| 3. The Layered Oceans: |
| Learning Objectives: |
-
Understanding of the structural features in individual oceans
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Recognition of the characteristics of different water masses
|
| Structure of Oceanic Waters: |
-
Atlantic and Arctic Oceans:
-
cooling at high N. latitudes produces North Atlantic Deep
Water
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NADW (2 - 4°C, 34.9â)
-
sinks, moves southward.
-
in South Atlantic:
-
Antarctic Intermediate Water (AAIW; 5°C,
34.4%o)
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Antarctic Bottom Water (AABW; 0.5°C, 34.8%o).
-
Surface waters: 25°C, 36.5%o.
-
Arctic Ocean controlled by salinity.
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surface low salinity waters
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affected by seasonal ice formation.
-
at intermediate depths: Norwegian and Greenland currents
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Pacific Ocean:
-
no counterpart of NADW, isolated from Arctic
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no source of deep water, sluggish deep water circulation
-
subtropical lens of warm, salty water.
-
Indian Ocean:
-
isolated from Arctic, no source of deep water
-
sluggish deep water circulation
-
Mediterranean:
-
Mediterranean Intermediate Water (MIW, 13°C, 37.3%o)
-
outflows at depth, mixes in Atlantic
-
Red Sea:
|
| Comparing the Oceans: |
-
Vertical distributions of temperature and salinity
-
similar in all three oceans
-
surface layer and pynocline thicker in Atlantic
-
affected by deep ocean currents.
|
| Temperature and Salinity Relationships: |
-
T-S Curves:
-
depth distribution of temperature and salinity are distinctive
-
plot of temperature vs. salinity forms a T-S diagram
-
depth plots are T-S curves
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T-S Curves and Water Masses:
-
T-S curves for large areas of the ocean are vertically similar
-
define water masses by depth and location
-
water masses are related by density.
|
| 4. Measurement Techniques: |
| Learning Objectives: |
-
Understanding of methods and approaches to seawater characteristization
|
| Determining Water Properties: |
-
Seawater samples taken by water bottles on a hydrowire
-
triggered by messenger
-
hydrocast.
-
CTD (conductivity-temperature-depth) sensors
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recorded parameters as electronic signals
-
Acoustic tomography.
|
| Temperature Measurements: |
-
Deep Sea Reversing Thermometer (DSRT)
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isolates temperature reading at desired depth
-
expensive, reusable but needs stationary platform.
-
Bathythermographs enable underway measurements
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either with mechanical or expendable BT (XBT).
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Key need is calibration of new versus old methods.
|
