Flashcards in Changing Climate Deck (42):
What is weather?
The state of the atmosphere at a given time and respect, with respect to variables such as temperature, moisture, wind velocity and barometric pressure
What is climate?
Long term weather pattern of a an area, including temperature, precipitation and wind, how weather acts over many years
What is icehouse?
Lower temperatures, ice caps and glaciers, huge increase in ice coverage then increases drop in global temperatures by reflecting more if subs radiation back into space, ice sheets present at poles
What is greenhouse?
Lack of ice coverage, overall increase in global temperatures, increase amount of solar radiation reaching earth or change in concentration off gases in the atmosphere
How can climate affect extinction events?
Extinction of species can be influenced by climate change, organisms thrive in limited range of conditions, if these change can lead to species wiped out
How can isotopes of oxygen be used to indicate climate change?
Atoms of oxygen within water can vary, 99.76% O16 and 0.20% O18. O16 lighter so evaporates easier, O18 left in the ocean. In icehouse, O16 locked on land as precipitated as snow or ice, so conc of O18 in sea increases in cooler climate. Evidence in caco3 shells
How can carbon isotopes be used to indicate temperature change?
Common is C12, 98.9%, and less common C13, 1.1%. Plants preferentially take up C12, so in hotter tropical climates, more tree ratfish biomass, and concentration of C13 in the ocean increases
What am causes climate change?
Change to amount of heat energy from solar radiation reaching the surface
What is a runway effect?
Equilibrium changes and causes positive feedback
How does positive feedback occur in an icehouse?
Increased snowfall, reflects now radiation as high albedo, temperatures drop even further, results in increases snow and ice so even more reflection, could lead to snowball earth
How does positive feedback occur in a greenhouse?
Small inc in temp allows oceans to release more Co2 than they absorb, traps not IR radiation, raising temperature and releasing more Co2
How can climate changes be predicted?
Milankovich cycles, cycle cause by changes in amount if radiation reaching the earth from the sun over time, not because sun changes output in energy, but due to earths orbit around the sun that varies in three predictable cycles
What is eccentricity?
Earths orbit changes shape to become more elliptical over a period of 100 000 years, means increased difference in seasons
What is obliquity?
The tilt if the earths axis which is responsible for our changing seasons, changes up to 3 degrees over cycle of 41000 years . Smaller tilt promotes growth of ice sheets as warmer winters result in more moisture and snowfall
What is precession?
Eccentricity and obliquity together cause this cycle where the inclination if the earths axis changes in relation to where it is in the orbit period of 19 000 and 23 000 years
What is aphelion?
Point in a planets orbit when it is furthest from the sun, usually elliptical
What is perihelion?
The point in a planets orbit when it is closest to the sun
What is the evidence for milankovich cycles?
Blue Lias and kimmeridge clay in Lyme Regis in Dorset, cyclic pattern of beds in 41 000 year cycle, correlates with obliquity cycle
What is a Milankovich cycle?
Cyclical changes in the rotation and orbit if the earth, correlating with climactic effects
What are the concerns surrounding global climate change?
Sea level rise leading to coastal flooding and erosion, cities close to the sea at risk
Why is sea level difficult to measure?
Sea level varies with tide, atmospheric pressure, wind, temperature and salinity, and isostatic changes
What are isostatic changes in sea level?
Se level changes due to uplift or subsidence of the continental crust. Often sinks when loaded with ice or sediment, rising again when such loads are removed. Only seen in affected region
What are eustatic changes in sea level?
Sea level changes are due to changes in the volume of the ocean basins it volume of water in them. Changes are seen worldwide
How are last sea levels measured?
Seismic evidence to find Unconformities due to transgression or regression
Using exposed geology to estimate the areas of flooded continents through time
Oxygen isotopes to assess the last temperatures and therefore amount of ice
What geological features indicate changes in sea level?
Raised beached and cliff lines, submarine forests, marine organisms found in younger sediment
What are Vails sea level curves?
Data collected to show patterns at many levels, high level in Cretaceous with MOR activity, linked to astronomical cycles
What geological evidence is there for sea level changes in the Pleistocene?
Studies if deep sea microfossils from Atlantic cores show 30 glacial events during Pleistocene
Measurement of oxygen isotope ratio, show volume of ice temporarily removing water from the system
Study if uplifted coral reef terraces on tropical islands show sea level was higher
What added the mechanisms of sea level change?
Eustatic, changes when volume of water in oceans change, or volume of ocean basin changes
How does volume of water on ocean change?
Linked with climate change and involves locking up water on land as ice and snow resulting in sea level fall. Glacial episode results in marine regression, ice melt results in marine transgression
Change in volume of surface water as it expands or contracts with temperature
How does volume of the ocean basin change?
Involves altering relative levels of continents and ocean basins. MOR activity results in smaller volume as it takes up lots of space-calculations fit with Vails curve. Results in increase subduction and flooding of margins. Variation in rate of mantle convection
Effects of mountain building and erosion
Breaking up of continents cause isostatic sinking
How is mass extinction correlated with sea level falling?
Area of shallow seas benefits marine life so high diversity. Sea label fall reduces amount of continental shelf submerged, reduced habitat, so lower biodiversity and extinctions occur. Rapid fluctuations most damaging
How does sea level rising correlate with mass extinction?
Increase in area of shallow waters, triggers bloom if marine plankton, bacterial decomposition results in high biological oxygen demand, so anoxic conditions and mass extinction. Anoxic events recognised by formation of black shales rich in organic material
Where was Britain located in the Cambrian?
Located 60 degrees south of the equator, drifted northwards due to plate tectonics
What was the climate of Britain before the most recent quaternary ice age?
Elephants bison and lions present in deciduous forests, sun tropical climate, died out due to advance of ice sheets
How can corals be used as evidence for paleoclimactic change?
Modern reefs live in narrow range of conditions, thrive 30 degrees N/S of the equator assume fossil reefs requires similar conditions. Found in Silurian and lower Carboniferous in Britain
How can plants be used as evidence for paleoclimactic change?
Tree rings indicate dry seasons
Tree rings indicate variation in growth, due to seasonal climate - none in tree rings if the Carboniferous
Upper Carboniferous plants grew to extreme heights, in tropical climate
Lead size correlated to climate temperature and humidity
Pollen grains, from birch and pine indicate cooler, from oak and beech, warmer
How can coal be used as evidence for paleoclimactic change?
Sufficient thickness of peat needed to create economic coal deposit, need highly productive ecosystem, tropical in Equatorial
How can desert sandstone be used as evidence for paleoclimactic change?
Formed in desert, 20/30 degrees from equator
How can evaporites be used as evidence for paleoclimactic change?
Form where rainfall is low and evaporation rapid in hot deserts
How can tillites be used as evidence for paleoclimactic change?
Ancient Boulder clay deposits are glacial in low latitude areas or high altitude
How can reef limestone be used as evidence for paleoclimactic change?
Mainly formed if colonial corals, restricted to latitudes that provide conditions