climate observations

Climate and Global Change Notes

9-1

Stable Isotope Analysis

• 16O and 18O Isotope Analysis

- Oxygen isotope ratio (18O) is a measure of the ratio of heavy oxygen

(18O) to light oxygen (16O)

- Used as a proxy measure for paleotemperature

- More negative values indicate “colder” temperatures

• 12C/13C and 15N/14N Isotope Analysis

- “You are what you eat”, thus the building blocks that make your body,

have been taken from foods you have eaten over your lifetime.

- Specifically, the elements C and N in your bone are the same C and N

atoms that were in the foods you ate.

- Again we can measure the ratio of C isotopes and N isotopes to create

13C and 15N values similar to the 18O ratio above

Climate Observations

http://www.staff.brad.ac.uk/mprichar/PRGIntrotoIsotopes.html


9-2

Stable Isotope Analysis (Con’t)

• 12C/13C and 15N/14N Isotope Analysis (Con’t)

- 13C and 15N values of various foods are fairly well known

- 13C and 15N values are signatures specific to different types of foods,

- Measuring the 13C and 15N values of your bone, we can infer from what

foods the bone C and N came

- Why bone - its is best preserved over time

- Analysis of the extracted protein portion of the bone, collagen, (and for

radiocarbon dating) reflect the protein part of our diets

- Adult collagen in our bones is constantly being replaced and completely

turned-over in about 10 years



9-3


• 12C/13C and 15N/14N Isotope Analysis (Con’t)

- 13C indicates how much marine protein (e.g., fish, shellfish) was in the

diet, compared to terrestrial proteins (e.g., grains, breads, cattle meat and

milk)- 15N indicates how much plant food

was in the diet, compared to animal foods (like meat and milk)

- Typical collagen isotope values Holocene Western Europe

> 13C distinguishes between

terrestrial (-20%) and marine (-12%) ecosystems

> 15N of terrestrial herbivores are approximately 5%, terrestrial carnivores are at about 9%

> For omnivores like humans the 15N indicates if they are behaving

more like herbivores (plant protein) or carnivores (animal protein)


http://www.staff.brad.ac.uk/mprichar/PRGIntrotoIsotopes.html

Terrestrial Ecosystems

Marine Ecosystems

13C

15Ncarnivore

herbivore

fish

shellfish


9-4


• Example - Ice Core Analysis

- 18O (green line) and glacial ice accumulation (blue line) for 10,000-17,400 y B.P.

> Colder climate associated with lower accumulation values

> Note how quickly the climate shifted from cold to warm phases during

the glacial-interglacial transition > Research suggests that major climatic changes such

as these may have occurred over just a few years, i.e., climate

during the last glacial period was inherently unstable and subject

to rapid fluctuations

> The last 10,000 years have been the most consistent and stable

climate in the 200,000 Greenland ice record> This same period appears to have been less stable at

lower latitudes

Climate Observationshttp://www.ngdc.noaa.gov/paleo/slides/

slideset/15/15_292_slide.html

18O

Years Before Present

Periods of Rapid Change

Accumulation (m ice / year)


9-5


• Example - Ice Core Analysis (Con’t)

- Quelccaya ice cap (5,670 m altitude; 164 m thick) provides clues about South American tropical climatic variability

- Note Little Ice Age is identified in the 18O between

1550 and 1900 A.D.

Climate Observationshttp://www.ncdc.noaa.gov/paleo/slides/


QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

http://www.ncdc.noaa.gov/paleo/slides/slideset/20/20_400_slide.html


9-6


• Example - Coral Analysis- Ambient water conditions (i.e., Sea Surface Temperature

(SST) and, possibly, fresh water influx and precipitation) when a

layer of coral skeletons was deposited determine the 18O within ice

cores). Thus, analyses of 18O can yield information about past water

conditions- Note that red spikes

(high 18O anomaly) in 18O correspond to the red spikes (high SST anomaly)in SST

- Yellow zones indicate El Nino/Southern Oscillation (ENSO) warm phases

- Coral records can yield information 500-800 years into the past in many tropical areas



SST Anomaly (°C)

18O Anomaly


9-7

Palynology

• Pronounced pal-ih-nol-o-jee, the "a" as in "map”

• “Palyn” comes from a Greek word that means “I sprinkle” that is also a cognate

of the Latin word “Pollen” which means dust or fine flour.

