The Second String: A Proposal to Improve Argo Salinity Data from CTDs with Onboard Dynamic Corrections

The best practice for CTD data is to apply dynamic corrections to raw temperature, conductivity and pressure data, calculate derived variables (e.g. practical salinity) then bin average for data reduction. Due to the limitations of satellite data transmission and the potential to add additional error that cannot be removed if the wrong correction is applied, data from CTDs on Argo floats are telemetered back to shore bin averaged and without dynamic corrections. Recent work has shown that dynamic corrections to raw Argo CTD temperature and conductivity has the potential to substantially improve practical salinity, but there is still a risk if the true corrections deviate from idealized models. We propose a solution: add a second practical salinity data stream where dynamic corrections have been applied onboard the float before bin-averaging. This allows for direct comparisons of corrected and uncorrected data, flexibility to refine dynamic corrections in the future, and retain continuity with historical Argo data. We will discuss the work that has been done to determine the optimal dynamic corrections and recommendations for implementation onboard Argo floats.