History of Earth’s climate
Content
-History of Earth’s Climate
Background reading:
-Past Climate forcing mechanisms
D. Hartman Chapter 8 and 11
B. Saltzmann: Dynamical Paleoclimatology
F. Ruddiman: Earth’s Climate
-Types of observational records
Roderik van de Wal
http://www.staff.science.uu.nl/~wal00105/climdyn/climdynUU.html
[email protected]
Space and time scales
(320.000 yr)
Rationale
1012
(3200 yr)
Why study past climates?
•  Provides clues on how the climate system works.
•  Past is the key to the future
•  Gives perspective on range of climate change possible.
(variability of the system)
(0.32 yr)
height of the tropopause
radius of the earth
1
Geological
Hymalayan
calendar
Background
Paleo-climatology
Age of Mammals
Alpine
Rockies
Age of Dinosaurs
Sea-level
Breakup Pangea
climate
proxy
Final assembly Pangea
Consolidation continents
δ180
time?
Earliest known life (~3500)
dating
Formation of Earth (~5000)
Forcing Mechanisms for the Climate
Example of different forcings
*Variations in solar forcing:
-Solar constant
-Earth Orbit
Eccentricity (~400 and 100 ka)
Obliquity (~41 ka)
Precession (~19, 23 ka)
*Continental geography and topography
Oceanic gateway location and bathymetry
*Concentration of atmospheric greenhouse gases
*Volcanic activity
De Conto and Pollard 2003
2
Surface Ocean Circulation
Surface Ocean Circulation
65 million years ago
Today
Cretaceous model runs
Red:CT1250
Green:CT2500
Black data δ18O
Dotted:seasons
psu
T
3
Proxies
Instrumental records
http://www.ipcc.ch/
Historical records
•  Written or oral accounts of past events
•  Problem:
•  Likely biased to extreme events
•  How to link these records to climate
parameters; temperature, precipitation, wind.
transfer functions?
•  Type of data:
•  Agricultural
•  Weather diaries
•  Ship logs
•  Flooding information
•  Ancient art and cultures
•  etc
Historical records
Sea ice occurrence in months per year on the northern
tip of Iceland
Vikings in Greenland
980 - 1350 AD
Rock painting Tassili-N-Ajjer,
Southern Algeria, ±5000 BP
4
Proxy Records
Surface biological and geomorphological:
Tree rings
Corals (Marine)
Shorelines
Subsurface, cores:
Marine and lake sediment cores
Ice cores
Analyses:
Non-isotopic stratigraphic analyses
Non-isotopic geochemical methods
Isotopic methods
Tree rings
Surface proxi evidence:
biological
Biological entities that exhibit annual layering
•  tree rings
•  corals
•  molluscan shells
Corals
Information on water temperature, salinity,
sea level
Shells
Information on temperature, day length
Example: Tree rings
•  Very well dated by counting rings and cross
matching of records
•  Information in width, structure and isotopic
contents
•  Growth rate proportional to temperature and
moisture availability
•  Information on temperature, precipitation and soil
moisture
5
Surface proxi evidence:
Geomorphological
Information in the landscape itself
•  Surface geomorphological evidence
•  marine shorelines
•  lake shorelines
•  soils
•  ice and glacier signatures
Shorelines
•  Marine shorelines
•  Information in coastal features, reef growth
•  Information on sea level, ice volume
•  Lake shorelines
•  Information in level and sediments
•  Information on temperature, precipitation,
evaporation, runoff
0 kyr
Soils
6 kyr
400-kyr Eccentricity
minimum
Obliquity
• Ancient soils
Information in type of soil
on temperature, precipitation, drainage
100-kyr Eccentricity
minimum
Precession
minimum
Precession
maximum
• Glaciers and ice sheets:
Information in terminal position
Information on extent of glaciers and area of ice sheets
Hilgen, pers. Com.
Sapropel-marl cycles of late Miocene age
(Gibliscemi section, Sicily, Italy)
6
Marine Cores
Marine and lake cores
The Cenozoic Isotopic Record
from Zachos et al., 2001
•  Fossil pollen (biological, terrestrial):
•  Information in type and concentration
•  Information on vegetation, temperature, precipitation, soil
moisture
Eocene-Oligocene Transition:
•  δ18O shift of ~0.8 ‰ in ~50 kyr
•  Mg/Ca record shows this is mostly
due to ice volume, not deep-water
temperature (Lear et al., 2000)
• Sediments (marine):
•  Information in:
•  Accumulation rates
•  Fossil plankton and benthic types
•  Mineralogical composition
•  Information on wind direction, SST + salinity, sea ice
extent, global ice volume, bottom water temperature,
chemistry and water flux.
