Properties of Sea Properties of Sea WaterWaterAugust 27August 27

RemindersReminders

Text copies – Kinkos?Text copies – Kinkos? New Student Orientation – 11:45 am New Student Orientation – 11:45 am

Today – MSL Conference RoomToday – MSL Conference Room Send E-Mail to Heather – Send E-Mail to Heather –

hhavens@marine.usf.eduhhavens@marine.usf.edu

Figure 3.14 (Stewart): The sea-floor topography of the ocean with 3km resolution produced from satellite altimeter observations of the shape of the sea surface. From Smith and Sandwell.

Physical Properties of Physical Properties of Sea WaterSea Water

Water = HWater = H22OO

- Can dissolve more substances than any other fluidCan dissolve more substances than any other fluid- Polar molecule – can form chains (polymers) up to Polar molecule – can form chains (polymers) up to 8 molecules long8 molecules long - leads to very high specific heat – large heat - leads to very high specific heat – large heat

capacitycapacity- Molecular chains lead to high surface tension, highMolecular chains lead to high surface tension, high viscosityviscositySurface Tension -> Capillary Waves -> Air-Sea Surface Tension -> Capillary Waves -> Air-Sea

momentum transfer -> Gravity Waves and momentum transfer -> Gravity Waves and Ocean CirculationOcean Circulation

H+ H+

O-2

Polar Molecule

Physical Properties of Physical Properties of Sea WaterSea Water

Density (Density (ρρ) – kg/m) – kg/m3 3 – determined by temp. and – determined by temp. and salinity (conductivity)salinity (conductivity)

Pressure (p)Pressure (p)Viscosity (Viscosity (νν) – causes resistance) – causes resistanceSurface TensionSurface TensionThermal ConductivityThermal ConductivityThermal ExpansionThermal ExpansionFreezing PointFreezing PointBoiling PointBoiling PointLatent Heat Latent Heat CompressibilityCompressibilityHeat CapacityHeat Capacity

All Conservative - All scalar quantities - no All Conservative - All scalar quantities - no direction involveddirection involved

Other PropertiesOther Properties

- Dissolved OxygenDissolved Oxygen- PhosphatePhosphate- NitrateNitrate- SilicateSilicate- Optical Char.Optical Char.

*Not Conservative* - depend on *Not Conservative* - depend on biology and geochemistrybiology and geochemistry

Temperature and SalinityTemperature and Salinity

- Two most important properties of sea water Two most important properties of sea water – control density– control density

- Density increases with depth, otherwise, Density increases with depth, otherwise, would be unstable would be unstable

- If surface waters cool, become heavier and If surface waters cool, become heavier and sinksink

- deep water is formed in the polar - deep water is formed in the polar regions this regions this wayway

- If excess evaporation over precipitation, get If excess evaporation over precipitation, get dense saline water at the surface, causes dense saline water at the surface, causes overturningoverturning - overturning occurs at low latitudes and in - overturning occurs at low latitudes and in the the Mediterranean SeasMediterranean Seas

SalinitySalinity

- Defined as a ratio of conductivities between Defined as a ratio of conductivities between sea water sample and standard samplesea water sample and standard sample

- No units – psu is not a unit – will get nasty No units – psu is not a unit – will get nasty letter from Mileroletter from Milero

- Salinity is composed mostly of ClSalinity is composed mostly of Cl-- (chloride) (chloride) ions (~19 ‰) and Naions (~19 ‰) and Na++ (sodium) ions (~10.6 (sodium) ions (~10.6 ‰) but many other components‰) but many other components

- Salts come from weathering of rocks on land Salts come from weathering of rocks on land and from hydrothermal ventsand from hydrothermal vents

- Ratio of components is constantRatio of components is constant

Salinity changesSalinity changes

Due to:Due to:- Evaporation vs. Precipitation- Evaporation vs. Precipitation- Runoff from land- Runoff from land- Mixing of water masses- Mixing of water masses- Freezing and melting of sea ice- Freezing and melting of sea ice

- Highest salinities are found in surface Highest salinities are found in surface layers at mid latitudes due to evaporationlayers at mid latitudes due to evaporation

- S = 35.0 to 36.5 above permanent S = 35.0 to 36.5 above permanent thermoclinethermocline

- Below 1000m, S= 34.5-35.0Below 1000m, S= 34.5-35.0

Figure 6.3A: Sea-surface temperature anomaly for January 2005 relative to mean temperature shown in Figure 6.2 using data published by Reynolds and Smith (1995) in the Climate Diagnostics Bulletin for February 1995.

