Ocean Floor Observation and Bathymetry System (OFOBS) seafloor images of the Gakkel Ridge in the Arctic Ocean collected during RV POLARSTERN cruise PS137

During the RV POLARSTERN cruise PS137 (2023-06-21 to 2023-07-31) to the Gakkel Ridge the Ocean Floor Observation and Bathymetry System (OFOBS) was used to collect still and video images from various locations surveyed during the expedition. The OFOBS consisted of a towed underwater camera system equipped with a high-resolution photo-camera (iSiTEC, CANON EOS 5D Mark III) and a high-definition video-camera (iSiTEC, Sony FCB-H11) as well as an integrated sidescan sonar system. The cameras were mounted on a steel frame (140 L x 92 W x 135 H cm), together with two strobe lights (iSiTEC UW-Blitz 250, TTL driven), three laser pointers spaced with a distance of 50 cm used to estimate the size of seafloor strcutures, four LED lights, and a USBL positioning system (Posidonia) to track the position of the OFOBS during deployments, with additional positioning information provided by the integrated INS and DVL systems. An automatic seafloor image was taken every 20 seconds to obtain 'TIMER' stills distributed at regular distances along each of the survey profiles. Additional 'MANUAL' photos were triggered individually when interesting objects appeared in the live feed. In total, 5 OFOBS deployments were carried out. The third OFOBS deployment failed and all position data provided with the image data sets are based on the ships position as the USBL positioning system of the OFOBS could not be reached. Here we present all seafloor images collected during four successful OFOBS deployments with the responding ships position. Metadata in the form of iFDOs are available for each deployment containing a detailed description of the image collection and curation process.