1
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Yang Y, Zhang L, Yi L, Zhong F, Lu Z, Wan S, Du Y, Xiang R. A contracting Intertropical Convergence Zone during the Early Heinrich Stadial 1. Nat Commun 2023; 14:4695. [PMID: 37542043 PMCID: PMC10403598 DOI: 10.1038/s41467-023-40377-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 07/14/2023] [Indexed: 08/06/2023] Open
Abstract
Despite the fact that the response of tropical hydroclimate to North Atlantic cooling events during the Heinrich Stadial 1 (HS1) has been extensively studied in African, South American and Indonesia, the nature of such responses remains debated. Here we investigate the tropical hydroclimate pattern over the Indo-Asian-Australian monsoon region during the HS1 by integrating hydroclimatic records, and examining a δ18Oseawater record from Globigerinoides ruber (white) in the tropical Indian Ocean. Our findings indicate that tropical hydrological conditions were synchronously arid in both hemispheres during the early HS1 (~18.3-16.3 ka) in the Indo-Asian-Australian monsoon region, except for a narrow, wet hydrological belt in northern low latitudes, suggesting the existence of a contracted tropical precipitation belt at that time. This study reveals that the meltwater discharge and resulting changes in global temperatures and El Niño exerted a profound influence on the tropical hydroclimate in the Indo-Asian-Australian monsoon region during the early HS1.
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Affiliation(s)
- Yiping Yang
- Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
| | - Lanlan Zhang
- Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
| | - Liang Yi
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, 200092, China
| | - Fuchang Zhong
- Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
| | - Zhengyao Lu
- Department of Physical Geography and Ecosystem Science, Lund University, 22362, Lund, Sweden
| | - Sui Wan
- Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
| | - Yan Du
- State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Rong Xiang
- Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
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2
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Baxter AJ, Verschuren D, Peterse F, Miralles DG, Martin-Jones CM, Maitituerdi A, Van der Meeren T, Van Daele M, Lane CS, Haug GH, Olago DO, Sinninghe Damsté JS. Reversed Holocene temperature-moisture relationship in the Horn of Africa. Nature 2023; 620:336-343. [PMID: 37558848 PMCID: PMC10412447 DOI: 10.1038/s41586-023-06272-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Accepted: 05/25/2023] [Indexed: 08/11/2023]
Abstract
Anthropogenic climate change is predicted to severely impact the global hydrological cycle1, particularly in tropical regions where agriculture-based economies depend on monsoon rainfall2. In the Horn of Africa, more frequent drought conditions in recent decades3,4 contrast with climate models projecting precipitation to increase with rising temperature5. Here we use organic geochemical climate-proxy data from the sediment record of Lake Chala (Kenya and Tanzania) to probe the stability of the link between hydroclimate and temperature over approximately the past 75,000 years, hence encompassing a sufficiently wide range of temperatures to test the 'dry gets drier, wet gets wetter' paradigm6 of anthropogenic climate change in the time domain. We show that the positive relationship between effective moisture and temperature in easternmost Africa during the cooler last glacial period shifted to negative around the onset of the Holocene 11,700 years ago, when the atmospheric carbon dioxide concentration exceeded 250 parts per million and mean annual temperature approached modern-day values. Thus, at that time, the budget between monsoonal precipitation and continental evaporation7 crossed a tipping point such that the positive influence of temperature on evaporation became greater than its positive influence on precipitation. Our results imply that under continued anthropogenic warming, the Horn of Africa will probably experience further drying, and they highlight the need for improved simulation of both dynamic and thermodynamic processes in the tropical hydrological cycle.
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Affiliation(s)
- A J Baxter
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands.
| | - D Verschuren
- Department of Biology, Limnology Unit, Ghent University, Gent, Belgium
| | - F Peterse
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands
| | - D G Miralles
- Department of Environment, Hydro-Climate Extremes Lab (H-CEL), Ghent University, Gent, Belgium
| | | | - A Maitituerdi
- Dr. Moses Strauss Department of Marine Geosciences, Leon H. Charney School of Marine Sciences, University of Haifa, Mount Carmel, Israel
| | - T Van der Meeren
- Department of Biology, Limnology Unit, Ghent University, Gent, Belgium
| | - M Van Daele
- Renard Centre of Marine Geology, Department of Geology, Ghent University, Gent, Belgium
| | - C S Lane
- Department of Geography, University of Cambridge, Cambridge, UK
| | - G H Haug
- Department of Climate Geochemistry, Max Planck Institute for Chemistry, Mainz, Germany
| | - D O Olago
- Institute for Climate Change and Adaptation, Department of Earth and Climate Science, University of Nairobi, Nairobi, Kenya
| | - J S Sinninghe Damsté
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands
- Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, Den Burg, The Netherlands
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3
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Du X, Russell JM, Liu Z, Otto-Bliesner BL, Oppo DW, Mohtadi M, Zhu C, Galy VV, Schefuß E, Yan Y, Rosenthal Y, Dubois N, Arbuszewski J, Gao Y. North Atlantic cooling triggered a zonal mode over the Indian Ocean during Heinrich Stadial 1. SCIENCE ADVANCES 2023; 9:eadd4909. [PMID: 36598985 PMCID: PMC9812376 DOI: 10.1126/sciadv.add4909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 11/23/2022] [Indexed: 06/17/2023]
Abstract
Abrupt changes in the Atlantic meridional overturning circulation (AMOC) are thought to affect tropical hydroclimate through adjustment of the latitudinal position of the intertropical convergence zone (ITCZ). Heinrich Stadial 1 (HS1) involves the largest AMOC reduction in recent geological time; however, over the tropical Indian Ocean (IO), proxy records suggest zonal anomalies featuring intense, widespread drought in tropical East Africa versus generally wet but heterogeneous conditions in the Maritime Continent. Here, we synthesize proxy data and an isotope-enabled transient deglacial simulation and show that the southward ITCZ shift over the eastern IO during HS1 strengthens IO Walker circulation, triggering an east-west precipitation dipole across the basin. This dipole reverses the zonal precipitation anomalies caused by the exposed Sunda and Sahul shelves due to glacial lower sea level. Our study illustrates how zonal modes of atmosphere-ocean circulation can amplify or reverse global climate anomalies, highlighting their importance for future climate change.
