“Salty Drift” of Argo Floats Affects the Gridded Ocean Salinity Products

Abstract

Salinity is an essential variable for characterizing and understanding the state of the ocean and its role in the climate system. Gridded ocean salinity products, heavily reliant on Argo float measurements since the early 2000s, are widely used in oceanographic and climate research. However, a concerning issue of instrument drift leading to spurious salinity increases (“salty drift”) has been identified in a significant number of Argo floats since 2015. This study investigates the potential consequences of this “salty drift” issue on various gridded salinity products. We compare a suite of these products and evaluate their consistency, particularly from 2015 to 2019. Our analysis reveals two major issues with the gridded salinity products after 2015: a sudden increase in global mean salinity and elevated inconsistencies between gridded salinity products. In 2015–2019, the North Indian and North Atlantic Oceans emerged as regions displaying particularly large disagreements between gridded products compared to the prior period, 2010–2014. These findings highlight the substantial impact of the “salty drift” on the reliability of the gridded salinity products. They also underline the critical need for the oceanography community to address these issues to ensure the validity of future ocean and climate studies that utilize gridded salinity products.