Observing Climate Proxy Data

1
Observing Climate - Proxy Data
Science Concepts Pollen analysis

• Paleo Proxy Data (Cont)
• Stable Isotope Analysis
• Palynology
• Midden Analysis
• Sedimentary Analysis

The Earth System (Kump, Kastin Crane) Chap.
15 (p. 292)
The Earth System (Kump, Kastin Crane) Chap.
15 (p. 292)
2
Observing Climate - Proxy Data
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
http//www.staff.brad.ac.uk/ mprichar/PRGIntrotoIs
otopes.html
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Observing Climate - Proxy Data
Stable Isotope Analysis (Cont) 12C/13C and
15N/14N Isotope Analysis (Cont) - ?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
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Observing Climate - Proxy Data
Stable Isotope Analysis (Cont) 12C/13C and
15N/14N Isotope Analysis (Cont) - ?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 gt ?13C distinguishes between
terrestrial (-20) and marine (-12)
ecosystems gt ?15N of terrestrial herbivores
are approximately 5, terrestrial
carnivores are at about 9 gt 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/ PRGIntrotoIs
otopes.html
Terrestrial Ecosystems
fish
?15N
carnivore
shellfish
herbivore
Marine Ecosystems
?13C
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Observing Climate - Proxy Data
http//www.ngdc.noaa.gov/paleo/slides/ slideset/15
/15_292_slide.html
Stable Isotope Analysis (Cont) Example - Ice
Core Analysis - ?18O (green line) and
glacial ice accumulation (blue line) for
10,000- 17,400 y B.P. gt Colder climate
associated with lower accumulation
values gt Note how quickly the climate shifted
from cold to warm phases during the
glacial-interglacial transition gt 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 gt The last 10,000 years
have been the most consistent and stable
climate in the 200,000 Greenland ice
record gt This same period appears to have been
less stable at lower latitudes
Periods of Rapid Change
Accumulation (m ice / year)
?18O
Years Before Present
6
Observing Climate - Proxy Data
http//www.ncdc.noaa.gov/paleo/slides/ slideset/20
/20_409_slide.html
Stable Isotope Analysis (Cont) Example - Ice
Core Analysis (Cont) - 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.?
http//www.ncdc.noaa.gov/paleo/slides/slideset/20/
20_400_slide.html
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Observing Climate - Proxy Data
Stable Isotope Analysis (Cont) 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
http//www.ncdc.noaa.gov/paleo/slides/ slideset/13
/13_240_slide.html
SST Anomaly (C)
?18O Anomaly
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Observing Climate - Proxy Data
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. Reference Milne, L., 1998 Forensic
Palynology. Pollen and spores, Nature's
Fingerprints of Plants. http//science.uniserve.
edu.au/faces/milne/milne.html
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Observing Climate - Proxy Data
Palynology (Cont) 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
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Observing Climate - Proxy Data
http//www.ncdc.noaa.gov/paleo/slides/ slideset/16
/16_307_slide.html
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 masses of crystallized urine
that can persevered for tens of thousands of
years
Bushy-tailed woodrat http//www.ncdc.noaa.gov/ pa
leo/slides/slideset/16/ 16_308_slide.html
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Observing Climate - Proxy Data
http//www.ncdc.noaa.gov/paleo/slides/ slideset/16
/16_313_slide.html
Midden Analysis (Cont) 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
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Observing Climate - Proxy Data
http//www.ncdc.noaa.gov/paleo/slides/ slideset/16
/16_316_slide.html
Midden Analysis (Cont) Results for 89 Packrat
Middens - Elevation zones for vegetation has
shifted over the last 24,000 years in the
Grand Canyon
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Observing Climate - Proxy Data
Midden Analysis (Cont) 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
http//www.ncdc.noaa.gov/paleo/slides/ slideset/16
/16_320_slide.html
14
Observing Climate - Proxy Data
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/Paleoclimat
ology_SedimentCores/
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Observing Climate - Proxy Data
http//www.ncdc.noaa.gov/paleo/slides/slideset/19/
19_380_slide.html
Sediment Analysis What could cause these
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