Cruise Report, RV ATAIR, Cruise 0671021-1, Bremerhaven - Thyboron - Aberdeen, 18 Jul —- 10 Aug 2023 | 
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resulting in large differences between the sensor packs. Both profiles needed further post- 
vrocessing before publishing. 
Due to strong currents on station #090/GN053A located south of the Shetland Islands, the 
water sampler carrying the CTD unit was not in a straight vertical position during the cast. The 
altimeter was looking to the side, so lowering of the water sampler was stopped at a safety 
distance to the bottom. Due to the currents, the water sampler and the CTD were lifted during 
bottle stops and thus, the bottom samples were not taken at the deepest part of the profile. 
Nevertheless, processed data showed good quality as the water column was well mixed from 
the surface into depths. 
Overall, the performance of the CTD sensor unit during the cruise was good. Several profiles 
showed larger spikes most times within the gradients or layers of high biological activity, which 
might have let to clogging of one or both sensor packs. More spikes were observed under bad 
weather conditions as was expected. Figure 5.3 shows a typical CTD cast conducted at fa- 
vourable weather conditions, while Figure 5.4 shows an example of a cast impacted by rough 
weather conditions. 
Stations #029/GN022 and #082/GN056 required a second CTD cast. The computer used for 
the data recording came to an unexpected malfunctioning in the first case, while the termina- 
tion of the conducting wire that provided the power supply to the CTD system was faulty in the 
second case. 
The supplementary SBE 35 temperature sensor was read out after every station and compared 
to CTD-derived temperature recorded at the time of closing the Niskin bottles during the up- 
cast. Data was downloaded directly from the sensor using the software Sea Term, version 1.59. 
Temperature differences between the systems were within a range of +0.03°C for 90% of the 
SBE35 measurements. Bottles were often closed in layers with high temperature gradients, 
which can explain the high range of differences. The median of temperature differences over 
all data is -0.0016°C, which is within the range of the instrument uncertainties.