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Affiliation(s)
- Xiaojing Du
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, USA
- Institute at Brown for Environment and Society, Brown University, Providence, RI, USA
| | - James M. Russell
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, USA
- Institute at Brown for Environment and Society, Brown University, Providence, RI, USA
| | - Zhengyu Liu
- Atmospheric Science Program, Department of Geography, The Ohio State University, Columbus, OH, USA
| | - Bette L. Otto-Bliesner
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
| | - Delia W. Oppo
- Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Mahyar Mohtadi
- MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Chenyu Zhu
- Frontier Science Center for Deep Ocean Multispheres and Earth System (FDOMES) and Physical Oceanography Laboratory, Ocean University of China, Qingdao, China
| | - Valier V. Galy
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Enno Schefuß
- MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Yan Yan
- State Key Laboratory of Isotope Geochemistry, CAS Center for Excellence in Deep Earth Science, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
| | - Yair Rosenthal
- Department of Marine and Coastal Sciences and Department of Earth and Planetary Sciences, Rutgers, State University of New Jersey, New Brunswick, NJ, USA
| | - Nathalie Dubois
- Department of Surface Waters Research and Management, Eawag, Dübendorf, Switzerland
- Department of Earth Sciences, ETH Zürich, Zürich, Switzerland
| | - Jennifer Arbuszewski
- Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Yu Gao
- Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing, China
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4
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Chen Z, Zhou T, Chen X, Zhang W, Zhang L, Wu M, Zou L. Observationally constrained projection of Afro-Asian monsoon precipitation. Nat Commun 2022; 13:2552. [PMID: 35538080 PMCID: PMC9090792 DOI: 10.1038/s41467-022-30106-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 04/06/2022] [Indexed: 11/09/2022] Open
Abstract
The Afro-Asian summer monsoon (AfroASM) sustains billions of people living in many developing countries covering West Africa and Asia, vulnerable to climate change. Future increase in AfroASM precipitation has been projected by current state-of-the-art climate models, but large inter-model spread exists. Here we show that the projection spread is related to present-day interhemispheric thermal contrast (ITC). Based on 30 models from the Coupled Model Intercomparison Project Phase 6, we find models with a larger ITC trend during 1981-2014 tend to project a greater precipitation increase. Since most models overestimate present-day ITC trends, emergent constraint indicates precipitation increase in constrained projection is reduced to 70% of the raw projection, with the largest reduction in West Africa (49%). The land area experiencing significant increases of precipitation (runoff) is 57% (66%) of the raw projection. Smaller increases of precipitation will likely reduce flooding risk, while posing a challenge to future water resources management.
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Affiliation(s)
- Ziming Chen
- State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Tianjun Zhou
- State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China. .,University of Chinese Academy of Sciences, 100049, Beijing, China. .,CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences (CAS), Beijing, China.
| | - Xiaolong Chen
- State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China.,CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences (CAS), Beijing, China
| | - Wenxia Zhang
- State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China
| | - Lixia Zhang
- State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China.,CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences (CAS), Beijing, China
| | - Mingna Wu
- State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Liwei Zou
- State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China
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5
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Shipton C, Blinkhorn J, Archer W, Kourampas N, Roberts P, Prendergast ME, Curtis R, Herries AIR, Ndiema E, Boivin N, Petraglia MD. The Middle to Later Stone Age transition at Panga ya Saidi, in the tropical coastal forest of eastern Africa. J Hum Evol 2021; 153:102954. [PMID: 33714916 DOI: 10.1016/j.jhevol.2021.102954] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 01/18/2021] [Accepted: 01/19/2021] [Indexed: 12/26/2022]
Abstract
The Middle to Later Stone Age transition is a critical period of human behavioral change that has been variously argued to pertain to the emergence of modern cognition, substantial population growth, and major dispersals of Homo sapiens within and beyond Africa. However, there is little consensus about when the transition occurred, the geographic patterning of its emergence, or even how it is manifested in the stone tool technology that is used to define it. Here, we examine a long sequence of lithic technological change at the cave site of Panga ya Saidi, Kenya, that spans the Middle and Later Stone Age and includes human occupations in each of the last five Marine Isotope Stages. In addition to the stone artifact technology, Panga ya Saidi preserves osseous and shell artifacts, enabling broader considerations of the covariation between different spheres of material culture. Several environmental proxies contextualize the artifactual record of human behavior at Panga ya Saidi. We compare technological change between the Middle and Later Stone Age with on-site paleoenvironmental manifestations of wider climatic fluctuations in the Late Pleistocene. The principal distinguishing feature of Middle from Later Stone Age technology at Panga ya Saidi is the preference for fine-grained stone, coupled with the creation of small flakes (miniaturization). Our review of the Middle to Later Stone Age transition elsewhere in eastern Africa and across the continent suggests that this broader distinction between the two periods is in fact widespread. We suggest that the Later Stone Age represents new short use-life and multicomponent ways of using stone tools, in which edge sharpness was prioritized over durability.
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Affiliation(s)
- Ceri Shipton
- Institute of Archaeology, Gordon Square, University College London, London, WC1H 0PY, UK; Centre of Excellence for Australian Biodiversity and Heritage, The Australian National University, Canberra, ACT, 2000, Australia.
