An ice-tethered buoy system (2020O10) carrying 5 CTDs was deployed by RV Polarstern in the central Arctic Ocean in August 2020 as part of MOSAiC Leg 5 (PS122/5). The buoy was equipped with 5 Seabird SBE37IMP Microcat CTDs mounted along an 100m long inductive modem tether at depths of 10, 20, 50, 75 and 100m. The buoy was installed close to the main buoy site in the central observatory of Leg 5, and co-located with multiple Snow Buoys, Ice Mass Balance Buoys and other, more complex instruments. The individual instruments were programmed to record oceanographic data internally at 2-minute intervals. The surface unit of the buoy prompted the instruments for an additional measurement every 10 minutes, which was then transmitted to a base station via iridium along with GPS position and time, as well as surface temperature. After a several months long drift through the central Arctic Ocean and Nordic Seas, the buoy was recovered in Húnaflói, Iceland in October 2022. As a result, the internally recorded 2-minute data from the CTDs could also be secured. The attached zip archive comprises the unprocessed 10-minute data transmitted by the buoy, the 2-minute data downloaded and converted from the 5 individual CTDs after their recovery, as well as selected auxiliary information. A processed and quality controlled version of this dataset will be provided and linked to upon completion.

Acknowledgments: The data were produced as part of the international Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC) with the tag MOSAiC20192020 (grant number AWI_PS122_00). The instruments were funded through the MIDO (Multidisciplinary Ice-based Drifting Observatory) infrastructure program, and built by Pacific Gyre, USA. We thank the crew, captain and scientific staff of RV Polarstern during MOSAiC Leg 5 for their field support. We are most grateful to the crew of the icelandic research vessel Bjarni Sæmundsson, and in particular to the chief scientist, Ingibjörg Jónsdóttir, for the recovery of the instruments.