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Late Quaternary (esp. post-LGM) environmental change in the humid and seasonal tropics

Late Quaternary (esp. post-LGM) environmental change in the humid and seasonal tropics. Palaeoprecipitation: was the LGM drier (and by how much)? Palaeotemperatures: was the LGM much cooler? - South American and PNG evidence

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Late Quaternary (esp. post-LGM) environmental change in the humid and seasonal tropics

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  1. Late Quaternary (esp. post-LGM) environmental change in the humid and seasonal tropics • Palaeoprecipitation: was the LGM drier (and by how much)? • Palaeotemperatures: was the LGM much cooler? - South American and PNG evidence • Vegetation and faunal response: the rise (and fall?) of refuges - South America, Africa and Indo-Australia • Holocene droughts and cultural responses - the Mayan example

  2. Cautionary note: geo-generalizations ahead!(blame large scale and a low density of palaeo-sites) 200 sites? 20 sites?

  3. Were the tropics arid during the LGM ? (climate model output) from: Ganopolski et al., (1998) Nature, 391, 351-6

  4. LGM aridity:the evidence from the Amazonian fan and Lake Junin, Peru from:Maslin and Burns (2000) Science, 290, 2285-2287.

  5. Status Low Intermediate High No record (= dry?) African lake level status at LGM

  6. LGM and Holocene pollen record, Lake Victoria From: Stager et al. (1997)Quaternary Research, 47, 81-89.

  7. Palaeo-lake shorelines inEast Africa +100 0 -100 L. Victoria L. Turkana (Rudolf) ? ? metres (rel. to PD) ? ? 0 10 20 30 ka, BP 200 km Base map: Good’s Atlas

  8. LGM palaeo-temperature:the CLIMAP model (1970’s). CLIMAP Project Members,  (1976) The surface of the ice-age Earth.    Science 191, 1131-1137 SST (August) Apart from the areas influenced by the eastern boundary currents, tropical SST values at the LGM were estimated (from foram d18O values) to be only about 1°C less than at present.

  9. Coupled-climate model output of glacial conditions: tropical air temperatures about 5°C less; SST 3-4°C less than at present from: Ganopolski et al., (1998) Nature, 391, 351-6

  10. LGM palaeotemperatures:evidence from tropical ice cores Sajama From: Thompson et al., (2000) Quaternary Science Reviews, 19, 19-35.

  11. LGM palaeotemperatures:evidence from tropical ice cores 0 5 10 15 20 25 ka BP 4.5°C 5°C 5°C From: Thompson et al., (2000) Quaternary Science Reviews, 19, 19-35.

  12. LGM palaeotemperatures:palaeoecological evidence • d18O values from corals dating from 18 ka BP in Barbados indicate SST values ~5° C lower than at present (de Villiers, et al., (1995) Science 269, 1247-1249.) • changes in vegetation at numerous sites in the montane tropics suggest that the altitudinal limits of vegetation belts were ~ 900 m lower at LGM than at present (equivalent to a temperature lowering of 5°C)(Bush, et al., (2001) in Markgraf (ed.), Interhemispheric Climate Linkages, Academic Press, pp. 293-306.)

  13. LGM palaeotemperatures in the Neotropics Site Country Lat. Alt (m) Cooling(°C) Age(cal ka) El Valle Panama 8 N 500 -6 14 San Juan Bosco Ecuador 3 N 970 -7.5 35 Lagoa Pata Brazil 0 300 -5 17 Lagoa Verde Brazil 0 300 -5 ? Carajas Brazil 6 S 700 -5 10 Serra Grande Brazil 7 S ? -5 ? Aguas Emedadas Brazil 15 S 1040 -5 17 Serra Negra Brazil 19 S 1170 -5 ? Salitre Brazil 19 S 1050 -5 13 Catas Altas Brazil 20 S 755 -7 21-31 Botucatu Brazil 23 S 770 -5 to -7 ? from: Bush et al., (2001) in Markgraf (ed.) “Interhemispheric Climate Linkages”, Academic Press, Table 1.

  14. The effects of a 5°C lowering of air temperature at LGM in the Neotropics

  15. Temperature (coldest month) in the tropics at LGM compared to PD Was cooling around Atlantic greater than around margins of Indian and Pacific Oceans? www.bgc-jena.mpg.de/bgc_prentice/ databases/ferrara/fig4.jpg

  16. or not? (data from PNG highlands)

  17. PD vs. LGM: the effects of lowered temperature and reduced rainfall

  18. LGM in the humid tropics: plant and animal responses Were tropical rain forests restricted to small refuges at LGM?

  19. The rise of refuge theory*:endemism in the Neo-tropical forest avifauna * Haffer (1969) Science, 165, 131-137. from: Prance and Lovejoy (1985) Amazonia, Oxford U.P.

