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NOTICE: Oxygen Sensor Calibration Issue

OOI Net Users,

A data anomaly came to our attention during the Portland workshop last month regarding some of the OOI oxygen data (DOSTA). After investigating this anomaly, the OOI Data and MIO Teams were able to diagnose a data issue and establish key action steps. It appears that many of the currently deployed Aanderaa optode oxygen sensors (see specific list below) may have had an error during the manufacturer’s calibration of the instruments. Incorrect offset values are causing the OOI algorithm to report processed O2 values an order of magnitude higher than expected. Note that due to the source of the error, the raw data reported from these sensors has not been affected. As such, correct O2 values can likely still be calculated from raw phase & temperature data, and this error should not ultimately lead to a gap in overall O2 data.

The OOI Data Team is taking several actions to remediate this issue. First and foremost is to make sure to inform, you, the user of the error so you know which data may be affected and can proceed with caution. Second, we are removing the current erroneous calibration values to keep the system from continuing to produce incorrectly derived O2 products. In the medium term, the Data Team will use a back-calculation from the phase data to try to replace the calibration values. The data team will keep a careful record of what was done and add that information to the annotations and the website. And in the long term, once the instruments have been recovered and returned to the vendor, we will enter the new official corrections in the calibration sheets, and inform users about the time-frame and the change history.

If you have any questions about the state of the sensors, the data products affected, or the procedures outlined above, please send your query to the OOI Help Desk.

Thank you for your patience,
The OOI Data Team

Impacted OOI Sensors

The derived O2 products (L1 Temperature Compensated and L2 Salinity Corrected Dissolved Oxygen) from the following instruments are suspect, due to errors during vendor calibration. Until a correction can be applied, the derived data from the latest deployment date onwards for affected instruments should not be used.

Currently the only deployed instruments that have been affected are those on the Cabled Array and cabled Endurance platforms (specific list below). None of the deployed uncabled Coastal Endurance or Pioneer Array sensors have been affected. Some of the Pioneer Array sensors in storage contain the erroneous calibration, but those specific sensors were never deployed and will be returned to the vendor for re-calibration. Global instruments are still being evaluated, as several of the suspect instruments may have just been deployed.

List of impacted Cabled Array and cabled Endurance Array Sensors:

  • Coastal Endurance Oregon Offshore Cabled Benthic Experiment Package
    • CE04OSBP-LJ01C-06-CTDBPO108 + ctdbp_no_sample (CE04OSBP-LJ01C-06-DOSTAD108)
  • Coastal Endurance Oregon Offshore Cabled Shallow Profiler Mooring
    • CE04OSPS-PC01B-4A-CTDPFA109 + ctdpf-optode-sample (CE04OSPS-PC01B-4A-DOSTAD109)
  • Coastal Endurance Oregon Shelf Cabled Benthic Experiment Package
    • CE02SHBP-LJ01D-06-CTDBPN106 + ctdbp-no-sample (CE02SHBP-LJ01D-06-DOSTAD106)
  • Cabled Axial SeamountAxial Base Seafloor
    • RS03AXBS-LJ03A-12-CTDPFB301 + ctdpf-optode-sample (RS03AXBS-LJ03A-12-DOSTAD301)
  • Cabled Continental Margin Oregon Slope Base Seafloor
    • RS01SLBS-LJ01A-12-CTDPFB101 + ctdpf-optode-sample (RS01SLBS-LJ01A-12-DOSTAD101)
  • Cabled Continental Margin Oregon Slope Base Shallow Profiler Mooring
    • RS01SBPS-PC01A-4A-CTDPFA103 + ctdpf-optode-sample (RS01SBPS-PC01A-4A-DOSTAD103)
  • Coastal Endurance Oregon Offshore Cabled Deep Profiler Mooring
    • CE04OSPD-DP01B-06-DOSTAD105 + dpc_optode_instrument_recovered
  • Cabled Continental Margin Oregon Slope Base Deep Profiler Mooring
    • RS01SBPD-DP01A-06-DOSTAD104 + dpc_optode_instrument_recovered