The Hydrosphere

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The Hydrosphere

• Observatory textbook pages 200 to 213

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2. The Hydrosphere

• The hydrosphere consists of the Earths water
  resources oceans, lakes, rivers, streams,
  groundwater, and glaciers
• 97.5 of water on Earth is salt water
• Only 2.5 is freshwater!
• Fig. 6.26 on p. 201

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2.1 Inland Waters

• Inland waters are all the freshwater resources
  found on the continents (lakes, rivers,
  groundwater)
• A watershed is an area of land in which all
  inland waters drain into the same larger body of
  water (also called catchment area or drainage
  basin)
• eg St.Lawrence River watershed

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What is a watershed?
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St. Lawrence River Watershed
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Factors that affect how water flows within a
watershed

• Topography? slope of the land steep slopes drain
  easily and quickly
• Geology? type of rock holes or gaps in rock vs.
  compact clay
• Climate? rainfall, winds and temperature
• Vegetation? highly vegetated areas can slow water
  flow
• Development? a dam can prevent water from flowing
  freely

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2.2 The Oceans

• Five major oceans
• Pacific Ocean
• Atlantic Ocean
• Arctic Ocean
• Indian Ocean
• Southern Ocean (as of 2000)
• Two important factors when studying oceans are
  temperature and salinity

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Ocean Temperature

• Ocean temperature varies with depth, season and
  latitude

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Depth

• Sunlight warms the top layer of ocean water which
  is called the mixed layer
• Below 200m temperature drops quickly this zone
  of rapid temperature change is called the
  thermocline
• Beneath the thermocline at about 1000m, water
  temperatures are uniformly cold at about 4oC

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Ocean Temperature and Depth
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Season

• Oceans warm slightly in summer and cool slightly
  in winter.
• The changes in temperature are less pronounced
  than on the land because water loses or gains
  heat much more slowly than land.

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Latitude

• Ocean waters are 25oC to 28oC at the equator and
  only 12oC to 17oC in the temperate zones.
• They are colder still at extreme northern and
  southern latitudes (lt10oC).

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Ocean Salinity

• Salts dissolved from the lithosphere create a
  salty ocean. These salts dissolve as rivers flow
  over the ground and empty into the ocean.
• Salinity is a measure of the amount of salt
  dissolved in a liquid.
• Ocean salinity is about 3.4 to 3.7

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Ocean Circulation

• Water in the ocean is in constant motion.
• An ocean current is the movement of seawater in a
  certain direction.
• Ocean circulation is the combined effect of all
  currents that move in oceans.

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Surface Currents

• Wind driven ocean currents
• Push the top 400m of water
• eg The Gulf Stream current
• See map diagram on p. 204-205 of Observatory

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Ocean surface currents
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Subsurface Currents

• Occur at depths of more than 800m
• Due to variations in density between layers of
  water
• Cold water is more dense and tends to sink
• High salinity water is also more dense and sinks
  below less saline water

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Thermohaline Circulation

• The combined effect of surface and subsurface
  currents is termed thermohaline circulation
• Results in water being moved all around the globe
• Accounts for major transfers of heat
• Dramatically affects global weather patterns

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2.3 The Cryosphere

• The cryosphere is all the frozen water on the
  surface of the earth (pack ice, glaciers, frozen
  lakes, permafrost).

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Pack Ice

• Composed of the ice floating on the oceans near
  the North and South poles
• Extent of pack ice changes with seasons
• Due to the effect of global warming the extent of
  pack ice is shrinking

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Glaciers

• A glacier is a mass of ice on land, formed by
  compressed snow
• Contain 79 of worlds freshwater
• Largest glaciers are at the poles (eg Greenland
  icecap), but some smaller glaciers exist in
  mountain ranges (eg in BC and Alberta)
• Glaciers are also melting at a fast rate due to
  global warming
• The melting of glaciers and pack ice may lead to
  a rise in sea level and consequent flooding of
  low lying lands (eg Florida)

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A high alpine glacier
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2.4 Energy Resources from the Hydrosphere

• Hydraulic energy? energy derived from moving
  water
• Three main sources of hydraulic energy rivers,
  waves and ocean currents

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Hydroelectric Dams

• Convert a rivers hydraulic energy into
  electrical power
• Quebec derives almost all of its electricity from
  hydro dams
• Water flowing through the dams turbine creates
  electricity which is then distributed to cities
  and factories.
• Produce little greenhouse gases, but cause large
  areas of flooding upstream of the dam
• This flooding, in turn, can release toxic mercury
  into the environment

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James Bay Hydroelectric Dam
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Waves and Ocean Currents

• Buoys that rise and fall with the waves can be
  attached to turbines to create electrical energy
• Underwater turbines can harness ocean current
  energy much the same way a windmill operates
• Most of these ideas are still in the prototype
  stage

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2.5 Pollution and Degradation of Water Resources

• Chemical pollution? metals, mercury, PCBs, mine
  drainage
• Thermal pollution? heat discharge from factories
  can decrease oxygen content and lead to fish
  kills
• Oil spills? 6 million tonnes per year
• Plastics? north Pacific Gyre an ocean garbage
  dump

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Fish Kill
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Oil Spills
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North Pacific Trash Gyre
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Eutrophication

• Farming activities add excess fertilizers to
  rivers and lakes (mostly phosphorus and
  nitrogen).
• These excess fertilizers can stimulate algae
  growth.
• Excess algae growth can then lead to algae
  blooms, toxins being produced, reduced oxygen
  levels, fish kills and green scum forming on
  lakes.
• This whole process is called eutrophication.

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Eutrophication
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Eutrophication experiment conducted by the
University of Manitoba.Can you guess to which
side of the lake fertilizer was added?
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Hydrosphere Review

• Answer questions 20 to 36 on pages 215-216.
• Use your notes and refer to pages 200 to 213 in
  Observatory to guide you in your answers.

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