Properties of Seawater Properties of Seawater and Water Mass Analysisand Water Mass Analysis

CE410/510CE410/510Fall 2009Fall 2009

By David A. JayBy David A. Jay

Why do we Care about HWhy do we Care about H220 Properties? 0 Properties? ––►► Water covers 70% of globeWater covers 70% of globe►► Properties of seawater and freshwater are quite Properties of seawater and freshwater are quite

different different ►► These differences are very important to climate These differences are very important to climate

and human alteration of climateand human alteration of climate►► Properties (salinity, temperature, density) and Properties (salinity, temperature, density) and

thermodynamics of water have a strong influence thermodynamics of water have a strong influence on motion in oceans, estuaries, rivers and lakeson motion in oceans, estuaries, rivers and lakes

Therefore, we look at water properties to see what Therefore, we look at water properties to see what determines density, which affects currents and determines density, which affects currents and layering of water masseslayering of water masses

Important Properties of Water Important Properties of Water ––►► OOur atmosphere and oceans function as they do because ur atmosphere and oceans function as they do because

of certain vital and unusual properties of Hof certain vital and unusual properties of H220:0:Large latent heat of vaporization of waterLarge latent heat of vaporization of water ---- 2.25 2.25 --2.5 x 102.5 x 1066 J kgJ kg--11. Vaporization . Vaporization

of water is a very energetic process, and large amounts of energof water is a very energetic process, and large amounts of energy are released y are released when water vapor condenses. Latent heat plays an important role when water vapor condenses. Latent heat plays an important role in the in the atmospheric energy balance.atmospheric energy balance.Water also has the Water also has the highest heat capacityhighest heat capacity of any common substance, except liquid of any common substance, except liquid NHNH33: 1.95 x 10: 1.95 x 1033 J kgJ kg--11 KK--11 at constant pressure. Note that heating water from 0 to at constant pressure. Note that heating water from 0 to 100 100 °°C takes 1.95 x 10C takes 1.95 x 1055 J kgJ kg--11, still less heat than freezing or vaporization. Water , still less heat than freezing or vaporization. Water vapor therefore play a huge role in atmospheric vapor therefore play a huge role in atmospheric energeticsenergetics and climate!and climate!

From Wallace and Hobbs:

Important Properties of Water (cont.) Important Properties of Water (cont.) ––

Large latent heat of fusion of water at 0 Large latent heat of fusion of water at 0 °°C C ---- 3.34 x 3.34 x 101055 J kgJ kg--11. It also takes a large amount of heat to melt . It also takes a large amount of heat to melt ice. Ice plays multiple roles in climate: ice. Ice plays multiple roles in climate: ►► the amount of energy required to form or melt ice retards the amount of energy required to form or melt ice retards

temperature swings in the atmosphere/oceantemperature swings in the atmosphere/ocean►► ice formation decreases loss of energy from the ocean to the ice formation decreases loss of energy from the ocean to the

atmosphere by shielding warmer water below the ice from the atmosphere by shielding warmer water below the ice from the atmosphere, atmosphere,

►► brine formed when the oceans freeze at high latitudes drives brine formed when the oceans freeze at high latitudes drives the oceanthe ocean’’s deep (s deep (thermohalinethermohaline) circulation. ) circulation.

Maximum density above freezing for lowMaximum density above freezing for low--salinity water salinity water (discussed below)(discussed below)Surface tension allows formation of capillary wavesSurface tension allows formation of capillary waves

Density of Seawater Density of Seawater ––►► The density of seawater The density of seawater ρρ is a function of salinity is a function of salinity SS, ,

temperaturetemperature TT, and pressure , and pressure PP; call it ; call it ρρ(S,T,P)(S,T,P)►► Standard freshwater at atmospheric pressure has Standard freshwater at atmospheric pressure has ρρ = 1 = 1

gm/cmgm/cm33 of 1000 kg/mof 1000 kg/m33

►► SPM (suspended particulate matter) also affects bulk SPM (suspended particulate matter) also affects bulk density, but is a separate phase. For low SPM density, but is a separate phase. For low SPM concentrations, we treat the two together as one fluid concentrations, we treat the two together as one fluid for purposes of determining densityfor purposes of determining density

