"Salty Drift" of Argo Floats Affects the Gridded Ocean Salinity Products.

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. Plain Language Summary: Salinity is crucial for understanding our planet's oceans and climate. Since 2015, some Argo floats have produced inaccurate salinity measurements that drift to higher values. This study examined several widely used ocean salinity products that were produced primarily based on Argo float measurements to assess how they are affected by the "salty drift" floats. We found that between 2015 and 2019, most of the examined products showed unrealistic increases in global mean salinity and became less consistent than before. Regions most likely affected include the North Indian and North Atlantic Oceans. This "salty drift" issue can impact previous and future global and regional studies using gridded salinity products after 2015 and needs further detailed study by the oceanography and climate communities. Key Points: Multiple gridded salinity products show an unrealistic rise in global mean salinity after 2015, with increases of up to 1.3 × 10−3 per yearThe spread of global mean salinity tripled between 2015 and 2019, translating to an uncertainty of about 1 cm in halosteric sea levelAfter 2015, over 60% of the global ocean, including the North Atlantic and North Indian Oceans, exhibited increased uncertainty in salinity change [ABSTRACT FROM AUTHOR]