AND future climates on Earth and other planets we must learn about past climates what affected them and how they have changed Chapter 9 Reconstructing Past Climates Proxy data Any set of nonclimatic evidence collected that is a function of temperature moisture wind speed and direction ID: 797945
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Slide1
In order to understand the present AND future climates on Earth and other planets, we must learn about past climates, what affected them, and how they have changed.
Chapter 9 - Reconstructing Past Climates
Slide2Proxy data Any set of non-climatic evidence collected that is a function of temperature, moisture, wind speed and direction
Examples:
Pollen
Lake levels
Fossils
Chemical isotopes
Dunes
Slide3Slide4Ice coresUsed for centuries as crude climate indicators
If present = cold; if thicker=more snow; if thinner=warmer and less snow
First ice cores extracted (1950
’
s) were used in old ways1980’s everything changedUtilized dust, gases, and chemicals
Slide5Oxygen isotopes-paleotemperature proxy an isotope is an element with extra neutrons in the nucleus of the atom
Means there is a weight difference
Oxygen has two isotopes
18
O and 16O16O weighs slightly less so it evaporates more easily when attached to water (H2O)
Slide6As ocean water is depleted in 16O, it is enriched (relatively speaking) in 18O.In essence, as we enter a glacial period, ocean waters are enriched in
18
O.
In ice,
16O is enriched during glacial times.Values are typically presented as a % change or a ratio of 16O/18O, in part because the isotopes are also affected by temperature and can vary in the numeric values.
Slide7Greenland ice core-temperature proxy
Slide8Marine Isotope curve- showing stage designations
Slide9Composite Marine Oxygen Isotope Curve
Slide10Plants give us a good estimation of past climates due to their immobility and dependence upon precipitation and temperaturemodern climatological classification schemes exploit thisLook for relative abundance of preserved plant remains
Macrofossils- leaves, twigs, bark, etc
Microfossils- pollen and spores
Slide11Plots of pollen grains vs depth (time)Pollen plots look to exploit rapid shifts in the types of pollen grains found
Plants are great colonizers when an ecological niche is unoccupied due to extinction or extantism
Slide12Raw pollen plots- # of pollen grains
Slide13Pollen Plots
Slide14Pollen Plots
Slide15Dendrochronology- study of tree rings
trees record environmental stress
Thick rings = good growing conditions
Thin rings = stressed conditions
Slide16Slide17Slide18stressed
Non-stressed
Slide19Sea level curve (eustatic)Eustasy- a change in the volume of water held in the ocean basins
As sea rises or falls, landforms are created that give away the former position of water levels
beaches and wave cut platforms
coral reefs
Slide20Slide21Slide22Lake levelsWater accumulates in closed or semi-closed basinsoccurs due to increased precipitation and/or decreased evaporation
As levels rise, landforms are created
As levels fall, new landforms are created
Both leave an identifiable record of prior water levels, which reflect moisture in the region
Slide23Lake levels-
Lake Bonneville
Slide24Slide25Slide26Holocene climatic optimum 9-7 Kyr bp (7-5000 BC) many regions experience a climatic optimum- warm summers-mild winters.
Accelerates sea level rise due to deglaciation
Slide27Historic records of meteorological events non-instrumental accounts
restricted to weird or extreme events
Recorded in literature, birth and death records, art works and theater productions from those time periods.
instrumental accounts and records
In the renaissance, science became enamored with measuring stuff First temperature, then wind, moisture, and pressure
Slide28Little Climatic optimumoccurs from about 800 to 1300 ADrecords of civilizations abound in what are now harsh climatic regions
Greenland-
“
Norse
” coloniesWari Empire- Peru, South AmericaPueblo culture - Chaco Canyon, NM
Anasazi culture- Mesa Verde, CO
Causes problems in some coastal areas
Sea level rises flooding places along the Mediterranean Sea
Slide29Little “Ice Age”- Occurs from 1350- to 1850 AD
Produces cooler weather and forces the termination of all of the cultures mentioned in association with Climatic optimum
ice becomes commonplace in places that do not currently freeze
e.g., Thames River- England
Slide30Causes of these climate changes?We know that it wasn’
t people because we were not around in sufficient numbers!
This is key to understanding our involvement/role in modern climate change
Milankovitch Orbital cycles
influence solar radiation output
Sunspot variations
influence temperature and solar output
Slide31Eccentricity
Obliquity
Conditions now
Conditions in past
Conditions now
Conditions in past
RED=Conditions now
Green
& Yellow= Conditions in past
Precession
Slide3211 year sunspot cycles
Slide33Sunspots
Slide34Variations in atmospheric particulates Volcanic activity produces ash
blocks
sunlight
Example- 1815 Eruption of
Tambora yielded “the year without a summer” sandstorms produce dust also blocks sunlight can be human related as well…
Slide35Slide36“The Scream” by
Edvard
Munch has a deep red
sky
which is due
to sunsets being altered by excessive volcanic ash associated with the eruption of Krakatoa in
Indonesia in 1883