| | - James Blinkhorn
- Department of Geography, Royal Holloway, University of London, Egham, TW20 0EX, UK; Pan-African Evolution Research Group, Max Planck Institute for the Science of Human History, Kahlaische Strasse 10, 07745, Jena, Germany
| | - Will Archer
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Pl. 6, 04103, Leipzig, Germany; Department of Archaeology, University of Cape Town, Rondebosch, 7701, South Africa; Department of Archaeology, National Museum, Bloemfontein, 9300, South Africa
| | - Nikolaos Kourampas
- Centre for Open Learning, University of Edinburgh, Edinburgh, UK; Biological and Environmental Sciences, University of Stirling, Stirling, UK
| | - Patrick Roberts
- Department of Archaeology, Max Planck Institute for the Science of Human History, Kahlaische Strasse 10, 07745, Jena, Germany
| | - Mary E Prendergast
- Department of Sociology and Anthropology, Saint Louis University, Avenida del Valle 34, Madrid, Spain; Department of Anthropology, Rice University, Houston, TX, USA
| | - Richard Curtis
- The Australian Archaeomagnetism Laboratory, Department of Archaeology and History, La Trobe University, Melbourne Campus, Bundoora, 3086, Australia
| | - Andy I R Herries
- The Australian Archaeomagnetism Laboratory, Department of Archaeology and History, La Trobe University, Melbourne Campus, Bundoora, 3086, Australia; Palaeo-Research Institute, University of Johannesburg, Auckland Park, Gauteng, South Africa
| | - Emmanuel Ndiema
- Department of Earth Sciences, National Museum of Kenya, Museum Hill Road, Nairobi, Kenya
| | - Nicole Boivin
- Department of Archaeology, Max Planck Institute for the Science of Human History, Kahlaische Strasse 10, 07745, Jena, Germany; Department of Anthropology, National Museum of Natural History, Smithsonian Institution, 600 Maryland Ave SW, Washington, D.C., USA; School of Social Science, The University of Queensland, Brisbane, QLD, 4072, Australia; Department of Anthropology and Archaeology, University of Calgary, 620 2500, University Drive NW, Calgary, Canada
| | - Michael D Petraglia
- Department of Archaeology, Max Planck Institute for the Science of Human History, Kahlaische Strasse 10, 07745, Jena, Germany; Department of Anthropology, National Museum of Natural History, Smithsonian Institution, 600 Maryland Ave SW, Washington, D.C., USA; School of Social Science, The University of Queensland, Brisbane, QLD, 4072, Australia
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6
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Seasonal drought events in tropical East Asia over the last 60,000 y. Proc Natl Acad Sci U S A 2020; 117:30988-30992. [PMID: 33229562 DOI: 10.1073/pnas.2013802117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cause of seasonal hydrologic changes in tropical East Asia during interstadial/stadial oscillations of the last glaciation remains controversial. Here, we show seven seasonal drought events that occurred during the relatively warm interstadials by phytolith and pollen records. These events are significantly manifested as high percentages of bilobate phytoliths and are consistent with the large zonal sea-surface temperature (SST) gradient from the western to eastern tropical Pacific, suggesting that the reduction in seasonal precipitation could be interpreted by westward shifts of the western Pacific subtropical high triggered by changes of zonal SST gradient over the tropical Pacific and Hadley circulation in the Northern Hemisphere. Our findings highlight that both zonal and meridional ocean-atmosphere circulations, rather than solely the Intertropical Convergence Zone or El Niño-Southern Oscillation, controlled the hydrologic changes in tropical East Asia during the last glaciation.
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7
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Badino F, Pini R, Bertuletti P, Ravazzi C, Delmonte B, Monegato G, Reimer P, Vallé F, Arrighi S, Bortolini E, Figus C, Lugli F, Maggi V, Marciani G, Margaritora D, Oxilia G, Romandini M, Silvestrini S, Benazzi S. The fast-acting "pulse" of Heinrich Stadial 3 in a mid-latitude boreal ecosystem. Sci Rep 2020; 10:18031. [PMID: 33093492 PMCID: PMC7581741 DOI: 10.1038/s41598-020-74905-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 09/29/2020] [Indexed: 11/10/2022] Open
Abstract
A 3800 year-long radiocarbon-dated and highly-resolved palaeoecological record from Lake Fimon (N-Italy) served to investigate the effects of potential teleconnections between North Atlantic and mid-to-low latitudes at the transition from Marine Isotope Stage (MIS) 3 to 2. Boreal ecosystems documented in the Fimon record reacted in a sensitive way to millennial and sub-millennial scale Northern Hemisphere atmospheric circulation patterns. The high median time-resolution of 58 years allows the identification of five abrupt event-boundaries (i.e., main forest expansion and decline excursions) synchronous with the sharp stadial/interstadial (GS/GI) transitions within dating uncertainties. During Heinrich Stadial 3 (HS 3) we reconstruct more open and dry conditions, compared to the other GS, with a dominant regional scale fire signal. Linkages between local fires and climate-driven fuel changes resulted in high-magnitude fire peaks close to GI/GS boundaries, even exacerbated by local peatland conditions. Finally, palaeoecological data from the HS 3 interval unveiled an internal variability suggesting a peak between 30,425 and 29,772 cal BP (2σ error) which matches more depleted δ18O values in alpine speleothems. We hypothesise that this signal, broadly resembling that of other mid-latitudes proxies, may be attributed to the southward shift of the Northern Hemisphere storm tracks and the associated delayed iceberg discharge events as documented during other HS.
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Affiliation(s)
- Federica Badino
- Department of Cultural Heritage, University of Bologna, 48121, Ravenna, Italy. .,Research Group on Vegetation, Climate and Human Stratigraphy, Laboratory of Palynology and Palaeoecology, CNR-Institute of Environmental Geology and Geoengineering (IGAG), 20126, Milan, Italy.