  20. Ranges of related forest bird species and subspecies Trumpeters (Psophia) Jacamars (Galbula)

  21. Ranges of related forest bird species and subspecies Aracaris (Pteroglossus) Toucans (Rhamphastos)

  22. Species and subspecies ranges:Heliconius butterflies

  23. Inferred LGM forest refuges based on:1. birds2. lizards3. butterflies4. four tree families5. scorpions From: Nores (1999) J. Biogeography, 26, 475-485

  24. TRF refuges: a minimalist reconstruction Lake Pata forest desert from: Tallis (1991) Plant Community History, Chapman and Hall

  25. The demise of refuge theory?The Lake Pata record Trees from: Colinvaux et al., (1996) Science, 274, 85-88.

  26. Is a compromise possible? 2 1 3 Lake Pata, Brazil1. Laguna Chaplin, Bolivia 2. Laguna Sardinas, Colombia 3. Lago do Pires, Brazil Maps: Good’s Atlas

  27. The palaeoclimatic record from eastern Bolivia from: Mayle et al (2000) Science, 290, 2291-2294.

  28. Late Holocene expansion ofAmazonian rainforests “... the humid evergreen rain forests of eastern Bolivia havebeen expanding southward over the past 3000 years and that theirpresent-day limit represents the southernmost extent of Amazonianrain forest over at least the past 50,000 years. This rain forestexpansion is attributed to increased seasonal latitudinal migrationof the Intertropical Convergence Zone, which can in turn be explainedby Milankovitch astronomic forcing.” Mayle et al., (2000) Science. 290, 2291-2294.

  29. The palaeo-climatic record from east-central Brazil from: Grimm et al., (2001) in Markgraf (ed.) “Interhemispheric Climate Linkages”, Academic Press, pp. 324-367.

  30. The palaeo-climatic record from north-eastern Colombia from: Grimm et al., (2001) in Markgraf (ed.) “Interhemispheric Climate Linkages”, Academic Press, pp. 324-367.

  31. Long core sites (Australia-Indonesian region) 2 1 4 3 Numbers refer to cores on next slide

  32. Long cores: Australia-Indonesia 1 2 3 4

  33. Lynch’s Crater: Queensland

  34. Holocene climate change in East Africa humid period

  35. Late Holocene droughts on the margins of the humid tropics: the collapse of Mayan civilization

  36. Historical droughts A sustained drought in AD 1648-1654 left painful memories in the Yucatan: “ The starvation as it developed was terrible and desolating…The poor, wasted and gaunt, …pulling up grass and roots, ate them to avoid starvation; public places were sown with corpses; the inhabitants looked more like specters than living men, entire places were abandoned … the best populated sites of Yucatan were threatened with being left deserted and barren” Molina Hübbe (1941, p 20-21), quoted in Gill (2000) “The Great Maya Droughts”, University of New Mexico Press, p. 305

  37. Cultural chronology in the Mayan area Source: David A. Hodell Department of Geology, University of Florida

  38. Growth and demise of classic Maya culture Clusters of abrupt events (last dates on Maya monuments) [after Gill (2000) p. 326]. 810 860 890- 910 Source: David A. Hodell, Department of Geology, University of Florida

  39. Symptoms and possible causes of the Maya collapse • Symptoms: • Rapid depopulation of the countryside and ceremonial centres in 50-100 years; • Abandonment of administrative centres and palaces; • Cessation of building, monument construction, and pottery manufacture; demise of classic calendrical and writing systems. • Inferred Causes • Natural - soil exhaustion, soil ersion, hurricanes, drought, disease • Social - peasant revolt, civil war, invasion

  40. The case for mega-drought:palaeo-climatic results from Yucatan lakes Source: David A. Hodell Department of Geology, University of Florida Chicanacanab Lake

  41. Symptoms of drought in a closed lake basin in a karstic landscape Source: David A. Hodell Department of Geology, University of Florida

  42. Symptoms of drought; shelly layers point to low accumulation of plant organics Source: David A. Hodell Department of Geology, University of Florida

  43. The Holocene record from Lake Chichancanab Source: David A. Hodell Department of Geology, University of Florida

  44. 860 1650 The Holocene record from Lake Chichancanab: d18O in ostracode tests Source: David A. Hodell Department of Geology, University of Florida

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