►► Density at Density at sealevelsealevel pressure is shown as pressure is shown as σσTT, a non, a non--dimensional ratio to standard water; numerically: dimensional ratio to standard water; numerically:

σσTT = (= (ρρ(S,T) (S,T) -- 1) *1000 (in 1) *1000 (in cgscgs with standard water with standard water ρρ = 1 gm/cm= 1 gm/cm33))►► Use Use σσTT because because ρρ is always ~1, (from ~0.990 to 1.030) is always ~1, (from ~0.990 to 1.030)

σσTT goes from ~goes from ~--2 to ~30 for salinity from 02 to ~30 for salinity from 0--40. 40. Need to know Need to know σσTT to 4 significant digits in estuaries and 5 in the to 4 significant digits in estuaries and 5 in the open ocean open ocean Accurate measurements are essential!Accurate measurements are essential!Routines for calculating Routines for calculating σσT T only stabilized in the 1980sonly stabilized in the 1980s

Definition of Salinity Definition of Salinity ––►► Salinity (mass concentration of salt) is hard to measureSalinity (mass concentration of salt) is hard to measure►► Now done based on conductivity ratio of seawater to Now done based on conductivity ratio of seawater to

standard standard KClKCl solution (at 15solution (at 15°° C) in C) in ““Practical Salinity Practical Salinity UnitsUnits”” or PSU (salinity is formally or PSU (salinity is formally unitlessunitless!):!):

KK1515 = conductivity of seawater/conductivity of = conductivity of seawater/conductivity of KClKCl standardstandardS = 0.0080 S = 0.0080 ––0.1692 K0.1692 K1515

0.50.5 +25.3851 K+25.3851 K1515 + 14.0941 + 14.0941 KK1515

1.51.5 ––7.0261 K7.0261 K151522 + 2.7081 K+ 2.7081 K1515

2.52.5 in PSUin PSU

►► S in PSU x 1.0051 gives S in S in PSU x 1.0051 gives S in pptppt (old definition)(old definition)►► Average ocean salinity is ~30Average ocean salinity is ~30--37 PSU. So ~3+% of the 37 PSU. So ~3+% of the

weight of seawater is salt; 30weight of seawater is salt; 30--37 kg/m37 kg/m33

►► Estuarine salinities are ~0.1Estuarine salinities are ~0.1--50 PSU, but definition of 50 PSU, but definition of salinity is imprecise, because salt composition is variablesalinity is imprecise, because salt composition is variable

►► SPM concentrations are typically 0.01 to 10 kg mSPM concentrations are typically 0.01 to 10 kg m--33 (or (or 0.01 to 10 0.01 to 10 pptppt) in estuaries, <0.01 kg m) in estuaries, <0.01 kg m--33 offshoreoffshore

Importance of Density Gradients Importance of Density Gradients ––►► Oceanic motions are strongly influenced by Oceanic motions are strongly influenced by

density gradients:density gradients:Vertical gradient controls vertical mixing Vertical gradient controls vertical mixing Horizontal gradients drive currents directlyHorizontal gradients drive currents directly

►► Gradients in Gradients in ρρ are caused by gradients in T, S and are caused by gradients in T, S and SPMSPM

►► T often controls T often controls σσTT offshore, especially at polesoffshore, especially at poles►► SPM may control SPM may control σσTT near the seabed near the seabed ►► Salinity usually controls Salinity usually controls σσTT in estuaries; in estuaries; σσTT is is

~linear in S (~linear in S (σσ00 is is σσTT at 0at 0ºº C):C):σσ00 = (= (--.093 +0.8149 S .093 +0.8149 S –– 0.000482 S0.000482 S22 + 0.0000068 S+ 0.0000068 S33)/1.0051 )/1.0051

