Chapter 15
Ocean Water and
Ocean Life
Section 15.1
The Composition of
Seawater
The Composition of Seawater
Salinity – is the total amount of solid
material dissolved in water.
• Because the proportion of dissolved
substances in seawater is such a small
number, oceanographers typically express
salinity in parts per thousands.
• Most of the salt in seawater is sodium
chloride, common table salt.
The Composition of Seawater
• Sources of Sea Salt
– Chemical weathering of rocks on the
continents is one source of elements found in
seawater.
– The second major source of elements found
in seawater is from Earth’s interior.
• Volcanic eruptions emitted water vapor and
elements – chlorine, bromine, sulfur and boron.
Salts in Seawater
The proportion of dissolved
substances in seawater is usually
expressed in
A.
B.
C.
D.
Parts per hundred.
Parts per thousand.
Parts per ten thousand.
Parts per million.
Which of the following is a source of
dissolved substances in the ocean?
A. Chemical weathering of rocks
B. Evaporation of water from the seas and
ocean
C. Excretions from marine organisms
D. Melting icebergs and sea ice
The Composition of Seawater
Salinity
• Processes Affecting Salinity
– Processes that decrease salinity:
•
•
•
•
Precipitation
Sea ice melting
Icebergs melting
Runoff from land
The Composition of Seawater
Salinity
• Processes Affecting Salinity
– Processes that increase salinity:
• Evaporation
• Formation of sea ice
Natural Processes Affecting Salinity
Which does NOT decrease salinity?
A.
B.
C.
D.
Precipitation
Runoff
Evaporation
Ice melting
The Composition of Seawater
Ocean Temperature Variation
• The ocean’s surface water temperature
varies with the amount of solar radiation
received, which is primarily a function of
latitude.
• Temperature Variation with Depth
– The thermocline is the layer of ocean water
between about 300 meters and 1000 meters
where there is a rapid change of temperature with
depth.
– The thermocline is a very important structure
because it creates a barrier to marine life.
Variations in Ocean
Surface Temperature
Variations in Ocean
Water Temperature
The Composition of Seawater
Ocean Density Variation
• Density is defined as mass per unit
volume. It can be thought of as a measure
of how heavy something is for its size.
• Factors Affecting Seawater Density
– Seawater density is influenced by two main
factors: salinity and temperature.
The Composition of Seawater
Ocean Density Variation
• Density Variation with Depth
– The pycnocline is the layer of ocean water
between about 300 meters and 1000 meters
where there is a rapid change of density with
depth.
Variation in Ocean
Water Density
Differing amounts of solar radiation
across Earth’s latitude affect the
ocean’s
A.
B.
C.
D.
Salinity in the thermocline.
Density at the surface.
Temperature at the surface.
Density in the thermocline.
Which of the following occurs when
the ocean’s salinity increases?
A.
B.
C.
D.
Density increases
Density decreases
Temperature increases
Temperatures decreases
Which of the following occurs
when temperature decreases?
A.
B.
C.
D.
Density decreases
Density increases
Salinity increases
Nothing happens
The layer of ocean water between 300
meters and 1000 meters where there
is a rapid change in density.
A.
B.
C.
D.
Thermocline
Transition zone
Pycnocline
Deep zone
The Composition of Seawater
Ocean Layering
• Oceanographers generally recognize a threelayered structure in most parts of the open
ocean: a shallow surface mixed zone, a
transition zone, and a deep zone.
• Does not exist in high latitudes because there
is no rapid change in temp or density.
1. Surface Zone
•
•
•
Shallow (300 to 450 meters)
Zone of mixing
Sun-warmed zone
The Composition of Seawater
Ocean Layering
2. Transition Zone
– Between surface layer and deep zone
– Thermocline and pycnocline
3. Deep Zone
– Sunlight never reaches this zone.
– Temperatures are just a few degrees above
freezing.
– Constant high-density water
Ocean Zones
Which of these is NOT one of the three
layers of the ocean?
A.
B.
C.
D.
Photic zone
Surface zone
Transition zone
Deep zone
Where would you not find this threelayered structure of the open ocean?
A.
B.
C.
D.
High latitudes
Low latitudes
Deep ocean zone
Intertidal zone