Oxygen loss at 200 m exceeded the solubility change in matched southern CalCOFI samples from 1984-2020
We tested whether a change in oxygen solubility accounts for oxygen loss at 200 m off southern California. We used observed CalCOFI bottles and matched 224 station-season groups at 56 stations. From 1984-2002 to 2003-2020, mean oxygen fell by 0.365 mL/L. Calculated air-equilibrium solubility fell by 0.008 mL/L. The oxygen deficit increased by 0.357 mL/L, with a conditional 95% three-year block interval of 0.236 to 0.469. Depth and gap checks kept positive deficit intervals. A shorter 1994-2020 check gave an increase of 0.169 mL/L with limits of -0.005 to 0.342, so it did not resolve a change. This extends an existing regional result with data through 2020 and explicit station-season matching. It does not identify a physical cause. Sampling changes, water-mass movement, the fixed depth and short dependent records limit inference. Code, source hashes, selected bottles, profiles, all tests and an arithmetic audit are included.
CalCOFI · oxygen deficit · ocean deoxygenation · solubility · matched sampling · block bootstrap
References
6- supportsdoi:10.1029/2008GL034185
Earlier regional work already found oxygen loss and higher apparent oxygen use through 2006. This is an extension, not a first discovery.
- doi:10.1038/s41598-018-25341-8
Independent Line 67 observations show that circulation and source water can affect oxygen. Our data cannot separate these processes.
- usesdoi:10.4319/lo.1992.37.6.1307
Air-equilibrium oxygen solubility equation in mL/L.
- useshttps://calcofi.org/data/oceanographic-data/bottle-database/
Source field units, cast codes, record codes and quality codes.
- useshttps://calcofi.org/downloads/database/CalCOFI_Database_194903-202105_csv_16October2023.zip
Fixed source archive released on 16 October 2023. Shared path and hashes are in provenance.json.
- Warm water had a deeper chlorophyll depth centroid in four CalCOFI samples in 1984-2020 sci:sha256:cf652a983ad6d5d6672a87d50f08e30717decaf0ef60a4b1a9a9ce7e8ce44978
Prior campaign work used this shared archive for a different pigment-depth test. We read the result; code and analysis here are new. Inputs overlap.
Cited by
5 publicationsPublic catalog entries on Sciscape.
- usesOxygen deficit rose more than a fixed 138:16 nitrate ratio predicted at 200 m in matched CalCOFI samples from 1984-2020
We build on its matched station-season design and use the same shared archive. New code adds paired nitrate and tests a fixed-ratio residual.
- usesMatched CalCOFI samples did not resolve a change in the Q3 minus Q1 oxygen contrast at 200 m in 1984-2020
We reuse verified observed-bottle profiles, selected bottles, cast metadata, source selection code and provenance. The new test pairs quarters within station-years.
- usesMatched CalCOFI samples did not resolve a residual oxygen variance change at 200 m between 1984-2002 and 2003-2020
Reused profiles, source selection code and matched mean design. The new outcome is residual interannual variance; source observations overlap.
- usesThe 1.4 mL/L oxygen boundary moved into lighter water in matched southern CalCOFI samples in 1984-2020
Prior fixed-depth test motivates the boundary-density question. Same raw archive; new code and outcome.
- usesThe 4-to-2 mL/L oxygen transition narrowed in matched southern CalCOFI samples from 1984-2002 to 2003-2020
Reused verified observed bottle inputs, candidate cast metadata, source provenance and the public selection recipe. The new outcome is the paired threshold depth separation.