Multi-domain environmental sensing for underwater acoustics in the Arctic marginal ice zone.

Recent and rapid environmental changes in the Arctic Ocean lead scientists to re-evaluate the way they operate in this area. NATO STO Centre for Maritime Research and Experimentation (CMRE) leads the Nordic Recognised Environmental Picture (NREP) trial series in order to understand how a better characterization of the Arctic environment is possible and how it can help to build more accurate underwater acoustic modelling capabilities. NREP25 was conducted in the Greenland Sea from July 16th to July 27th 2025. On-board NATO Research Vessel (NRV) Alliance, underwater acoustic propagation experiments were performed in various Arctic environments (packed ice, marginal ice, open waters, brash ice), deploying in-house built receivers alongside other innovative solutions. NRV Alliance acted as the acoustic source, transmitting pre-defined sequences of known waveforms that will be used for probing the Arctic environment, in particular the interactions of sound waves with the space and time-dependent ice cover. The latter was estimated using a combination of remote sensing capabilities. First, a new prototype of ship-borne X-band RADAR provided a continuous estimation of the positions of the ice floes. Second, remote sensing imagery from diverse satellites (Sentinel, COSMO-SkyMed, SWOT and RADARSAT) provided high-resolution images of the sea ice cover, obtained from SAR processing, several times a day. NRV Alliance also served as a “floating ground control” for drone activities. Namely, high resolution photogrammetry and point-cloud LiDAR data were obtained from aerial drone surveys. 

Oceanographic characterization was carried out through extensive CTD casts, as well as glider missions (with acoustic payloads as well). This characterization was used to design experimental configurations that were more likely to generate interactions of acoustic paths with the sea ice at the surface.

In addition, CMRE conducted specific characterization of the water ice interface by ROV inspection (with video, acoustic camera and altimetry data), and also ice coring (to be analysed at the centre).

An overall description of the experiment is presented, as well as an analysis of the data collected focusing on the contribution of remote sensing to the understanding of the underwater acoustic observations.