Kermadec Ventilation

This project will conduct the first physical oceanography survey of a deep ocean trench allowing examination of spatial gradients and potential mechanisms of hadal ventilation. The Kermadec Trench, northeast of New Zealand, is the world's fifth deepest trench. The Kermadec Trench is expected to be have short residence time and detectable spatial gradients as the South Pacific Deep Western Boundary Current transporting Antarctic Bottom Water along its 1200 km length and the generation of strong internal tides on the neighboring Kermadec Ridge. Multiple collocated and overlapping deployments on free-falling 11 km depth rated instruments and the ship's 6km rated CTD will be conducted at 12 sites along the trench axis and additional 15 off-axis sites. The 11 km rated instruments are: 1) The University of Hawaii's Hadal Water Column Profiler (HWCP) records full depth vertical profiles of temperature, conductivity, dissolved oxygen, turbulent microstructure (mixing), horizontal current velocity via a geo-electromagnetic current meter, 200 kHz bioacoustic backscatter, and video. It also has a small 11 bottle water trace metal clean water sampler. 2) The University of Rhode Island's Deep Autonomous profiler (DAP) is a lander, water column profiler, and Niskin-based sampler capable of collecting environmental data (T, S, oxygen, density, camera, and sound), recording video segments, and collecting water samples throughout the water column or while resting at the seafloor. 3) At six multiday stations a small bottom mooring consisting of a single point acoustic current meter, a temperature/pressure logger and two acoustic releases will also be deployed. All three of the above 11 km rated instruments use syntactic foam for flotation. A 150 kHz upward looking and a 300 kHz downward looking Lowered ADCP will be attached to the ship's CTD frame.