HYDROSPHERE

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HYDROSPHERE

• Liquid part of the earth including oceans, ice
  caps, lakes, rivers, underground aquifers, soil
  water, atmosphere, living organisms
• How much of earths water is fresh? salt?
• 97.4 salt water - only 2.6 fresh water
• Of that 2.6, over 80 is in ice caps glaciers
• 0.59 is in ground water
• lt0.001 in atmosphere
• Remainder in lakes, soil water, rivers and
  organisms (in decreasing order of storage)
• Earths water budget - water cycle!

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Freshwater as a resource

• Renewable through evaporation from the seas and
  precipitation (solar powered)
• Demands for freshwater include
• Human consumption (10)
• Irrigation (70)
• Industry (20)
• Demands increase with increasing population
• Unequal distribution of freshwater

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Human impacts on water cycle

• Global warming - may disrupt rainfall patterns
• Withdrawing of ground water faster than it can be
  replenished
• Pollution
• Deforestation
• Increased demand
• Inequity of use

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Sustainable use of freshwater

• Methods of increasing freshwater supply
• Rain barrels
• Dams and reservoirs
• Water purification
• Desalination (3/4,000L)
• Storm water management
• Methods of reducing use - Simon!

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Oceanic Circulation

• Major oceanic currents have an important role in
  the global transfer of energy
• 3 types of currents based on powering factor
• Tidal - small scale
• Wind - surface
• Density - subsurface

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Surface currents

• Caused by the drag of the wind on the water and
  the Coriolis Effect
• As you already know surface winds blow in regular
  patterns due to unequal heating of the earth and
  the Coriolis Effect
• Water is set in motion by these winds
• Coriolis effect is the same on moving water as it
  is on moving air - deflection to the right in N
  and to left in S

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More on surface currents

• Westerly winds produce eastward moving currents
  at mid latitudes in both hemispheres
• Trade winds produce westward moving currents at
  low latitudes
• Currents are deflected by the continents creating
  gyres
• North Pacific Gyre consists of California
  current, Kuroshio current , North Pacific current
  and a north Equatorial current

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Gulf Stream

• Part of North Atlantic Gyre
• Flow of warm water from equator northward
• Has an important role in climate regulation in
  eastern USA and western Europe
• Climate in western Europe is surprisingly mild
• San Francisco is 1,600 km further south than
  Dublin but has a similar climate

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El Niño

• Periodic disruption of trade winds due to
  breakdown of atmospheric pressure gradient
• Without wind water is no longer pushed offshore
  from eastern Pacific and piled up in western
  Pacific
• As a result there is no upwelling of cold
  nutrient-rich water in eastern Pacific which has
  many consequences

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Impacts of El Niño

• Warmer water expands north and south of the
  equator
• Warm water species range extensions e.g.
  sunfish (Mola mola)
• Atypical weather patterns

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More El Niño impacts

• Record rainfalls in Ecuador and NW Peru
• Droughts in agricultural regions of Bolivia and
  southern Peru
• Severe droughts in Australia, southern India,
  Indonesia and southern Africa
• Severe coastal storms along west coast of North
  America, mild winter in eastern NA
• Economic disasters - collapse of peruvian anchovy
  fishery due to decreased productivity (from lack
  of upwelling)

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Deep Ocean Currents

• Caused by density differences (deep water is not
  affected by wind)
• Density is a function of temperature and salinity
  - cold, salty water is more dense than warm, less
  salty water
• Dense water sinks and displaces less dense water
• Called thermohaline circulation

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Conveyor Belt

• Driven by sinking in northern N. Atlantic
• Warm salty surface water reaches the N. Atlantic
  (Gulf Stream) and cools becomes more dense as
  salt is excluded during ice formation
• This dense water sinks and flows south towards
  Antarctica (deep current)
• There it is cooled further and continues to flow
  along the bottom of the ocean into Atlantic,
  Indian and Pacific basins

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• Upwelling occurs in Pacific and Indian Oceans and
  water returns as surface flow to North Atlantic
• Significance
• Oxygenates deep oceans
• Redistributes heat from equator to poles
• Returns nutrients, CO2 from deep water to surface

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Will global warming affect thermohaline
circulation?

• Possibly!
• Through the melting of polar ice caps the density
  of water at the poles would be decreased
  resulting in a reduction of thermohaline strength