Freezing and T of Minimum Density Freezing and T of Minimum Density ––►► Behavior of Behavior of ρρ near freezing:near freezing:

Has a huge influence on climateHas a huge influence on climateVery different in fresh and salt Very different in fresh and salt waterwater

►► Controlled by Controlled by TTρρmaxmax: : TTρρmaxmax = ~ 3.95= ~ 3.95ºº –– 0.266 0.266 σσ00(Down to the freezing point curve) (Down to the freezing point curve)

Max density of freshwater is Max density of freshwater is 3.953.95ºº

►► Salt content causes freezing Salt content causes freezing point depression:point depression:

TTfreezingfreezing = ~ = ~ --0.03 0.03 –– 0.0527 S 0.0527 S –– 0.00004 S0.00004 S22

►► The two curves intersect at S =24.695, T= The two curves intersect at S =24.695, T= --1.33 1.33 ººCC, so , so inner parts of coastal seas like the Baltic (S <24) and the inner parts of coastal seas like the Baltic (S <24) and the Russian inner arctic shelf act like lakes Russian inner arctic shelf act like lakes

From Neumann and Pierson,p. 43-44

Freezing of Lakes and the Ocean Freezing of Lakes and the Ocean ––►► In a lake: In a lake:

Water cools to ~4Water cools to ~4ººCwith Cwith convection top to bottomconvection top to bottomThen lake stratifies and top freezesThen lake stratifies and top freezesTraps heat in lake, allowing severe Traps heat in lake, allowing severe inland climates; fish survive w/o inland climates; fish survive w/o freezingfreezing

►► In the ocean (S>24.7):In the ocean (S>24.7):Cold water is always denser and sinksCold water is always denser and sinksConvection occurs to bottom alwaysConvection occurs to bottom alwaysFreezing only occurs when whole Freezing only occurs when whole water column reaches freezing pointwater column reaches freezing point(much lower in ocean)(much lower in ocean)Freezing causes brine formation. Brine Freezing causes brine formation. Brine sinks and forms coldest water in the sinks and forms coldest water in the world ocean (off Greenland, Antarctic world ocean (off Greenland, Antarctic and Sea of Okhotsk)and Sea of Okhotsk)Drives Drives thermohalinethermohaline circulation of the oceanscirculation of the oceans

From Neumann and Pierson, p. 43-44

Molecular Viscosity Molecular Viscosity ––►► Viscosity is a measure of how sticky a flow is:Viscosity is a measure of how sticky a flow is:

Syrup is high viscositySyrup is high viscosityWater has a much lower viscosityWater has a much lower viscosity

►► All flows lose energy to viscosity, the rubbing of All flows lose energy to viscosity, the rubbing of molecules together.molecules together.

►► Viscosity is a Viscosity is a property of the fluidproperty of the fluid, not the flow, not the flow►► Turbulent viscosity is much larger and causes much more Turbulent viscosity is much larger and causes much more

energy loss if a flow is turbulent. Turbulent viscosity is a energy loss if a flow is turbulent. Turbulent viscosity is a property of the flowproperty of the flow not of the fluid.not of the fluid.

Molecular Viscosity Molecular Viscosity ––►► Dynamic viscosity Dynamic viscosity µµ is in M/(LT)is in M/(LT)►► KinematicKinematic viscosity viscosity υυ = = µµ//ρρ is in Lis in L22/T/T►► Typical value of Typical value of υυ is ~1.2x10is ~1.2x10--22 cmcm22/s at 15/s at 15°°C or C or

1.2x101.2x10--66 mm22/s /s ►► Viscosity decreases with increasing T for water Viscosity decreases with increasing T for water

and many other common fluids and solutionsand many other common fluids and solutions

