Past Climate Flashcards
(34 cards)
What data can we use to determine past climate in the quaternary?
Oxygen isotopes
(Ice cores)
How can oxygen isotopes help determine past climate?
Comparison of O16 and O18 (when in ice, it used to be water)
- O16 is lighter so more O16 will evaporate
- O18 is heavier so more O18 will condense
- the amount of O18 will depleted as the air moves northwards, as it gets colder
- in colder eras, even less O18 will evaporate from the equator, and then will fall more quickly. Very little will make it to the poles in a glacial
What physical evidence can be used to determine the oxygen isotopes ratio?
Ice cores
Foraminifera (forams)
How can ice cores be used to determine the oxygen isotopes ratio?
- banded: lighter = winter, darker = summer
- the bands vary in width due to: compaction, different levels of snowfall, some years more melting/snow blown away
- there are very small fluctuations/changes in the O18 concentration going back in time, showing different temperatures and how they changed
How can forams be used to determine the oxygen isotopes ratio?
Minute marine shelled creatures
- shells made of CaCO3 (CONTAINS OXYGEN)
- shells preserve 18:16O ratio so keep a record of the climate going back millions of years
What paleoclimatic factors can ice cores indicate?
- Oxygen isotope ratio
- atmospheric gas concentration in bubbles (CO2, CH4)
- volcanic eruptions in ash layers that can be dated radiometrically
(can go back 600,000 years)
What other factors often correlate with oxygen isotope ratio?
CO2 concentration
Temperature
How do warmer and cooler climates influence the 18O concentrations in
a) Ice cores
b) Sea
a) WARMER = more 18O
COOLER = less 18O
b) WARMER = less 18O
COOLER = more 18O
How do places at the same latitude compare with climate?
the climate differs
What factors can we use to find out Quaternary climate in Britain?
- DEPOSITS
- STRIATIONS AND ERRATICS
- POLLEN
- BEETLES (COLEOPTERA)
- TREE RINGS (DENDROCHRONOLOGY)
What kinds of deposits can be used to find out Quaternary climate in Britain?
- glacial
- periglacial
- fluvio-glacial
- interglacial
How can striations and erratics be used to find out Quaternary climate in Britain?
- orientation and distance
How can pollen be used to find out Quaternary climate in Britain?
- very abundant
- super readily preserved
- tells us the plants growing
How can beetles be used to find out Quaternary climate in Britain?
- more mobile than trees and therefore pollen
- rapidly responds to a change in climate
- hard parts are readily preserved
- some live in a very narrow temperature range
e.g. beetles in the fossil record found in the UK are now found in Northern Norway
How can tree rings be used to find out Quaternary climate in Britain?
- each ring is a new year
- Fat = good. Lots of precipitation, they grow faster
- Thin = poor, less precipitation
- scientists build tree ring chronologies by starting with living progressively older specimens (including archaeological wood) whose outer rings overlap with the inner rings of more recent specimens
- can put together to make up an history
How would you describe deciduous forest?
- warm and temperate summers
- nutrient rich soils
- has seasons so trees drop leaves in colder winter
How would you describe boreal forest?
- cold and frigid temperatures year round
- dry winters
- acidic, nutrient poor soils
How would you describe tundra?
- cold region with permafrost underneath
- frost moulded landscape
- treeless
What is ecological succession?
the change in an ecological community over time, from a relativelysparse landscape to a stable community of several different plants and animals
What is the process of ecological succession?
- Bare rock (glacial retreat?). No soil, no plants, the ground is exposed to weather with no shade
- Pioneer community - the first to colonise the land. They pave the way for the next stage of organisms
- Each stage results in the creation of more soil, bigger plants, more shade
- Succession moves through a series of successional stages, called seres
- Ultimately it ends up with a climatic climax
- Climatic climax in the climax community for that particular climate. In the UK this is often oak woodland
Describe the vegetation structure during succession
How quickly does this happen?
- Bare rock
- Lichens
- Mosses
- Grasses
- Herbaceous plants
- Small to large shrubs
- Large shrubs
- Established trees
Happens over hundreds of years
What is the name for ecological succession that started on a rock?
Lithosere
How many stages are in the Lithosere?
5
Describe the stages in the Lithosere
- A bare exposed rock site colonised by bacteria and then lichens
- they are pioneer species able to tolerate the lack of soils and water and widely fluctuating temps - Decay of lichens enables moss growth. Mosses retain water. Death of lichens and growth of mosses assist weathering and formation of organic matter that can be exploited by more complex plants
- Thus, grasses, ferns and small herbs colonise e.g. in water-retaining pockets
- their eventual death and decay further adds to the organic matter, increasing nutrient levels and water availability - Small shrubs e.g. gorse, bramble and broom colonise. they shade out some of the smaller grass species
- Pioneer trees such as birch, hawthorn and N-fixing Alder colonise and out-compete smaller species
- Larger trees such as ash colonise and out-compete smaller species. Slower growing deciduous trees such as oak colonise and shade out smaller species
- a stable, climax community forms such as a temperature deciduous woodland
