Chapter 5 Water and Seawater by nskW5k

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									    Chapter 5
Water and Seawater

Essentials of Oceanography
        7th Edition
         Atomic structure
Atoms are the building
blocks of all matter
Nucleus contains:
  Neutrons (no charge)
  Protons (+ charge)
Outer shell(s) contain:
  Electrons (– charge)    Figure 5-1
      The water molecule
Composed of 1 oxygen and
2 hydrogen atoms (H20)
Contains strong (covalent)
bonds between atoms
Unusual bend in geometry
Has polarity (oppositely
                             Figure 5-2a
charged ends)
  Interconnections of water
         molecules
Polarity causes water
molecules to form weak
(hydrogen) bonds
between water molecules
Water sticks to itself and
to other substances
Allows water to be the
universal solvent            Figure 5-3
        Water as a solvent
Water dissolves table
salt (NaCl) by
attracting oppositely
charged particles
Pulls particles out of
NaCl structure to
dissolve it

                         Figure 5-4
Water in the 3 states of matter
Latent (hidden) heat = energy that is either
absorbed or released as water changes state




                                 Figure 5-5
The ocean moderates coastal
       temperatures
Water has high
heat capacity, so it
can absorb (or
release) large
quantities of heat
without changing
temperature
Moderates coastal
temperatures           Figure 5-6
Hydrogen bonds in H2O




         Figure 5-8
       The formation of ice
As water cools to 4°C:
  Molecules slow
  Water contracts
  Density increases
Below 4°C:
  Hydrogen bonds form
  Water expands
As water freezes:
                         Figure 5-11
  Expands by 9%
      Snowflake geometry
All snowflakes
have 6-sided
geometry
Caused by
water’s polarity
and ability to
form hydrogen
bonds              Figure 5-12
                 Salinity
Salinity = total amount
of solid material
dissolved in water
Can be determined by
measuring water
conductivity
Typically expressed in      Figure 5-15

parts per thousand (‰)
Constituents of ocean salinity
Average seawater
salinity = 35‰
Main constituents
of ocean salinity:
  Chloride (Cl–)
  Sodium (Na+)
  Sulfate (SO42–)
  Magnesium (Mg2+)
                            Figure 5-13
       Salinity variations
    Location/type           Salinity
Normal open ocean           33-38‰
Baltic Sea               10‰ (brackish)
Red Sea                 42‰ (hypersaline)
Great Salt Lake              280‰
Dead Sea                     330‰
Tap water                 0.8‰ or less
Premium bottled water        0.3‰
        Ocean buffering
Ocean pH = 8.1
(slightly basic)
Buffering
protects the
ocean from
experiencing
large pH changes

                    Figure 5-18
Processes affecting seawater
          salinity
Processes that decrease seawater salinity:
  Precipitation
  Runoff
  Icebergs melting
  Sea ice melting
Processes that increase seawater salinity:
  Sea ice forming
  Evaporation
The hydrologic cycle




                  Figure 5-19
  Surface salinity variation
Pattern of surface
salinity:
  Lowest in high
  latitudes
  Highest in the
  tropics
  Dips at the Equator
Surface processes       Figure 5-20
help explain pattern
   Surface salinity variation
High latitudes have low surface salinity
  High precipitation and runoff
  Low evaporation
Tropics have high surface salinity
  High evaporation
  Low precipitation
Equator has a dip in surface salinity
  High precipitation partially offsets high evaporation
Global surface salinity




    Figure 5-21
Salinity variation with depth
Curves for high and
low latitudes begin at
different surface
salinities
Halocline = layer of
rapidly changing
salinity
At depth, salinity is
uniform                  Figure 5-22
         Seawater density
Factors affecting seawater density:
  Temperature ↑, Density ↓ (inverse relationship)
  Salinity ↑, Density ↑
  Pressure ↑, Density ↑
Temperature has the greatest influence on
surface seawater density
Density and temperature
 variations with depth




                 Figure 5-24
Pycnocline and thermocline
Pycnocline = layer of rapidly changing
density
Thermocline = layer of rapidly changing
temperature
Present only in low latitude regions
Barrier to vertical mixing of water and
migration of marine life
Ocean layering based on density
Mixed surface layer (surface to 300 meters)
  Low density; well mixed by waves, currents, tides
Upper water (300 to 1000 meters)
  Intermediate density water containing thermocline,
  pycnocline, and halocline (if present)
Deep water (below 1000 meters)
  Cold, high density water involved in deep current
  movement
     Seawater desalination
                                    Distillation
Desalination
                                            Figure 5-25
methods:
  Distillation
     Solar
     Heat
  Electrolysis         Reverse
  Reverse osmosis      Osmosis
                      Figure 5-26
  Freeze separation
 End of Chapter 5


Essentials of Oceanography
        7th Edition

								
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