Other dated evidence from
circum-Antarctic sediments:
•  Ice-Rafted Debris
•  Clay mineralogy
Challenged recently Science 2009
A high latitude SST
(composite)
Bottom line E-O
transition
not just inception
also cooling
Ice cores
•  Information in ice itself, air bubbles in the ice and empty borehole
•  Oxygen isotope concentration
•  Layer thickness
•  Mechanical + electrical properties of the ice
•  Dust, trace elements concentration
•  Chemical composition of air bubbles
•  Temperature and deformation borehole
•  Information on temperature, accumulation, chemical composition
atmosphere
10 m
120 m
550 m
(from R. Mulvaney)
7
Example: Ice cores
Type of analyses
Non-isotopic stratigraphic analyses
Non-isotopic geochemical methods
Isotopic methods
Nonisotopic stratigraphic
analyses
Deposition of sediments in oceans and lakes which
consolidate into layered sedimentary rock
•  Surface exposed layering
•  Marine and lake cores
•  Ice sheets
•  Physical indicators
•  Drainage from size material
•  Glacial extent from ice rafted debris
•  Wind and aridity from deposition of dust and ashes
•  Paleobiological indicators
•  Pollen and spores
•  Imprints of plant fossils
•  Bone material large animals
•  Calcerious or siliceous shells of marine organisms
Non-isotopic geochemical
methods
Cadmium concentration
Indirect method which gives information on deep
ocean circulation
Greenhouse gasses in trapped air in ice cores
Information on greenhouse gasses in the
atmosphere over period of 100 - 800 kyr
Dust layers in ice cores
Chemical and biological constituents of these
layers give information on wind, aridity, ocean
currents
8
Precambrian
Why stable isotopes?
*
*
Natural concentrations are constant
Differences between reservoirs and phases as a result
they can be used as tracers
Physical and chemical processes influence the isotope ratio
(fractionation)
Examples
oxygen: 16O, 18O
hydrogen: H, 2H = D
Oxygen: 18O/16O, Hydrogen: D/H
Carbon: 13C/12C
Archean 4.5 - 2.5 Ga
Development atmosphere, ocean, continents
Primary atmosphere
•  Solar nebula removed by solar winds
(less noble gases)
Secondary atmosphere
•  Outgassing (volcanic eruptions)
•  H2O, CO2, N
•  O2 from life (3.5 Ga)
Ocean forms
0.57 Ga
Earliest known life (~3500)
4.5 Ga
Info lost due to erosion
Archean 4.5 - 2.5 Ga
Continents
•  Crust formation 4.3 - 3.8 Ga (cooling)
•  Micro continent scale landmasses, small
plates 3.8 - 2.5 Ga
•  Large continents, large plates 2.5 Ga
(changes in interior thermal regime)
Climate
•  20 - 30% lower solar luminosity
•  CO2 concentration 30 - 300 times present
value
•  Water on continents
•  Evidence of life in combination with CO2
concentrations constrain temperature to
<60°C at 4.2 Ga (present 15°C).
•  First evidence of glacial conditions 2.7 Ga
9
Proterozoic 2.5 - 0.57 Ga
Evidence for low latitude glaciation
•  2.7 - 2.3 Ga
•  0.9 - 0.6 Ga
Questions:
•  Why glaciation? Snul low, CO2 Low?
•  Why moderate climate between 2.3 0.9 Ga?
Major tectonic events:
•  Super continent Rodinia breaks up to
form Gondwanaland and Laurasia
• North America
• South America
• Afrika
• Eurasia
• Australia
• Antarctica
Paleozoic
Climates on super continents
Formation Pangaea
0.2 Ga
• North America
• South America
• Afrika
• Eurasia
• Australia
• Antarctica
0.57 Ga
General climate knowledge:
•  Life
•  Water
Paleozoic
0.57 - 0.23 Ga
•  Generally mild with 2
major glaciation events
•  0.44 - 0.41
•  0.33 - 0.23
•  Sea level variations
•  NOT glacio-eustatic
•  Variations in tectonic
activity (ocean ridges)
Cambrian 0.57 - 0.46 Ga
• North America
• South America
• Afrika
• Eurasia
• Australia
• Antarctica
•  Knowledge still limited (no plant
life yet)
•  Relatively warm period
•  Sea levels high (enhanced
volcanic activity after break up of
Rodinia)
•  CO2 estimates 10 times present
value
10
Late Ordovician
0.44 - 0.41 Ga
• North America
• South America
• Afrika
• Eurasia
• Australia
• Antarctica
CO2 levels still high (10 times),
in contrast to pleistocene
glaciation indicating low CO2
values in glacial times.
