Using a regional ocean model to understand the structure and sampling variability of acoustic tomography arrivals in Fram Strait

Abstract

A regional ocean model for Fram Strait allows to understand the variability and structure of acoustic tomography arrivals. The eddy-permitting model (52 vertical layers and 4.5 km horizontal resolution) was evaluated using long-term moored hydrography data and time series of depth-range averaged temperature obtained from the inversion of acoustic tomography measurements. Geometric ray modelling on the ocean model fields reproduces the measured arrival structure of the acoustic tomography experiment. The combination of ocean and acoustic model gives insights into acoustic propagation during winter and spring. Overlapping arrivals coming from different vertical angles can be resolved and explained. The overlapping arrival of sound channel rays and bottom-reflected rays has implications for the inversion of tomography data in Fram Strait. The increased knowledge about the ray-length variations of bottom-reflected rays is valuable information for choosing appropriate observation kernels for the data assimilation of acoustic tomography data in Fram Strait.