The Hawaii-2 Observatory: New Capabilities and Instrumentation

The Hawaii-2 Observatory (H2O) is a permanent deep ocean research facility located about halfway between California and Hawaii. The H2O infrastructure consists of a submarine cable termination and junction box which provides two-way digital data communications and power for seafloor instruments. Prior to 2003, H2O instrumentation consisted of a buried broadband seismic sensor. In September 2003, a major upgrade to the H2O junction box was completed which changed the communications architecture to TCP/IP, making reconstruction of data streams on shore a system rather than a user task. A new biological experiment, two seafloor geomagnetic observatories (SGO; one US and one French), a high frequency hydrophone, and a Small Experiment Module (SEM) were also installed at the H2O site. The goal of the biological experiment is determination of the short and long-term responses of benthic fauna to a temporally-variable food supply in a very food-limited environment. An instrument platform was installed which includes cameras to photograph the activities of animals near the seafloor and a sedimentation sensor to monitor the seafloor flux of particulates and phytoplankton pigments. The SGOs each incorporate vector and scalar sensors for the relative geomagnetic field and its absolute magnitude, along with a gyrocompass-based method to measure the instantaneous absolute direction of the field. In addition, the SGOs measure the vector electric field, including removal of electrode drift. The hydrophone is suitable for high frequency seismic studies and whale monitoring. The SEM was installed to supply a secondary interface to experiments. It provides data interfaces and power for the H2O seismic system and up to eight additional low-data rate and low-power sensors