Figure 6.3B: Annual range of sea-surface temperature in °C calculated from the Reynolds and Smith (1995) mean sea-surface temperature data set. Contour interval is 1°C with heavy contours at 4°C and 8°C. Shaded areas exceed 8°C.

Figure 6.5 Zonal average of sea-surface salinity calculated for all oceans from Levitus (1982) and the difference between evaporation and precipitation (E - P) calculated from data shown in Figure 5.14.

Figure 6.6 Water transported by the atmosphere into and out of the Atlantic. Basins draining into the Atlantic are black, deserts are white, and other drainage basins are shaded. Arrows give direction of water transport by the atmosphere, and values are in Sverdrups (1Sv=106 m3). Bold numbers give the net transport for the Atlantic. Overall, the Atlantic loses 0.32Sv, an amount approximately equal to the flow in the Amazon River. From Broecker (1997).

DensityDensityDetermined by temperature, salinity, and pressureDetermined by temperature, salinity, and pressureTemperature (T) – ranges from ~-3°C to 34°CTemperature (T) – ranges from ~-3°C to 34°C

- mean temperature of the ocean's waters is: - mean temperature of the ocean's waters is: TT = = 3.5°C3.5°C- easiest to measure - easiest to measure - temperature differences are expressed in - temperature differences are expressed in Kelvin (K) to avoid confusion with actual Kelvin (K) to avoid confusion with actual temperaturetemperature

K = °C + 273.15K = °C + 273.15Salinity (S) – ranges from 0 to 36.5 ‰Salinity (S) – ranges from 0 to 36.5 ‰

- mean salinity is - mean salinity is SS = 34.7 = 34.7- T and S often used as a tracer of water masses- T and S often used as a tracer of water masses

The distribution about the mean is small: 50% of The distribution about the mean is small: 50% of the water is in the range: 1.3°C <T< 3.8°C 34.6 the water is in the range: 1.3°C <T< 3.8°C 34.6 < < SS < 34.8 < 34.8

DensityDensity

- Surface waters have high T and higher Surface waters have high T and higher S – How can this be stable?S – How can this be stable?

- T effects out weigh S effects, so - T effects out weigh S effects, so warmer, saltier warmer, saltier water is still lighter water is still lighter than cooler, fresher than cooler, fresher water.water.

= = (S,T,P)≈1000 kg/m(S,T,P)≈1000 kg/m33 to 1030 kg/m to 1030 kg/m33

- SeeSee

http://fermi.jhuapl.edu/denscalc.htmlhttp://fermi.jhuapl.edu/denscalc.html

The Oceanic Mixed Layer and The Oceanic Mixed Layer and Thermocline Thermocline

Wind blowing on the ocean stirs the upper layers leading Wind blowing on the ocean stirs the upper layers leading to a thin to a thin mixed layermixed layer at the sea surface having constant at the sea surface having constant temperature and salinity from the surface down to a depth temperature and salinity from the surface down to a depth where the values differ from those at the surface – where the values differ from those at the surface – typically 0.02-0.1°C colder than at the surface typically 0.02-0.1°C colder than at the surface

The depth and temperature of the mixed layer varies from The depth and temperature of the mixed layer varies from day to day and from season to season in response to two day to day and from season to season in response to two processes: processes:

Heat fluxes through the surface heat and cool the surface Heat fluxes through the surface heat and cool the surface waters. Changes in temperature change the density waters. Changes in temperature change the density contrast between the mixed layer and deeper waters. The contrast between the mixed layer and deeper waters. The greater the contrast, the more work is needed to mix the greater the contrast, the more work is needed to mix the layer downward and visa versa. layer downward and visa versa.

