Bias Evaluation for Sensor-based Dissolved Oxygen from CTD and Profiling Floats in the World Ocean Database

Details

• Journal Title:
  Journal of Atmospheric and Oceanic Technology
• Personal Author:
  Wang, Zhankun ; Garcia, Hernan E. ; Boyer, Timothy P. ; Reagan, James R. ; Maurer, Tanya ; Ito, Takamitsu ; Sharp, Jonathan D. ; Cross, Scott ; Bouchard, Courtney
• NOAA Program & Office:
  NESDIS (National Environmental Satellite, Data, and Information Service) ; OAR (Oceanic and Atmospheric Research) ; CICOES (Cooperative Institute for Climate, Ocean and Ecosystem Studies) ; NCEI (National Centers for Environmental Information) ; PMEL (Pacific Marine Environmental Laboratory)
• Description:
  Sensor-based O2 measurements in the ocean have become the dominant data source for in situ O2 since 2010. We examine the overall quality of the shipborne conductivity-temperature-depth (CTD)- and Argo-measured O2 in the World Ocean Database (WOD) and evaluate biases by comparing them to independently-measured reference bottle-sampled profiles. No significant O2 difference is found between CTD and bottle data for the global ocean, suggesting high quality of CTD O2 observations generally. A negative residual bias is found in both post-corrected delayed-mode (−1.69±5.15 μmol kg−1, fitted mean±standard deviation) and real-time adjusted (−4.68±6.99 μmol kg−1) Argo O2. Residual biases have both spatial (basin-scale and vertical) and temporal variations, indicating the complexity of residual biases. We also examine Argo O2 biases based on the type of calibration methods. For the Argo delayed-mode O2 profiles calibrated using World Ocean Atlas (WOA), on average, are offset by −1.60±5.30 μmol kg−1, while a larger bias (−3.29±4.86 μmol kg−1) is found for profiles calibrated using in-air measurements for the global ocean. The Argo delayed-mode data calibrated with O2 profiles from the WOD have a slight positive bias (0.33±4.16 μmol kg−1). Further analysis demonstrates that the O2 profiles without matched reference profiles also have negative bias similar to those with matched reference profiles when they are compared to WOA. This analysis suggests the negative residual biases in Argo post-corrected O2 should be carefully considered when using Argo O2 data to draw conclusive inferences about anthropogenic impacts on ocean oxygen concentrations and/or derived quantities in a changing ocean.
• Source:
  Journal of Atmospheric and Oceanic Technology (2025)
• DOI:
  https://doi.org/10.1175/JTECH-D-25-0027.1
• ISSN:
  0739-0572 ; 1520-0426
• Format:
  pdf
• Publisher:
  American Meteorological Society
• Document Type:
  Journal Article
• Rights Information:
  Other
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha-512:ced90ca242fff682a97f905647bed1c2b214a894ae366c0c66999a371532f70546861d699ee0fa2b72ca67f1ea5513b83c6ca053fb0e20964ef06cda0449a391
• File Type: