Chemistry - Ice Coring Flashcards
What is the basis of using 018 for determining past carbon cycles?
CO2 readily dissolves in water for CO2-H20 exhange, measured in foraminifera
How do foraminifera measure past temperatures?
O18 and O16 ratio determines temperature of surrounding water at time shell was formed.
How can O18 be used to measure evaporation?
O16 is lighter, thus surfaces contain greater proportions of O18 where more evaporation occurs.
How does O18 measure precipitation?
O18 condensates quicker than O16
How does O18?O16 relate lattiduinally in rain?
It is composed of more O16 due to less O18(precipitating first)
How does O18/O16 precipitation ratio relate to ice ages?
Colder temperatures in ice ages extend equatorially more-so, O18 thus rains at even lower latitudes, meaning higher O18 concentration than usual, whilst ice higher O16 concentration than usual.
How can past water ocncnetraiton be inferred?
Water trapped in glaciers or marine plants and animals.
Why can shells be harder to measure?
Because as they form, they incorporate more O18 than they do O16 regardless of oxygen ratio.
What is less O18 proportional to?
Colder temperatures
How else can temperature be inferred from shells?
Strontium and calcium balance
What is ice coring data based on?
Build up of distinct snow layers on glaciers and ice sheets.
What material in glaciers can be used for past climate inferrance?
Trapped bubble gas composition.
Pollen
Ions
Why is trapped ice usually younger than it actually should be?
Because snow and firn in the upper 10 meters must be compacted to trap air bubbles, meaning air can still diffuse.
What is past temperature determination based on?
O18 concentration.
Istotopic Fractionation
The relative partioniing of the heavier and lighter isotopes between two co-existing phases in a natural system
What is Oxygewn istootopic fractionation caused by?
Evaportation, condensation, thermal diffusion.
What is thermal diffusion caused by?
Temperature gradients, heavier isotopes moving towards colder regions.
How can thermal diffusion be used in measuring abrupt climate change?
Gas diffse in firn pores faster than heat does, meaning isotopic signals reach bubble trapping death before heat does, the degree of enrichnment telling you magnitude of climate change.
What does pollen tell you?
Terrestial activity nearby.
What do ions tell you?
Salinity and biogenic information.
How can ice layers be chronologically ordered?
Preserved annual layers dated through seasonal variations displayed isotopic compositions, dust content,.
Why cant seasonal variations be applied to antartica?
Earths orbital variations and their insolation.
What are ice core climatic records measured by?
Insolation changes that can be accurately calculated in passed millions of years
Orbital Turning
The process of adjusting geologic time scales to the corresponding milankovitch cycles in Earths orbital motion.
What is orbital turning based on
?
Orbital changes affect insolation and thus climate, sedimentation should reflect this.
What is another way of measuring time in ice?
Volcanic eruptions exhibited in the ice cores composition.
