A set of eight ice-tethered buoy systems (2019O1 to 2019O8) were deployed by the Akademik Fedorov in the Northern Laptev Sea in early October 2019 as part of the MOSAiC Distributed Network. Each buoy consisted of 5 Seabird SBE37IMP Microcat CTDs mounted along an inductive modem tether at depths of 10, 20, 50, 75 and 100m. The buoys were installed on stable sea ice floes (designated as “M-sites”) at a distance of 15-35 km around the main MOSAiC ice camp, and co-located with Snow Buoys, Ice Mass Balance Buoys and D-TOP ocean profilers. 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, 4 out of 8 buoys were recovered in August 2020, and the internally recorded data from the CTDs were secured. The attached zip archive comprises the unprocessed 10-minute data transmitted by buoy 2019O4 (.txt file), as well as the 2-minute data downloaded and converted from the 5 individual CTDs after their recovery (either .cap or .cnv). A processed and quality controlled version of this dataset will be supplemented and linked to upon completion. A link to a data paper describing the processing will be given below.

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 numbers AWI_PS122_00 and AFMOSAiC-1_00). The instruments were funded through the MIDO (Multidisciplinary Ice-based Drifting Observatory) infrastructure program, and built by Pacific Gyre, USA. We thank the crews of the research vessels Akademik Fedorov, Akademik Tryoshnikov and RV Polarstern, and in particular the chief scientists, Thomas Krumpen and Markus Rex. We thank the helicopter company Naryan-Marsky for their great logistical support that made this effort possible. We express our gratitude to all participants of these expeditions, and particularly to the MOSAiC School for their field assistance during the set-up. We appreciate the efforts of Kirstin Schulz, Julia Regnery, Ingo Schuffenhauer, Morven Muilwijk, Sandra Tippenhauer and the entire Leg 4 Team for the recovery of the instruments.