GEOG%20415%20Advanced%20biogeography:%20Quaternary%20environments

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GEOG 415Advanced biogeographyQuaternary
environments

• Ian Hutchinson (RCB 7226)
• Office hours Thursday 300-430
• Office phone [phone]
• email ianh_at_sfu.ca

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GEOG 415 - Housekeeping

• Course email geog415-all_at_sfu.ca
• Lecture slides and all handouts will be posted on
  the course web sitewww.sfu.ca/ianh/geog415/
• Thumbnails of lecture slides (6/page) available
  from instructor
• No text

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GEOG 415 - Grades, etc.

• Laboratory assignments 30(see schedule)
• Term project 30
• Final exam 40

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Why study Quaternary environments? Reason 1
Modern landscapes, both physical and biotic
(particularly at polar and north temperate
latitudes), have been strongly influenced by
Quaternary glaciations and associated
environmental changes.
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Why study Quaternary environments? Reason 2
Resource management decisions (e.g. groundwater
utilization, peat extraction, placer mining, soil
conservation, habitat management) may be
considerably enhanced by an understanding of
glaciology, Quaternary geology, and Quaternary
palaeoclimates
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Reason 3 the Quaternary is the period of
hominid radiation
Late Tertiary Quaternary
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Reason 4 The recent past may hold the key to
the near future
A) Is the current increase in global temperature
merely a blip, within the domain of natural
variation? B) Will global warming produce a
super-interglacial? C) Will global warming shut
down oceanic circulation, and initiate a new Ice
Age?
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Reason 4 (contd.)
A) Domain of natural variation can be established
by analysis of climatic and proxy environmental
records for the late Quaternary B) Previous
super interglacials may be good analogues for
current global warming C) Phases of abrupt
climate change in late Quaternary may provide
clues to triggers forcing a switch to another
climatic state.
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Ice-Ages in geological history
Permo- Carboniferous
Quaternary
Sturtian
Varangian
Gnejsö
Ordovician
0 200 400 600 800
1000
million years BP
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Greenhouse Icehouse
Strong circum-tropical current promotes
efficient transfer of heat to polar areas
Strong circum-polar currents inhibit transfer of
heat to polar areas
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Cenozoic climate decline
Mean annual temperatures in NW Europe and NW
North America (reconstructed from pollen) shown
in red based on Table 1.9 in Goudie (1992)
Environmental Change, Oxford. U.P.
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Tertiary cooling in sub-Antarctic waters the
drift to an icehouse world
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What prompted Cenozoic climate decline and the
onset of glaciation?
Main factors 1. Continental drift Isolation
of Antarctica and initiation of sub-Antarctic
oceanic circulation ice-sheet formationIsolation
of Arctic Ocean sea-ice formation 2.
OrogenesisIsolation of continental interiors,
particularly of Central Asia, as a result of
uplift of the Himalayas and Tibetan Plateau.
High altitude areas more snow cover high
albedo regional cooling.
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Palaeocene palaeogeography
http//www.scotese.com/paleocen.htm
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Oligocene palaeogeography
http//www.scotese.com/oligocen.htm
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Initiation of glaciation of Antarctica in the
early Oligocene the record from the Kerguelen
Plateau
Rapid northward movement of Australia after late
Eocene
Kerguelen
Drake Passage (early Oligocene)
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Uplift of the Tibetan Plateau
Fig. 7.7 in Goudie (1992) Environmental Change
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Tertiary cooling leads to Quaternary ice ages
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Climatic decline in the Cenozoic
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So if the Quaternary is defined as the most
recent Ice Age, when did it begin?
perhaps the most stirring impression produced by
recent great advances in the study of the
Quaternary period is that the Quaternary itself
is losing its classical identity Flint, R.F.
1971. Glacial and Quaternary Geology, p. 2
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Locating the Pliocene-Pleistocene boundary (Ma
BP)
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Quaternary time scale (ka BP)
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Glaciations in the Alpsthe Penck-Bruckner model
(1909)
the great interglacial
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Quaternary temperaturepulses
interglacial glacial
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Quaternary palaeothermometer stable isotopes of
oxygen
Evaporation of a water molecule containing18O
(heavy water) requires 12 more energy than
one containing 16O. Condensation of heavy
water requires 12 less energy.
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16O/18O ratios recorded in oceanic sediments
Two sources of information deep-sea cores or ice
cores. Oceanic record primarily reflects changes
in ice volume ice-core record primarily reflects
changes in temperature
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Calcareous tests of planktonic foraminifera
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d18O calculation
(18O/ 16O) sample - (18O/ 16O) standard
d18O
x 1000
(18O/ 16O) standard
Results expressed as 0/00, ppt, or per mil(le)
Standards are For forams PDB (Pee Dee Formation
belemnite from North Carolina) For water SMOW
(standard mean ocean water) O 0/00
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Universality of the oceanic record(hence oxygen
isotope stages)
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The ice-core record
ice crystals
trapped air
dust particles?
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Spectral analysisof Vostok d-18O time series
Four superimposed pulses (105 ka, 41 ka, 23 ka,
19 ka), butwhat is the pacemaker?
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Astronomical/celestial mechanics
explanationsJames Croll (1821-1890)

