properties of seawater density review mixing dissolved gases
TRANSCRIPT
Properties of Seawater
Density reviewMixingDissolved Gases
Pressure in the Ocean
p g h
0
( )z
p z g dz
( )p zg
z
Hydrostatic Equation
Hydrostatic Balance
Density: amount of mass per unit volume
T S
Units: kg m-3
Linear Equation for “in situ” Density
Thermal expansion coefficient
Saline contraction coefficient
A different way to express density
-31000 km mt
T S
In situ TemperatureTemperature of a particle of water measured at a particular depth and pressure (no correction for compressibility effects)
Surface
Deep ocean
T1
T2
T1=θ1
T2≠θ1
At the ocean surface In Situ and Potential Temperature are the same!
θ1
θ1
Potential TemperatureTemperature that a particle would have if raised adiabatically to the surface of the ocean (corrects for the effects of compression
occurring at great depth make the particle warmer)
( , )
1000
,
T
pST
In situ Density
( , )
1000
,S p
Potential Density
Tracking Water Masses on TS diagrams
Worlds ocean Water Masses
How do you mix water masses in the ocean?
Molecular diffusion
Turbulent diffusion
Horizontal Stirring and Mixing
Horizontal Stirring and Mixing
Mixing of two water masses with same Density
O1T1 S1 O2T2 S2
2
1
3
Vertical Stirring and Mixing
y
z +
_
Mixing along surfaces of Constant Density
Surfaces ofconstant density
y
z
+
_
Mixing along surfaces of Constant Density
Along - Isopycnal diffusive mixing
Surfaces ofconstant density
y
z +
_
Along - Isopycnal diffusive mixing
Across - Isopycnal diffusive mixing
Mixing across surfaces of Constant Density
Surfaces ofconstant density
y
z
b
+
_
the “skew flux”
Diapycnal Mixing
Definitions of Mixing
Surfaces ofconstant density
y
z
b
+
_
the “skew flux”advection
Diapycnal Mixingturbulent diffusion
Definitions of Mixing
Surfaces ofconstant density
Diabatic exchanges with the atmosphere at the surface
Adiabatic changes and Mixing in ocean interior
T1 S1 T2 S2
Surface:Wind stirring and vertical mixing in the surface layer
Surface fluxes of heat and salt buoyancy fluxes
Surface Waves
Interior:Along Isopycnal
eddies and fronts
Across Isopycnalinternal wave breaking
Bottom:Breaking internal waves over rough topography (ref: article)
Summary of major mixing processes in the Ocean
Dissolved GassesAir
Seawater
Total pressure = sum of partial pressures
Oxygen
Dissolved Gases in the OceanOxygen profile
Anoxic environment
compensation depth
Respiration:Animal, plants and microbial decomposition
Dissolved Gases in the OceanOxygen profile
Why is the pH of seawater close to neutral?
10log [ ]pH H
seawaterpH=7.5-8.5
Carbon Dioxide and Carbonate system
Why is it important?
1. Regulates temperature of the planet2. Important for life in the ocean 3. Regulates the pH of water
Carbonic Acid
2 2 2 3 3H O CO H CO H HCO
Bicarbonate Ion
Sources for acidity in the ocean
Carbon Dioxide and Carbonate system
23 3HCO H CO
Carbonate
10log [ ]pH H