Ship-based observations: CTD, Nansen and Niskin bottles, inverting thermometer and

Acoustic Doppler Current Profiler

Ben LeeDecember 2, 2005

EPS 131

Topics

• Overview of ocean sampling and measurement

• CTD (Conductivity, Temperature, Depth)

• Acoustic Doppler Current Profiler

• Niskin bottles

• Nansen bottles

• Inverting or reversing thermometers

Measurement and Sampling of the Ocean

CTD (Conductivity, Temperature, Depth)

Conductivity measurement

Temperature measurement

• Thermistor (Pt)

• Range: -1 to 40 deg C

• Accuracy: +/- 0.1deg C

• Accuracy: 0.75 psu (practical salinity unit)

• Ocean water: 35 psu = 35,000 ppm (by weight) of salt in water

Niskin bottles

• Bottles can be closed when desired by researchers on the ship

• Water samples can be obtained to calibrate the CTD and to investigate properties not measured by the CTD such as dissolved nutrient content, carbon dioxide, chlorofluorocarbons, and others tracers.

Acoustic Doppler Current Profilers

• Can be mounted horizontally to sea walls or bridge pilings in rivers

• anchored to seafloor

• to the bottoms of ships

• lowered on a cable from ships

• Utilizes the Doppler affect to calculate particle speed in water

• Transmits “pings” and records signals that have ricocheted off particles

ADCP

• In deep oceans (> 1000 m) two ADCP are lowered together one facing the surface and the other facing the bottom, to double the length of the current profile

• Petroleum jelly and chili powder repel barnacles without interrupting sound waves

• Garbage bags and electrical tape can keep the rest of the instrument clean

Nansen bottles

• Approximately 12 to 24 Nansen bottles are attached in series at predetermined intervals along a cable

• Deployed with both ends open

• Closes as the bottles are reversed

• Used in conjunction with inverting or reversing thermometers

Inverting thermometers

• Has a constriction in the capillary that allows it to retain its reading upon being inverted

• Deployed in pairs, one protected and the other unprotected from high pressures. Combination of the two gives temperature and pressure at the depth where reversal took place

References:

• Ocean Explorer, National Oceanic and Atmospheric Administration, http://oceanexplorer.noaa.gov/welcome.html

• Introduction to Physical Oceanography, Robert H. Stewart, http://oceanworld.tamu.edu/resources/ocng_textbook/contents.html

• Oceanic In-Situ Data Access, National Oceanic and Atmospheric Administration, http://www.epic.noaa.gov/epic/ewb/ewb_help_ctd.htm

• Ocean World, http://oceanworld.tamu.edu/index.html

• Edge of the Arctic Shelf, Woods Hole Oceanographic Institution, http://www.whoi.edu/arcticedge/index.html

• Coastal Ocean Institute and Rinehart Coastal Research Center, http://www.whoi.edu/institutes/coi/facilities/instrument.htm

• Glossary of Meteorology, American Meteorological Society, http://amsglossary.allenpress.com/glossary

Any Questions?