1) Salinity
a) Total amount of solid material dissolved in water
b) Salinity expressed as parts per thousand (0/00)
c) Average salinity of saltwater is 3.5%
d) Most is sodium chloride, common table salt
2) Sources of Sea Salt
a) Chemical weathering of rock is one source
i) Dissolved minerals reach the ocean through runoff from rivers and streams
ii) About 2.3 billion metric tons per year
b) Earth’s interior is second major source
i) Water vapor from volcanoes filled the ocean
ii) Many elements were brought to the ocean in this water vapor
3) Processes Affecting Salinity
a) Salinity is relatively constant throughout the ocean
b) Salinity ranges from 3.3% to 3.8%
c) Precipitation, runoff, and melting ice add water to the ocean and lower
the salinity
d) Evaporation and freezing remove fresh water from the ocean and
increase salinity
4) Temperature Variations
a) The ocean’s temperature varies with amount of solar radiation
b) Solar radiation varies with latitude
5) Temperature variation with depth
a) Temperature profiles change as latitudes change
b) High latitudes have very little change from top to bottom
c) Low latitudes have little change from surface to 300m
d) 300m to 1000m (thermocline) is a steady decrease in temperature
e) >1000m the temperature levels off at its coldest temperature
6) Ocean density variations
a) Density = mass per unit volume
b) Density changes the vertical position of seawater
i) Low density water rises
ii) High density water sinks
7) Factors affecting seawater density
a) Density influenced by salinity and temperature
b) Temperature has the greatest effect on density
i) Warm water = low density
ii) Cold water = high density
c) Density increases as salinity increases
8) Density Variation with depth
a) High latitudes have very little change in density from surface to bottom
b) Low latitudes, changes in density are opposite the change in
temperature (temp down, density up) through the pycnocline
c) Pycnocline acts as barrier between high density and low density
9 ) Ocean Layering
a) The ocean is layered according to density
b) Three layers based on density- surface zone, transition zone and deep zone
10) Surface zone
a) Surface gets the most solar radiation
b) Surface water is mixed by wind and waves
c) Steady temperature and density profile down to about 300m
11) Transition zone
a) 300m to 1000m in depth
b) Rapid decrease of temperature with depth
c) Rapid increase of density with depth
12) Deep zone
a) Below transition zone, no sunlight reaches this zone
b) Temperature and density stay constant in this zone
c) Contains about 80% of the water in the ocean
13) Surface Circulation
a) Ocean currents-masses of ocean water that flow from one place
to another
b)Surface currents- water that flows horizontally in the upper part
of the ocean’s surface
c) Develop due to friction between the ocean and the wind
d) Can be a seasonal current or a long term general circulation
pattern
14) Gyres
a) Large whirls of water within an ocean basin
b) Five main ocean gyres: North Pacific, South Pacific, North Atlantic, South
Atlantic and the Indian Ocean
c) The Coriolis Effect influences the movement pattern of the currents
d) Northern Gyres flow clockwise
e) Southern gyres flow counter-clockwise
15) Ocean currents and climate
a) Warm water currents help to move heat to cooler areas
b) Cold water currents help to moderate the temperature of warmer areas
c) Ocean water movement accounts for about 25% of the heat transfer in
the Earth’s system
16) Upwelling
a) Rising of cold water from deeper layers to replace warmer surface
water
b) Wind, combined with the Coriolis Effect move warm surface water
allowing cold water to come up from deeper layers
c) Brings greater concentrations of nutrients to the surface
17) Density currents
a) Vertical currents of ocean water that result from density
differences among water masses
b) Denser water sinks, less dense water rises
c) Density changes due to temperature and salinity variations
18) High Latitudes
a) Most deep-ocean density currents start at latitude
b) Decreased temp, increased salinity cause an increase in
density and a sinking of water
c) Water then works its way towards the equator
d) Warmer surface water takes the place of the cold dense water
19) Evaporation
a) Density is increased by the removal of the fresh water thru
evaporation
b) Increased salinity causes the water to sink
20) Conveyor Belt
a) Ocean water travels from the Atlantic to the Indian to the
Pacific and then back
b) Surface water near the equator is warmed and moves towards
the poles
c) Cools at the poles and sinks and moves back towards the
equator and is upwelled