Lecture 26: Last 1000 years Flashcards
What has the last 1000 years consisted of and what period did it begin after?
Beginning after the medieval warm period, the last 1000 years has been characterised by major climatic events alongside the acceleration of anthropogenic changes
What has knowledge of the last 1000 years been substantially aided by?
People writing things down i.e. there are more instrumental and documental records, there is a plethora of palaeoclimate data
What two types of information can tree rings provide us with about the past?
Dendroclimatology and Dendrochronology
What are some of the oldest trees in the world?
Bristlecone Pine (>5kya) but suggestions that ones in Sweden are older
Why are Giant Sequoia trees good for palaeoclimate data? Where are they found?
They are large and provide magnified image of the past. California
What does the presence of scars on tree cores suggest?
Fires or pests may have hindered growth patterns
What climate characteristics can tree rings provide us with?
Temperature, precipitation, extreme events
What is a huge benefit of the tree ring data?
It is of extremely high resolution and can provide us with seasonal variation data
What are the two parts of tree ring bands which tell use about seasonal variation?
Early and Late wood
What is dendroclimatology?
This determines the climate conditions of the past predominantly by looking at the isotope composition
What can analysing the ratio of carbon 13 tell us in dendroclimatology about climate?
It determines the co2 concentration within cells of the tree which is then an indication of different climate characteristics such as temperature and precipitation
What can analysing the ratio of oxygen 18 tell us in dendroclimatology?
It determines the source of precipitation that the tree is experienced to which then provides information on the global temperature because (think to the ice/sea oxygen balance thing)
What is dendrochronology?
Constructing a chronological order of how the tree rings growth has changed over time
What can we do in dendrochronology to construct a longer term record of climate?
Pair up different parts of tree growth or from different trees with each other as some will cover an older period (they have died and so do not contain information on more recent periods) and others will be younger trees and cover the more recent period
What state can tree remains be in in order to be used for dendrochronology?
Dead, alive or fossilised
What are dendrochronology’s especially useful for?
radiocarbon dating
What type of carbon decays?
Radiocarbon e.g. 14C
What happens to radiocarbon over time?
It decays, at a known rate
How do we determine how radiocarbon has decayed?
Half life - this is when the atoms within the molecule start to transfer from the parent nuclei to the daughter nuclei
Simplify what half life means
The time it takes for half of the atoms that make up the molecule of 14C at a given point to have ‘decayed’ (been lost) from their initial state to their new state
What is the known rate of radiocarbon (14C) decay?
5730 + or - 30 years
What marks the starting point for when radiocarbon decay? Why?
All living things absorb radiocarbon and so when they die this absorption stops and so we have a starting point of how much radiocarbon it holds and therefore from which to work back from how much it has decayed since
How is the age of things determined using radiocarbon dating?
Looking at how much unstable radiocarbon (the radiocarbon which still has to decay) and stable radiocarbon (that which has decayed) is left in the molecule, then using the known rate of decay to work back when the decay process would have begun and therefore when the living thing died and its age.
How far back can radiocarbon dating stretch back to?
50kya