| | - Roberta Pini
- Research Group on Vegetation, Climate and Human Stratigraphy, Laboratory of Palynology and Palaeoecology, CNR-Institute of Environmental Geology and Geoengineering (IGAG), 20126, Milan, Italy
| | - Paolo Bertuletti
- Research Group on Vegetation, Climate and Human Stratigraphy, Laboratory of Palynology and Palaeoecology, CNR-Institute of Environmental Geology and Geoengineering (IGAG), 20126, Milan, Italy.,Department of Environmental and Earth Sciences, University of Milano-Bicocca, 20126, Milan, Italy
| | - Cesare Ravazzi
- Research Group on Vegetation, Climate and Human Stratigraphy, Laboratory of Palynology and Palaeoecology, CNR-Institute of Environmental Geology and Geoengineering (IGAG), 20126, Milan, Italy
| | - Barbara Delmonte
- Department of Environmental and Earth Sciences, University of Milano-Bicocca, 20126, Milan, Italy
| | - Giovanni Monegato
- CNR-Institute of Geosciences and Earth Resources (IGG), 35131, Padua, Italy
| | - Paula Reimer
- School of Natural and Built Environment, Queen's University Belfast, Belfast, BT7 1NN, UK
| | - Francesca Vallé
- Department of Environmental and Earth Sciences, University of Milano-Bicocca, 20126, Milan, Italy
| | - Simona Arrighi
- Department of Cultural Heritage, University of Bologna, 48121, Ravenna, Italy.,Dipartimento di Scienze Fisiche, della Terra e dell'Ambiente, Università di Siena, 53100, Siena, Italy
| | - Eugenio Bortolini
- Department of Cultural Heritage, University of Bologna, 48121, Ravenna, Italy
| | - Carla Figus
- Department of Cultural Heritage, University of Bologna, 48121, Ravenna, Italy
| | - Federico Lugli
- Department of Cultural Heritage, University of Bologna, 48121, Ravenna, Italy.,Dipartimento di Scienze Chimiche e Geologiche, Università di Modena e Reggio Emilia, 41125, Modena, Italy
| | - Valter Maggi
- Department of Environmental and Earth Sciences, University of Milano-Bicocca, 20126, Milan, Italy
| | - Giulia Marciani
- Department of Cultural Heritage, University of Bologna, 48121, Ravenna, Italy.,Dipartimento di Scienze Fisiche, della Terra e dell'Ambiente, Università di Siena, 53100, Siena, Italy
| | - Davide Margaritora
- Department of Environmental and Earth Sciences, University of Milano-Bicocca, 20126, Milan, Italy.,Dipartimento di Studi Umanistici, Sezione di Scienze Preistoriche e Antropologiche, Università di Ferrara, 44100, Ferrara, Italy
| | - Gregorio Oxilia
- Department of Cultural Heritage, University of Bologna, 48121, Ravenna, Italy
| | - Matteo Romandini
- Department of Cultural Heritage, University of Bologna, 48121, Ravenna, Italy.,Dipartimento di Studi Umanistici, Sezione di Scienze Preistoriche e Antropologiche, Università di Ferrara, 44100, Ferrara, Italy
| | - Sara Silvestrini
- Department of Cultural Heritage, University of Bologna, 48121, Ravenna, Italy
| | - Stefano Benazzi
- Department of Cultural Heritage, University of Bologna, 48121, Ravenna, Italy.,Department of Human Evolution Max Planck Institute for Evolutionary Anthropology, 04103, Leipzig, Germany
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8
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Ellison D, Ifejika Speranza C. From blue to green water and back again: Promoting tree, shrub and forest-based landscape resilience in the Sahel. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 739:140002. [PMID: 32846505 DOI: 10.1016/j.scitotenv.2020.140002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 05/29/2020] [Accepted: 06/03/2020] [Indexed: 06/11/2023]
Abstract
Enjoying the potential climate benefits of restoration requires linking key forest-water and land-atmosphere interactions to the existential benefits provided on the ground. We apply what we call the "forest-water and land-atmosphere interaction lens" to current strategies for improving landscape resilience in the West African Sahel and the concept of the Great Green Wall (GGW). The severe and extensive drought of the 1970's-1990's led many to assess future climate and promote strategies to counter the gradual southward expansion of the Sahara. The idea for the GGW, a wall of trees intended to slow desert encroachment, grew out of this period of tremendous upheaval and human tragedy. Despite partial recovery in the local rainfall regime, we know far too little about whether the GGW strategy can even work. Further, it seems disingenuous to ignore the climatic envelope, which sets the boundaries within which forest-water and land-atmosphere interactions occur. Applying the "forest-water and land-atmosphere interaction lens" to landscape restoration as a tool for achieving improved resilience and human welfare in the Sahel provides meaningful input for re-thinking the GGW strategy. We upgrade current knowledge with the specific biophysical conditions likely to better support appropriate forest-water and land atmosphere interactions in the region and further fit such approaches within the context of the climatic envelope. The principal components of an improved strategy include a focus on large scale precipitation recycling all the way from the West African coast on into the Sahel, as well as improved tree, shrub and forest cover in the Sahel proper to promote infiltration, groundwater recharge, rainfall triggering potential and land surface cooling. Agroforestry can further broadly promote landscape resilience in the greater region. Strategies broadly focused on increasing rainfall recycling, water availability and the promotion of landscape resilience appear more likely to steer future efforts in useful directions.
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Affiliation(s)
- David Ellison
- Land Systems and Sustainable Land Management Unit, Institute of Geography, University of Bern, Switzerland; Department of Forest Resource Management, Swedish University of Agricultural Sciences, Umeå, Sweden; Ellison Consulting, Baar, Switzerland.
| | - Chinwe Ifejika Speranza
- Land Systems and Sustainable Land Management Unit, Institute of Geography, University of Bern, Switzerland
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9
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Elevated dust depositions in West Asia linked to ocean-atmosphere shifts during North Atlantic cold events. Proc Natl Acad Sci U S A 2020; 117:18272-18277. [PMID: 32690680 DOI: 10.1073/pnas.2004071117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Rapid North Atlantic cooling events during the last deglaciation caused atmospheric reorganizations on global and regional scales. Their impact on Asian climate has been investigated for monsoonal domains, but remains largely unknown in westerly wind-dominated semiarid regions. Here we generate a dust record from southeastern Iran spanning the period 19 to 7 cal. ka B.P. We find a direct link between frequent occurrences of dust plumes originating from the Arabian Peninsula and North Africa and rapid southward shifts of the westerlies associated with changes of the winter stationary waves during Heinrich Stadial 1, the Younger Dryas, the Preboreal Oscillation, and the 8.2-ka event. Dust input rises and falls abruptly at the transitions into and out of these cooling events, which we attribute to changes in the ocean circulation strength that are modulated by the North Atlantic winter sea-ice cover. Our findings reveal that waxing and waning of North American ice sheets have a stronger influence than those of European ice sheets on the winter climate over West Asia.
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10
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Klein RG. Population structure and the evolution of
Homo sapiens
in Africa. Evol Anthropol 2019; 28:179-188. [DOI: 10.1002/evan.21788] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 05/27/2019] [Accepted: 06/04/2019] [Indexed: 01/01/2023]
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11
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Jiang W, Wang G, Sheng Y, Shi Z, Zhang H. Isotopes in groundwater ( 2H, 18O, 14C) revealed the climate and groundwater recharge in the Northern China. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 666:298-307. [PMID: 30798239 DOI: 10.1016/j.scitotenv.2019.02.245] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 02/02/2019] [Accepted: 02/15/2019] [Indexed: 06/09/2023]
Abstract
We collected 3275 sets of δD and δ18O and 1451 14C data of groundwater in 14 basins or plains in the Northern China from the published sources in an attempt to investigate the isotopic characteristics of groundwater and their possible link with groundwater recharge and modern and past climate conditions in regional scales. The results showed that the deuterium excess of groundwater in the Monsoon regions were generally lower than that in the Westerly regions in the Northern China, reflecting the influences of different vapor sources and transmission modes. The δD and δ18O in groundwater lied closely to the Asian summer monsoon limit (ASML) were affected by both the Asian monsoon and Westerlies. The δD and δ18O of groundwater exhibited obvious latitude effect in the monsoon region, while it seemed to be dominated by the continental and elevation effects in the Westerly region both in the late Pleistocene and the Holocene. Based on the isotopic proxy records of climates, the depletion in 18O and D of the groundwater recharged in last glacial period in the late Pleistocene was observed which indicated that it was cooler especially in the Last Glacial Maximum (LGM), while the 18O and D were enriched in groundwater recharged in the Holocene. The transition from the late Pleistocene to Holocene was characterized by higher frequency fluctuation of δ18O in the groundwater, probably suggesting that the climatic conditions were unstable. The groundwater recharge could be roughly divided into three main periods under relative warm and humid climates. The variation of regional climate was one of the driving forces for the recharge and regeneration of groundwater. Our results may enhance the understanding of groundwater recharge and its connection with the climate changes in the regional scales.
