GEOG 415Advanced biogeography:Quaternary environments

Ian Hutchinson (RCB 7226)Office hours: Thursday 3:00-4:30Office phone: 778.782.3232email: ianh@sfu.ca

GEOG 415 - Housekeeping

• Course email: geog415-all@sfu.ca• Lecture slides and all handouts will

be posted on the course web site:www.sfu.ca/~ianh/geog415/

• Thumbnails of lecture slides (6/page) available from instructor

• No text

GEOG 415 - Grades, etc.

•Laboratory assignments: 30%(see schedule)

•Term project: 30%•Final exam: 40%

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.

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

Reason #3: the Quaternary is the period of hominid radiation

Late Tertiary | Quaternary

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?

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.

Ice-Ages in geological history

0 200 400 600 800 1000

Qu

ate

rnary

Perm

o-

Carb

onife

rou

s

Ord

ovicia

n

Vara

ng

ian

Stu

rtian

Gn

ejsö

million years BP

“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

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.]

Tertiary cooling in sub-Antarctic waters: the drift to an icehouse

world

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.

Palaeocene palaeogeography

http://www.scotese.com/paleocen.htm

Oligocene palaeogeography

http://www.scotese.com/oligocen.htm

Initiation of glaciation of Antarctica in the early Oligocene: the record

from the Kerguelen Plateau

Kerguelen

Drake Passage(early Oligocene)

Rapid northward movementof Australia after late Eocene

Uplift of the Tibetan Plateau

Fig. 7.7 in Goudie (1992) “Environmental Change”

Tertiary cooling leads to Quaternary ice ages

Climatic decline in the Cenozoic

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

Locating the Pliocene-

Pleistocene boundary (Ma BP)

Quaternary time scale (ka BP)

Glaciations in the Alps:the Penck-Bruckner model

(1909)

“the great interglacial”

Quaternary temperature‘pulses’

interglacialglacial

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.

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

Calcareous tests of planktonic foraminifera

18O calculation

18O = (18O/ 16O) sample - (18O/ 16O) standard

(18O/ 16O) standard

x 1000

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

Universality of the

oceanic record(hence oxygen isotope stages)

The ice-core record

ice crystals

trapped air

dust particles?

Spectral analysisof Vostok -18O time series

Four superimposed pulses (105 ka, 41 ka, 23 ka, 19

ka), butwhat is the

‘pacemaker’?

Astronomical/celestial mechanics explanations:

James 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

Orbital eccentricity(product of

gravitational pull of other planets)

aphelion perihelion

Croll’s model

Ice Ages

~30% variation in solar radiation receipt between aphelion and perihelion at maximum eccentricity at

210 ka.

Milutin Milankovitch

• Serbian physicist; elaborated Croll’s model of effects of periodic variations in Earth orbit:

• 100 ka (eccentricity)• 41 ka (tilt)• 19-23 ka (precession)

Obliquity: axial tilt varies from 21.8° - 24.4° over 41 ka cycle as a result

of rotational wobble

strongly seasonal weakly seasonal

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.

Effects of astronomical forcings on summer solar radiation receipt at

65°N

glacials = cool northern summers?

interglacials = warm northern summers?

Synthesis of ocean-core evidence*

* Ruddiman and Raymo 1988. Phil. Trans. Royal Soc., B318, 411-430

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.

Solar activity and irradiance

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

Image credit: NASA (Catania Astrophysical Laboratory)

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 Earth’s 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 Earth’s Climate”. Praxis

Solar activity and Earth’s climatic phases in the last 1150 yrs

Om Wm Sm Mm Dm

MM

“Medieval warm period” “ Little Ice Age”

New Scientist, Nov. 12, 2003.

Phases of solar activity in last millennium

Approximate times of sunspot minima (Xm)

AD 1000 - 1050 Om = Oort minimumAD 1280 - 1340 Wm = Wolf minimumAD 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 maximumAD 1900 - 2000… (current maximum)

Future global temperature change scenarios (A, B, C)

2000 2050 2100

350

700

CO

2 (

pp

m)

B

A

C

+5°

0°

-5°

Thermohaline circulation I

= ‘The Great Salty”

Thermohaline circulation IIFormation 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

see: Stocker, T.F. and Schmittner, A. 1997, Nature 388, 862-865.

Collapse of ADW formation at CO2 levels >750 ppm

CO

2 p

pm