⇒ Location pole
•  Glaciation triggered by uplifting of
Australia and South America, extend
similar to Pleistocene
• North America
• South America
• Afrika
• Eurasia
• Australia
• Antarctica
Transition
•  No evidence for glaciation
•  Drop in sea level restricts ocean
circulation
•  Increase in seasonal cycle of
temperature over land
•  Expansion of plant life
⇒ affects climate
•  decrease surface albedo
•  decrease in CO2
•  change in hydrological cycle
First period with glacial
evidence:
Sahara desert, located at south
Pole.
Paleozoic glaciation
0.33 - 0.23 Ga
Mid paleozoic
0.41 - 0.33 Ga
• North America
• South America
• Afrika
• Eurasia
• Australia
• Antarctica
Paleozoic glaciation
0.33 - 0.23 Ga
• North America
• South America
• Afrika
• Eurasia
• Australia
• Antarctica
Sea level variations now linked to
glacial extend
•  Removal of ice sheet could have
happened very quick
•  Characteristic time scale of
variations is ~400 000 yrs,
suggesting orbital insolation changes
•  Massive coal deposition
•  Final formation of Pangea
11
Mesozoic
Break up of Pangea
Age of the Dinosaurs
0.2 Ga
Late Cretaceous
•  Evidence for mid- and high latitude
warmth, Antarctica still ice free?
• Poles 20 degrees warmer than P-D?
•  Explained by
•  Changes in land-sea distribution
•  Changes in ocean heat transport
•  Higher levels of CO2
•  Ends with a big bang!
• North America
• South America
• Afrika
• Eurasia
• Australia
• Antarctica
•  Extremely continental climates,
large seasonal variations
•  Temperature same range as
present, but warmer
•  Salt deposits indicate very arid
conditions
•  CO2 4 - 6 times higher
•  Break up of Pangea starts 140 Ma
•  Regional seas enhance
precipitation regionally
•  Some evidence in orbital induced
variations in monsoon intensity
0.065 Ga
Cretaceous
136 - 65 Ma
Mesozoic
0.33 - 0.065 Ga
• North America
• South America
• Afrika
• Eurasia
• Australia
• Antarctica
End Cretaceous/Mesozoic 65 Ma
•  K-T Boundary ⇒ clay deposits
marked by anomalously high
iridium content
• ~75% of all living species
became extinct
•  Evidence suggests some
species earlier than 65 Ma
•  Cycles of extinction?
12
The end of the Cretaceous /
Mesozoic 65 Ma
The end of the Cretaceous /
Mesozoic 65 Ma
•  Evidence (high iridium content)
suggests an asteroid impact
•  Diameter of ~ 10 km
•  Likely impact site near Yucatan
Peninsula in Gulf of Mexico
Summary
•  Not much knowledge on the early climate
history of the Earth
•  Large climate variations
•  Increasing knowledge towards the present
•  Decrease in temperature, CO2, sea level
•  Interesting questions arise
•  Faint Young Sun paradox (S0 and CO2)
•  Mild conditions 2.3 - 0.6 Ga (??)
•  High CO2 during Ordovician glaciation
0.44-0.41 Ga (Location pole)
• Small meridional gradient in warm climates
•  Pleistocene glacial variability forcing
(Orbital)
Nitric acid production
Water pollution
Reduction ozone
Burning vegetation
Shock waves
Tsunami’s
Dust in stratosphere
Summary
•  3 types of records:
•  Instrumental
•  Historical
•  Paleoclimatological
•  Different types of records have their own specific problems
•  Continuity
•  Length, period open to study
•  Accuracy
•  Sampling interval
•  Dating of records is crucial
•  Correct transfer functions necessary
13
What did we learn?
*Background concept of paleoclimatology
transfer function/dating problem
*Geological calendar
*Forcing mechanisms
*Concept of proxies
biological,tree rings, shore lines, marine sediments,
ice cores
14