, we study the fine-scale transport properties not resolved by nadir altimetry and that will be observable by SWOT. Two Lagrangian diagnostics are computed on geostrophic velocity maps derived from sea surface height outputs from a model at two resolution: maps at 1/20° representative of SWOT observations, and maps at 1/4° representative of products provided by nadir altimetry. Results show that the stirring is underestimated in the nadir-like data set by a factor of 2 to 3 on average, and follow the underestimation of the strain rate. Retention patterns by eddies also differ between 1/20° maps (SWOT) and 1/4° maps (nadir). A new class of eddy, not found in 1/4° maps, is highlighted. Implications for marine ecosystems, biogeochemical cycles and the ocean dynamic are discussed as well as opportunities for in-situ experiments during the SWOT satellite mission.