• Scottish mechanic, hotelkeeper, life insurance
  salesman, janitor and scientist
• Argued that greater orbital eccentricity led to
  colder winters and development of ice sheets in
  northern hemisphere

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Orbital eccentricity(product of gravitational
pull of other planets)
aphelion
perihelion
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Crolls model
Ice Ages
30 variation in solar radiation receipt between
aphelion and perihelion at maximum eccentricity
at 210 ka.
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Milutin Milankovitch

• Serbian physicist elaborated Crolls model of
  effects of periodic variations in Earth orbit
• 100 ka (eccentricity)
• 41 ka (tilt)
• 19-23 ka (precession)

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Obliquity axial tilt varies from 21.8 - 24.4
over 41 ka cycle as a result of rotational wobble
strongly seasonal
weakly seasonal
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Precession of the equinoxes
Precession results from changing position of
North Pole. Pole position rotates because the
Earth is not a perfect sphere hence equinoxes
change through year. At present northern
hemisphere tilted toward sun at aphelion.
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Effects of astronomical forcings on summer solar
radiation receipt at 65N
interglacials warm northern summers?
glacials cool northern summers?
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Synthesis of ocean-core evidence
late Pliocene (3.4 - 2.4 Ma) ice sheets in
northern hemisphere small extent controlled by
small-scale quasi-periodic oscillations. early
(Lower) Pleistocene (2.4 - 0.7 Ma) moderate
amplitude climate changes controlled by 41 ka
cycle of obliquity. late (Middle and Upper)
Pleistocene (0.7 Ma - present) large amplitude
climate changes controlled by 100 ka cycle of
orbital eccentricity.
Ruddiman and Raymo 1988. Phil. Trans. Royal
Soc., B318, 411-430
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Solar activity and irradiance
Image credit NASA (Catania Astrophysical
Laboratory)
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Is global warming a product of increased solar
activity?

• How do we track solar activity?
• 10-Be (beryllium-10) is a cosmogenic isotope
  that is produced when high-energy particles
  bombard Earths atmosphere. When the sun is
  active (during periods of increased sunspot
  activity) its magnetic field protects the Earth
  and little 10Be accumulates in ice and sediments.
• see Benestad, R.E. (2002) Solar Activity and
  Earths Climate. Praxis

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Solar activity and Earths climatic phases in the
last 1150 yrs
New Scientist, Nov. 12, 2003.
Om Wm Sm Mm Dm
MM
Medieval warm period Little
Ice Age
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Phases of solar activity in last millennium
Approximate times of sunspot minima (Xm) AD
1000 - 1050 Om Oort minimum AD 1280 -
1340 Wm Wolf minimum AD 1420 - 1540 Sm
Spörer minimumAD 1650 - 1710 Mm Maunder
minimumAD 1795 - 1825 Dm Dalton
minimum Approximate times of sunspot maxima
(XM) AD 1100 -1230 MM medieval maximum AD 1900
- 2000 (current maximum)
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Future global temperature change scenarios (A, B,
C)
B
700
5 0 -5
CO2 (ppm)
A
350
2000 2050 2100
C
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Thermohaline circulation I
The Great Salty
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Thermohaline circulation II
Formation of Atlantic Deep Water (ADW) takes
place in N. Atlantic. Downwelling initiated by
density differences between convergent tropical
(dense) and polar (light) shallow water masses.
Density differences are a product of contrasting
temperature and salinities (hence
thermohaline). ADW formation and circulation
is an important control on oceanic structure in
the Indian and Pacific Oceans, and hence global
climate. Shutdown of the Great Salty conveyor
may initiate near-glacial conditions in Europe
(Paris modern Spitzbergen?)
see Broecker, W. 1995. Chaotic climate Sci.
Amer., November, 62-68
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Collapse of ADW formation at CO2 levels gt750 ppm
CO2 ppm
see Stocker, T.F. and Schmittner, A. 1997,
Nature 388, 862-865.