Underway and quality-controlled surface fCO2 data collected from voyage 3 of RSV Nuyina, February to March 2026

Full description

Delayed-mode quality-controlled surface underway fCO2 data collected on RSV Nuyina, Voyage 3 of the 2025_26 field season.

Data collected on RSV Nuyina contributes to Australian Antarctic Division (AAD) Project 4652 (PI: P. Miloslavich) and is a is part of an AAD-CSIRO collaborative effort. The CSIRO contribution is supported by the Integrated Marine Observing System (IMOS) Biogeochemical Sensors Sub-Facility (PI: B. Tilbrook). IMOS is enabled by the National Collaborative Research Infrastructure Strategy (NCRIS).


Raw CO2 data were measured as mole fractions with a General Oceanics pCO2 system equipped with a LI-COR 7000 CO2 sensor. The CO2 sensor response was calibrated at 3-4 hour intervals using CO2-in-air reference gases on the WMO X2019 scale with the zero and span set daily using the low and high reference gas standards.

Expocode: 09NX20260212

Variables Information:
Variable Name: Organization
Description of Variable: participating institutions.
Variable Name: Vessel
Description of Variable: Ship name.
Variable Name: CruiseID
Description of Variable: Cruise designation.
Variable Name: Day_GMT
Description of Variable: UTC (ddd.hhhh).
Variable Name: Date
Description of Variable: Observation date UTC (yyyy/mm/dd).
Variable Name: Time
Description of Variable: Observation time UTC (hh:mm:ss).
Variable Name: Lat
Description of Variable: Latitude (decimal degrees).
Variable Name: Long
Description of Variable: Longitude (decimal degrees).
Variable Name: xCO2EQ_PPM
Description of Variable: Mole fraction of CO2 (dry) in the equilibrator head space at equilibrator temperature (ppm).
Variable Name: xCO2ATM_PPM
Description of Variable: Mole fraction of CO2 in the atmosphere (dry), measured every 3-4 hours after standard gas measurements. These values are linearly interpolated with times between good atmospheric CO2 measurements. There was no air intake for the 2025_26 field season and atmospheric values are set to -999 (missing).
Variable Name: Press_Equil
Description of Variable: Equilibrator head space pressure (hectopascal).
Variable Name: Press_ATM
Description of Variable: Barometric pressure at sea level(hectopascal).
Variable Name: TEQ
Description of Variable: Equilibrator water temperature (degrees Celsius).
Variable Name: SST
Description of Variable: Sea surface temperature (degrees Celsius).
Variable Name: SAL
Description of Variable: Sea surface salinity.
Variable Name: fCO2SW_UATM
Description of Variable: Fugacity of carbon dioxide at surface water salinity and temperature and 100% humidity (microatmosphers).
Variable Name: fCO2ATM_UATM _INTERPOLATED
Description of Variable: Fugacity of CO2 in the atmosphere from xCO2ATM_PPM at sea surface salinity and temperature and 100% humidity (microatmospheres).
Variable Name: DfCO2_UATM
Description of Variable: Sea water fCO2 minus interpolated air fCO2 (microatmospheres).
Variable Name: WindSpd_True
Description of Variable: Wind speed (knots).
Variable Name: WindDirn_True
Description of Variable: Wind direction, where 0 is North and 90 is East (degrees).
Variable Name: Type
Description of Variable: Measurement type (EQU = equilibrator head space, ATM = atmosphere).
Variable Name: WOCE_QC_FLAG
Description of Variable: WOCE quality control flag (2=good, 3=questionable, -999=missing).

Lineage

Progress Code: completed

Statement: Processing comments: There was no atmospheric intake to the pCO2 system for the 2025_26 field season and atmospheric measurements and air-sea gradients in fCO2 were recorded as -999 (missing). Raw data were flagged as bad and removed from calculations for the following periods: During the following periods, the pCO₂ system was turned off and no data were recorded: 13/02/26 02:47:05 to 13/02/26 03:28:24, 13/02/26 03:28:24 to 13/02/26 04:08:37, 23/02/26 19:07:20 to 26/02/26 05:16:49, 03/03/26 05:07:47 to 03/03/26 06:14:41, 08/03/26 04:53:55 to 08/03/26 10:20:36, and 09/03/26 11:31:52 to 11/03/26 04:13:40. Between 12/02/26 22:06:11 and 14/02/26 05:58:44 at the start of the cruise, some of the TSG data is missing and the equilibrator temperature sensor was not turned on. These data were flagged as bad and excluded from calculations. Between 16/02/26 06:04:28 and 16/02/26 07:14:34, there was insufficient seawater flowing through the pCO₂ system. Data from this period were flagged as bad and excluded from calculations. Heavy ice intermittently blocked the seawater supply while the vessel was approaching and departing Mawson between 23/02/26 13:51:28 and 26/02/26 05:41:55, and Davis between 07/03/26 15:24:44 and 11/03/26 04:38:46, resulting in noisy data. These periods include 23/02/26 19:07:20 to 26/02/26 05:16:49 and 09/03/26 11:31:52 to 11/03/26 04:13:40, when the vessel was near the respective stations and the pCO₂ system was turned off. Data from both periods were flagged as bad and excluded from calculations. EQU fCO2 observations: 29442, QCed: 90% good 10% bad. ATM fCO2 observations: 0.

Notes

Purpose
These delayed mode data used for constructing global and regional carbon budgets and for the tracking variability in ocean CO2 uptake and ocean acidification. A measurement uncertainty of ±2 μatm for the fCO2 of surface waters meets the carbon measurement criteria for the Global Ocean Observing System Essential Ocean Variable (EOV) and the Essential Climate Variable requirement (ECV) for the Global Climate Observing System. The EOV/ECV measurement criteria are needed to constrain global ocean CO2 uptake to within 10%, and to detect decadal trends in surface ocean carbon. Data release follows FAIR principles for transparent and traceable data. These data are also made available in annual updates of the Surface Ocean Carbon Atlas, a uniformly quality-controlled data product for the ocean and contribute to the Surface Ocean CO2 Reference Network within the Global Ocean Observing System.