Surface Tension Surface Tension ––►► Surface tension is a measure of the energy needed to Surface tension is a measure of the energy needed to

expand the surface are of a fluidexpand the surface are of a fluid►► Just as with gravitational potential energy, exchange of Just as with gravitational potential energy, exchange of

kinetic with surface tension energy is the basis for a type kinetic with surface tension energy is the basis for a type of wave that is important on cm scales. Surface tension of wave that is important on cm scales. Surface tension waves are used widely in remote sensingwaves are used widely in remote sensing

►► Surface tension [dyne/cm] = 75.64 Surface tension [dyne/cm] = 75.64 --0.144 T(0.144 T(°°C) +0.0399 C) +0.0399 ClCl

►► ClCl is is ChlorinityChlorinity, an early measure of salinity based only on , an early measure of salinity based only on the the ClCl content of content of seawateerseawateer

Sound in Seawater Sound in Seawater ––►► Why do we care:Why do we care:

Much ocean instrumentation is acousticMuch ocean instrumentation is acousticIncreasing concerns Increasing concerns r.er.e. . ““sound pollutionsound pollution”” in seain sea

►► Water in not very compressible relative to air, so Water in not very compressible relative to air, so sound moves fast:sound moves fast:

VVSS = = SqrtSqrt[[γγ/(/(ρρ K)] ~ 1543 K)] ~ 1543 m/sm/s in seawaterin seawaterγγ = 1.0 = 1.0 -- 1.02 = ratio of the specific heats at constant pressure 1.02 = ratio of the specific heats at constant pressure

and constant volumeand constant volumeK is the compressibility coefficient = K is the compressibility coefficient = --1/1/αα ddαα/dP/dPαα = the specific volume of seawater == the specific volume of seawater = 1/1/ρρ

►► VVS S depends on T, S and P (or depth D): depends on T, S and P (or depth D): VVSS =1449 + 4.6 T =1449 + 4.6 T ––0.55 T0.55 T22 + 1.4(S+ 1.4(S--35) + 0.017 D in ms35) + 0.017 D in ms--11

►► VVSS varies by ~10% in ocean as controlled by T, but varies by ~10% in ocean as controlled by T, but S controls VS controls VSS in estuaries in estuaries

Sound in Seawater (More) Sound in Seawater (More) ––►► VVS S variations cause refraction, like light in a lensvariations cause refraction, like light in a lens

SnellsSnells Law: sound ray turns in direction of slower speedLaw: sound ray turns in direction of slower speed““SOFAR ChannelSOFAR Channel”” associated associated with subwith sub--surface sound speed surface sound speed minimum in ocean, allows long minimum in ocean, allows long range communication with range communication with low frequency sound (100s of low frequency sound (100s of Hz)Hz)Sound speed increases with Sound speed increases with S and T

From Neumann and Pierson, p. 43-44

S and T

Sound Transmission in Seawater Sound Transmission in Seawater ––►► Left Left –– typical temperate ocean S, T and Vtypical temperate ocean S, T and VSS profilesprofiles►► Right Right –– typical sound paths for a shallow source in Arctic typical sound paths for a shallow source in Arctic

(top) and temperate ocean (bottom)(top) and temperate ocean (bottom)

VSFrom Emery and Pickard, p. 26-27

Sound Absorption in Seawater Sound Absorption in Seawater ––►► Absorption limits performance of acoustic instruments Absorption limits performance of acoustic instruments –– big problem:big problem:

LowLow--frequencies (<100 kHz) penetrate water well, but have long frequencies (<100 kHz) penetrate water well, but have long waves/low resolution waves/low resolution High frequencies >100 KHz have better resolution but increasing High frequencies >100 KHz have better resolution but increasing losses to losses to absorptionabsorptionExample: 37.5 kHz Acoustic Doppler Current Profiler (ADCP) Example: 37.5 kHz Acoustic Doppler Current Profiler (ADCP) ““seessees”” to to 500500-- 1500 m with 32 m bin size1500 m with 32 m bin size1200 kHz ADCP sees 51200 kHz ADCP sees 5--25 m with 0.1 to 1 m bins25 m with 0.1 to 1 m bins

