4.12: Ocean Observatories

If robots had underwater cities, they might look like ocean observatories, an integrated array of ocean-observing sensors and platforms on and above the seafloor designed to address questions of scientific and societal importance (e.g., Crise et al. 2018). Ocean observatories were conceived in the 1980s by American geological oceanographers as the oceanographer’s version of an astronomical or volcano observatory (Delaney et al. 1987). Like these observatories, ocean observatories carry out observations over broad spatial and temporal scales. Uniquely, however, ocean observatories span hundreds of miles in waters thousands of feet deep. They involve fixed and mobile platforms connected either physically via cables or virtually via acoustic or optical signals. At heart, ocean observatories provide long-term and sustained observations of the ocean, in contrast to the brief encounters offered by shipboard oceanography.

To get an idea of what they look like, imagine an oceanic neighborhood with strings of instrumented moorings and AUV docking stations spaced at regular intervals like gas stations. Bottom-attached instruments of all shapes and sizes cover the seafloor like tiny houses. Attached cables act as their power lines. Dish-shaped antennae transmit and receive acoustic and optical data. Drifters and gliders and AUVs fly through the surrounding water like a scene from The Jetsons (Hanna-Barbera 1962–1963). Bottom-roaming benthic explorers excavate sediments and retrieve and deploy instrument packages like All-Terrain Walkers on an undersea Tatooine (e.g., Lucas 1977–2019). Of course, the occasional human visitor interrupts the robotic seascape—arriving via ship or submersible or as a deep-sea diver—acting as a necessary overlord to keep the city operating smoothly.

Ocean observatories generally fall into one of three categories, regional cabled arrays, coastal arrays, and global arrays. Each serves different goals and purposes.

Regional cabled arrays represent what geologists envisioned when they proposed ocean observatories in the 1980s. These arrays use optical-electrical telecommunication cables to provide power and two-way communication capabilities to suites of instruments on the seafloor. The regional cabled array off the coasts of Washington and Oregon serves as the best example. This array, touted as “the first US ocean observatory to span a tectonic plate,” consists of seven primary nodes, each with its own set of instruments and name (such as International District Vent Field 1). One array, the Axial Caldera Cabled Array, captured the eruption of an active undersea volcano on the Juan de Fuca Ridge on April 24, 2015 (Delaney et al. 2016).

Coastal arrays focus on oceanographic processes that occur on or above the continental shelf (e.g., Trowbridge et al. 2019). A coastal array off the Oregon Shelf, the Coastal Endurance Array, employs moorings (fixed and profiler) in concert with gliders to provide high-resolution, top-to-bottom observations of ocean and atmospheric processes. The Coastal Endurance Array has observed hypoxia events (i.e., low oxygen), ocean heatwaves, and the response of marine organisms to a solar eclipse (Barth et al. 2018).

Global arrays refer to ocean observatories in select deep water locations that shed light on major science themes, such as air–sea exchange, climate variability, ocean circulation, and ocean ecosystems. Global arrays rely on deep ocean moorings and gliders to sample vertical and horizontal variability in the upper ocean. The Global Irminger Sea Array off Greenland has already provided tantalizing new observations that may change how we view circulation in this part of the world ocean (de Jong et al. 2018).

Ocean observatories represent an emerging conceptual, technological, and strategic shift in how oceanographers carry out their work. But there are concerns that the enormous financial outlay needed to build and sustain ocean observatories will drain resources from traditional approaches (Witze 2013; Kintisch 2015). As stated by the National Research Council (2015), a “healthy balance” should be sought between “infrastructure to provide access to the ocean and advance the science . . . funds for scientists and trainees to conduct research and provide value for the infrastructure investment.” How oceanographers and funding agencies achieve this balance may determine the long-term vitality of future oceanographic research.

As a final note, I want to emphasize that ocean observatories will prove a massive undertaking. They represent, perhaps, the culmination of nearly 150 years of oceanographic research that began with the Challenger expedition. Heightened awareness of the rapid changes in Earth’s climate and the growing knowledge of multiple stressors on the marine environment makes the mission of ocean observatories ever more urgent (e.g., Speich et al. 2019). With the UN Decade of Ocean Science for Sustainable Development upon us (2021–2030), the opportunities for ocean scientists look ever more promising. As Visbeck (2018) put it:

The increased awareness of the importance of the ocean to the future of humanity gives grounds for cautious optimism and motivation for ambitious multilateral cooperation. The scientific community has been given a stage on which to shine during the Decade of Ocean Science for Sustainable Development. Let us come together, respect our disciplines and agendas, but also be ready to embark on an exciting and transformative journey to realize the ocean we need for the future we want.