Maintaining Deep Ocean Observations: The ALOHA Cabled Observatory

University Of Hawaii, Honolulu

Investigators

Abstract

The long-term ocean monitoring site 100 km north of Oahu, Hawaii known as station ALOHA (A Long-term Oligotrophic Habitat Assessment) has been the location of repeated observations since the late 1980's. More recently, a deep-sea observatory, cabled to shore, was established near station ALOHA. The ALOHA Cabled Observatory (ACO) was deployed in June 2011 and supports innovative scientific research at Station ALOHA. The ACO provides the ocean science community with essential infrastructure and access for sustained science at Station ALOHA, an oligotrophic (desert) site representative of a large fraction of the global ocean. As the deepest operational cabled station, it enables the development, testing and operation for science of new ocean observing sensors and technology, from the abyss to the surface. ALOHA is one setting where it will be possible to connect the ocean from top to bottom, both literally and figuratively, to improve understanding so we can model and predict for human impacts biogeochemical and physical processes at all temporal and spatial scales. The ALOHA Cabled Observatory (ACO) is the deepest operating cabled ocean observatory on our planet. Situated on the seafloor at Station ALOHA in 4728 m water depth, the ACO provides infrastructure and data for new and exciting, globally relevant science and technology. The observatory complements the quasi-monthly Hawaii Ocean Timeseries (HOT) ship-based measurements and Woods Hole/HOT (WHOTS) surface mooring co-located at Station ALOHA. Together, these three programs uniquely provide high-resolution, full-water column measurements in the open ocean. These data together with those from many associated process studies form a unique, multivariate, long-term data set of the ocean state centered at one location. With the availability of relatively high power (1200 W), data bandwidth (100 Mb/s) and precise timing, a basic suite of core observations, and a new remotely operated vehicle (ROV) coming on-line, the ACO can support new and innovative science studies, in their own right as well as to complement HOT and other Station ALOHA science. Science questions include: How much carbon is exported to pelagic depths, the benthos and the sediment? What governs nutrient injection events into the euphotic zone, and export events to the deeper sea? What are the coupled biological and physical details and impacts of mixing throughout the water column? What are the biological and physical energetics in the abyssal ocean? How well are infra-gravity wave models performing? How do marine mammal populations and behaviors change over time? Can passive acoustics be used to infer ocean temperature? What can we learn about tsunamis and seismic events from the bottom pressure? Addressing such challenging questions will require technology advances such as distributed bottom arrays and water column profiling moorings. This grant supports continued ACO operations and maintenance for the scientific community. Core instrumentation will be repaired, deployed, and maintained, including a basic sensor package (pressure, fluorometer, and temperature/salinity). All data, including real time video and audio streams, are publicly available. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.