Seawater properties Flashcards
Distribution of free water on Earth
Ocean - 97%
Ice caps and glaciers - 2%
Rivers, lakes, wetlands, grasslands - <1%
Residence times
Ocean - 4,100 years
Atmosphere - 9 days
Properties of the water molecules
polar
cohesion, adhesion, dissolution, capillary action
cohesion
attachment of water molecules by hydrogen bonds
strong ‘skin’ on water surface
dissolution
action of water molecule separating component elements
due to polarity
adhesion
attachment of water molecules to other substances by hydrogen bonds
sticks to other stuff
sticks to solids (wetting)
capillary action
e.g. cohesion, adhesion, tendency of water to spread if a textile is dipped in water
Heat
energy produced by random vibration of atoms or molecules
Temperature
The response of an object to the input or removal of heat energy
Heat capacity
measure of heat required to raise the temp of one gram of a substance by 1 deg C
Thermal inertia
tendency of a substance to resist change in temp
Solvent
a substance capable of dissolving other polar molecules and ionic compounds
e.g. water
Salinity
measure of dissolved solids in seawater
seawater of salinity of 35% means that 3.5% of the seawater is dissolved substances and boiling away 100kg of seawater produces 3.5kg of residue
ocean salinity is 33-37%
constituents of seawater
origin: weathering of rock and input from deep crustal and upper mantle through volcanism
Na and Cl
Trace element
less than 1%
Dissolution of gases
gases from atmosphere dissolve in seawater at surface
found in different proportions due to different solubilities
increases with cold temp
N2 - 48%
O2 - 36%
C - 15%
pH
Water separates to form H+ ions and OH- (hydroxide) ions
acids release H ions and bases combine with themchange of pH unit is a ten-fold change in ion conc
Density of seawater
mass/volume in kg/m^3
pure water - 1000 kg/m3
seawater - 1020-1030
increases with salinity and pressure and decreases with temperature
Ice formation
Freezing point of pure water 0 deg C
of seawater -2 deg C
sensible heat - heat exchange accompanied by temp change
latent heat - heat exchange without change in temp (change in state)
latent heat of fusion - heat removed from a liquid during freezing or added to a solid during freezing that produces state change but not temp change
Vapor formation
evaporation - type of evap without reaching boiling temp
more energy needed to change water into vapor than vapor into ice
approx 50% of solar energy entering ocean results in evap
Propagation of light
sunlight is reflected, scattered, and absorbed on its way to and across the ocean
reflection - change in direction of light to return to medium of origin
scattering - dispersion or bounce of light waves
absorption - conversion of light energy into heat
Water absorbs all EM radiation - top meters absob all wavelengthsbut violet, green, and blue travel deeper into water column
Zones in water column
photic - thin film of lighted water on surface, 50-100m in depth but as deep as 600m, hosts most life
aphotic - dark, deep ocean that light cannot penetrate
Propagation of sound
sound - a form of energy transmitted by rapid pressure changes in an elastic medium
sound intensity decreases with depth due to spreading (propagation away from source), scattering (bouncing off bubbles and particles and organisms), absorption (conversion to heat)
sound travels much more efficiently than light in water
1500 m/s - increases with temp and pressure
min sound velocity at 1000m
Refraction - bending of light or sound waves as they move at an angle other than 90 deg between media of diff optical or acoustic densities
SOFAR layer - layer of min sound velocity in which sound transmission is unusually efficient for long distances - refraction
sonar - sound navigation and ranging
active sonar - device that sends pulses of high freq sound and analyzes echoes (for dpth measurements, geol, etc.)
