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CTD-Rosette

CalCOFI 24 bottle CTD-RosetteSince August 1993, CalCOFI has deployed a 24 bottle CTD-Rosette. The CTD-Rosette consists of two integrated components: the Seabird 911+ CTD electronic sensor array and carousel surrounded by a ring of 24-10 liter PVC bottles that collect seawater at various depths.
The Seabird 911+ CTD electronic sensor array sends real-time data to a shipboard computer via the winch's conductive wire. As the CTD-Rosette is lowered, depth profiles of several sensor measurements display on the CTD computer screen. Based on the downcast profiles, the 10 liter bottles are closed at target depths as the CTD-Rosette is brought back to surface, trapping seawater for analysis.
The CTD-Rosette is typically lowered to terminal depth of 515 meter (1690 feet), bottom-depth permitting. On basin stations or stations less than 515 meters, it is routinely deployed within ~10 meters from the seafloor. To improve the sampling resolution in areas with significant hydrological and biological gradients, the CTD-Rosette is lowered a speed of ~30 m/min for the first 100 m then ~60 m/min to depth without stopping. During retrieval, the CTD-Rosette stops for at least 20 seconds at target bottle depths to adequately flush the 10 liter sample bottle prior to closure. Seawater samples are analyzed onboard for salinity, oxygen, nutrients & chl and are used to cross-check & correct matching depth CTD sensor measurements.

Seabird 911+ CTD Sensors & Rosette Bottle Samples
CTD Sensors: Seawater Samples:
Temperature x 2 Salinity
Conductivity x 2 Oxygen
Oxygen x 2 Nutrients
Fluorescence Primary Productivity
Transmissometer Chlorophyll-a
PAR Phaeopigments
pH DIC-pCO2-pH
ISUS Nitrate HPLC
Altimeter LTER Additional Sampling

CTD-Rosette Seawater Sampling

CTD Downcast ProfileCalCOFI collects vertical profile data through Seasave V7 using a Seabird 911plusV2 CTD and deck unit. Our SBE 911plus CTD system includes: 9plus Underwater Unit and a 11plus V2 Deck Unit.

Current sensor complement includes:

• Dual Temperature - SBE 3plus
• Dual Conductivity - SBE 4
• Dual Oxygen - SBE 43
• Fluorometer - Wetlabs Fluorometer
• Nitrate Sensor - Satlantic ISUS V2
• pH Sensor - SBE 18
• Transmissometer - WetLabs 25cm 650nm
• Underwater PAR - Biospherical QSP-2300
• Surface PAR - Biospherical QSP-240
• Carousel Water Sampler - SBE 32

 

Seabird CTD-Carousel Setup & Deck Unit Diagnostics
(pdf version)

Deck Unit 00000000SIO-CalCOFI’s method of terminating the sea cable uses a 4-pin custom pig-tail to terminate a multi-strand conductive wire that allows each individual conductor to be used in any combination. Terminating the sea cable using this technique may be viewed on in the CalCOFI Handbook: CTD Termination Section.

Conventional two-pin Seabird pigtail terminations are standard on NOAA vessels and usually performed by the ET. So interfacing the CTD deck unit only requires the attachment of the sea cable to the deck unit. This is done by connecting a two-conductor wire, such as Seabird part no. 31371 (http://www.seabird.com/sales_info/Cables/31371b.pdf) or a coaxial cable equipped with MS3106A connector, from the winch junction box in the CTD lab to the Sea Cable port on the back of the deck unit.
Once the sea cable is connected to the Seabird 9+ and Seabird 11 deck unit, the deck unit can be powered on. If cabled properly and all electronics are functioning, the numeric LED panel of the deck unit should display non-zero numbers. These values are different for each channel which can be selected by rotating the Word Select dial to the right of the LED panel.

Deck Unit LED Panel Numbers

If the LED panel displays “0.0.0.0.0.0.0.0” then the deck unit and CTD “fish” are not handshaking correctly. Turn the deck unit off and wait 60secs before touching any exposed wire. Typically, with only two pins, the problem is reversed polarity so switching the wires in the junction box will correct this issue. Please note that powering on the deck unit with reversed polarity may blow the fuse(s). So after switching the wires and before re-powering on the deck unit, check both the 1/2A and 2A fuses on the back of the deck unit & replace if necessary. It is prudent to keep a good supply of these fuses on hand. Power on the deck unit and hopefully, the LED panel has numbers.

Please note in the photos, yellow tape is used to keep the deck unit Signal Source set to Fish. If the switch is toggled to Tape, the deck unit will not communicate with the CTD. The yellow tape prevents the switch from changing from Fish to Tape unintentionally.

