PHYSICAL OCEANOGRAPHY.Part 1: Introduction, Measurements,

Instruments, etc.

GEOL 1033

(Lesson 26)

Ppt file 103-22

PHYSICAL OCEANOGRAPHERS• Interested in

– Heat exchange– Evaporation– Density– Temperature– Water movements: currents, waves, tides, etc.– Other physical properties of water

• Measures:– Temperature– Salinity– Density– Oxygen content– Pressure – Currents

Some Physical Oceanography Instruments

• Nansen bottle– For water sample collection

– Lowered on a cable

– Activate with a “messenger” (= a little weight that slides down the cable until it hits and triggers the bottle to take a sample.)

Some Physical Oceanography Instruments

• Nansen bottle Collecting water samples at some depth

Some Physical Oceanography Instruments

• Bathythermograph– BT = acronym

– Usually lowered on a cable

– Sensitive to

• Temperature and

• Water pressure, which is related to depth

– Measures any changes in temperature as depth increases

– XBT = acronym for “expendable” bathythermograph

• Dropped from – a moving boat or

– even from an airplane

• Radio sends data back to ship/plane

Some Physical Oceanography Instruments

• BT (bathythermograph)

• Graphic profile of temperature variation with depth inscribed on a black-coated glass slide

Some Physical Oceanography Instruments

• XBT =

Expendable BT• Can be attached

by a cable to a recorder on ship

• Depth can be calculated because of known rate of descent.

• Data is radioed back to an airplane that drops one

Some Physical Oceanography Instruments

• STD device– Electronic– Lowered on a cable– Measures while

being raised or lowered:

• Salinity

• Temperature

• Depth (by measuring associated pressure changes)

– Transmits data by cable back up to ship

Some Physical Oceanography Instruments

• Rosette, a STD device:– Collect many water samples

– Up to 10 x30 L Nansen bottles

– Can be triggered electronically

– Pinger used to locate depth (or depth can be determined by pressure changes)

– Can record other information at the same time:

• suspended particle matter

• oxygen

MEASURING CURRENTS

MEASURING CURRENTS

• Current meters– Mechanical

• A fan-like device (rotor) spins on a shaft of a generator

• Electrical output is calibrated to water speed

– Induction• Applies the principle

that salt water is a conductor, so as water flows through a coil of wire an electric current is generated that can be calibrated.

MEASURING CURRENTS

• Indirect methods of studying water currents:– Measure other water properties whose variations indicate

water movements

– Study:• Oxygen content

• Temperature

• Salinity

• Density

• Radioactive isotopes, e. g., 90Sr

• Distribution of warm- or cold- water organisms (Gulf Stream example)

• Imagery– Airplane = Aerial photographs, e. g., visible spectrum,

infrared, etc.

– Satellite = infrared, reflectivity, visible-light, radar, etc.

MEASURING CURRENTS

• Determining coastal surface ocean current systems using aerial photography

Satellite Remote Sensing of the Grand Banks • Renewed petroleum exploration in the 1980's inspired

greater oceanographic research 370 km Canadian exclusive fishing zone

SATELLITE IMAGERY TO MEASURE SURFACE TEMPERATURES

SATELLITE IMAGERY TO MEASURE SURFACE TEMPERATURES

• Calibrations permit mapping surface temperature variations

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