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Affiliation(s)
- Wanjun Jiang
- State Key Laboratory of Biogeology and Environmental Geology & MOE Key Laboratory of Groundwater Circulation and Environment Evolution, China University of Geosciences, Beijing 100083, China; School of Water Resources & Environment, China University of Geosciences, Beijing 100083, China
| | - Guangcai Wang
- State Key Laboratory of Biogeology and Environmental Geology & MOE Key Laboratory of Groundwater Circulation and Environment Evolution, China University of Geosciences, Beijing 100083, China; School of Water Resources & Environment, China University of Geosciences, Beijing 100083, China.
| | - Yizhi Sheng
- State Key Laboratory of Biogeology and Environmental Geology & MOE Key Laboratory of Groundwater Circulation and Environment Evolution, China University of Geosciences, Beijing 100083, China; School of Water Resources & Environment, China University of Geosciences, Beijing 100083, China
| | - Zheming Shi
- State Key Laboratory of Biogeology and Environmental Geology & MOE Key Laboratory of Groundwater Circulation and Environment Evolution, China University of Geosciences, Beijing 100083, China; School of Water Resources & Environment, China University of Geosciences, Beijing 100083, China
| | - Hui Zhang
- State Key Laboratory of Biogeology and Environmental Geology & MOE Key Laboratory of Groundwater Circulation and Environment Evolution, China University of Geosciences, Beijing 100083, China; School of Water Resources & Environment, China University of Geosciences, Beijing 100083, China
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12
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Muschick M, Russell JM, Jemmi E, Walker J, Stewart KM, Murray AM, Dubois N, Stager JC, Johnson TC, Seehausen O. Arrival order and release from competition does not explain why haplochromine cichlids radiated in Lake Victoria. Proc Biol Sci 2019; 285:rspb.2018.0462. [PMID: 29743255 DOI: 10.1098/rspb.2018.0462] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 04/12/2018] [Indexed: 12/31/2022] Open
Abstract
The frequent occurrence of adaptive radiations on oceanic islands and in lakes is often attributed to ecological opportunity resulting from release from competition where arrival order among lineages predicts which lineage radiates. This priority effect occurs when the lineage that arrives first expands its niche breadth and diversifies into a set of ecological specialists with associated monopolization of the resources. Later-arriving species do not experience ecological opportunity and do not radiate. While theoretical support and evidence from microbial experiments for priority effects are strong, empirical evidence in nature is difficult to obtain. Lake Victoria (LV) is home to an exceptional adaptive radiation of haplochromine cichlid fishes, where 20 trophic guilds and several hundred species emerged in just 15 000 years, the age of the modern lake that was preceded by a complete desiccation lasting several thousand years. However, while about 50 other lineages of teleost fish also have established populations in the lake, none of them has produced more than two species and most of them did not speciate at all. Here, we test if the ancestors of the haplochromine radiation indeed arrived prior to the most competent potential competitors, 'tilapias' and cyprinids, both of which have made rapid radiations in other African lakes. We assess LV sediment core intervals from just before the desiccation and just after refilling for the presence of fossil fish teeth. We show that all three lineages were present when modern LV began to fill with water. We conclude that the haplochromines' extraordinary radiation unfolded in the presence of potentially competing lineages and cannot be attributed to a simple priority effect.
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Affiliation(s)
- Moritz Muschick
- Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, CH-3012 Bern, Switzerland .,Department of Fish Ecology and Evolution, EAWAG, Swiss Federal Institute for Aquatic Science and Technology, CH-6047 Kastanienbaum, Switzerland
| | - James M Russell
- Department of Earth, Environmental, and Planetary Sciences, Brown University, 324 Brook St, Providence, RI 02912, USA
| | - Eliane Jemmi
- Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, CH-3012 Bern, Switzerland.,Department of Fish Ecology and Evolution, EAWAG, Swiss Federal Institute for Aquatic Science and Technology, CH-6047 Kastanienbaum, Switzerland
| | - Jonas Walker
- Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, CH-3012 Bern, Switzerland.,Department of Fish Ecology and Evolution, EAWAG, Swiss Federal Institute for Aquatic Science and Technology, CH-6047 Kastanienbaum, Switzerland
| | - Kathlyn M Stewart
- Palaeobiology Section, Canadian Museum of Nature, P.O. Box 3443, Station D, Ottawa, Ontario, Canada K1P 6P4
| | - Alison M Murray
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
| | - Nathalie Dubois
- Department of Earth Sciences, ETHZ, CH-8092 Zurich, Switzerland.,Department of Surface Waters-Research and Management, EAWAG, Swiss Federal Institute for Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland
| | - J Curt Stager
- Natural Sciences, Paul Smith's College, 7777 State Route 30, Paul Smiths, NY 12970, USA
| | - Thomas C Johnson
- Large Lakes Observatory, University of Minnesota Duluth, 2205 E. 5th Street, Duluth, MN 55812, USA
| | - Ole Seehausen
- Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, CH-3012 Bern, Switzerland.,Department of Fish Ecology and Evolution, EAWAG, Swiss Federal Institute for Aquatic Science and Technology, CH-6047 Kastanienbaum, Switzerland
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13
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Lézine AM, Izumi K, Kageyama M, Achoundong G. A 90,000-year record of Afromontane forest responses to climate change. Science 2019; 363:177-181. [DOI: 10.1126/science.aav6821] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Accepted: 12/06/2018] [Indexed: 11/02/2022]
Abstract
Pollen records from African highlands are scarce; hence, the paleoecology of the Afromontane forest and its responses to glacial cycles are poorly known. Lake Bambili (Cameroon) provides a record of vegetation changes in the tropical mountains of Africa over the past 90,000 years, with high temporal resolution. Pollen data and biome reconstructions show a diverging response of forests to climate changes; the upper tree line was extremely unstable, shifting substantially in response to glacial-interglacial climate alternation, whereas the transition between the montane and lowland forests remained remarkably stable. Such ecological instability may have had a critical influence on species richness in the Afromontane forests.