Read more of CTD Setup & Diagnostics Instructions

 

CTD Operator’s Duty List

(CTDOperator Duty List2017.doc 08/09/2017 - CURRENT VERSION)

These instructions are designed for use by CalCOFI CTD operators and describe our step-by-step protocol for CTD operations at sea. They outline our preferred method but are not considered "gospel" - there are many techniques that result in good data from the Seabird 911+ CTD. But based on our long history of using Seabird hardware & software, we've established these guidelines for our CTD operators to follow. Standardizing our methodology between operator improves our data continuity, format consistency, and makes problems with our system easier to catch.

1). CTD Prep: ~20 minutes before station arrival, rally the troops for CTD prep. If weather-decks are secured because of rough weather, wait until arrival to station.

  • Rig the bottles open, lanyards right, bottom caps left; bottles left of stanchions (5, 11, 17 & 23; with extra lanyard extension loops) should be rigged lanyards left, bottom caps left; tighten breathers valves finger-tight, pull spigots out to close then rotate off pins. Note: bottle valves should be oriented at "4 o'clock" to allow bottom caps to angle to the left easily and easy access for seawater sampling.
  • Pull pump DI rinse tubes, uncap PAR & pH sensors; rinse the transmissometer optics with RBS (squirt bottle).
  • Plug in the ISUS battery ~15mins before cast - this can be done when bottles are being prep but postpone if secchi cast or net tows are first. Unplug the battery is there is going to be a delay of more than 20mins.

2). Prep Seasave on CTD Computer:

  • ~15 minutes before cast, power-up the CTD deck unit and start data acquisition in Seasave without archiving data to file. Carefully verify the Cast ### & data filename (YYMM###) and directory are correct. Data files are moved & stored in the ‘archive’ dir but data should not be acquired there or the ctdbackup utility will not be able to find the files. Leaving the "Not archiving data" dialog box on-screen as a reminder data are not being archived is highly recommended.
  • Fill out the Seasave header form – be sure to use the long version of line and sta (ie 93.3 45.0, not 93.45).  Add any comments that might be worth noting or effect data processing such as calm or rough weather, rain, equipment changes, or any startup glitches. Be sure to triple-check the ‘Station#’, ‘Cast #’ and ‘Cast Type’ (ROS, PRODO, SCCOOS) are correct.
  • Connect the ISUS battery if not already connected. After letting the deck unit & CTD electronics warm up for several minutes, log the lowest deck pressure on the station sequence (“cheat sheet”) clipboard or console ops form.

3). Upon station arrival:

  • Work vests & hard hats are required for everyone participating in deck ops
  • Ready the launch of the CTD if it is the first operation - secchi or nets may be 1st on morning prodo station. If CTD ops are 1st then untie/unstrap the CTD from deck eyes.
  • Double-check the tubes are pull, sensors uncapped, ISUS battery plugged-in
  • On SIO vessels:
    • The restech or watchleader requests permission from the bridge to launch the CTD after checking the ocean surface for hazards (kelp, oil or diesel slicks for example)
    • With permission granted, instruct the winch operator to engage the auto-deployment (on ships with LARS like RV Sally Ride) or manually deploy the rosette and lower to sea surface.
  • On NOAA vessels:
    • Tell the survey technician and deck ABs the CTD is ready - they can deploy whenever they and the bridge are ready. I usually stay on deck to lend a hand if there are any issues then once the CTD is zeroed at surface, go inside to start the 2 minute timer.
    • When the weather is rough, insist the survey tech & ABs use taglines when deploying and recovering the rosette, if they are not.
  • Send the CTD down to 10m - be sure there is at least 15m of bottom before sending the package down to 10m by checking the bottom depth before deployment.
  • Once inside, start the 2min timer. On vessels with echosounder: check the Knudsen for a bottom depth otherwise ask for a bottom depth from the acoustics or survey tech.  Use the clipboard "cheatsheet" to estimate where bottom should be and record the bottom depth if reasonable

Since 1993, the CalCOFI program has deployed a Seabird 911 CTD mounted on a 24-bottle rosette during seasonal, quarterly cruises off California. The CTD-rosette is lowered into the ocean to 515m, depth-permitting, on 75 hydrographic stations using the ship's conductive-wire winch. Data from the sensors are transmitted up the conductive wire and displayed real-time on a data aquistion computer. Discrete seawater samples are collected in 10L bottles at specific depths determined by the chlorophyll maximum and mixed layer depth. These samples are analyzed at sea and used to assess the CTD sensor data quality plus measure additional properties. Processed CTD sensor data are compared to the seawater sample data and corrected when necessary. Preliminary data are available on CalCOFI's website, calcofi.org, while the cruise is at sea when internet is available. Preliminary processed data files are online shortly after the cruise returns. Final, publication-quality bottle & CTD data are available once the bottle data have been fully processed & scrutinized.

Read Methods: CTD General Practices>

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