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How stable or variable is the climate of Amazonia?

Frank MayleMitch PowerBronwen WhitneyUniversity of Edinburgh

Mark BushFlorida Institute of Technology

Paul Baker, Sheri Fritz etc etc etc

Glacial-interglacial climate change

• The last glacial period• The Holocene • High-frequency oscillations &

teleconnections

2

• Temperature• Carbon dioxide• Precipitation

• Temporal patterns• Spatial patterns• Drivers

Palaeoclimate proxies

Diatoms

Ice-cores

Pollen

Stalagmites/stalactites

Charcoal

3

Last Glacial Maximum (LGM)• 21,000 years ago• Sea-level 120 m

below present• CO2 180 ppm

Temperature

4

Modified ecoregion map Olson et al., 2000

LGM ca. 5°C colder

Andean taxamove downslope800 – 1500 m

PodocarpusDrimysAlnusWeinmanniaHedyosmum More frequent polar incursions

associated with expanded ice-sheets?

Reduced greenhouse effect due to low atm CO2?

Was cooling synchronous acrossAmazonia?

Only 2 records from Amazon interior!

Precipitation

5

Modified ecoregion map Olson et al., 2000

Much higher than present

Similar to present

Lower than present

Precipitation during the LGM

Titicaca

Salar de Uyuni La Gaiba

SpeleothemsChaplin

Pata

Amazon Fan

Porto Velho

Forested AmazonBasin(Haffer was wrong!)

Only 2 records from Amazon interior!

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Modified ecoregion map Olson et al., 2000

Much higher than present

Similar to present

Lower than present

Precipitation during the LGM

Titicaca

Salar de Uyuni

Umayo satellite imageLake Titicaca

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Salar de Uyuni

130 m deep at the LGMBaker et al., 2001

Salar de Uyuni drill coresedimentology

Lacustrine MudsSalts (halite)

Courtesy of Sheri Fritz

8

Salar de UyuniWet – dry cycles

Hol

ocen

e

Eem

ian

130 m deep lakeat the LGM

Lake

Salt pan

Courtesy of Sheri Fritz

Modified ecoregion map Olson et al., 2000

Much higher than present

Similar to present

Lower than present

Precipitation during the LGM

La Gaiba

Titicaca

Salar de Uyuni

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Laguna La Gaiba

Modified ecoregion map Olson et al., 2000

Much higher than present

Similar to present

Lower than present

Precipitation during the LGM

Titicaca

Salar de Uyuni La Gaiba

Chaplin

10

Outline NKMNP

Mayle et al. (2000) Science 290, 2291-2294.

Burbridge et al. (2004)Quaternary Research 61,215-230.

Laguna Chaplin

Noel Kempff Mercado National Park, NE Bolivia

0

50

100

150

200

250

300

350

-30 -25 -20 -15

Delta 13CTOC

‰ vs. PDB

Wet?LGM

11

Wang et al., 2004Nature, 432

Auler et al., 2004JQS, 19

Speleothems & travertines, caatinga, NE Brazil

LGM

Bush et al., 2007

Ice-Age Amazonia was both wet and dry!But Amazon remained forested!

• 20,000-yr periodicity • correlates with the precession

orbital cycle• change in seasonal amplitude

of insolation• change in strength of South

American summer monsoon

LGM

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The Holocene

Modified ecoregion map Olson et al., 2000

Early-Mid Holocene aridity

Arid episodebetween 9 & 3 ka BP

Ecotonal areas

13

Umayo satellite imageLake Titicaca

Mid-Holocene lowstandca. 8,000 to 3,000 yrs ago

90 m below present6,000 years ago(shown by seismic data)

0

50

100

150

200

250

300

350

-30 -25 -20 -15

Delta 13CTOC

‰ vs. PDB

Mid Holocene aridity

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Early-mid Holocene aridity

Northern Bolivia, Sep 14th 2004

Courtesy of Yadvinder Malhi

Biomass burning21,000 yr BP to present

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High-frequency climatic oscillations&

inter-hemispheric teleconnections

Holocene record of Lake TiticacaBaker et al., 2005, JQS, 20

• Centennial-scale fluctuations in organics• Correlate with North Atlantic SST fluctuations

Tipping points??

16

Salar de UyuniWet – dry cycles

Hol

ocen

e

Eem

ian

Lake

Salt pan

Courtesy of Sheri Fritz

Synchronous with North Atlanticsea-surface temp oscillations Tipping points??

• Millennial-scale glacial pluvial phases

• Synchronous with:– Cold episodes in

Greenland & North Atlantic

– Decreased river runoff in Cariaco Basin

– Weak East Asian summer monsoon

Speleothemscaatinga, NE Brazil

Wang et al., 2004, Nature, 432

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Salar de UyuniGlacial-Holocene transition

Lake

Salt pan

Courtesy of Sheri Fritz

Wet period synchronous with North Atlantic Younger Dryas cold period?

Laguna La Gaiba Correlative with EuropeanYounger Dryas cooling?

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Conclusions• The orbital 20-kyr precession cycle drives long-

term Amazon climate change– via changes to seasonal amplitude of insolation– contrasts with 100-kyr eccentricity cycle in mid-high

latitudes• Short-term (centennial/millennial-scale) climatic

variations– inter-hemispheric connections

• Amazonia’s climate has never been stable!!– Stable Holocene climate in Oxford but high amplitude

climate change during Holocene in Amazonia• Mid-Holocene aridity

– best analogue for future mid-21st C Amazon??

Questions please