Deep Circulation in the North Atlantic from Ocean Bottom Seismometer Noise: Insights from the UPFLOW/iReverb Project

Ocean Bottom Seismometers (OBS) face unique challenges in recording seismic events due to their exposure to harsh oceanic conditions. The UPFLOW project deployed 50 OBS of various instrument types in the North Atlantic Ocean. The iReverb project aims to investigate the tidally-modulated current-induced noise generated by water flow around the instrument's frame. This study presents an analysis of seasonal variations in tidal-induced noise on different OBS types across the Azores, Madeira and Canaries region.  In some instances, the detected harmonics allow the identification of individual frame components contributing to the noise, offering, on the one hand, insights into potential mitigation solutions for future deployments. On the other hand, our project's main focus - large-scale detection of non-seismic or current-induced reverberation events on OBS - provides valuable data for mapping resonances and tracking ocean currents.  Our study uses machine learning/deep learning algorithms, automating the mapping of resonances across large datasets and obtaining a proxy for Ocean Bottom Circulation (OBC) patterns. Here, we present a brief overview of our methodology, describe our results and compare them to classical oceanographic methods to determine ocean currents. This project was funded by the UPFLOW project (ERC grant 101001601), and by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020 (DOI: 10.54499/UIDB/50019/2020), UIDP/50019/2020 (DOI: 10.54499/UIDP/50019/2020) and LA/P/0068/2020 (DOI: 10.54499/LA/P/0068/2020).