Enquiry question one Flashcards
(30 cards)
Who discovered ice ages and how?
Louis Agassiz - 1830s
In the Swiss Alps
He noticed that certain areas had similar features
What is Uniformitarianism?
The assumption that the same natural laws and processes that operate in our scientific observations now have always operated in the universe in the past and apply everywhere
Also known as the Doctrine of Uniformity or the Uniformitarian principle
What are ice cores and how do they help us?
They are large cylinder samples of ice
Bubbles trapped in the ice contain CO2 from the atmosphere
Low conc = glacial periods
High conc = interglacial periods
What period do we currently live in?
Quaternary period - started 2.588 million years ago
What are epochs?
Periods of geological time - relating to times where geological strata were laid down
They denote changes during the Earths time e.g mass extinctions
What are the different epochs of the Quaternary period?
Pleistocene - the beginning of the period about 2,588,000 to 11,700 years ago
Holocene - an interglacial period, age of man
Anthropocene - from 1950 starting when there was significant human impacts of Earth until now
Why is it hard to reconstruct the past using glacial landscapes?
Each time a glacial period occurs, the previous features and landforms are remoulded
What are geomorphological processes and their impact?
Types of Mechanical, Chemical and Biological weathering
How often do glacial periods occur?
Round about every 100,000 years
What are stadial and interstadial periods?
Stadial - A short period of intense cold
Interstadial - A short period of intense warmth (relative to the intense cold)
What are the Milankovitch theories (long term) on the causes of glacial cycles?
Eccentricity of orbit - Changes from elliptical to more circular orbit and back every 100,000 years approx. Low eccentricity = low seasonality, so promotes glaciation
Axial tilt/Obliquity - varies between 22.8 and 24.4 degrees over 41,000 years. Impacts the intensity of light hitting the poles. Low obliquity = low seasonality
Wobble/Precession - The Earth wobbles on its axis over a 21/22,000 year cycle. ⬆️ in the variation of irradiation of the N hemisphere —> Causes summer and winter temperature variation —> variations in ice volume. Precession works with eccentricity to control the level on insolation at 65 degrees N. Glaciation favorited when N.hem summer are at the largest earth-sun distance
- These three come together to minimize the amount of solar energy reaching the N.hem in the summer
- cooler summers means less ice melts, allowing it to build up
What are feedback mechanisms?
Positive - climatic feedback can either amplify a small change
Negative - or diminish the change and make it smaller
Example of positive feedback?
1) Small increases to snow and ice cover can increase surface albedo
2) More solar radiation is reflected back into space
3) Could lead to more snow and ice cover
Example of negative feedback?
1) increased global warming & industry —> more evaporation—> increase in cloud cover
2) Increased cloud cover reflects solar energy back into space
3) Reducing intensity of global warming
1) Ice sheet dynamics disrupt THC
2) Warming waters in the Arctic disrupts ocean currents
3) Less warm water from the gulf stream creating global cooling in N.Europe
What are the short term factors that cause climate change?
Solar forcing:
Energy emitted by ☀️ varies due to ☀️spots.
cycles every 11 years
reliable records dating back 400yrs
Maunder minimum - 1645 - 1715 - little ice age, temp = 1 degree lower than today
Medieval warm period - 950 - 1250 - temp = 1 degree hotter than today
Volcanic causes:
Volcanoes have altered temperature
Highly explosive volcanoes (VEI 7+) eject huge amounts of ash, sulphur dioxide, CO2, and water vapor into the atmosphere
spreads globally, blocking out sunlight (global dimming)
1815- Tambora in Indonesia: temps dropped by 0.4-0.7 degrees for 2-3 years
ENSO cycles
Case study—> Loch Lomond Stadial
( Younger Dryas event )
- occurred 11,700BP to 12,900BP
- ice sheets began melting 18,000BP
- rapid deglaciation 15,000BP ago due to similar temps as today
- 12,500BP glacial conditions reoccurred and by 11,500BP temps were 6-7 degrees lower than today
- glaciers readvanced all over the world inc scotland, lake district and snowdonia
Reason: believed to be due to the draining of Lake Agassiz ( glacial lake in N. America) into Atlantic disrupting the THC (Thermohokine circulation) by cutting off the poleward heat from the gulf stream
Case study —> The little ice age
Proxy records - tell us that between 1550 - 1750 there was a trough of cold temps (perhaps 1-2 degrees lower) having many impacts
Abandonment of many hill farms in n europe
glaciers advanced down valleys
arctic sea ice spread further south with polar bears found in Iceland
rivers froze in UK, lowland europe and NYC
curling developed in scotland
argued that it never developed into a full blown stadia due to the onset of the industrial revolution GHGs creating a warming effect
What is the Cryosphere?
The parts of the Earths crust and atmosphere subject to temps below 0 degrees for some part of the year
2 roles:
- help regulate climate via the albedo effect
- it is a global store of freshwater
What are the different ice masses?
Ice sheet - a layer of ice covering an extensive tract of land for a long period 10-100,000 km2
Ice cap - miniature ice sheets in polar and sun polar regions that are relatively flat and high in elevation 3-10,000
Ice field - large expanse of ice covering a mountainous region and consisting of several interconnected glaciers 10-10,000
Valley glacier - glacier confined by valley walls 3-1500
Piedmont glacier - occur when steep valley glaciers flow onto relatively flat plains, where they spread out into lobes 3-1000
Cirque glacier - named for the bowl like hollows they occupy: cirques 0.5-8
Ice shelf - floating sheet of ice permanently attached to a land mass 10-10,000
What’s the difference between constrained/unconstrained glaciers?
Constrained - Have a physical limit such as valley glaciers where the landscape constrains where they are & tend to only drain one way
Unconstrained - Tend to be larger forms e.g ice sheets & caps. Thick, extensive and often submerge the landscape
What are the the two main types of glaciers?
WARM BASED 🔥
- other names: temperate, wet, alpine
- occur at high altitudes (outside of polar regions)
- water exists undersurface at temps below 0 due to a build up of pressure
- this melt water causes them to melt continually —> basal ice (ice at bottom of glacier)
- also has lots of debris at bottom, creating many subglacial deposits and landforms
COLD BASED 🥶
- occur in polar regions
- surface temps of -20 to -30 meaning temp at base still below 0
- limited surface melt in polar summer, so glacier is permanently frozen to the bed
- therefore basal layer has far less debris within it
What are the other two types (don’t really need to know)
Polythermal glacier -
Warm based but the margin is cold based
upper zone is cold based whilst the lower zone is cold based
due to extending into warmer climate zones
e.g glaciers on Svalbard
Surging glaciers -
can occur within warm based or polythermal glaciers
can flow at up to 100m a day
greenland outer glacier - 30m a day
leads to increased calving
What is the pressure melting point?
Defined as the temperature at which ice begins to melt under a given amount of pressure
Water melts at 0 degrees under ordinary atmospheric conditions
At hugger pressures, the melting point is lower
Allowing it to remain a liquid at below its normal freezing point
Describe the graphs
