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Cruise Report, RV ATAIR, Cruise 0671013-1, Bremerhaven - Skagen - Aberdeen, 19 Jul - 11 Aug 2022
Post-cruise quality control showed that differences between the sensor pairs and between
sensors and the AUTOSAL data were small. All comparisons revealed differences that were
within the error bounds, with the smallest differences observed for temperature, conductivity
and salinity from the secondary sensors. In summary, any post-cruise correction was not ap-
plied, and the temperature, conductivity and salinity data were made available with flag 1 (good
data). Using the data from the secondary sensors is recommended.
Sampling and subsequent titration of oxygen samples were not performed on cruise 067/013-
1. However, respective data is available from the subsequent cruise 067/013-2 to the German
Bight. The CTD sensor setup, and therefore the use of an CTD-based SBE43 oxygen sensor,
remained the same throughout both cruises. The oxygen analysis including a comparison be-
tween CTD-derived oxygen and bottle oxygen was thus solely based on the data set obtained
from cruise 067/013-2. Any correction recommendations resulting from this analysis using the
multi-parameter-fit (MPF) method were subsequently applied to the oxygen data from cruise
0671013-1.
Regarding oxygen, corrections are made when the difference between the CTD-derived oxy-
gen and titrated bottle samples exceeds 1% (titration measurement accuracy). For measured
values of 5-6 ml/l, this threshold corresponds to 0.055 mI/l. Without correction, the average
difference of the oxygen data is 0.0967 ml, 1.e. greater than 1%; with correction, it is well
below 1%. CTD oxygen was corrected according to:
Qcorr (MI/I) = 3.778859056281 + -0.0167016 16065 * time + 0.03236 1569854 * oxygen (mV/l) +
-0.000808096866 * pressure + 0.001502723496 * temperature
Oxygen saturation was recalculated afterwards. The corrected CTD-derived oxygen data was
given the quality flag 1 (good data). Any quality control of fluorescence, turbidity or pH-value
data was not performed. Thus, the data were made available with flag 0 (no quality control
applied). It should be noted that the SBE18 pH sensor has a rather reduced accuracy (+0.1
pH, according the manufacturer’s data sheet).