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14
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Li X, Cui X, He D, Liao J, Hu C. Evaluation of the Heshang Cave stalagmite calcium isotope composition as a paleohydrologic proxy by comparison with the instrumental precipitation record. Sci Rep 2018; 8:2615. [PMID: 29422625 PMCID: PMC5805754 DOI: 10.1038/s41598-018-20776-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 01/22/2018] [Indexed: 11/23/2022] Open
Abstract
With their merits of precise dating and sensitivity to climate changes, laminated stalagmites are an important terrestrial archive for reconstructions of paleohydrological changes. In particular, the Ca isotope composition (δ44/42Ca) of the Heshang Cave stalagmite has been documented to record a precipitation decrease during the 8.2 ka event in central China. As an extension, this study directly compares near-annual resolution δ44/42Ca data with an instrumental precipitation record to evaluate the fidelity of δ44/42Ca as a paleohydrologic proxy on annual to decade timescales. Over the period 1881-2001 AD, the δ44/42Ca values correlate significantly with both precipitation from a nearby weather station and the dryness/wetness index in the middle Yangtze River, with a stronger correlation on decadal smoothed data. These results clearly show that the δ44/42Ca ratio from stalagmites is an effective proxy for paleohydrological changes on a decadal timescale. More study is encouraged to refine understanding of stalagmite Ca isotope ratios and hydrological conditions and their application in paleohydrologic reconstructions.
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Affiliation(s)
- Xiuli Li
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074, China.
| | - Xueping Cui
- Department of Geography, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, China
| | - Dong He
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074, China
| | - Jin Liao
- Department of Geography, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, China
| | - Chaoyong Hu
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074, China
- Department of Geography, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, China
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15
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Lamb HF, Bates CR, Bryant CL, Davies SJ, Huws DG, Marshall MH, Roberts HM, Toland H. 150,000-year palaeoclimate record from northern Ethiopia supports early, multiple dispersals of modern humans from Africa. Sci Rep 2018; 8:1077. [PMID: 29348464 PMCID: PMC5773494 DOI: 10.1038/s41598-018-19601-w] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 01/02/2018] [Indexed: 01/10/2023] Open
Abstract
Climatic change is widely acknowledged to have played a role in the dispersal of modern humans out of Africa, but the timing is contentious. Genetic evidence links dispersal to climatic change ~60,000 years ago, despite increasing evidence for earlier modern human presence in Asia. We report a deep seismic and near-continuous core record of the last 150,000 years from Lake Tana, Ethiopia, close to early modern human fossil sites and to postulated dispersal routes. The record shows varied climate towards the end of the penultimate glacial, followed by an abrupt change to relatively stable moist climate during the last interglacial. These conditions could have favoured selection for behavioural versatility, population growth and range expansion, supporting models of early, multiple dispersals of modern humans from Africa.
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Affiliation(s)
- Henry F Lamb
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK.
| | - C Richard Bates
- Department of Earth and Environmental Sciences, Irvine Building, University of St Andrews, St Andrews, Fife, KY16 9AL, UK
| | - Charlotte L Bryant
- NERC Radiocarbon Facility, Scottish Enterprise Technology Park, Rankine Avenue, East Kilbride, G75 0QF, UK
| | - Sarah J Davies
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK
| | - Dei G Huws
- School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey, LL59 5AB, UK
| | - Michael H Marshall
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK.,West Park School, West Road, Spondon, Derby, DE21 7BT, UK
| | - Helen M Roberts
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK
| | - Harry Toland
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK
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16
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Singarayer JS, Valdes PJ, Roberts WHG. Ocean dominated expansion and contraction of the late Quaternary tropical rainbelt. Sci Rep 2017; 7:9382. [PMID: 28839263 PMCID: PMC5571209 DOI: 10.1038/s41598-017-09816-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 07/31/2017] [Indexed: 11/09/2022] Open
Abstract
The latitude of the tropical rainbelt oscillates seasonally but has also varied on millennial time-scales in response to changes in the seasonal distribution of insolation due to Earth's orbital configuration, as well as climate change initiated at high latitudes. Interpretations of palaeoclimate proxy archives often suggest hemispherically coherent variations, some proposing meridional shifts in global rainbelt position and the 'global monsoon', while others propose interhemispherically symmetric expansion and contraction. Here, we use a unique set of climate model simulations of the last glacial cycle (120 kyr), that compares well against a compilation of precipitation proxy data, to demonstrate that while asymmetric extratropical forcings (icesheets, freshwater hosing) generally produce meridional shifts in the zonal mean rainbelt, orbital variations produce expansion/contractions in terms of the global zonal mean. This is primarily a dynamic response of the rainbelt over the oceans to regional interhemispheric temperature gradients, which is opposite to the largely local thermodynamic terrestrial response to insolation. The mode of rainbelt variation is regionally variable, depending on surface type (land or ocean) and surrounding continental configuration. This makes interpretation of precipitation-proxy records as large-scale rainbelt movement challenging, requiring regional or global data syntheses.
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Affiliation(s)
- Joy S Singarayer
- Department of Meteorology and Centre for Past Climate Change, University of Reading, Reading, United Kingdom. .,Bristol Research Initiative for the Dynamic Global Environment (BRIDGE), School of Geographical Sciences, University of Bristol, University Road, Bristol, United Kingdom.
