Glacier – A slowly moving mass or river of ice formed by the accumulation and compaction of snow on mountains or near the poles.
Ice Cap – Mass that covers less than 50,000 km² of land area (usually covering a highland area). E.g Iceland
Ice Sheet – Mass of glacier ice that covers surrounding terrain and is greater than 50,000 km2, also known as continental glacier. It can be several kilometres thick. E.G. Antarctic Ice Sheet.
The Quaternary Period – last c.2 million years
• The Pleistocene Epoch – from 11,700 yrs to 1.8 million years bp
• The Holocene Epoch – last 11,700 yrs
The Pleistocene
• At the time of the Pleistocene, the continents had moved to their current positions.
• Sheets of ice covered all of Antarctica, large parts of Europe, North America, and South America, and small areas in Asia.
• There were about 20 cycles when the glaciers would advance and retreat as they thawed and refroze.
Climate in the Pleistocene
• The epoch experienced both warmer periods (INTERGLACIALS) and colder periods (GLACIALS)
• Each lasting thousands of years each
• The processes of erosion, transportation and deposition by ice, have had a dramatic effect on the landscape
Evidence for Climate Change
• Ice cores are cylinders of ice drilled out of an ice sheet or glacier
• Ice cores contain information about past temperature, and about many other aspects of the environment
• Ice encloses small bubbles of air that contain a sample of the atmosphere – CO2 levels indicate global temperatures at the time.
• Oxygen Isotopes from ocean bed cores, indicate past climatic conditions
• The ratio between heavy and light oxygen in marine sediments is a universally accepted technique.
Causes of Climate Change
Milankovich Cycles
• Eccentricity – Earth’s orbit moving from circular to more elliptical, changing the amount of radiation the Earth receives
o Every 100,000 years
• Obliquity – Tilt of Earth’s axis, affects the Earth’s seasonal extent
o Every 41,000 years
• Precession – Direction of the Earth’s axis rotation, affects the timing of the seasons
o Every 21,000 years
Other Causes of Climate Change
• Variations in Solar Energy
o Increasing evidence suggesting sunspot activity may significantly effect our climate
• Changes in Oceanic Circulation
o Effects exchange of heat between oceans and atmosphere
o Long term effects on climate
o Short term effects on climate – El Nino
• Meteorites
o Reduction of incoming radiation
o Lowering global temperatures
• Volcanic Activity
o World temperatures lowered by single eruption
• Plate tectonics
o Redistributions of land masses
o Long term effect on climate
o Drifting into different latitudes
• Composition of Atmosphere
o Gases increased or changed following eruptions
o Greenhouse gases leading to global warming
Shorter-term Climate Change
Loch Lomond Stadial (12,500 yrs bp)
A rapid decline in temperature, by around 6-7C, resulting in ice sheet advance for approximately 1,000 years.
The Little Ice Age (1300-1900)
Temperatures fell by around 1-2C on average, resulting in abandoning of farming in Scandinavia, rivers freezing in the UK and many alpine glaciers re-advancing.