Term 1 Isotopes & Climate Questions Flashcards
learn the concepts (36 cards)
How does isotope weight impact energy gain?
Heavier molecules have stronger bonds and are harder to bump up in energy level
Which isotope is preferentially used in reactions, and therefore more common in the product?
Lighter isotopes, as they have weaker bonds that are easier to break
What does a positive ratio of comparison mean?
A sample is enriched, or heavier than the standard
What does a negative ratio of comparison mean?
A sample is depleted, or lighter than the standard
How is the hydrological cycle isotopically monitored?
Through stable O and H isotopes in relation to VSMOW measured from seawater and precipitation, as condensation and precipitation correspond to isotopic fractionation
Which isotope preferentially occurs as gas?
Lighter isotopes, as their bonds are weaker to break and bump up an energy level into a gaseous state
Which isotope preferentially occurs as a liquid or solid?
Heavier isotopes, as their bonds are stronger and harder to break and bump up an energy level into a higher energy state
Where does Rayleigh Fractionation occur?
Deserts, evaporative lakes, and polar environments
What is the relationship between δ2H SMOW and δ18O SMOW and how is it used?
Linear, so it is used to determine H isotope value for a given O data point
How do polar O records indicate global temperature?
Precipitation sets in earlier in colder climates, depleting snow clouds of heavy water and leaving behind less of the heavier isotopes to fall in the poles than in warmer climates, creating an increase in 16O
How do isotope records indicate glacial periods?
Oceans become richer in heavier isotopes during glacial periods, as lighter water is trapped in the glaciers
What is a potential cause of Dansgaard-Oeschenger periods?
Changing circulation patterns of the Northern Atlantic Ocean through the bipolar seesaw
What conditions affect the CCD?
Water temperature, depth, CO2 content, pH, carbonate supply, and terrigenous sediment supply
Why are colder marine zones limited in productivity
They lack nitrogen, iron, and phosphorous
What are planktic forams used for and why?
Dating rocks, as they are more susceptible to changes in the upper water column and display highly variable temperatures
What are benthic forams used for and why?
Analysing long-term environmental change, as they live in stable, constant environments and are sessile, recording ice volume effects while remaining unaffected by regional and climatic changes
What conditions affect the δ18O preserved in foraminifera?
Diagenesis, light cycles, water composition, and growth rate, which relate back to the ice volume effect and salinity
How are conodonts used to track sea levels?
The changes in composition of carbonate fluoropatite in their phosphatic teeth resulting from diagenetic processes while preserved in the bio-stratigraphic record seawater signals
What factors control large scale carbon cycles?
Volcanism, tectonics, fossil fuel burning, and deforestation
What are the most common carbon sink processes?
Photosynthesis, rock weathering, carbonate deposition, and ocean adsorption
How do paleosols form a climate proxy?
Oxygen isotopes represent geochemical atmospheric conditions, while carbonate nodules mark movement of the water table
How is carbon fractionation in alkenones representative of dissolved CO2?
Algal cells allow CO2 to enter in aqueous form, preferentially accepting lighter isotopes to form a lighter composition when dissolved CO2 is high
What types of marine organisms can be used to determine atmospheric CO2
Planktic forams and nanofossils, as only the sea surface experiences exchange between aqueous and atmospheric CO2
How is the stomatal index used to predict CO2 present in fossils?
The number of stomata increases when CO2 is low to help with the capture of carbon
