glaciers Flashcards
Glacier
a body of ice formed on land and in motion contained by terrain, most commonly valleys.
how is a glacier formed?
-Removing air makes snow solid
Mass of ice that moves over land
-ice sheets
-snow compresses forming layers of glaciers
-glaciers provide fresh water
-indicate global warming
-snow that doesn’t melt before the next year
Accumulation
annual snowfall + ice which does not entirely melt in the summer months builds up over time
Terminus
where glacier ice starts to melt
Ablation
the process of melting ice on a glacier
Glacier Mass Balance
The mass balance of a glacier is the gain and loss of ice from the glacier system. A glacier is the product of how much mass it receives and how much it loses by melting.
cryosphere
frozen water part of the Earth’s system (covers about 20% of Earth’s surface)
Natural Characteristics of Glaciers + Ice Sheets
- Sea ice
- land covered by glaciers
- land covered by ice sheets, including ice shelves
- land such as tundra covered by snow every year
- land underlain by permafrost
- peri-glacial zones on the margins of ice-bound land
Tundra
Permafrost
Permafrost is a permanently frozen layer on or under Earth’s surface. It consists of soil, gravel, and sand, usually bound together by ice. Permafrost usually remains at or below 0°C
Peri-glacial zones
The periglacial environment is a cold climate, frequently marginal to the glacial environment, and is characteristically subject to intense cycles of freezing and thawing of superficial sediments.
Natural Processes Causing the Melting of Glaciers + and Ice Sheets
-Variations in Solar Energy
-Volcanic Activity
-Oceanic Circulation Changes
-Plate Tectonics
Natural Processes - Variations in Solar Energy
the solar energy received by the Earth is not constant, earth is subject to three independent cycles every 26,000 40,000 and 100,000 years producing natural climatic cycles.
Natural Processes - Volcanic Activity
this can cause significant amounts of dust and gases to be injected into the atmosphere. Lead to both warming and cooling, greenhouse gases from volcanoes can lead to warming.
Natural Processes - Oceanic Circulation Changes
the direction of ocean currents has changed regularly in recent geological times and many continents have experienced changed climate as a result, as there is an exchange of heat between oceans + the atmosphere.
Natural Processes - Plate Tectonics
the redistribution of landmasses has long been caused by plate tectonics. The movement of plates causes variation
Human Activities Causing the Melting of Glaciers + and Ice Sheets
-Alteration of the composition of gases in the atmosphere
-Alteration of landscapes
-Direct addition of heat to the atmosphere
Human Activities - Alteration of the composition of gases in the atmosphere
this factor is considered by scientists to be the greatest cause of global warming. Increased injection of greenhouse gases such as carbon dioxide, methane + ozone etc. into the atmosphere.
Human Activities - Alteration of landscapes
this factor is considered to be the second most important in causing global warming. Removing forests for crops reduces evaporation and changes the dynamics of radiation created by forest canopies.
Human Activities - Direct addition of heat to the atmosphere
many of the activities associated with everyday life directly add heat to the atmosphere. Burning fossil fuels for electricity production, transportation, heating, and cooling of residents and workplaces.
Last Glacial Maximum
17,000-21,000 years ago, temperatures were 6°C cooler, most liquid water was held in ice caps, sea levels were 125m lower + there were land bridges between landmasses.
Holocene Climatic Optimum
De-gelation following the LGM, a period between 9000 + 5000 years ago when global annual average surface temperatures were warmer than today, the climate was wetter, sea level + coasts further inland.
The Greenhouse Effect
effect is a process that occurs when gases in Earth’s atmosphere trap the Sun’s heat.
Burning fossil fuels like coal and oil puts more carbon dioxide into our atmosphere.
Too much of these greenhouse gases can cause Earth’s atmosphere to trap more and more heat. This causes Earth to warm up.
Fossil Fuels
natural fuels such as coal, oil or gas formed in the geological past from the remains of living organisms.
Where does CO2 come from?
- life
- volcanoes
- ocean
- fossil fuels
Gases contributing to global warming
- methane
- CFCs
- Ozone (O₃)
- Nitrous oxide (N₂O)
What are the impacts of melting glaciers and ice sheets?
- Sea Level Rise
- People Movement
- Agricultural Output
- Freshwater Resources
- Plant + animals communities
- Disease
- Natural disasters
Impact - Sea Level Rise
-during 20th century sea levels rose by 20cm
-predicted to rise another 20 – 60cm by 2100
-Since water expands as it warms, as ice melts into the ocean it expands.
Impact - People Movement
-people who rely on glaciers + ice sheets for freshwater
-people moving due to their not being traditional food
-people moving since their homes have become inundated.
Impact - Agricultural Output
-crops yield will decrease by 30%
-water sources become unreliable + crop failures increased
Impact - Freshwater Resources
-increased melting can lead to enlarged glacial lakes causing lake banks to burst
-once a glacier is gone that water source is gone
-glacier stores 75% of the world’s freshwater
Impact - Plant + animals communities
-animals lose their habitats as ice retreats
-changes in temp are changing migration patterns
-impacting ecosystems
Impact - Disease
-mosquitoes + ticks may expand their range as temp rise
-impacting people + animals living in cold places
Impact - Natural disasters
-flooding increased + other natural disasters
-expanding populations + deforestation can make areas suspectable to flooding
-change ecosystems
Accelerated melting processes
- Surface melting due to warmer temperatures which can reveal dirty (dark) ice and speed up melting.
- Moulins lubricate and accelerate the flow of glaciers to the coast.
- Sea ice shelves melt as warmer oceans melt the underside of the shelves.
Dark Ice
Dark ice speeds up the melting process (less reflection of heat due to the darker colour).
Moulins
A vertical cylindrical shaft in the ice by which surface meltwater flows down from the surface to the base of a glacier.
Cryoconite
a grey to black coloured mineral composed of windblown sediments such as soot, dust & soil.
Cryoconite can accelerate ice melting (due to reducing albedo- reflectiveness) and lead to the formation of moulins that can cause the ice sheet to melt from its base.
