Proxies

Question 1

paleoenvironmental reconstructions

Answer 1

use proxies to recreate environmental shifts in the earth’s geological history (Raymond, 2015)

Question 2

external causes of climate change: plate tectonics, orbital forcing, insolation

Answer 2

internal changes of climate change: land, ice, vegetation and atmosphere often exacerbated through amplification and dampening

Question 3

sensor

Answer 3

“something that responds to shifts in the earth system”

Question 4

proxy

Answer 4

“measurable physical characteristics of the sensor”

Question 5

multiproxies are required and draw on multiple sources

Answer 5

to determine the cause of the sensored change -> improve equafinality

Question 6

ice is multiproxy

Answer 6

isotopes, microparticles, aerosols, air bubbles (ghgs) (Raymond, 2015)

Question 7

Vostok ice core -> 3,623m and 4 glacial cycles -> identified the correlation between ghgs and deglaciation (Petit et al., 1999)

Answer 7

Greenland ice core -> 250kyr -> benthic δ O-18 validated with pollen and C14 (Dansgaard et al., 1993)

Question 8

LR04 Stack (Lisiecki and Raymo, 2005)

Answer 8

produced from 57 benthicδ O-18 records to infer ocean temp and ice volume -> SpecMAP orbitally tuned the data -> foundation for environmental reconstructions globally

Question 9

proxies are limited by temporal resolution

Answer 9

e.g. tree rings from 10,000-present day while marine sediments 10,000,000-500yrs (Ruddiman, 2002).

Question 10

marine cores calcareous oozes formed of foraminifera, right coil = warm and left coil = cold

Answer 10

Silliceous oozes formed of diatoms and radioloria

Question 11

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)

Answer 11

1947 piston corer has made them easier to acquire (Raymond, 2015)

Question 12

marine cores have a low resolution

Answer 12

as they are limited by slow rates of sedimentation 1cm/1000 yrs

Question 13

Terrestrial cores range in type e.g. glacio-marine sediments, aeolian sediment, fluvial sediment, tree rings, peat, pollen and speleothems

Answer 13

they respond rapidly to temporal changes and so have a higher resolution

Question 14

terrestrial cores are often harder to interpret

Answer 14

diagenesis e.g. glacial advance reshaped terminal moraine (Raymond, 2015; Anderson et al., 2007).

Question 15

types of dating

Answer 15

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

Question 16

OSL -> time it takes to bleach and reverse the decay damage that radioactive elements did to sand grains as they became buried -> length of time for reversal = length of burial (Thomas and Wiggs, 2008)

Answer 16

cosmogenic nuclide dating -> cosmic rays (from space) lead to the production of cosmogenic nuclides within rock -> it is possible to estimate the age of boulders or glacial material as the concentration of nuclides results in the length of exposure (Anderson et al., 2007)

Question 17

half life dating

Answer 17

cosmic-nuclide dating
carbon dating
potassium dating
uranium dating

Question 18

oxygen fractionation -> O-16 (lighter) and O-18 (heavier) -> during glacial periods more O-16 locked in ice as it evaporates more readily and therefore enters the cryosphere as precipitation

Answer 18

CaCO3 in forams shells -> more O-18 in shells during glacial periods

Question 19

Ca2+ and Mg2+ -> ratio in shells of organisms shift based on environmental changes (Saraswat et al., 2005) -> variable between species

Answer 19

C3 and C4 plants -> used to infer past climates as C4 plants have a higher rate of photosynthesis so tend to be more common in drier environments -> but variable

Question 20

aeolian sediment -> Loess Plateau Chine 2.5Myr (Anderson et al., 2007)

Answer 20

geochemical elements -> leaf wax -> temperatures and precipitation rates (Tierney?)

