Trinidad Head Ocean Observing Node (THOON)


The Trinidad Head Ocean Observing Node (THOON) is designed to measure ocean conditions in shelf waters off northern California, with a focus on measuring variability in ocean acidification and hypoxia (OAH) in the context of physical and biological dynamics. THOON is deployed seasonally (spring to fall) due west of Trinidad Head in about 75 m of water at Station TH02 along the Trinidad Head Line (archived observations). 

THOON includes three co-located instrument packages:

  1. A profiling mooring that measures conditions throughout the water column at high temporal and spatial (vertical) resolution.
  2. A benthic platform equipped to support continuous monitoring of conditions near the seafloor and to resolve currents throughout the water column.
  3. A surface mooring to measure waves and temperature at the sea surface.

Profiling mooring

The profiling mooring is a wave-powered WireWalker equipped with an RBR sensor package to profile temperature, salinity, chlorophyll, and dissolved oxygen throughout the water column at high temporal resolution (roughly every 8 minutes) and to transmit the data in near-real-time to shore via cellular communications. To measure pH throughout the water column, a Deep-Sea-DuraFET was integrated into the sensor package, building on recent progress towards configuring the sensor for rapid profiling applications.

Sea-floor Mooring

The sea-floor mooring is anchored approximately 2 m above the bottom, and carries a Deep SeapHOx to collect continuous observations of pH, dissolved oxygen, temperature and salinity near the seafloor, and an upward looking Teledyne Sentinal V Acoustic Doppler Current Profiler (ADCP) that uses sound to profile currents throughout the water column.  Data from these instruments are archived, and downloaded when the instruments are recovered at the end of the deployment season.

Surface mooring

A solar-powered Sofar Spotter buoy is deployed with the sea-floor mooring to mark the approximate location of the sea-floor mooring and to assist with its recovery.  The Sofar Spotter measures temperature, wave height and direction, and (based on the wave data) also reports wind speed and direction.  Observations are communicated to land in near-real-time.

Profiling mooring
Sea-floor mooring
Surface mooring

Summer 2024 THOON Deployments

THOON is presently in the water. The sea-floor & surface mooring combination was deployed in mid-April, and the profiling mooring in late-May.

Access near real-time information on conditions from these platforms below!

2023 Spring - October 2023 THOON Deployments 

The THOON WireWalker and Bottom Lander were deployed intermittently for extended periods between May - October 2023. These deployments allowed us to observe high-resolution variability in the water column during periods of coastal upwelling, and to develop experience in the operations of these instruments and moorings. Data from one of these deployments are shown below.

An upwelling event was observed between October 2 - 10 2023, reflecting an ocean response consistent with positive Coastal Upwelling Transport Index (CUTI) values and upwelling favorable winds. These conditions led to cold, low-dissolved oxygen, low-pH, and nutrient rich water being upwelled onto the shelf into shallower waters. Full depth temperature profiles from the Wire Walker during this period allowed us to observe the onset and relaxation of this event as it happened.