Research methods Flashcards
What methods can we use to research past conditions on Earth?
Boreholes
Ice cores
Pollen
Insects
Paleo modelling
Paleo oceans
Caves
Lakes
Coral
Fauna
Historical
Plant Macros
What data can we use to research the past conditions on Earth?
Proxy data
Direct data
What is Proxy data?
Preserved physical characteristics of the environment that can stand in for direct evidence of past climates
- stuff that is inferred from evidence
What is direct data?
Data that is gathered from an original first hand source
- stuff that is recorded
Give examples of proxy data
Animal and plant fossils
C12-C14 isotope ratio
O16-O18 isotope ratio
Mg-Ca in calcite deposits
Rock deposits
Air bubbles in ice cores
Give examples of direct data
Written accounts
Historical record (meteorological)
What does the strength of a record depend on?
The timescale (Length of time and resolution)
The geographical area
The ability to accurately record an event
What happens to raw proxy data?
Gets calibrated against modern record climate data. If there isn’t any, it gets more qualitative than quantative
What are ice cores? What can they show us?
A cylinder of glacial ice made up of layers that preserve climate evidence from the past.
- Accumulation rate
- air temperature
- summer temperatures
- atmospheric gas concentration
- volcanic activity
- sea ice concentration
- atmospheric circulation
- solar activity
How do ice cores show accumulation rate?
thickness of layer = rate of precipitation
more thick = more snow
more snow = warmer temp
How do ice cores show summer temperatures?
Give example
melt layers = layers without gas in
more melt layers = warmer summer because the water melts, dispelling gas
e.g. trends in melt layers of ice in NE Antarctic Peninsula
How do ice cores show us atmospheric gas concentrations?
bubbles in ice can be shaved, melted or crushed to release gas. Gas can then be tested
How can ice cores show us air temperatures?
Analyse the gas concentrations. More greenhouse gases = warmer because they would have insulated more.
Analyse the water isotope ratio. More O-18 than O-16 means warmer because it requires more energy to evaporate O-18 = heavier.
How can ice cores show us volcanic activity?
Layers of ash in the ice = volcanic activity
Tephra can spread a long way. If geochemically identical ice is found in two separate places, we can find the extent of the eruption
Test for acidity - more acid, more volcanic. Run electric current because acid is conductive
How can ice cores show us sea ice concentration?
Test salinity. More salinity = more sea ice because sea ice is made from frozen sea water (-1.8) rather than freshwater.
Can be used to predict extent by comparing different places.
How can ice cores show us atmospheric circulation?
Aerosols carried in air currents get deposited on glaciers e.g. dust from storms.
- the more aerosols found mean better circulation because dust storms do not start in icy places
Can also be used to predict climate changes in other parts of globe - conditions such as drought needed to start the storm
How do ice cores show us solar activity?
Beryllium-10 is made by Beryllium reacting with cosmic rays near surface of earth. More Beryllium-10 means more cosmic rays, means anomalies in solar radiation e.g. solar wind or Milankovitch theories of orbit. (eccentricity)
INDIRECT
Pros of ice cores
- will reliably give evidence
- gives huge range of proxy data in a small sample
- hundreds/thousand of years
- relatively easy to collect/access
Cons of ice cores
- EXPENSIVE
- demanding (-36)
- permanent/semi permanent camps
- drills can malfunction
- kerosene
- gas can diffuse
What is radioisotope analysis?
Using radiation given off by C-14 to determine the movement of elements through natural systems
How does radio isotope analysis work?
- Living organisms absorb C-14 into their tissue
- when they die, C-14 decays into other atoms
- when they decay they release gamma rays
- these strike RIIDs and convert it to an electrical signal
What is radioisotope analysis used for?
- what plants and animals lived where and how long ago
- how much carbon in atmosphere when animal was alive
- temperature ranges can be found by comparing it to the dead animals temperature preferences
- trophic levels and food chains/webs
- how plants and animals spread after glacial retreat
Pros of radioisotope analysis
- samples can be moved to examination site
- gains info that cannot be gained any way else
- dates ancient materials
- pretty accurate
- small samples
- 63,000YA is a while ago
Cons of radioisotope analysis
- radioactive samples need to be shielded
- radiation damage to humans
- sample has to contain C-14 to be studied
- half life = 5000 years. Some stuff e.g. rocks just too old
- expensive
- sample is destroyed
- sample can be contaminated
What is oxygen isotope analysis?
Method using the ratio of oxygen isotopes in a sample to gather information about past environmental conditions such as past temperatures, rainfall, and water quantity in ice sheets
O-16 and O-18 are analysed
How does oxygen isotope analysis work?
The mass of O-16 and O-18 in a sample are taken and then the ratio of these masses are calculated
More O-16 means temps were cooler - it is lighter and therefore condenses last
More O-18 means temps were warmer - it is heavier and therefore evaporates last.
Pros of oxygen isotope analysis
- available anywhere that water chemistry has been preserved
- not limited by age
- good understanding of natural climate cycles changing over time and the human impact
- accurate
Cons of oxygen isotope analysis
- expensive
- complicated
- ratios can be influenced by other factors
- marginal seas may not represent the big picture
- cannot be applied below CCD
What are magnesium/calcium ratios?
Using the magnesium/calcium ratio in samples such as foraminifera, water and soil to determine past conditions
How does the Mg/Ca ratio in foraminifera show past conditions?
Mg/Ca ratio in shells tells us about temperature.
- Warm temperatures = more Mg. Expends energy to use Mg but it’ll be okay in warm temps
How does the Mg/Ca ratio in water show past conditions?
Shows alteration in water chemistry and trends can be used to predict past and future data
- ratio increased over past 10s of millions of years. Triggered changes in organisms that build massive CaCO3 reefs
- ratio identifies processes that alter the oceans physiochemical properties
What physiochemical properties can Mg/Ca ratios influence?
Why are they important?
- physical properties e.g. freezing/boiling point
- solvation properties
- molecular properties e.g. size/shape/volume
- amino acid properties e.g. acidity
Allows scientists to understand a substance’s behaviour and predict hazards. How to help environment.
How can the Mg/Ca ratios in soil show past conditions?
- good soil structure has Mg/Ca ratio of 1:2
- any less is instable, and more than 10:1 is a deficiency.
Bad because:
- poor aeration (bad gas exchange and harmful pathogens)
- bad plant growth (bad roots and mineral uptake)
- bad plant health (bacteria/viruses)
- bad crop yields
Identifying these in a sample can point to bad soil quality in the past, so we can predict condition that could have lead to it.
How has life on earth influenced transpiration?
- plants evolve and colonise land
- transpiration returns water vapour to the atmosphere which increases rainfall in other areas and can make new plants grow, which build up the stream
