Sound speed inversion of modal group delays of broadband 35-Hz transmissions during the Coordinated Arctic Acoustic Thermometry Experiment

The Arctic Ocean is evolving in response to climate change. In addition to the dramatic reduction in sea ice, the interior of the ocean is changing as the amount of warmer water that advects into the Arctic from the North Pacific and North Atlantic Oceans has increased. This paper applies linear inverse methods to the modal group delays of broadband 35-Hz transmissions across the Canada Basin during the Coordinated Arctic Acoustic Thermometry Experiment (CAATEX) in an effort to measure and understand the changes in the interior of the western Arctic. Modal dispersion along a ∼850-km transmission path leads to modal arrivals that can be separated in both time and space using data from 1200-m long vertical receiving arrays. The range-independent sound speed profile is estimated as a function of time over the year 2019–2020 from the measured modal group slowness. The inversion uses the Ice-Tethered Profiler (ITP) dataset to constrain the sound speed.