| | - Paul J Valdes
- Bristol Research Initiative for the Dynamic Global Environment (BRIDGE), School of Geographical Sciences, University of Bristol, University Road, Bristol, United Kingdom
| | - William H G Roberts
- Bristol Research Initiative for the Dynamic Global Environment (BRIDGE), School of Geographical Sciences, University of Bristol, University Road, Bristol, United Kingdom
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17
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18
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Defrance D, Ramstein G, Charbit S, Vrac M, Famien AM, Sultan B, Swingedouw D, Dumas C, Gemenne F, Alvarez-Solas J, Vanderlinden JP. Consequences of rapid ice sheet melting on the Sahelian population vulnerability. Proc Natl Acad Sci U S A 2017; 114:6533-6538. [PMID: 28584113 PMCID: PMC5488922 DOI: 10.1073/pnas.1619358114] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The acceleration of ice sheet melting has been observed over the last few decades. Recent observations and modeling studies have suggested that the ice sheet contribution to future sea level rise could have been underestimated in the latest Intergovernmental Panel on Climate Change report. The ensuing freshwater discharge coming from ice sheets could have significant impacts on global climate, and especially on the vulnerable tropical areas. During the last glacial/deglacial period, megadrought episodes were observed in the Sahel region at the time of massive iceberg surges, leading to large freshwater discharges. In the future, such episodes have the potential to induce a drastic destabilization of the Sahelian agroecosystem. Using a climate modeling approach, we investigate this issue by superimposing on the Representative Concentration Pathways 8.5 (RCP8.5) baseline experiment a Greenland flash melting scenario corresponding to an additional sea level rise ranging from 0.5 m to 3 m. Our model response to freshwater discharge coming from Greenland melting reveals a significant decrease of the West African monsoon rainfall, leading to changes in agricultural practices. Combined with a strong population increase, described by different demography projections, important human migration flows could be potentially induced. We estimate that, without any adaptation measures, tens to hundreds million people could be forced to leave the Sahel by the end of this century. On top of this quantification, the sea level rise impact over coastal areas has to be superimposed, implying that the Sahel population could be strongly at threat in case of rapid Greenland melting.
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Affiliation(s)
- Dimitri Defrance
- Laboratoire des Sciences du Climat et de l'Environnement, Institut Pierre Simon Laplace, Commissariat à l'Energie Atomique et aux Energies Alternatives - CNRS - Université de Saint-Quentin-en-Yvelines, Université Paris-Saclay, 91141 Gif-Sur-Yvette, France;
- Université Pierre et Marie Curie - CNRS - Institut de Recherche pour le Développement - Muséum National d'Histoire Naturelle, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, Institut Pierre Simon Laplace, 75005 Paris, France
| | - Gilles Ramstein
- Laboratoire des Sciences du Climat et de l'Environnement, Institut Pierre Simon Laplace, Commissariat à l'Energie Atomique et aux Energies Alternatives - CNRS - Université de Saint-Quentin-en-Yvelines, Université Paris-Saclay, 91141 Gif-Sur-Yvette, France
| | - Sylvie Charbit
- Laboratoire des Sciences du Climat et de l'Environnement, Institut Pierre Simon Laplace, Commissariat à l'Energie Atomique et aux Energies Alternatives - CNRS - Université de Saint-Quentin-en-Yvelines, Université Paris-Saclay, 91141 Gif-Sur-Yvette, France
| | - Mathieu Vrac
- Laboratoire des Sciences du Climat et de l'Environnement, Institut Pierre Simon Laplace, Commissariat à l'Energie Atomique et aux Energies Alternatives - CNRS - Université de Saint-Quentin-en-Yvelines, Université Paris-Saclay, 91141 Gif-Sur-Yvette, France
| | - Adjoua Moïse Famien
- Université Pierre et Marie Curie - CNRS - Institut de Recherche pour le Développement - Muséum National d'Histoire Naturelle, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, Institut Pierre Simon Laplace, 75005 Paris, France
- Laboratoire de Physique de l'Atmosphère, Université Félix Houphouet Boigny, 22 BP 582 Abidjan, Côte-d'Ivoire
| | - Benjamin Sultan
- Université Pierre et Marie Curie - CNRS - Institut de Recherche pour le Développement - Muséum National d'Histoire Naturelle, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, Institut Pierre Simon Laplace, 75005 Paris, France
| | - Didier Swingedouw
- Environnements et Paléoenvironnements Océaniques et Continentaux, CNRS, Université de Bordeaux, 33615 Pessac, France
| | - Christophe Dumas
- Laboratoire des Sciences du Climat et de l'Environnement, Institut Pierre Simon Laplace, Commissariat à l'Energie Atomique et aux Energies Alternatives - CNRS - Université de Saint-Quentin-en-Yvelines, Université Paris-Saclay, 91141 Gif-Sur-Yvette, France
| | - François Gemenne
- Cultures Environnements Arctique Représentations Climat, Observatoire de Saint-Quentin-En-Yvelines, Université Paris-Saclay, 78280 Guyancourt, France
- The Hugo Observatory, Fonds de la Recherche Scientifique, University of Liège, 4000 Liège, Belgium
| | | | - Jean-Paul Vanderlinden
- Cultures Environnements Arctique Représentations Climat, Observatoire de Saint-Quentin-En-Yvelines, Université Paris-Saclay, 78280 Guyancourt, France
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19
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Putnam AE, Broecker WS. Human-induced changes in the distribution of rainfall. SCIENCE ADVANCES 2017; 3:e1600871. [PMID: 28580418 PMCID: PMC5451196 DOI: 10.1126/sciadv.1600871] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 04/13/2017] [Indexed: 05/24/2023]
Abstract
A likely consequence of global warming will be the redistribution of Earth's rain belts, affecting water availability for many of Earth's inhabitants. We consider three ways in which planetary warming might influence the global distribution of precipitation. The first possibility is that rainfall in the tropics will increase and that the subtropics and mid-latitudes will become more arid. A second possibility is that Earth's thermal equator, around which the planet's rain belts and dry zones are organized, will migrate northward. This northward shift will be a consequence of the Northern Hemisphere, with its large continental area, warming faster than the Southern Hemisphere, with its large oceanic area. A third possibility is that both of these scenarios will play out simultaneously. We review paleoclimate evidence suggesting that (i) the middle latitudes were wetter during the last glacial maximum, (ii) a northward shift of the thermal equator attended the abrupt Bølling-Allerød climatic transition ~14.6 thousand years ago, and (iii) a southward shift occurred during the more recent Little Ice Age. We also inspect trends in seasonal surface heating between the hemispheres over the past several decades. From these clues, we predict that there will be a seasonally dependent response in rainfall patterns to global warming. During boreal summer, in which the rate of recent warming has been relatively uniform between the hemispheres, wet areas will get wetter and dry regions will become drier. During boreal winter, rain belts and drylands will expand northward in response to differential heating between the hemispheres.