►► Define wavelength Define wavelength λλ = V= VSS//ωω = 1543/= 1543/ωω►► For 1.5 Hz and 1500 kHz sound, the results are For 1.5 Hz and 1500 kHz sound, the results are λλ = ~ 1.5 m and = ~ 1.5 m and λλ= =

~1.5 mm~1.5 mm►► Absorption varies with S. At 1500 kHz, differences are ~10% for Absorption varies with S. At 1500 kHz, differences are ~10% for

0<S<33. At 500 kHz, differences are 50%0<S<33. At 500 kHz, differences are 50%Salinity is a more important factor in calibrating backscatter fSalinity is a more important factor in calibrating backscatter for low or low frequencies than highfrequencies than high

Types of Acoustic Instrumentation Types of Acoustic Instrumentation ––►► Sonar Sonar –– measures distance to seabed using measures distance to seabed using

acoustic travel time of strongest acoustic travel time of strongest backscatter. Can also define:backscatter. Can also define:

density layers in water column density layers in water column (weaker backscattering layers)(weaker backscattering layers)Organisms (backscatter strength)Organisms (backscatter strength)Character of seabed by strength/Character of seabed by strength/variability of bed backscattervariability of bed backscatter

►► ADCP ADCP –– measures water velocity using Doppler measures water velocity using Doppler shift principle and 4 divergent sound beams shift principle and 4 divergent sound beams –– a a ““gated Doppler sonar.gated Doppler sonar.””Like Doppler weather radar, but operates with soundLike Doppler weather radar, but operates with sound

►► Doppler speed logs, measures ship/submarine speed Doppler speed logs, measures ship/submarine speed ►► MultiMulti--frequency acoustic backscatter measures size and frequency acoustic backscatter measures size and

concentration profiles for SPMconcentration profiles for SPM►► SideSide--scan sonar scan sonar –– can provide an can provide an ““imageimage”” of bed texture over a broad of bed texture over a broad

areaarea

An ADCP

Influence of SPM on Water Properties Influence of SPM on Water Properties ––►► SPM is a separate phase, but most of the time this is ignored; tSPM is a separate phase, but most of the time this is ignored; treat reat

SPM as if it were dissolvedSPM as if it were dissolved►► SPM falls with a settling velocity WSPM falls with a settling velocity WSS that is a function of size, that is a function of size,

density and shape, so SPM is found near beddensity and shape, so SPM is found near bed►► SPM concentration is drive by currents and WSPM concentration is drive by currents and WSS: :

Erosion is caused by strong bed stressErosion is caused by strong bed stressSPM settles when SPM settles when bedstressbedstress and turbulence are weakand turbulence are weakCoarse material settles faster and is harder to erode (nonCoarse material settles faster and is harder to erode (non--cohesive)cohesive)MudsMuds are cohesive, which reduces their tendency to erodeare cohesive, which reduces their tendency to erode

►► SPM affects water density near bed where mixing makes T and S SPM affects water density near bed where mixing makes T and S vertically uniformvertically uniform

►► SPM influences currents and SPM influences currents and bedstressbedstress through the effects of through the effects of stratification on vertical mixing:stratification on vertical mixing:

High SPM concentrations shield bed from further erosionHigh SPM concentrations shield bed from further erosionLiquid mud can form a separate layer with its own dynamicsLiquid mud can form a separate layer with its own dynamics

Measuring SPM in Seawater Measuring SPM in Seawater ––►► SPM can be measured as turbidity by: SPM can be measured as turbidity by:

Optical backscatter (optical backscatter sensor or OBS)Optical backscatter (optical backscatter sensor or OBS)Acoustic backscatter (ABS)Acoustic backscatter (ABS)Optical transmission or lack thereof (Optical transmission or lack thereof (transmissometertransmissometer))Forward scatter (Laser InForward scatter (Laser In--Situ Scattering Situ Scattering TransmissometerTransmissometer or or LISST)LISST)Filtered samples of water (gives actual mg/l)Filtered samples of water (gives actual mg/l)Settling tube Settling tube –– gives settling velocity distributiongives settling velocity distribution

