Ambient Sound at Challenger Deep, Mariana Trench

Abstract

We present a record of ambient sound obtained using a unique deep-ocean instrument package and mooring that was successfully deployed in 2015 at Challenger Deep in the Mariana Trench. The 45 m long mooring contained a hydrophone and an RBR™ pressure-temperature sensor. The hydrophone recorded continuously for 24 days at a 32 kHz sample rate. The pressure logger recorded a maximum pressure of 11,161.4 decibars, corresponding to a depth of 10,829.7 m, where actual anchor depth was 10,854.7 m. Observed sound sources included earthquake acoustic signals (T phases), baleen and odontocete cetacean vocalizations, ship propeller sounds, airguns, active sonar, and the passing of a Category 4 typhoon. Overall, Challenger Deep sound levels in the ship traffic band (20-100 Hz) can be as high as noise levels caused by moderate shipping, which is likely due to persistent commercial and military ship traffic in the region. Challenger Deep sound levels due to sea surface wind/waves (500 Hz to 1 kHz band) are as high as sea state 2, but can also be very low, equivalent to sea state 0. To our knowledge, this is the first long-term (multiday to week) broadband sound record, and only the fifth in situ measurement of depth, ever made at Challenger Deep. Our study indicates that Challenger Deep, the ultimate hadal (>6,000 m) environment, can be relatively quiet but is not as acoustically isolated as previously thought, and weatherrelated surface processes can influence the soundscape in the deepest parts of the ocean.

Baseline soundscapes of deep‐sea habitats reveal heterogeneity among ecosystems and sensitivity to anthropogenic impacts

“…Furthermore, we noticed the low‐frequency soundscape off Minamitorishima Island was quieter than that at Challenger Deep, Mariana Trench. The acoustic data reported by Dziak et al (2017) demonstrated a hadal environment influenced by numerous seismic activities, persistent shipping traffic, and the passing of a Category 4 typhoon, a pattern not found in the recordings collected off Minamitorishima Island. Due to the remote location of Minamitorishima Island and lower shipping activities around it, the discrepancy between the two acoustic data sets could imply the influence of anthropogenic and geophysical activities on deep‐sea soundscapes.…”

“…Despite comprising over 75% of the world's biosphere (Angel 1997), the deep sea remains the last frontier on Earth—but it is far from untouched by humankind. From plastic debris to shipping noise, our activities have cast vivid shadows to the deep, evident even at the bottom of the Mariana Trench (Dziak et al 2017; Chiba et al 2018). Recently, surging interests in mining the deep for minerals to feed the ever‐growing global needs have stepped our potential influence up to a new level (Van Dover et al 2018; Smith et al 2020).…”

“…To monitor changes in soundscapes, it is important to establish baselines of environmental sounds before the impacts occur. To date, relatively few soundscape baseline characterizations have been carried out at the deep seafloor (Dziak et al 2017), but the fact that mining activities can severely impact the local soundscape has been evident in oil and gas extraction—through both exploratory air guns and actual drilling (Hildebrand 2009; Kyhn et al 2014; Wiggins et al 2016).…”

Implosion in the Challenger Deep: Echo Sounding with the Shock Wave

“…The published results are representative of the unpublished results, most of which come from cruise reports. The methods used to measure such extreme ocean depths, besides traditional sounding with a weighted rope or cable, have included explosives and stopwatches (Carruthers and Lawford, 1952;Gaskell et al, 1953), single-beam sonar (Hanson et al, 1959;Mantyla and Reid, 1978;Taira et al, 2004Taira et al, , 2005Nakanishi and Hashimoto, 2011), multibeam sonar (Hydrographic Department and Japan Marine Safety Agency, 1984;Fujioka et al, 2002;Nakanishi and Hashimoto, 2011;Gardner et al, 2014;van Haren et al, 2017), side-scan sonar (Fryer et al, 2003), and pressure sensors (Piccard and Dietz, 1967;Todo et al, 2005;Bowen et al, 2009; 2012 James Cameron dive; Dziak et al, 2017;Fitzherbert, 2019). Gardner et al (2014) and Stewart and Jamieson (2019) both provide a review of previous investigations of the deepest part of the ocean.…”

“…obtained from Matthew's tables of sound speed (Matthews, 1939;Carruthers and Lawford, 1952;Mantyla and Reid, 1978;Zheng, 2015), comprising a compilation of historical measurements of water column chemistry by latitude and longitude. In modern times, direct measurements of the sound speed profile over the Challenger Deep have been made with conductivity, temperature, depth (CTD) sensors mounted on either deep submersibles or free-falling vehicles (Piccard and Dietz, 1967;Bowen et al, 2009;Taira et al, 2004;Barclay et al, 2017;Dziak et al, 2017;van Haren et al, 2017) and with expendable bathythermographs (XBTs; Fujioka et al, 2002;Gardner et al, 2014). Ideally, for depth estimation, such determinations of the sound speed profile should be concurrent with the acquisition of the time-of-flight data; otherwise, significant errors can arise in the acoustic estimate of the ocean depth (Beaudoin et al, 2009).…”