IB GEOGRAPHY

• Coastal margins


  All areas that are affected by coastal processes and that affect the coastline

  
• ENSO/ El Niño Southern Oscillation

  A reverse of the normal atmospheric circulation in the southern Pacific Ocean, bringing warm water and low pressure to the eastern Pacific, and cool water and high pressure to the western Pacific. It occurs once every 2-10 years.

  
• La Niña


  An intensified version of normal atmospheric processes, for example increased flooding in normally humid areas and increased drought in areas that are dry.

  
• Eustatic sea-level rise


  Worldwide changes in sea level caused by the growth and decay of ice caps, thereby locking up and later releasing water from ice
• Isostatic sea-level rise


  Localized changes in the relative level of the land and sea, caused by the depression of the Earth's crust, such as for the weight of an ice sheet. Following deglaciation, the crust beneath the weight begins to rise again, and relative sea level therefore falls.
• Advancing coastlines


  Coasts that grow either due to deposition or a fall in sea level

  
• Retreating coastlines


  Coasts that get smaller either due to erosion or a raise in sea level

  
• Global commons


  Resources that are outside the reach of any nation. They may be exploited or degraded and so need to be managed carefully.
• Surface ocean currents


  Caused by the influence of prevailing winds blowing steadily across the sea.

  
• Gyres


  Dominant pattern of surface ocean current, is circular flow. These patterns are clockwise in the northern hemisphere and anticlockwise in the southern hemisphere.

  
• Warm ocean currents


  Move water away from the equator
• Cold ocean currents


  Move towards the equator
• Warm ocean currents


  Lead to an increase in temperature at the polar areas

  
• Many eastern currents


  Move cold water, rich in nutrients, from the ocean floor to the surface, this support important fisheries.
• Specific heat capacity


  The amount of energy it takes to raise the temperature of a body
• Water needs more energy to heat up than land
• It takes longer for water to lose this heat, so places close to sea are cool by day but mild by night. This effect is reduced the more distance from the sea.</b>
• Land is hotter than the sea by day but colder by night
• Warm surface causes low pressure

  Air blows from high pressure to low pressure, causing a movement of water from the colder area to the warmer areas. This exposes colder deep water behind them, and so it repeats.
• Ocean conveyor belt


  Deep, grand-scale circulation of the ocean's waters effectively transfers heat from the tropics to colder regions, such as northern Europe.
• Oceanic convection


  Occurs from polar regions where cold salty water sinks into the depths and makes its way towards the equator.

  
• The north Atlantic is warmer than the North Pacific, so there is proportionally more evaporation in the North Atlantic. The water left behind has more salt in it due to the evaporation, and therefore it is much denser, which causes it to sink. Eventually the water is transported into the Pacific where it mixes with more water and its density is reduced.
• Density of seawater


  Affected by temperature (high = less dense), salinity (increases= more dense) and pressure (increases = more dense). Denser water sinks.
• El Niño


  A warming of the eastern pacific that occurs at intervals between 2-10 years, and last up to 2 years. It refers to the warm current that appeared off the coast of Peru, but it forms part of a much larger system.

  
• Normal conditions in the Pacific Ocean

  The walker circulation is the east-west circulation that occurs in low latitudes. Near South America winds blow offshore, causing upwelling of the cold, rich waters. By contrast, warm surface water is pushed into the western Pacific. Normally sea surface temperatures (SSTs) in the Western Pacific are over 28ºC, causing an area of low pressure and producing rainfall. By contrast, over coastal South America SSTs are lower, high pressure exists and conditions are dry.

  
• El Niño conditions in the Pacific Ocean

  During El Niño episodes the pattern is reversed. Water temps in the Eastern Pacific rise as warm water from the Western Pacific flows into the eastern Pacific. During ENSO events: SSTs of over 28ºC extend much further across the Pacific, low pressure develops over the eastern Pacific, high pressure over the west, heavy rainfall occurs over coastal South America, Indonesia and Oceania experience warm, dry conditions.

  
• Benefits of ENSO


  • Increased pacific storm activity → less Atlantic storm activity → US East Coast fewer hurricanes
  • Farms in the US Midwest → higher yields due to milder temperatures
  • US benefited by $15 billion in the 1997-98 El Niño event

  
• Drawbacks of ENSO


  • Indonesia → prolonged droughts → coffee production, oil palm production and its hydroelectric production affected
  • Dry conditions → Forest fires more likely to occur → 2 billion tonnes of carbon released
  • East Africa → heavy rainfall → stagnant pools →mosquitoes breed → disease
  • 2015-16 → caused water and food shortage for 100 million people
  • Philippines→ drought reduce rice harvest by 15%
  • Colombia → fish catches down 20%
• La Niña


  An intermittent cold current that flows from the east across the equatorial Pacific Ocean. It is an intensification of normal conditions whereby strong easterly winds push cold upwelling water off the coast of South America into the western Pacific. Its impact extends beyond the Pacific and has been linked with unusual rainfall patterns in the Sahara Desert, India and with unusual temperature patterns in Canada.

  
• Managing the impacts of El Niño and La Niña is difficult for many reasons. In the past, El Niño events couldn't be predicted with much accuracy. Now many sensors have been placed across the Pacific that predict El Niño months in advance. This allows Peru to stock up with food resources and to relocate people away from vulnerable areas.
• Cyclone


  Term used in the South Pacific and Indian Ocean

  
• Hurricanes


  Term used in the Atlantic Ocean and north-east Pacific
• Typhoons


  Term used in the north-west Pacific
• Characteristics of cyclones/hurricanes/typhoons


  • Low-pressure systems
  • Bring heavy rainfall
  • Strong winds
  • High waves
  • Cause hazards such as flooding and mudslides
  • Deliver enormous quantities of water to the areas they affect
  • Unpredictable, and it is not always possible to give more than 12 hours' notice → no time for proper evacuation systems to be implemented.
• How cyclones/hurricanes/typhoons develop


  1. Intense low-pressure systems over tropical oceans

  2. Winds spiral rapidly around a calm central area known as the eye

  3. The diameter of the whole hurricane may be as much as 800 km → although the very strong winds that cause most of the damage are found in a narrower belt, up to 300km wide.

  4. Pressure falls to as low as 880 millibars → very low pressure, and the strong contrast in pressure between the eye and outer part of the hurricane lead to strong gale-force winds

  5. They move excess heat from low latitudes to higher latitudes.

  6. They develop in the westward-flowing air just north of the equator (easterly wave)

  7. They begin as a small-scale tropical depression, localized areas of low pressure that cause warm air to rise

  8. These trigger thunderstorms that persist for at least 24h and may develop into tropical storms, which have greater wind speeds of up to 118km per hour.

  9. However, only about 10% of tropical disturbances become hurricanes
• Conditions needed for hurricanes to form

  • Sea temperatures must be over 27ºC to a depth of 60 m (it is the energy that drives the hurricane)
  • Low pressure area must be far enough away from the equator so that the Coriolis force (forced caused by the rotation of the earth) creates rotation in the rising air mass → if to close to the equator there is insufficient rotation for a hurricane to develop
  • Conditions must be unstable → some tropical low-pressure systems develop into hurricanes, but not all of them
• Saffir-Simpson scale


  Developed by the National Oceanic and Atmospheric Administration, assigns hurricanes to one of five categories of potential disaster based on wind intensity. Only used for the Hurricanes forming the Atlantic and Northern Pacific; other areas use different scales.
• The unpredictability of hurricane paths make the effective management of hurricanes difficult
• The strongest storms do not always cause the greatest damage
• The distribution of the population increases the risk associated with hurricanes (coastal settlements)