Physical Properties of Seawater Flashcards
What are the 3 main physical properties of seawater?
- Temperature
- Salinity
- Density
What is a isohaline?
A line joining equal points of salinity
What is a halocline?
An area of strong gradient in salinity. The most variation occurs in the surface waters (top 1000m)
What is an isotherm?
A line joining equal points of temperature
What does a thermocline represent?
Rapid change in temperature with depth. A mixed surface layer below which there is a permanent thermocline of 5 Degrees C decreeing to 0-3 Deg. C towards the bottom
4 Major Ions
Na+ , Mg 2+, Cl- , SO4 2-
What is the potential temperature?
The temperature of which a parcel of water would be if it was at the surface
What does a T-S Diagram show?
Contour values of salinity and temperature. They are used to identify water masses and the mixing between them
What are the 3 factors that control density?
- Temperature
- Salinity
- Pressure
What is the pycnocline?
A rapid increase in density with depth
What is a conservative property?
One that is only changed by mixing (e.g. temperature and salinity)
What is a non-conservative property?
One that is influenced by processes other than mixing (e.g. dissolved oxygen and nutrient concentrations)
What is a water mass?
A body of water formed at a particular place with characteristic values of temperature and salinity that are maintained over long distances and time
What are the 5 types of water mass you can get?
Surface, Central, Intermediate, Deep and Bottom
What is a T-S diagram?
Plotted curves of temperature and salinity based on oceanographic observations
What does AABW stand for and give 3 features of this water mass?
Antarctic Bottom Water
-0.5 Degrees C
Salinity of 34.6-34.7
Cold
What does NADW stand for and give 3 features of this water mass?
North Atlantic Deep Water
2-4 Degrees C
Salinity of 34.7-35
Warmer and Saltier
What does AIW stand for and give 3 features of this water mass?
Antarctic Intermediate Water
3-4 Degrees C
Salinity of 34.2-34.3
Warmer and Fresher
How is the AABW formed?
The Weddell and Ross Sea by deep convection mix with NADW, this is the circumpolar water
How is the NADW formed?
Product of deep convection in the Arctic Ocean, Greenland Sea and Labrador Sea. Most Antarctic Intermediate Water is formed by deep convection east of southern Chile and west of southern Argentina and spreads into all oceans with the Circumpolar Current. Intermediate Water in the northern hemisphere may be formed by convection or subduction.
What is Central Water?
The water of the permanent thermocline formed by subduction in the tropics
What are the Mediterranean and Red Seas?
Intrusions of high temperature, high salinity waters from two inland seas.
What are currents?
Large scale water movements that occur everywhere in the ocean from large scale (e.g. the Gulf stream) to small turbulence and eddies
4 Methods of Measuring Ocean Currents
- Eularian
- Lagrangian
- Chemical Tracers
- Satellites
What drives surface currents?
The global wind system
5 Facts about Eastern Boundary Currents
- Broad at ~1000km
- Shallow
3, slow at 10s km/day - Transport 10-15 SV (where SV = 1million cubic metres/second)
- Diffuse upwelling
5 Facts about Western Boundary Currents
- Narrow - <100km
- Deep ~2km
- Swift - 100s km/day
- 50 + SV (where SV = 1million cubic metres/second)
- Sharp, no upwelling
What is an oceanic front?
Any zone separating an area of water from another
What does Ekman Spiral do?
Pushes water to the right of the wind direction
What is thermohaline circulation?
The relatively slow movement of the water in the deep ocean produced by differences in density in the water. The density differences in turn are produced by variations in temperature and salinity
What is the annual rate of upwelling in the oceans?
~4m/year
What drives thermohaline circulation?
High latitude cooling with high surface densities causing convective mixing and sinking of deep waters.
Also pressure gradients at depth due to density differences in overlong waters drive the force
