F.Félix Zarzuela ffelixzarzu(at)hotmail.com
Institute of Marine Sciences - OKEANOS, University of the Azores & Institute of
Marine Research - IMAR, Horta, Portugal,
S.M. Jesussjesus(at)ualg.pt
LarSys, Universidade do Algarve, Campus de Gambelas, PT-8005-139 Faro, Portugal,
P.J. Wensveen pjw(at)hi.is
Westman Islands Research Centre, Institute of Research Centres, University of Iceland,
Vestmannaeyjar, Iceland
M. Romagosa and M.A. Silva
Institute of Marine Sciences - OKEANOS, University of the Azores & Institute of
Marine Research – IMAR, Horta, Portugal.
Comments: (no paper yet)
Ref.: Int. Conf. on the Effects of Noise on Aquatic Life, Prague (Czech Rep).
June-July 2025
Abstract:
Anthropogenic ocean noise has been increasing over the last decades, affecting marine ecosystems across
the world. Wind-generated sound is the dominant natural noise source for most ocean locations and commercial
shipping is the primary anthropogenic contributor, potentially interfering with marine animals' communication,
causing stress and disrupting vital behaviours. Spatially explicit risk assessments link pressures to
environmental sensitivity, supporting sustainable marine management and reducing conflicts among users.
Here, we present a novel modelling framework to estimate underwater sound levels across a large North
Atlantic area (~1.85 million km2) applicable to all marine fauna, showcased by noise exposure risk on
four cetacean species. This approach combines estimations of shipping noise distribution—derived from
sound propagation modelling-with an empirical wind model. Open-source shipping data from the Global
Maritime Traffic Density Service, along with environmental variables (bathymetry from GEBCO, generic
bottom composition, and salinity and temperature from Copernicus), serve as key inputs. The BELLHOP
beam-tracing model was used as the acoustic propagation engine, and monthly shipping densities (ships
per hour per 1 km2) were combined with source levels from ships (cargo, tanker, fishing and passenger
from JOMOPANS-ECHO model). We generated 36 underwater noise maps for the Azores EEZ during 2023, covering
combinations of months (from May to October), 1/3 octave band central frequency (64 Hz and 126 Hz) and
depth (100 m and 500 m). Model outputs were currently validated with acoustic recordings from a calibrated
hydrophone and 2 Ocean Bottom Seismometers, showing average overestimation discrepancies of 10 (+/-3.8) dB
and underestimations of 13 (+/-2.6) dB depending on the region. At a depth of 100 m, the average Sound
Pressure Levels values were 99.95 (+/-3.16) dB for 64 Hz and 100.16 (+/-3) dB for 126 Hz. Analysis of cell
percentages for 64 Hz and 125 Hz at this altitude revealed that 0.13% of the study area exhibited values
exceeding 110 dB, an intensity threshold at which behavioural responses have been observed in various marine
animals. These high-intensity areas were primarily associated with port entrances and inter-island routes.
To assess the potential impact on masking, Excess Noise Levels will be evaluated for four species of large
whales. Further validation is needed to assess framework performance across the water column. However, this
approach provides a scalable, open-source data method for ocean noise estimation which can contribute to risk
assessment across deep offshore areas, supporting conservation efforts and environmental management.