Flashcards in Climate Change KQ1 Deck (88)
what is proxy data?
preserved physical characteristics of the environment that can stand in for direct measurements.
where do paleoclimatologists gather proxy data from?
natural recorders of climate variability like trees or ice
how can sediments indicate past ocean temperatures?
the chemical composition of foraminifera shells in sea-floor sediments
how can pollen indicate past climates?
it is preserved as fossils in layers of lake sediments, so can be used to identify the plants growing at that time (each layer can be dated)
what are varves?
layers of sediment in lakes next to glaciers
how can varve layers be dated?
each layer alternates as either summer or winter, so every two layers represents a year. Scientists can accurately count a year from thousands of years ago.
what do varves tell us?
where glacial ice was and in what year
how can ice cores be used to indicate past climates?
they contain tiny bubbles of air that allow scientists to measure the relative frequency of hydrogen and oxygen atoms with stable isotopes. Colder climates have less stable isotopes.
how can tree rings be used to indicate past climates?
each year of growth is represented by a ring. Thinner rings indicate dryer or colder years.
how can the location of fossils indicate past climates?
different organisms require different conditions. For example coral reefs only grow in tropical waters, so where their fossils are found indicates past tropical conditions.
how can raised or drowned beaches indicate past climates?
they are formed when sea levels change, which is often caused by the formation or melting of glaciers. Dating these beaches indicates when glaciers were formed or melted, indicating past changes in climate.
what is classed as documentary data?
paintings, diaries, photos, books, ship's logs etc...
what is good about documentary data?
provide specific dates e.g. Little Ice Age
what are the limitations of documentary data?
only go back as far as human records
may be opinionated
limited to locations with long literary histories
how can landscapes indicate past climates?
glacial activity shapes landscapes e.g. U-shaped valleys - shoes where glaciers extended to
what rocks indicate past cold climates?
what rocks indicate past hot climates?
red with iron deposits, or contain salt from seawater evaporation
what is a limitation of proxy data?
larger uncertainties the further back you go
why should we use both proxy and documentary data?
both together create a more complete picture
when was continental drift?
what was the huge mass of all continents called?
what was the climatic impact of continental drift?
it changed air and water circulation patterns as new oceans were created. More land mass at the poles means more snow so more global albedo so cooler climate
when was the mid-cretaceous?
what were global temperatures in the mid-cretaceous?
6-8 *C above current levels
what was atmospheric CO2 in the mid-cretaceous?
5X higher than today and coincided with an exceptional warm phase
where was sub-tropical during the mid-cretaceous?
Antarctica to Alaska - no polar ice caps
why were ocean currents different in the mid-cretaceous?
different continental configuration
when was the Paleocene - Eocene thermal maximum?
what were temperatures like in the Eocene thermal maximum?
average temperature around 23*C. This period had a short spike in global temperatures