Turbulence in the mixed layer mixes heat downward. The Turbulence in the mixed layer mixes heat downward. The turbulence depends on the wind speed and on the turbulence depends on the wind speed and on the intensity of breaking waves. Turbulence mixes water in intensity of breaking waves. Turbulence mixes water in the layer, and it mixes the water in the layer with water in the layer, and it mixes the water in the layer with water in the thermocline. the thermocline.

Figure 6.7 (Stewart): Growth and decay of the mixed layer and seasonal thermocline from November 1989 to September 1990 at the Bermuda Atlantic Time-series Station (BATS) at 31.8°N 64.1°W. Data were collected by the Bermuda Biological Station for Research, Inc. Note that pressure in decibars is nearly the same as depth in meters (see §6.8 for a definition of decibars).

Figure 6.8 Typical temperature and salinity profiles in the open ocean. AAC: At 62.0°S, 170.0°E in the Antarctic Circumpolar Current on 16 January 1969 as measured by the R/V Hakuho Maru. Warm Pool: At 9.5°N, 176.3°E in the tropical west Pacific warm pool on 12 March 1989 as measured by Bryden and Hall on the R/V Moana Wave. BATS: At 31.8°N, 64.1°W near Bermuda on 17 April and 10 September 1990 as measured by the Bermuda Biological Station for Research, Inc. Data are included with Java Ocean Atlas.

- In-situ temperature: what you In-situ temperature: what you measure - decreases with depthmeasure - decreases with depth

- Potential temperature (Potential temperature (θθ): ): temperature water would have if temperature water would have if raised “adiabatically” to the surfaceraised “adiabatically” to the surface

- adiabatic: no exchange of heat with - adiabatic: no exchange of heat with surroundingssurroundings

Define: Define: σσtt==(S,T,0) – 1000 (S,T,0) – 1000 - shorthand for density of seawater at - shorthand for density of seawater at atmosphericatmospheric pressure pressure

At great depths, must account for At great depths, must account for

compressibility of seawater by using compressibility of seawater by using Potential Temperature to compute Potential Temperature to compute Potential Density - σPotential Density - σθ - the density a parcel - the density a parcel of water would have if it were raised of water would have if it were raised adiabatically to the surface without change adiabatically to the surface without change in salinity in salinity

σσθθ==(S,(S,θθ,0) – 1000,0) – 1000

Figure 6.9 (Stewart): Profiles of Left in situ and potential temperature and Right sigma-t and sigma-theta in the Kermadec Trench in the Pacific measured by the R/V Eltanin during the Scorpio Expedition on 13 July 1967 at 175.825°E and 28.258°S. Data from Warren (1973).

Figure 6.10 (Stewart): Vertical sections of density in the western Atlantic. Note that the depth scale changes at 1000 m depth. Upper: σθ, showing an apparent density inversion below 3,000 m. Lower: σ4 showing continuous increase in density with depth. From Lynn and Reid (1968).

Figure from http://www.cygres.com/OcnPageE/OcnPageFig4E.html

T-S diagrams:

Figure from http://www.cygres.com/OcnPageE/OcnPageFig4E.html

Figure from http://www.es.flinders.edu.au/~mattom/ShelfCoast/notes/figures/fig10a1.html

From http://www.es.flinders.edu.au/~mattom/ShelfCoast/notes/figures/fig10a2.html

Sketch of a TS-time diagram as it is developed from frequent observations. Measurements are made every other day. Each dot represents a measurement. Colors indicate different months. Changes from one measurement to the next indicate the variability on time scales of days. On a few occasions several measurements were made in a single day, and the resulting standard deviations in temperature and salinity are indicated by vertical and horizontal lines. They represent the daily variability.