Contributions of Altimetry and Argo to Non‐Closure of the Global Mean Sea Level Budget Since 2016

• Published in: Geophysical research letters 2021-07, Vol.48 (14), p.n/a
• Main Authors: Barnoud, Anne, Pfeffer, Julia, Guérou, Adrien, Frery, Marie‐Laure, Siméon, Mathilde, Cazenave, Anny, Chen, Jianli, Llovel, William, Thierry, Virginie, Legeais, Jean‐François, Ablain, Michaël
• Format: Article
• Language: English
• Subjects: Argo; Earth Sciences; GRACE; GRACE‐FO; Oceanography; satellite altimetry; Sciences of the Universe; sea level; sea level budget
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2021GL092824

Over 1993–2016, studies have shown that the observed global mean sea level (GMSL) budget is closed within the current data uncertainties. However, non‐closure of the budget was recently reported when using Jason‐3, Argo and GRACE/GRACE Follow‐On data after 2016. This non‐closure may result from errors in the data sets used to estimate the GMSL and its components. Here, we investigate possible sources of errors affecting Jason‐3 and Argo data. Comparisons of Jason‐3 GMSL trends with other altimetry missions show good agreement within 0.4 mm/yr over 2016–present. Besides, the wet tropospheric correction uncertainty from the Jason‐3 radiometer contributes to up to 0.2 mm/yr. Therefore, altimetry alone cannot explain the misfit in the GMSL budget observed after 2016. Argo‐based salinity products display strong discrepancies since 2016, attributed to instrumental problems and data editing issues. Reassessment of the sea level budget with the thermosteric component provides about 40% improvement in the budget closure. Plain Language Summary Sea level rise, due to the addition of meltwater from glaciers and ice‐sheets in the oceans and to the thermal expansion of seawater, is commonly used as an indicator for climate change. The sea level budget provides information on temporal changes in one or more components of the budget, on process understanding, on missing contributions and allows cross validation of the observing systems involved in the sea level budget (satellite altimetry, Argo oceanic float and GRACE/GRACE Follow‐On satellite gravimetry). The sea level budget was closed until 2015–2016, that is, the observed global mean sea level agrees well with the sum of components. However, since 2016, the budget is not closed anymore. In this study, we show that errors in Argo salinity measurements are responsible for about 40% of the budget error while the altimetry data cannot explain the remaining error. Other sources of errors should be further investigated to fully understand the error in the budget after 2016, in particular satellite GRACE/GRACE Follow‐On gravity measurements or missing physical contributions. Key Points The global mean sea level budget is not closed after 2016 from altimetry, Argo and GRACE/GRACE Follow‐On data We show that errors in Argo salinity data lead to non‐physical halosteric sea level negative trends responsible for ∼40% of the non‐closure We also show that Jason‐3 altimeter and radiometer are unlikely to play a major role in the re