June 2025

June 2025 | Oceanography

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An important visualization is the tri-level spectrogram, which

presents the acoustic recordings from a lander in an easy-to-use

exploratory interface (Figure 7b). Using a color scale perceptu­

ally optimized to highlight marine mammal sounds, spectro­

grams are pre-processed into image files sufficiently compressed

to be loaded faster than users can scroll, allowing for seamless

exploration. The top level of the spectrogram viewer displays

weeks to months of audio (depending on monitor resolution)

and allows users to quickly peruse the entire dataset, see trends,

and spot major events. The middle level shows roughly a day of

spectrogram data, while the bottom level shows a few minutes

at full resolution. The levels are linked, so clicking on one level

centers the other levels around the same time. Selections can be

made in the lower-level view, allowing in-browser playback or

download of sound files from specific time ranges, with options

to select and filter by frequency.

An event viewer presents marine mammal detections in

an interactive heatmap (Figure 7c). Users select an event type

(e.g., dolphin click) and view a plot of detected events over the

entire project duration. Alternatively, all years can be stacked

to produce a cyclic visualization that reveals repeated seasonal

patterns, with an option to interactively emphasize contribu­

tions from each year. The heatmap can be shifted in direction to

center patterns. Clicking on individual heatmap cells switches

over to the spectrogram viewer, which jumps to the correlating

timestamp. Additional context is provided via a day/night indi­

cator band and environmental data plots (e.g., chlorophyll). A

second lander can be selected to perform direct comparisons

within a single heatmap (using multiple colors).

Finally, the deviations viewer presents a similar tri-level

interface, but instead of spectrograms, it displays times and fre­

quency ranges in which the soundscape was unusually loud or

quiet, based on a weekly, monthly, or quarterly moving win­

dow analysis (Figure 7d). For the data displayed in the viewer,

recordings were processed into 60-second, decidecade fre­

quency bins. Running means and standard deviations were cal­

culated for each window length, and the number of standard

deviations above or below the running mean was mapped to a

diverging blue-white-red heatmap. See Butkiewicz et al. (2021)

for additional details. Since project completion, the visualiza­

tion interface has been successfully used by the public as indi­

cated by the project webpage visitor log, and it provides a valu­

able tool to other researchers for studying a wide range of topics

from marine mammal behavior to extracting training data for

AI/ML detection applications.

SUMMARY

The ADEON team designed and deployed an ocean acous­

tics observation network on the US OCS between Virginia

and Florida from November 2017 to December 2020. The

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NASC (m2 nmi–2)

HAT NRS Med (125 kHz)

HAT NRS Large (125 kHz)

HAT RS Small (38 kHz)

HAT RS Large (38 kHz)

DISTRIBUTIONAL AND

BEHAVIORAL DATA

Presence/absence of prey from active

acoustics and predator from passive

acoustics and sightings

OCEANOGRAPHIC DATA

Sea surface temperature and

chlorophyll from satellite measurements

ENSEMBLE MODELS

Generalized additive

mixed models,

boosted regression

trees, Bayesian

approaches

SPATIAL AND

TEMPORAL PREDICTIONS

Probability of occurrence of mid-trophics

and top predators, time series of

abundance of mid-trophics and

top predators

FIGURE 6. (a) Ecosystem modeling framework. (b) Example of a daily spatial prediction of relative fin whale

call density on September 7, 2018, using preliminary fitted relationships from a generalized additive model.

(c) Acoustic backscatter can be apportioned to different taxonomic or size classes of scatterers (i.e., NRS

and RS, non-resonant and resonant scatterers respectively; medium NRS at 125 kHz [10–25 mm], large NRS

at 125 kHz [25–122 mm], small RS at 38 kHz indicative of small swim-bladdered fish, and large RS at 38 kHz

indicative of larger swim-bladdered fish based on animal total length; Miksis-Olds et al., 2021). These param­

eters (representing the abundance or biomass of different types of zooplankton or fish) can then be used as

model input parameters to determine relationships between prey abundance and marine mammal predator

presence or vocal behavior. These are the time series of size classes from the HAT lander.

74°W

40°N

38°N

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78°W

80°W

76°W

Fin

Activity

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