►► The last two methods are direct but VERY slow. Others The last two methods are direct but VERY slow. Others give volume concentration not mass concentration give volume concentration not mass concentration –– a a DIFFICULT calibration problem to get mass DIFFICULT calibration problem to get mass concentrationconcentration

Evolving Fraser River Plume SPM Evolving Fraser River Plume SPM Distributions from Ebb to Flood Distributions from Ebb to Flood ––

ABS Flocs

►► Aggregates get exported, but sand stays mostly in Aggregates get exported, but sand stays mostly in estuary or on entrance barestuary or on entrance bar

Analyzing Water Properties Analyzing Water Properties ––►► Analyzing water properties to understand oceanic motions Analyzing water properties to understand oceanic motions

goes back to beginnings of oceanography ca. 1870goes back to beginnings of oceanography ca. 1870►► S,T,S,T,ρρ vary as vary as f(x,y,z,tf(x,y,z,t) ) –– complicated!complicated!►► NonNon--conservative properties are even more complex conservative properties are even more complex ►► Some ways to describe/analyze:Some ways to describe/analyze:

TimeTime--series at a point (e.g., a mooring)series at a point (e.g., a mooring)Vertical profilesVertical profilesPropertyProperty--property Diagrams; e.g., Tproperty Diagrams; e.g., T--SSProperty sections or surface values along a ship pathProperty sections or surface values along a ship path

►► At right: S at a mooring At right: S at a mooring S. of the CR mouth, near S. of the CR mouth, near the CR plume. S is low whenthe CR plume. S is low whenwinds from N. push plumewinds from N. push plumeover mooring. Tidal S over mooring. Tidal S variations are larger whenvariations are larger whenS is low S is low

Time Series of S at a coastal mooring

Types of Property Diagrams Types of Property Diagrams ––►► Sections and surface traces in CR Plume area:Sections and surface traces in CR Plume area:

WaterWater--Mass Analysis Mass Analysis ––►► Concept: water masses are extreme types of water that Concept: water masses are extreme types of water that

mix together to form observed of water properties mix together to form observed of water properties ►► Mixing is linear on a TMixing is linear on a T--S diagram (T, S are conserved) S diagram (T, S are conserved) ►► Examples:Examples:

A rum and coke is a mixture of rum (T = 23A rum and coke is a mixture of rum (T = 23ºº C, 40 proof, zero C, 40 proof, zero sugar, no COsugar, no CO22) with coke (T = 1) with coke (T = 1ºº, 0 proof, lots of sugar and CO, 0 proof, lots of sugar and CO22). ). The properties at any point in the drink can be explained as a mThe properties at any point in the drink can be explained as a mix ix of these two of these two ““water masseswater masses””, but , but ––►► COCO22 is unreliable for determining how much rum and coke are at any is unreliable for determining how much rum and coke are at any

given point, because the COgiven point, because the CO22 is is ““nonnon--conservativeconservative”” –– it forms bubbles it forms bubbles and exchanges with the atmosphere. and exchanges with the atmosphere.

Waters off the OR/WA coast is a mix of: Waters off the OR/WA coast is a mix of: ►► Columbia River Water (CRW: S = 0, T variable)Columbia River Water (CRW: S = 0, T variable)►► Surface Ocean Water (SOW: S = 32.5, T= 11Surface Ocean Water (SOW: S = 32.5, T= 11--13 13 ºº C)C)►► SubSub--Surface Ocean Water (SSOW: S > 33.5, T = 7Surface Ocean Water (SSOW: S > 33.5, T = 7--9 9 ºº C)C)►► Temperature is nonTemperature is non--conservative at the surface due to conservative at the surface due to

heating/coolingheating/cooling►► Nutrients and pollutants are also usually nonNutrients and pollutants are also usually non--conservativeconservative

PNW Water Properties PNW Water Properties ––►► Columbia River Water (CRW: S = 0, T variable):Columbia River Water (CRW: S = 0, T variable):