• Branch of science dealing with microscopic (5 m to about 500 m), decay-

resistant remains (such as pollen and spores, living and fossil) of certain plants

and animals




Figs. 1-8. Examples of pollen from flowering plants. Scale bar = 10 µm.Fig. 9. Pollen from a cone-bearing plant (e.g., pine). Scale bar = 10 µm.

ReferenceMilne, L., 1998: Forensic Palynology. Pollen and spores, Nature's Fingerprints of Plants.

http://science.uniserve.edu.au/faces/milne/milne.html


9-8

Palynology (Con’t)

• Lennart von Post (1916) suggested that buried sediments of fossil pollen was

a precise method for determining past vegetation regimes and cycles of

vegetation change - Many plants produce great quantities of pollen or

spores that are dispersed by the wind

- Pollen and spores have very durable outer walls that can remain preserved

for thousands or even millions of years- Unique morphological features of each type of pollen

and spore remains consistent within each species, yet each different

species produces its own specific form

- Each pollen and spore-producing plant is restricted in its distribution by

environmental conditions that include moisture, temperature and soil type

- Most wind-dispersed pollen and spores rarely travel very far before falling

to the surface• Thus, by counting a sufficient number of fossil pollen and spores recovered

from each stratum in a deposit, one could reconstruct the types and abundance

of plants represented by those fossil grains


http://www.scirpus.ca/cap/articles/paper29.htm


9-9

Midden Analysis

• Middens are amalgamations of plant and animal remains encased in crystallized packrat urine

• First noted by military and scientific expeditions in the West as early as 1849

• During 1960s paleoecologists began to fully recognized potential for reconstructing past environmental change

• Packrats or woodrats gather and accumulate plant materials typically within 100 m of their den in dry caves and crevices

• Plant remains and other debris (including insect and vertebrate remains) are cemented into large massesof crystallized urine that can persevered for tens of thousands of years


Bushy-tailed woodrat

http://www.ncdc.noaa.gov/

paleo/slides/slideset/16/

16_308_slide.html



9-10

Midden Analysis (Con’t)

• Thus, midden materials represent the local environment when material was collected

• Middens tend to be preserved in some environments better than others; arid climates good

• Midden analysis locations




9-11


• Results for 89 Packrat Middens

- Elevation zones for vegetation has shifted over the last 24,000+ yearsin the Grand Canyon




9-12


• Summary

- Plants have shifted upward on the Colorado Plateau from last glacial period to the present

- During the last glacial period, the timber line was lower than today

- Also tree species have shifted upward




9-13

Sediment Analysis

• North Atlantic oceanic sediment cores are used to understand climatic variations during and since the last ice age but not just confined to local regions of the northeastern Atlantic

• Analyze cores by counting the number of both lithic (rock) and

plankton shell fragments

• Total number of particles fluctuate with climate changes

• Analysis of long cores indicate that plankton fragments dominated

(warm periods) for long stretches of time, while rock sediments

(cold periods) dominated in six spikes

• These sudden changes in sediments (referred to as Heinrich events; cold events) are also visible in X-rays of

sediment cores as sharp transitions between dark-colored (plankton-

dominated) and light-colored (lithic-dominated) segments








http://earthobservatory.nasa.gov/Study/Paleoclimatology_SedimentCores/


9-14

Sediment Analysis

• What could causethese different sediments?

- Heinrich events: A significant SST drop occurs; reduces plankton fragments; extends the ice sheet onto the continental shelf; icebergs with lithic material breakoff; float off and melt depositing lithic

material over ocean bottom

- Non-Heinrich events: Deposited during warm periods with more plankton

material and fewer icebergs to transport lithic material

Climate Observationshttp://www.ncdc.noaa.gov/paleo/slides/slideset/19/19_380_slide.html

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