GoNorth 2023 Cruise Report

Norway’s outer border north of Svalbard crosses deep-sea plains in the Nansen Basin and onto the southern flank of the Gakkel Ridge. Nansen discovered the mountain ridge when he drifted across the Arctic Ocean with the Fram and measured the ocean depth along the way. Today we know that this is the northernmost part of a 65,000 km long mountain ridge that extends from the Arctic Ocean through the Norwegian Sea and the Atlantic Ocean, further through the Indian Ocean to the Pacific Ocean. The seabed is forming along this ridge at a rate ranging from about 1 centimeter at the Gakkel Ridge to over 10 centimeters in the Pacific Ocean. The Gakkel Ridge is not only a geographical endpoint of the global mid-ocean ridge, it is also a geodynamic end link in the Earth’s system of spreading ridges. The Gakkel Ridge, as well as the sections of the spreading ridge that extend through the Fram Strait, has largely been inaccessible to research because of drifting sea ice. RV Kronprins Haakon, which is adapted for the use of the remotely operated underwater vehicle Ægir 6000 has opened new opportunities to explore this mostly inaccessible part of the global ridge system. The Gakkel Ridge was designated as a target for GoNorth from the initial planning of the project. It also became clear early on that such expedition to the Gakkel Ridge should be carried out as a two-ship operation. To this end, a collaboration with the Alfred Wegener Institute (AWI) outlining joint operations with RV Kronprins Haakon and RV Polarstern began at an early stage. Despite detailed plans, the drifting ice took command—just as it did for the Fram expedition and many later Arctic Ocean expeditions. Neither RV Polarstern nor RV Kronprins Haakon were able to reach the main survey areas. The plans had to be adapted to the ice conditions along the way. The research activities were conducted along the westernmost part of the Gakkel Ridge, where a volcanic area and a hydrothermal field were mapped and visited with underwater vehicles. The deployment of oceanographic moorings had to be postponed to a later cruise, while other parts of the plans were carried out as far as conditions allowed. It was possible to conduct ice studies using instruments on board and at stations on the ice. Seafloor sediment samples were also taken for various purposes, and an oceanographic transect across the Fram Strait was carried out. Once out of the most difficult ice areas, and on the way to investigate the “Lucky Ridge” and the continuation of the Gakkel Ridge through the Fram Strait, fortune finally turned. With the help of a skilled crew and excellent ROV pilots, a unique hydrothermal field 3000 metres beneath the sea ice was discovered. Jubilant researchers streamed Ægir 6000 video of eerie mineral formations and an oasis of life. The heat source was given the mythical name “Ultima Thule” — a place to the north, beyond the bounds of the world. A cruise that began with major challenges ended in success and celebration. This report summarizes the activities conducted during the GoNorth 2023 cruise, and presents preliminary results.