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Offshore Mooring and Buoy Observations > BML offshore mooring and buoy

  • Description
  • Instruments/Sensors
  • Data Access

BML BuoyFormer BML Mooring and Buoy (Deployed from 8/04-1/4/08)

Bodega Marine Laboratory (BML) operated an oceanographic buoy on the 30m isobath, immediately offshore of the Lab. Deployed in August 2004, the buoy provided data on currents at all depths, seawater temperature, salinity, chlorophyll fluorescence and light transmissivity.

Also see currently deployed BML Buoy

Seawater Temperature, Conductivity & SalinityBML mooring CTD

Instrument Type:  Sea-Bird Electronics SBE 16+ Seacat

Description: Temperature is acquired by applying an AC excitation to a bridge circuit containing an ultra-stable aged thermistor and VISHAY precision resistors.  Conductivity is acquired using an ultra-precision Wein-Bridge oscillator to generate a frequency output in response to changes in conductivity.  Salinity values are calculated from the 1978 Practical Salinity Scale Equations.

Location: Suspended from a chain off the BML oceanographic mooring, ~1.2 km off Bodega Head.
Latitude 38° 18' 42.2" N
Longitude 123° 04' 57.4" W

Installed: Deployed intermittently

Specifications: Temperature
Range:  -5 to +35 °C
Resolution:  0.0001 °C
Accuracy:  0.005 °C

Specifications: Conductivity
Range:  0 to 9 S/m
Resolution:  0.00005 S/m
Accuracy:  0.0005 S/m

Acquisition Settings:
Sample interval:  300 seconds
Measurements per Sample:  25
No Pump

 

Seawater TransmittanceBML mooring transmissometer

Instrument Type:  WETLabs C-Star Transmissometer

Description:  The C-Star measures light transmittance at a single wavelength over a known path. The LED light source provides light that transmits within a narrow bandwidth. A portion of the transmitted light is monitored by a reference detector and used in a feedback circuit to account for variations in the LED source over time, as well as changes in the instrument’s internal temperature. The light transits the sample volume and enters the receiver optics, where it passes through additional focusing optics and finally strikes a silicon photodiode detector which converts the amount of received light to a corresponding 0–5 V analog output signal which represents the amount of light received.  The ratio of light gathered by the receiver to the amount originating at the source is the beam transmittance.

In general, losses of light propagating through water can be attributed to two primary causes: scattering and absorption.  Suspended particles, phytoplankton, bacteria and dissolved organic matter, as well as the intrinsic optical properties of the water itself, all contribute to the losses sensed by the instrument.

Location:  Suspended from a chain off the BML oceanographic mooring, ~1.2 km off Bodega Head.
Latitude 38° 18' 42.2" N
Longitude 123° 04' 57.4" W

Installed:  Deployed intermittently

Specifications:
Wavelength: 660 nm
Pathlength: 25 cm
Sensitivity: 1.25 mV
Beam Divergence: 0.8° in water
Bandwidth: ~ 20 nm

Acquisition Settings:
Sample interval:  300 seconds
Measurements per Sample:  25

Seawater FluorescenceBML mooring flourometer

Instrument Type:  WETLabs ECO FL Fluorometer

Description: The Environmental Characterization Optics or ECO miniature fluorometer allows the user to measure relative chlorophyll concentrations by directly measuring the amount of fluorescence emission in a sample volume of water. The ECO uses an LED to provide the excitation source. An interference filter is used to reject the small amount of out-of-band light emitted by the LED. The light from the source enters the water volume at an angle of approximately 55 – 60° with respect to the end face of the unit.  Fluoresced light is received by a detector positioned where the acceptance angle forms a 140° intersection with the source beam. An interference filter is used to discriminate against the scattered excitation light.

Location: Suspended from a chain off the BML oceanographic mooring, ~1.2 km off Bodega Head.
Latitude 38° 18' 42.2" N
Longitude 123° 04' 57.4" W

Installed: Deployed intermittently

Specifications:
Excitation Wavelength:  470 nm
Emission Wavelength:  695 nm
Sensitivity:  0.01 µg/l
Linearity:  99% R2
Range:  0.01 – 125 µg/l

Acquisition Settings:
Sample interval:  300 seconds
Measurements per Sample:  25
Biowiper opens for sample

ACOUSTIC DOPPLER CURRENT PROFILER - CURRENT VELOCITY AND DIRECTION

BML mooring adcp platform

Instrument Type: RD Instruments 300-kHz Workhorse Sentinel

Description: Acoustic Doppler Current Profiler (ADCP) produces a vertical profile of current velocities. The ADCP transmits sound at a fixed frequency and listens for the Doppler (frequency) shift in the echoes returning from sound scatters in the water. The ADCP uses multiple beams pointed in different directions to compute water velocities in three dimensions. Echoes with different delays allow measurements of current velocities at different depths.

Location: Approx. 1.2 km off Bodega Head at a depth of 30 m
Latitude 38° 18' 42.2" N
Longitude 123° 04' 57.4" W

Installed: August 2004 - 04 January 2008

Specifications:

Depth cell size: 2 m (0.2 to 8 m)
Number of depth cells: 14 (1 to 128)
Velocity range: 5 m/s
Accuracy: 60 mm/s (standard deviation)
Echo intensity: 1.5 dB

Acquisition Settings:
10 minute averaging
1st Bin Range = 4.22 m
Bin Size = 2 m
Number of Bins = 17
55 pings per ensemble