Rich in Fe (micronutrient), Si (make diatom shells), has some N Rich in Fe (micronutrient), Si (make diatom shells), has some N and P, and organic/metallic pollutants. SPM and P, and organic/metallic pollutants. SPM –– 30 to 1000 mg/l30 to 1000 mg/lRiver is too dark for much primary production, but CRW fertilizeRiver is too dark for much primary production, but CRW fertilizes s coastal waterscoastal waters

►► Surface Ocean Water (SOW: S = 31.5Surface Ocean Water (SOW: S = 31.5--32, T= 1132, T= 11--13 13 ºº C):C):Devoid of N and P, low SPM but has lots biology Devoid of N and P, low SPM but has lots biology Productive if mixed with SSOW and CRWProductive if mixed with SSOW and CRW

►► SubSub--Surface Ocean Water (SSOW: S > 33.5, T= 6.5Surface Ocean Water (SSOW: S > 33.5, T= 6.5--88ºº C)C)THE major source of N and PTHE major source of N and PLow in Si and FeLow in Si and FeUnproductive if not brought to surface (low light)Unproductive if not brought to surface (low light)

►► Optimal production occurs if all three types are brought Optimal production occurs if all three types are brought together, but especially SSOW + CRWtogether, but especially SSOW + CRW

PNW Coastal Water Properties PNW Coastal Water Properties ––►► Water properties defined in Water properties defined in PruterPruter and and AlversonAlverson (1972)(1972)►► These have changed somewhat due to PDO cycle and warmingThese have changed somewhat due to PDO cycle and warming►► Small changes can have big impacts: Small changes can have big impacts:

Whether high nutrient water gets to the surface, or just almost Whether high nutrient water gets to the surface, or just almost doesdoesWhether we good low DO Whether we good low DO ““dead zonedead zone”” in summer off the coast in summer off the coast

►► pH of coastal waters is changing due to COpH of coastal waters is changing due to CO22 input; may effect input; may effect exoskeletons of some marine species exoskeletons of some marine species

PNW Coastal Water Properties PNW Coastal Water Properties ––►► From From PruterPruter and and AlversonAlverson (1972):(1972):

T-S Diagrams, processes and origns

T-S Diagrams with nutrients

Columbia River Estuary Mixing Columbia River Estuary Mixing ––►► TT--S diagrams, S diagrams,

summer mixing:summer mixing:

►► Winter mixing: Spring mixing:Winter mixing: Spring mixing:

UpwellingNo upwelling

KnudsenKnudsen’’s Relations s Relations ––►► Combining linear mixing with conservation of mass yields powerfuCombining linear mixing with conservation of mass yields powerful constraints l constraints

for layered channel flowsfor layered channel flows

►► The The net transport of waternet transport of water is conserved along the channel:is conserved along the channel:

Net transport = ANet transport = A11 uu11 –– AA11’’ uu11’’ + F V+ F V= A= A22 uu22 –– AA22’’ uu22’’

►► Layer salinityLayer salinity is steady: is steady:

SS11 AA11 uu11 = S= S11’’ AA11’’ uu11’’ and and SS22 AA22 uu22 = S= S22’’ AA22’’ uu22’’

►► This can be reThis can be re--arranged to:arranged to:

(1(1-- SS22/S/S22’’) A) A22 uu22 = (1= (1-- SS11/S/S11’’) A) A11 uu11 + F V or+ F V or

(S(S22’’/S/S22 --1) A1) A22’’ uu22’’ = (S= (S11’’/S/S11 --1) A1) A11’’ uu11’’ + F V+ F V

►► This can be used to determine the ratio of the velocities in theThis can be used to determine the ratio of the velocities in the two layers, the two layers, the nonnon--conservative term, or salinity depending on what is known. Multiconservative term, or salinity depending on what is known. Multiple layers ple layers and mixing between layers can be added and mixing between layers can be added –– ““Box ModelsBox Models””. .