Temporal and spatial dependence of a yearlong record of sound propagation from the Canada Basin to the Chukchi Shelf

Abstract

The Pacific Arctic Region has experienced decadal changes in atmospheric conditions, seasonal sea-ice coverage, and thermohaline structure that have consequences for underwater sound propagation. To better understand Arctic acoustics, a set of experiments known as the deep-water Canada Basin acoustic propagation experiment and the shallow-water Canada Basin acoustic propagation experiment was conducted in the Canada Basin and on the Chukchi Shelf from summer 2016 to summer 2017. During the experiments, low-frequency signals from five tomographic sources located in the deep basin were recorded by an array of hydrophones located on the shelf. Over the course of the yearlong experiment, the surface conditions transitioned from completely open water to fully ice-covered. The propagation conditions in the deep basin were dominated by a subsurface duct; however, over the slope and shelf, the duct was seen to significantly weaken during the winter and spring. The combination of these surface and subsurface conditions led to changes in the received level of the sources that exceeded 60 dB and showed a distinct spacio-temporal dependence, which was correlated with the locations of the sources in the basin. This paper seeks to quantify the observed variability in the received signals through propagation modeling using spatially sparse environmental measurements.

A Virtual Ocean framework for environmentally adaptive, embedded acoustic navigation on autonomous underwater vehicles

“…These updates are scalable for range dependence, where updates could correspond to the amplitude and period of EOFs, a geometrical approach of amplitude and extent, or two-dimensional probability distributions. 4 But providing this extra information may be trivial given the sparse nature of sampling in ice-covered environments. Turning to models to supplement horizontal variability is promising, but publicly available models like HYCOM" 5 a sea-ice coupled, three-hour resolution, 1/12 degree resolution model well used by the ocean acoustics and naval intelligence communities currently lacks realism for the Beaufort Lens and its the spatial resolution is 1 12 of a degree.…”

“…This work is motivated by challenges from ice-covered AUV operations in March 2016, when a prominent sound speed lens significantly disrupted communication and navigation. 4 The success of this approach is ultimately demonstrated by field results from AUV operations in March 2020. I will give a brief overview of why the Arctic is a region of significant overlapping interests before discussing the operational challenges faced in March 2016.…”

“…The Arctic is one of the most sensitive regions to anthropogenic climate change, in part due to the feedback mechanism of water absorbing a greater proportion of the sun's heat than ice does. 5 Permafrost melt threatens existing Arctic social, military, and commercial infrastructure 6 while also destabilizing the region's role in the global carbon cycle, from carbon sink to 4 Schmidt et al, "Acoustic Communication and Navigation in the New Arctic -A Model Case for Environmental Adaptation". 5 Chapin et al, "Role of Land-Surface Changes in Arctic Summer Warming".…”

“…The physics behind their propagation introduces several important limiting factors compared to that of electromagnetic waves through the atmosphere. 4 1. Spreading loss-the expansion of a fixed amount of energy over a larger and larger surface area.…”

“…Many studies using ITP data employ either a single representative observation 2 or observations with respect to the profiler (e.g., ITPs 3, 14, and 15) and the path they take. 3 The data assimilation framework introduced in this thesis, used to seed simulation cases in Chen et al, 4 is agnostic to the profiler itself. It assimilates each observation to a desired depth grid, and treats each profile as an independent observation with a time, latitude, and longitude.…”