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
Climate and Global Change Notes
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
Climate Observations
Climate and Global Change Notes
9-3
Stable Isotope Analysis (Con’t)
• 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)
Climate Observations
http://www.staff.brad.ac.uk/mprichar/PRGIntrotoIsotopes.html
Terrestrial Ecosystems
Marine Ecosystems
13C
15Ncarnivore
herbivore
fish
shellfish
Climate and Global Change Notes
9-4
Stable Isotope Analysis (Con’t)
• 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)
Climate and Global Change Notes
9-5
Stable Isotope Analysis (Con’t)
• 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/
slideset/20/20_409_slide.html
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
http://www.ncdc.noaa.gov/paleo/slides/slideset/20/20_400_slide.html
Climate and Global Change Notes
9-6
Stable Isotope Analysis (Con’t)
• 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
Climate Observations
http://www.ncdc.noaa.gov/paleo/slides/slideset/13/13_240_slide.html
SST Anomaly (°C)
18O Anomaly
Climate and Global Change Notes
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
Climate Observations
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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
Climate and Global Change Notes
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
Climate Observations
http://www.scirpus.ca/cap/articles/paper29.htm
Climate and Global Change Notes
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
Climate Observations
Bushy-tailed woodrat
http://www.ncdc.noaa.gov/
paleo/slides/slideset/16/
16_308_slide.html
http://www.ncdc.noaa.gov/paleo/slides/slideset/16/16_307_slide.html
Climate and Global Change Notes
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
Climate Observationshttp://www.ncdc.noaa.gov/paleo/slides/
slideset/16/16_313_slide.html
Climate and Global Change Notes
9-11
Midden Analysis (Con’t)
• Results for 89 Packrat Middens
- Elevation zones for vegetation has shifted over the last 24,000+ yearsin the Grand Canyon
Climate Observationshttp://www.ncdc.noaa.gov/paleo/slides/
slideset/16/16_316_slide.html
Climate and Global Change Notes
9-12
Midden Analysis (Con’t)
• 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
Climate Observations
http://www.ncdc.noaa.gov/paleo/slides/slideset/16/16_320_slide.html
Climate and Global Change Notes
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
Climate Observations
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
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QuickTime™ and aTIFF (Uncompressed) decompressor
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http://earthobservatory.nasa.gov/Study/Paleoclimatology_SedimentCores/
Climate and Global Change Notes
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