New (and old) oceanographic New (and old) oceanographic toolstools

2012 2012 WorkshopWorkshop

DHP 2012DHP 2012Tina Miller-WayTina Miller-Way

Properties of water of interest

• Parameters, units, significance– Temperature– Salinity– Dissolved oxygen – Turbidity– Light levels– Depth…

Tools to measure these properties - depth• Sounding lines

– Problems…

• Pressure sensor

• Sonar

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Tools to measure these properties - temperature

• Thermometer - Hg-based

• how to do at depth? - reversing

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Tools to measure these properties - salinity

• Direct or indirect measurement

• Refractometer

• Conductivity sensor

Tools to measure these properties - turbidity

• Secchi disk

• transmissometer

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Tools to measure these properties - dissolved oxygen

• Methods - chemical, electrical, optical

Optode

Polarigraphic electrode

Winkler

Dissolved oxygen

• Concentration vs saturation• Saturation -

– expected amount given temp, pressure, salinity (ideal gas law) = 100% saturation

– Under, over or at saturation– Units = %

• Concetration - units = mg/l (or ppm, mmol)

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Temperature (°C)

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Dissolved oxygen nomographs

• Use nomographs to determine expected DO levels (100% saturation)

Dissolved oxygen nomographs

• use to determine saturation level

Example O2 data

Tools to measure these properties - light

• What wavelengths?– Photosynthetically active

radiation (PAR) sensor

• How to account for changes in incident light?– Deck sensor

Other parameters

• Chlorophyll levels - fluorometer

But these properties vary with depth

thermocline

Temperature (°C)

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th (

km)

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halocline

Salinity (‰)

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Density (g/ml)

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pycnocline

• Typical open ocean profiles• Called - a hydrocast

Monitoring units

• Hydrolab/YSI = brands

Combined units

• moored, deployed, mobile

• CTD

• Argo ’floats’

Hydroloab hydrocast

CTD hydrocast

See our CTD hydrocast

Other oceanographic tools

• Water samplers– Nansen / Niskin bottle– messengers