Table 1 Sources of data.

From: Improved winter data coverage of the Southern Ocean CO2 sink from extrapolation of summertime observations

Variable

Used for

Data source

Product and reference

Sea surface fCO2

SOM-FFN

https://www.socat.info/index.php/version-2020/

SOCAT V20205

Sea surface temperature

SOM-FFN, fCO2 temperature correction and air-sea flux

https://www.emc.ncep.noaa.gov/research/cmb/sst_analysis/

NOAA Optimum Interpolation product v236

Sea surface salinity

SOM-FFN

https://www.metoffice.gov.uk/hadobs/en4/download-en4-2-1.html

Hadley Centre EN4 version EN4.2.156

Sea ice concentration

SOM-FFN

https://www.metoffice.gov.uk/hadobs/hadisst/

HadISST57

Mixed layer depth

SOM-FFN

https://resources.marine.copernicus.eu/product-detail/MULTIOBS_GLO_PHY_TSUV_3D_MYNRT_015_012/INFORMATION

CMEMS ARMOR3D REP40,41

Chlorophyll

SOM-FFN

https://www.globcolour.info/

Globcolour58,59

Marine boundary layer atmospheric xCO2

SOM-FFN and air-sea flux

ftp://aftp.cmdl.noaa.gov/data/trace_gases/co2/flask/surface/.

NOAA ESRL50,51

Sea ice concentration

Air-sea flux and pseudo observations

https://nsidc.org/data/g02202/versions/3

NOAA/NSIDC v360,61

Sea level atmospheric pressure

Air-sea flux

www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis.surface.html

NCEP reanalysis53

Winds

Air-sea flux

https://www.remss.com/measurements/ccmp/

CCMP46,47

Temperature and salinity

Pseudo observations

https://sio-argo.ucsd.edu/RG_Climatology.html

Roemmich and Gilson climatology34

Biogeochemical tracers

Pseudo observations

https://www.glodap.info/

GLODAP v2.202114,18

Oxygen

Pseudo observations adjustment for surface oxygen undersaturation

https://soccompu.princeton.edu/www/index.html

SOCCOM float data11,32