The Xiamen Symposium on Marine Environmental Sciences

2027 Xiamen Symposium on Marine Environmental Sciences

January 12-15, 2027

Development of an adjusted biogeochemical Argo float oxygen dataset to address observed biases in relation with shipboard data
ID:1031 Poster Presentation

2027-01-15 16:15 (China Standard Time)

Session: Session 39 - Leveraging BGC-Argo Observations to Advance Marine Biogeochemical Cycles and Ecosystem Dynamics

Abstract
Biogeochemical (BGC) profiling floats can be used to study oceanic processes over large spatial and temporal scales. As the number of BGC float deployments continue to increase and BGC floats represent an ever-larger fraction of our BGC observing system, it will be essential that float measurements be free of bias relative to shipboard data. Biases in float data could create spurious variability or long-term changes in oxygen and other BGC float parameters that are either derived from (e.g., total carbon) or quality controlled using oxygen (e.g., pH and nitrate). Argo float oxygen data undergoes a drift correction being adjusted to ship deployment casts, to ship-based oxygen climatologies, or to float measurements of atmospheric oxygen (in-situ calibration). However, recent studies have shown the in-situ surface adjustment while good in the upper ocean, may not be fully sufficient to adjust oxygen at depth. In this study we perform a crossover comparison between the oxygen Argo dataset and a secondary quality-controlled shipboard dataset between 1450 and 2000 db. We have identified persistent negativeoxygen offsets (float minus ship) with a median of -2.1 µmol kg-1 (mean of 1.98 ± 3.93 (1 SD) μmol kg-1 and a 95% confidence interval (CI) around the mean of {-2.36 to -1.85}). These oxygen offsets translate to float parameter biases in nitrate with a median of 0.18 μmol kg-1(mean of 0.18 ± 0.59; CI95%{0.12 to 0.24}), in pH with a median of -5.57 mpH (mean of -5.92 ± 7.71; CI95%{-7.12 to -4.72}), and in DIC with a median of 3.2 μmol kg-1 (mean of 3.84 ± 6.76; CI95%{2.93 to 4.75}). To address this problem, we apply a correction scheme derived from the relationship between each float’s crossover offsets in dissolved oxygen and the corresponding float oxygen percent saturation which creates a corrected float-based oxygen synthesis product that is consistent with shipboard measurements and internally consistent among BGC float observations. We have also created a merged oxygen product containing the corrected BGC float data and shipboard observations that has been gridded to a monthly resolution with 1° x 1° bin-averaged fields at standard depth and density levels that will be useful to communities interested in ocean deoxygenation, acidification, changes to the carbon cycle, and air-sea fluxes of oxygen and carbon.  
Speaker
Zachary Nachod University of Hawaiʻi at Mānoa

Author
Zachary Nachod University of Hawaiʻi at Mānoa

    Important Dates

    • Jan 30

      2026

      Session / Event proposals open

    • Mar 31

      2026

      Session / Event proposals close
      (Extended to April 7)

    • Apr 30

      2026

      Session acceptance notifications

    • Apr 30

      2026

      Abstract submissions & registration open

    • Jun 30

      2026

      Abstract submissions close
      (Extended to July 21)

    • Aug 31

      2026

      Abstract acceptance notifications

    • Sep 15

      2026

      Scientific program released

    • Oct 15

      2026

      Early bird registration closes

    • Jan 12–15

      2027

      XMAS 2027