Question 21

dendrochronology and dendroclimatology

Answer 21

use tree rings to infer environmental changes (Anderson et al., 2007)

Question 22

noise -> harder to infer the climate signal

Answer 22

precision (values close to one another) v accuracy (true value)

Question 23

Modelling types

Answer 23

multi-component -> non-lab based research
Empirical/statistical models -> look for relationships between variables
Conceptual models -> devise ideas based on understandings of the earth system
physically-based models -> empirically testing ideas

Question 24

MSA concentrations were analysed in the Weddell Sea -> paper determined that the concentration increases during ablation due to increasephytoplankton activity near the edge of the ice

Answer 24

validated that the plankton were the source by analysing three different sites -> Berkner Island had the highest concentration of MSA and greatest plankton population (Abram et al., 2007) -> though previous papers and trend at Amudsen-Bellinghausen Seas did not correlate

Question 25

Greenland Ice Core and Vostok Ice Core -> similar conclusions for climatic shifts

Answer 25

ice extent changes more dramatic across Greenland -> due to changes induced across the North Atlantic Ocean (Dansgaard et al., 1993)

Question 26

Stalagmite in Southern Oman -> used to understand the Indian Ocean Monsoon -> analysed O isotope ratios -> drop in O-18 indicative of increased monsoon activity but also since precipitation and temperature control stalagmite formation

Answer 26

10.3-8ky B.P. -> glacial boundaries controlled the IO monsoon = behaviour correlated with the Greenland Ice core shifts After 8ky B.P. -> NH solar insolation controlled the IO monsoon = no ice sheets and increased stability of the North Atlantic Ocean = weakening the land-sea thermal contrast (Fleitmann et al., 2003)

Question 27

Mg/Ca ratios from G. ruber extracted from a core taken from the Comorin ridge in the Indian Ocean

Answer 27

Inferred temp changes to reveal that MIS2, 3 and 4 temperatures were lower than the West Pacific -> on the whole similar changes to the Pacific and therefore mechanism connecting them (Saraswat et al., 2005)

Question 28

LGM (20,000 yrs ago) -> IO temperatures were 2.1°C cooler than present-day temperatures

Answer 28

Isotope Stage 5 (130,000-80,000 yrs ago – referred to as final interglacial prior to the Holocene) -> 1.4°C warmer than present-day temperatures (Saraswat et al., 2005)

Question 29

Paper drew up a comparison between terrestrial pollen records and benthic δ O-18 records from marine cores to determine the correlation between the sources and therefore validate the earth’s climate history over the last 500,000yrs

Answer 29

concluded that the records did yield similar events, but that pollen tended to react more severely to climatic shifts, and often earlier than the marine cores. There was also more variability between the terrestrial pollen records and would need to be tuned to something separate to marine cores/orbital forcing (Tzedakis et al., 1997)

Question 30

Marine and Ice cores -> often the backbone for geoproxies (Thomas and Burrough, 2012)

Answer 30

OSL -> used to determine rates of sedimentation and sand dune ages (Thomas and Wiggs, 2008)

Question 31

Dongge Cave stalagamite -> South of China -> 9,000yr environmental history of the region by analysing O isotope ratios from 2124 measurements -> 2 seasons in the cave – dry and cool or wet and warm – controlled by shifts in the ITCZ as a northward displacement brings the Indian Ocean Monsoon into the region

Answer 31

IO Monsoon in the Holocene -> weakening due to NH solar radiation decreasing -> no northward displacement of the ITCZ and land-sea thermal contrast is weaker -> also some proposed links to ice rafting across the NH -> likely the weakening was triggered 8.2ka yrs due to a shift in North Atlantic Ocean circulation (Wang et al., 2005)

Question 32

Vostok Ice core -> 4 glacial cycles -> emphasised the importance of

Answer 32

orbital forcing, greenhouse gases and the ice albedo effect on the global climate (Petit et al., 1999)

Question 33

Analysis of an endorheic basin in Jubbah, Nefud Desert -> orbital cycles lead to the formation of lakes across the region

Answer 33

research on the basin used multiproxy analysis -> O isotopes, C isotopes, sediment size and mass spectroscopry -> revealed sediment layers two layers were 9m, another was 4m and the last was 2m -> determined that lakes formed during interglacial periods and evaporated during glacial periods over the last 360,000 years, i.e. Lake formation through MIS 11/9, 7, 5, 3 and parts of the early Holocene (Parton et al., 2018)

Question 34

dating is complex

Answer 34

proxy data can often lead to inaccurate inferences (Parton et al., 2018)