Submarine Telecommunication Cables as part of the Arctic Ocean Observing System The Nansen Center participated at the 31st NORDUnet conference held in Reykjavik, Iceland 13-15 September 2022. NORDUnet is a Nordic research and education network (REN) enabling scientists, educators, and students to work and share knowledge globally. At the conference the Nansen Center put the spotlight on the sparsely observed ocean under the sea ice in the Arctic. We noticed a clear interest from the participants, which resulted in a new and larger Nordic collaboration aiming for cables across the Arctic. To advance the observing capability, connections from underwater observing platforms to cables should be developed. This will provide sustained observations delivered in real-time. The Nansen Center has been involved in initiatives working for cables across the Arctic for more than a decade as part of the Joint Task Force SMART Subsea. Since SMART measurements (with sensors integrated into repeaters every 70 km or so) are limited to where the cable is laid (Figure 1), a SMART subsea cable should be linked to other observing platforms. Combining SMART subsea cables with a fixed network of ocean moorings with acoustic sources and receivers, an underwater GPS system can be built to support navigation and communication with moving underwater platforms, as well as acoustic tomography for ocean heat content (inset Figure 1 and Figure 2). The Nansen Center has for several years advocated the strength of combining SMART cables with an underwater GPS system in the Arctic. As part of previous projects, technology for the acoustic network has been proven in the Arctic. With funding from the EU, further developments will come in the next few years. From 2024 an acoustic network will be operated for 2 years in the Nansen and Amundsen Basins in the high Arctic (Figure 2). For more information, please contact Hanne Sagen and Espen Storheim. Figure 1: The conceptual Trans Arctic Cable with indication of frequently spaced SMART repeaters with sensors, and branches to underwater observing systems. Figure was presented by Bruce Howe and Bjørn Rønning at the Arctic Science Summit Week, 2022. The figure is based on J. Orcutt’s figure in Mikhalevsky et al. 2015 (http://dx.doi.org/10.14430/arctic4449), and in Baggeroer, A. B., et al. 2018, Ocean Observatories: An Engineering Challenge, The Bridge. https://aco-ssds.soest.hawaii.edu/Baggeroer-etal_Bridge_Fall2018.pdf Figure 2: Concept of multipurpose mooring system to be deployed in 2024 and operated for 2 years. (High Arctic Ocean Observation System-HiAOOS, Hanne Sagen, et al. 2022) NORDUnet NORDUnet er et nordisk forsknings- og utdanningsnettverk (REN) som gjør det mulig for forskere, lærere og studenter å arbeide og dele kunnskap globalt.