MGIS process (AOS_2)

Question 1

the spatial distribution of land cover (define land cover)

Answer 1

according to the FAO (Food and Agricultural Organisation of the United States), ‘land cover is the observed biophysical cover on the Earth’s surface’, including vegetation, water bodies, plantations and built environments

Question 2

spatial distribution of MGIS during the LGM

Answer 2

• 20,000 years ago
  
  • Global mean temperature cooled by ~8◦C
  • Tropical land temperature cooled by ~2.6◦C
  • Sea level was 125 metres lower than present
  • Ice sheets extended to approx. 40◦N because cooling amplified at high latitudes and over the ice sheets
• High latitude regions were drier than today, causing drought and desertification

Question 3

spatial distribution of MGIS during the HCO

Answer 3

• 8,000 years ago
  
  • Increases of up to 4◦C near the North Pole
  • Temperatures were generally warmer than today, but only in summer and in the northern hemisphere
  • Sea levels rose by ~3 metres
  • Current desert regions of Central Asia were extensively forested due to higher rainfall
• The Sahara desert was dotted with numerous lakes due to higher rainfall

Question 4

distribution of MGIS on a global scale

Answer 4

• Ice covers 20% of the Earth’s surface
  
  • Located on every continent except Australia
• Antarctica the largest covering (9% of the Earth’s land area)

Question 5

Milankovitch Cycles

Answer 5

Over long timescales, big changes in climate can be explained in the way the Earth orbits the sun, also known as the Milankovitch cycles:

- Eccentricity where the Earth's orbit changes shape (is sometimes circular, and sometimes more of an ellipse), happens over 100,000 year period; works against the season (titled towards in summer but sun is far away/titled away in winter, near sun)
- The Earth's axis tilts (every 41,000 years; more tilt equals less ice equals warmer climate)
- Precession where the Earth's axis wobbles; 13,000 years ago the tilt of the Earth was reversed (winter, sun is far/summer, sun is near) resulting in warm summers -- more melting -- warm globally
- These cycles of changes vary the distance between the Earth and the Sun, changing the amount of sunlight the Earth receives, and where that sun is received

Question 6

natural proccesses MGIS: changing ocean currents

Answer 6

• Air above the water is affected by the temperature of the water as it passes over
  
  • The ocean current system in the Atlantic Ocean, called the Atlantic Meridional Overturning Circulation (AMOC), is responsible for western Europe’s warm temperatures
  • Rising water temperatures and changes to the salinity of the world’s oceans is causing the AMOC to weaken
  • The addition of the significant amounts of fresh water from melting glaciers makes the salty surface water lighter and less likely to sink, clogging up the circulation’s flow and weakening the AMOC, resulting in more extreme weather
  • According to a 2018 study, the AMOC is the weakest it’s been in at least 1,600 years
• Greenland’s ice is melting six times faster now than it was four decades ago

Question 7

natural processes: volcanic activity

Answer 7

• If significant amounts of dust and gases can rise high enough, they will be spread around the Earth in the stratosphere by high level winds
  ○ Dust can lead to cooling because sunlight is reflected back into space
  ○ Gases lead to warming because it traps sunlight
• Mount Agung eruption in Bali in 1963 caused large amounts of ash, blocking solar radiation, reducing global average temperature by 0.5 degrees Celsius in the 2 years after

Question 8

human processes (alteration of gases in the atmosphere)

Answer 8

• Industrialisation has increased injection of greenhouse gases such as CO2, methane and nitrous oxides (e.g. methane: est. preindustrial concentration was 848 parts per billion, 2010 concentration was 1800 parts per billion)
  
  • Destruction of ecosystems, forests and swamps that normally trap and reduces (sequester) greenhouse gases such as CO2 and methane, had led to the release of such gases
  • This increase in greenhouse gases results in global average temperature to increase
• The planet is around 1 degrees C warmer than it was 160 years ago

Question 9

human processes (windblown dust and soil or dark snow)

Answer 9

• Land clearing and farming (as well as natural disasters such as bushfires) have led to particulate matter such as soil and dust being taken by air currents and deposited on snow areas, accelerating melting
  
  • Dust deposition is a major cause of reduced albedo (solar radiation absorption) on ice surfaces and therefore is increasing ice melting
• Satellite data show that the margins of the ice sheet have darkened by as much as 5% per decade since 2001