Proxies Flashcards
ESD
paleoenvironmental reconstructions
use proxies to recreate environmental shifts in the earth’s geological history (Raymond, 2015)
external causes of climate change: plate tectonics, orbital forcing, insolation
internal changes of climate change: land, ice, vegetation and atmosphere often exacerbated through amplification and dampening
sensor
“something that responds to shifts in the earth system”
proxy
“measurable physical characteristics of the sensor”
multiproxies are required and draw on multiple sources
to determine the cause of the sensored change -> improve equafinality
ice is multiproxy
isotopes, microparticles, aerosols, air bubbles (ghgs) (Raymond, 2015)
Vostok ice core -> 3,623m and 4 glacial cycles -> identified the correlation between ghgs and deglaciation (Petit et al., 1999)
Greenland ice core -> 250kyr -> benthic δ O-18 validated with pollen and C14 (Dansgaard et al., 1993)
LR04 Stack (Lisiecki and Raymo, 2005)
produced from 57 benthicδ O-18 records to infer ocean temp and ice volume -> SpecMAP orbitally tuned the data -> foundation for environmental reconstructions globally
proxies are limited by temporal resolution
e.g. tree rings from 10,000-present day while marine sediments 10,000,000-500yrs (Ruddiman, 2002).
marine cores calcareous oozes formed of foraminifera, right coil = warm and left coil = cold
Silliceous oozes formed of diatoms and radioloria
marine cores tend to be multiproxy e.g. aeolian dust (aridity), clay minerals (weathering), iceberg rafting (calving), fluvial sediment (rivers), foraminifera (ocean temperature), oxygen isotope ratios (sea ice volume and SST) (Anderson et al., 2007)
1947 piston corer has made them easier to acquire (Raymond, 2015)
marine cores have a low resolution
as they are limited by slow rates of sedimentation 1cm/1000 yrs
Terrestrial cores range in type e.g. glacio-marine sediments, aeolian sediment, fluvial sediment, tree rings, peat, pollen and speleothems
they respond rapidly to temporal changes and so have a higher resolution
terrestrial cores are often harder to interpret
diagenesis e.g. glacial advance reshaped terminal moraine (Raymond, 2015; Anderson et al., 2007).
types of dating
radiative -> determining age relative to other sources
absolute dating -> identifying an event and dating it to determine when it took place
correlation -> determining whether things coincide in occurrence