Adapting in situ sampling strategies to SWOT-scale studies: The BioSWOT-Med campaign example as part of the SWOTAdopt-a-Crossover Consortium

The SWOT satellite measures sea surface height at an unprecedented resolution about ten times better than conventional altimetry products. SWOT data offer a unique opportunity of observing very fine-scale (~few km) surface dynamics from space. In situ samplings, aside from complementing the 2D picture, also provide a 3D view of the observed fine scale dynamics essential for interpretation of bio-physical interaction processes. Nevertheless, exploring this regime during field experiments remains challenging due to the difficulty to precisely locate fine-scale features in real time. A shift of a few km may not be of critical importance when sampling a large structure such as an eddy with a radius of about 100 km. However a similar sampling error could obviously lead to severe misinterpretations in the case of a 10 to 20 km wide eddy. The problem is even exacerbated by the fact that the lifetime typically decreases with the size of eddies and filaments. One way to address this problem with field experiments at the SWOT scales is therefore to update and adapt the sampling location and shape, with synoptic near-real time information of the sea state provided by available high resolution remote sensing (SST and Chlorophyll), and analysis of altimetry and model assimilation. Although vulnerable to cloud coverage and/or limited in resolution, this information can be complemented by near-real time Lagrangian analysis of the surface geostrophic fields providing finer diagnostics of the sampling site dynamics. Early SWOT data also filled some gaps in terms of parameters and spatiotemporal coverage. By using the BIOSWOT-Med cruise as an example, here we review the tools offered by the SWOT AdAC Consortium to the field experiments that have been deployed during the SWOT fast-sampling phase (March-June 2023). After evaluating synergies and shortcomings with in situ platforms, we will discuss how adaptive sampling strategies may evolve in the future to assist field experiments during the SWOT Science phase.