TY - JOUR
T1 - A 45kyr palaeoclimate record from the lowland interior of tropical South America
AU - Whitney, Bronwen S.
AU - Mayle, Francis E.
AU - Punyasena, Surangi W.
AU - Fitzpatrick, Katharine A.
AU - Burn, Michael J.
AU - Guillen, René
AU - Chavez, Ezequiel
AU - Mann, David
AU - Pennington, R. Toby
AU - Metcalfe, Sarah E.
N1 - Funding Information:
We thank the authorities of San Matias National Park and Otuquis National Park for permission to core LLG and Dr. Timothy J. Killeen and the Muséo de Historia Natural ‘Noel Kempff Mercado’ (MHNNKM), Santa Cruz, Bolivia, for logistical support. William Gosling, Phil Metcalfe, Huw Jones, and Erik de Boer assisted with the fieldwork. We acknowledge the Royal Botanic Gardens Edinburgh and the MHNNKM for herbarium material. Thanks also to Jim Ratter (RBGE) contributing to the interpretation of the fossil pollen data. Funding was provided by: the Natural Science & Engineering Research Council (Canada) PGS-D (BSW) , the National Geographic Society (FEM) , the Royal Society (FEM) , the Leverhulme Trust research fellowship (FEM) , the Natural Environment Research Council (NERC) (UK) PhD scholarship (KAF) , the University of Edinburgh PhD scholarship (MJB) , and the NERC Radiocarbon Facility (NRCF) (FEM) . Elaine Watts (University of Nottingham) helped with map production. We also thank Charlotte Bryant (NRCF) for guidance on selection of material for radiocarbon dating.
PY - 2011/7/1
Y1 - 2011/7/1
N2 - We present a well-dated, high-resolution, ~45kyr lake sediment record reflecting regional temperature and precipitation change in the continental interior of the Southern Hemisphere (SH) tropics of South America. The study site is Laguna La Gaiba (LLG), a large lake (95km2) hydrologically-linked to the Pantanal, an immense, seasonally-flooded basin and the world's largest tropical wetland (135,000km2). Lake-level changes at LLG are therefore reflective of regional precipitation. We infer past fluctuations in precipitation at this site through changes in: i) pollen-inferred extent of flood-tolerant forest; ii) relative abundance of terra firme humid tropical forest versus seasonally-dry tropical forest pollen types; and iii) proportions of deep- versus shallow-water diatoms. A probabilistic model, based on plant family and genus climatic optima, was used to generate quantitative estimates of past temperature from the fossil pollen data. Our temperature reconstruction demonstrates rising temperature (by 4°C) at 19.5kyr BP, synchronous with the onset of deglacial warming in the central Andes, strengthening the evidence that climatic warming in the SH tropics preceded deglacial warming in the Northern Hemisphere (NH) by at least 5kyr. We provide unequivocal evidence that the climate at LLG was markedly drier during the last glacial period (45.0-12.2kyr BP) than during the Holocene, contrasting with SH tropical Andean and Atlantic records that demonstrate a strengthening of the South American summer monsoon during the global Last Glacial Maximum (~21kyr BP), in tune with the ~20kyr precession orbital cycle. Holocene climate conditions occurred as early as 12.8-12.2kyr BP, when increased precipitation in the Pantanal catchment caused heightened flooding and rising lake levels in LLG. In contrast to this strong geographic variation in LGM precipitation across the continent, expansion of tropical dry forest between 10 and 3kyr BP at LLG strengthens the body of evidence for widespread early-mid Holocene drought across tropical South America.
AB - We present a well-dated, high-resolution, ~45kyr lake sediment record reflecting regional temperature and precipitation change in the continental interior of the Southern Hemisphere (SH) tropics of South America. The study site is Laguna La Gaiba (LLG), a large lake (95km2) hydrologically-linked to the Pantanal, an immense, seasonally-flooded basin and the world's largest tropical wetland (135,000km2). Lake-level changes at LLG are therefore reflective of regional precipitation. We infer past fluctuations in precipitation at this site through changes in: i) pollen-inferred extent of flood-tolerant forest; ii) relative abundance of terra firme humid tropical forest versus seasonally-dry tropical forest pollen types; and iii) proportions of deep- versus shallow-water diatoms. A probabilistic model, based on plant family and genus climatic optima, was used to generate quantitative estimates of past temperature from the fossil pollen data. Our temperature reconstruction demonstrates rising temperature (by 4°C) at 19.5kyr BP, synchronous with the onset of deglacial warming in the central Andes, strengthening the evidence that climatic warming in the SH tropics preceded deglacial warming in the Northern Hemisphere (NH) by at least 5kyr. We provide unequivocal evidence that the climate at LLG was markedly drier during the last glacial period (45.0-12.2kyr BP) than during the Holocene, contrasting with SH tropical Andean and Atlantic records that demonstrate a strengthening of the South American summer monsoon during the global Last Glacial Maximum (~21kyr BP), in tune with the ~20kyr precession orbital cycle. Holocene climate conditions occurred as early as 12.8-12.2kyr BP, when increased precipitation in the Pantanal catchment caused heightened flooding and rising lake levels in LLG. In contrast to this strong geographic variation in LGM precipitation across the continent, expansion of tropical dry forest between 10 and 3kyr BP at LLG strengthens the body of evidence for widespread early-mid Holocene drought across tropical South America.
KW - Diatoms
KW - Holocene
KW - Last Glacial Maximum
KW - Palaeoclimate
KW - Pollen
KW - Tropical South America
UR - http://www.scopus.com/inward/record.url?scp=79960384618&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=79960384618&partnerID=8YFLogxK
U2 - 10.1016/j.palaeo.2011.05.012
DO - 10.1016/j.palaeo.2011.05.012
M3 - Article
AN - SCOPUS:79960384618
SN - 0031-0182
VL - 307
SP - 177
EP - 192
JO - Palaeogeography, Palaeoclimatology, Palaeoecology
JF - Palaeogeography, Palaeoclimatology, Palaeoecology
IS - 1-4
ER -