Climate Archives, Data, and Models Flashcards
Climate Archive
A vast amount of data is stored about the Earth’s past
climate within numerous natural archives.
Major climate archives include:
1. Sediment
2. Ice cores
3. Tree rings
4. Corals
5. Speleotherms
6. Fossil Record
-pollen
-plankton
Sediment
Sediment deposits remain the only major climate archive for >99%
of Earth’s history.
They are usually continuous series deposited by fast-moving water
into slower-moving water to form an undisturbed succession.
The relative action of
erosion and plate
tectonics decrease the
likelihood that older
ocean sediment records
will be preserved.
Sediment part 2
Sediment deposit rates vary with changing sediment sources, basin
geometry, currents, water depth, ice and wind.
Sediment deposits can be disturbed or destroyed by dislodgement,
physical erosion, change in water currents, gradual chemical
dissolution in water, ice sheets, and tectonic recycling.
Cores are retrieved by drilling operations on lakes and oceans.
Radioactive Decay
Radiometric dating of nearby igneous rocks provides constraints
on the age of the sedimentary rocks based on the radioactive decay
of an unstable parent isotope to a stable daughter isotope.
Dating Sediments
Dating of sediments can be completed in a variety of ways, depending on the sediment type and age. Radiocarbon (14C) Dating can be used to date any carbon bearing material based on the measurement of the decay of radioactive carbon-14.
Radiocarbon Dating
Radiocarbon dating uses the naturally occurring radioisotope 14C
to estimate the age of carbon-bearing materials up to about 60,000
years.
14N + neutrons 14C 14N
Can only be used when geological deposits contain biologicallyfixed carbon.
Annual Layering
Seasonal changes
in the accumulation
of climate-sensitive
materials can lead
to annual layers
forming which can
be counted to
obtain an annually
resolved, or even
calendar-dated,
time frame.
Glacial Ice
Annual deposition of snow can pile up in continuous sequence in
very cold regions forming alpine glaciers and ice sheets that
contain many kinds of climatic information.
Drilling ice cores can be very challenging due to inhospitable
terrain, isolation and altitude.
Common measurements taken from ice
cores are δ18O values, dust
concentrations and gas concentrations
in air bubbles.
18O:16O is a measure of stable isotopes
whose value changes with temperature.
Therefore, δ18O values can be used as a
proxy for temperature.
Dust can be a proxy for desert area or
wind speed.
Air bubbles trap past atmospheric gas.
Tree Rings
At mid to high latitudes, trees produce annual rings which can be
measured, cross-dated and assigned a calendar-year.
Trees develop annual rings of different properties depending on
weather, rain, temperature, soil pH, plant nutrition, CO2
concentration, etc. in different years. These variations may be
used to infer past climate variations.
The study of tree-rings is called dendrochronology.
Corals
Corals grow by depositing an annual band of CaCO3. The oxygen
contained therein (from the surrounding seawater) provides a
record of the changes in the proportion of 18O and 16O from which
we can reconstruct historical ocean temperatures and El Niño
events.
Most corals analysed come from the tropical Pacific Ocean and
can span up to 400 years.
Speliotherms
Samples can be taken from speleothems to be used as a proxy
record of past climate changes. Speleothems can be accurately
dated using the uranium-thorium dating technique.
Stalagmites are particularly useful because of their relatively simple
geometry and because they contain several different climate
records, such as oxygen and carbon isotopes and cations. These can
provide clues to past precipitation, temperature, and vegetation
changes over the last ~ 500,000 years.
Fossil Record
Climate on the continents can be inferred from distinctive
fossilised vegetation, often pollen.
Climate in the oceans from animals and plant plankton.
Dendrochronology
The science that uses tree rings dated to their exact year of
formation to analyze temporal and spatial patterns of processes in
the physical and cultural sciences.
dendron = tree
chronos = time
logos = word = the science of
At mid to high latitudes (or mid to high altitudes), trees produce
annual rings which can be measured, cross-dated and assigned a
calendar-year.
Instrumental Record
The period for which reasonably reliable instrumental
records of near-surface temperature exist with quasiglobal coverage is generally considered to begin around
1850. Earlier records exist, but with sparser coverage and
less standardized instrumentation.
Types of Dendrochronology
Dendroarchaeology
The science that uses tree rings to date when timber was felled, transported,
processed, or used for construction or wooden artifacts.
Dendroclimatology
The science that uses tree rings to study present climate and reconstruct past
climate.
Dendroecology
The science that uses tree rings to study factors that affect the earth’s ecosystems.
Dendrogeomorphology
The science that uses tree rings to date earth surface processes that created,
altered, or shaped the landscape.
Dendroglaciology
The science that uses tree rings to date and study past and present changes in
glaciers.
Dendrohydrology
The science that uses tree rings to study changes in river flow, surface runoff, and
lake levels.
Dendropyrochronology
The science that uses tree rings to date and study past and present changes in
wildfires.
Dendroentomology
The science that uses tree rings to date and study the past dynamics of insect
populations.
