Vertical Structure of the Ocean Flashcards
List a processes for each spatial and temporal scale
Microscale: cm or less, such as molecular diffusion
Small Scale: m to kms, upswelling
Meso-Scale: tens to hundreds of kms, ocean eddies
Large Scale: thousands of km, major ocean currents
What do you understand about thermohaline circulation
Large scale circulation is caused by differences in density controlled by variations in temperature and salinity.
Density decreases with temperature and increases with salinity and pressure.
Denser water sinks under less dense water governing circulation of water types.
A water with σT= 23.8 has a density of ?
This water has a density of 1023.8 kg/m3
σT = Pressure-1000
Seawater density typicall ~ 1020 and 1030 kg/m³, which is annoying to do math with. By subtracting 1000, σT compresses the range of values to be easier, typically between 20 and 30.
σT is useful for studying surface ocean processes, but it is not conservative across different pressures or when mixing occurs. Potential density (σθ) is more conservative because it accounts for the temperature a water parcel would have if it were brought adiabatically (without heat exchange) to a standard pressure (usually surface pressure or a chosen reference depth).
What does the Equation of Sea water represent?
The Equation of Seawater describes how the density of seawater depends on its temperature, salinity, and pressure.
ρ=f(T,S,P)
A more modern take is the TEOS-10 (Thermodynamic Equation of Seawater) which provides the most accurate representation of seawater properties because uses conservative properties, Absolute Salinity and Potential Temperature instead.
ρ=ρ(SA,Θ,P)
What percentage of Earth’s surface is covered by oceans?
70.8%
What are the three main physical properties of seawater relevant to fluid dynamics?
Temperature, salinity, and pressure
Why are temperature and salinity important in oceanography?
They help identify water masses and determine seawater density, influencing vertical movement.
What is a typical range of ocean salinity? What are the units used?
30 to 40 PSU (Practical Salinity Units)
How does density vary with temperature, salinity, and pressure?
Density decreases with temperature and increases with salinity and pressure
Why is the potential temperature of a water parcel lower than its in-situ temperature? Define both terms.
The potential temperature of a water parcel is typically lower than its in-situ temperature due to the effects of adiabatic expansion during its ascent to a reference pressure (usually surface).
As the pressure decreases, temperature decreases.
In-Situ Temperature: The actual temperature of the water parcel at its current depth and pressure.
Potential Temperature (Θ): The temperature the parcel would have if brought to the surface adiabatically.
Adiabatic Process: When a water parcel rises from depth to the surface without exchanging heat with its surroundings (adiabatic process).
What is an Adiabatic Process?
An adiabatic process is a type of thermodynamic process that occurs without transferring heat or mass between the thermodynamic system and its environment. It only considers
compressibility, without exchanging heat with the surrounding environment
in oceanography adiabatic processes are used to calculate potential temperature which is a conservative property
What is hydrostatic pressure and was is the formula in the ocean?
Hydrostatic pressure is pressure due to the weight of water pressing on submerged objects
𝑝=𝜌𝑔𝑧
p is pressure
ρ is density
g is gravity
z is depth
Define sigma-t (𝜎𝑡 ) in oceanography.
is used in oceanography to measure the density of seawater at a given temperature.
σt=ρ(S,T,P)−1000, where
ρ is density at sea level pressure
What is the thermocline?
A layer in the ocean where temperature changes rapidly with depth.
What is the halocline?
A layer in the ocean where salinity changes rapidly with depth.