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Affiliation(s)
- Aaron E. Putnam
- School of Earth and Climate Sciences and Climate Change Institute, 224 Bryand Global Sciences Center, University of Maine, Orono, ME 04469, USA
- Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W/PO Box 1000, Palisades, NY 10964, USA
| | - Wallace S. Broecker
- Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W/PO Box 1000, Palisades, NY 10964, USA
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20
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Tierney JE, Pausata FSR, deMenocal PB. Rainfall regimes of the Green Sahara. SCIENCE ADVANCES 2017; 3:e1601503. [PMID: 28116352 PMCID: PMC5242556 DOI: 10.1126/sciadv.1601503] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 11/29/2016] [Indexed: 05/05/2023]
Abstract
During the "Green Sahara" period (11,000 to 5000 years before the present), the Sahara desert received high amounts of rainfall, supporting diverse vegetation, permanent lakes, and human populations. Our knowledge of rainfall rates and the spatiotemporal extent of wet conditions has suffered from a lack of continuous sedimentary records. We present a quantitative reconstruction of western Saharan precipitation derived from leaf wax isotopes in marine sediments. Our data indicate that the Green Sahara extended to 31°N and likely ended abruptly. We find evidence for a prolonged "pause" in Green Sahara conditions 8000 years ago, coincident with a temporary abandonment of occupational sites by Neolithic humans. The rainfall rates inferred from our data are best explained by strong vegetation and dust feedbacks; without these mechanisms, climate models systematically fail to reproduce the Green Sahara. This study suggests that accurate simulations of future climate change in the Sahara and Sahel will require improvements in our ability to simulate vegetation and dust feedbacks.
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Affiliation(s)
- Jessica E. Tierney
- Department of Geosciences, University of Arizona, 1040 East Fourth Street, Tucson, AZ 85721, USA
- Corresponding author.
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21
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Dirks PH, Placzek CJ, Fink D, Dosseto A, Roberts E. Using 10Be cosmogenic isotopes to estimate erosion rates and landscape changes during the Plio-Pleistocene in the Cradle of Humankind, South Africa. J Hum Evol 2016; 96:19-34. [DOI: 10.1016/j.jhevol.2016.03.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 03/05/2016] [Accepted: 03/07/2016] [Indexed: 10/21/2022]
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22
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Abrupt monsoon transitions as seen in paleorecords can be explained by moisture-advection feedback. Proc Natl Acad Sci U S A 2016; 113:E2348-9. [PMID: 27091960 DOI: 10.1073/pnas.1603130113] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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23
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Jacobel AW, McManus JF, Anderson RF, Winckler G. Large deglacial shifts of the Pacific Intertropical Convergence Zone. Nat Commun 2016; 7:10449. [PMID: 26794654 PMCID: PMC4735863 DOI: 10.1038/ncomms10449] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 12/11/2015] [Indexed: 11/30/2022] Open
Abstract
The position of the Intertropical Convergence Zone (ITCZ) is sensitive to changes in the balance of heat between the hemispheres which has fundamental implications for tropical hydrology and atmospheric circulation. Although the ITCZ is thought to experience the largest shifts in position during deglacial stadial events, the magnitude of shifts has proven difficult to reconstruct, in part because of a paucity of high-resolution records, particularly those including spatial components. Here we track the position of the ITCZ from 150 to 110 ka at three sites in the central equatorial Pacific at sub-millennial time resolution. Our results provide evidence of large, abrupt changes in tropical climate during the penultimate deglaciation, coincident with North Atlantic Heinrich Stadial 11 (∼136–129 ka). We identify this event both as a Northern Hemisphere increase in aeolian dust and as a shift in the mean position of the ITCZ a minimum of 4° southwards at 160° W. The extent to which the location of the Intertropical Convergence Zone (ITCZ)—a primary influence over tropical hydrology—varied in the past remains uncertain. Here, the authors use a transect of marine sediment cores to quantify latitudinal migrations of the ITCZ during the penultimate deglaciation.
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Affiliation(s)
- A W Jacobel
- Department of Earth and Environmental Sciences, Columbia University, New York, New York 10027, USA.,Lamont-Doherty Earth Observatory, Palisades, New York 10964, USA
| | - J F McManus
- Department of Earth and Environmental Sciences, Columbia University, New York, New York 10027, USA.,Lamont-Doherty Earth Observatory, Palisades, New York 10964, USA
| | - R F Anderson
- Department of Earth and Environmental Sciences, Columbia University, New York, New York 10027, USA.,Lamont-Doherty Earth Observatory, Palisades, New York 10964, USA
| | - G Winckler
- Department of Earth and Environmental Sciences, Columbia University, New York, New York 10027, USA.,Lamont-Doherty Earth Observatory, Palisades, New York 10964, USA
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24
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Robbins LH, Brook GA, Murphy ML, Ivester AH, Campbell AC. The Kalahari During MIS 6-2 (190–12 ka): Archaeology, Paleoenvironment, and Population Dynamics. AFRICA FROM MIS 6-2 2016. [DOI: 10.1007/978-94-017-7520-5_10] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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25
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Burrough SL. Late Quaternary Environmental Change and Human Occupation of the Southern African Interior. AFRICA FROM MIS 6-2 2016. [DOI: 10.1007/978-94-017-7520-5_9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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26
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West African monsoon dynamics inferred from abrupt fluctuations of Lake Mega-Chad. Proc Natl Acad Sci U S A 2015; 112:8543-8. [PMID: 26124133 DOI: 10.1073/pnas.1417655112] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
From the deglacial period to the mid-Holocene, North Africa was characterized by much wetter conditions than today. The broad timing of this period, termed the African Humid Period, is well known. However, the rapidity of the onset and termination of the African Humid Period are contested, with strong evidence for both abrupt and gradual change. We use optically stimulated luminescence dating of dunes, shorelines, and fluviolacustrine deposits to reconstruct the fluctuations of Lake Mega-Chad, which was the largest pluvial lake in Africa. Humid conditions first occur at ∼ 15 ka, and by 11.5 ka, Lake Mega-Chad had reached a highstand, which persisted until 5.0 ka. Lake levels fell rapidly at ∼ 5 ka, indicating abrupt aridification across the entire Lake Mega-Chad Basin. This record provides strong terrestrial evidence that the African Humid Period ended abruptly, supporting the hypothesis that the African monsoon responds to insolation forcing in a markedly nonlinear manner. In addition, Lake Mega-Chad exerts strong control on global biogeochemical cycles because the northern (Bodélé) basin is currently the world's greatest single dust source and possibly an important source of limiting nutrients for both the Amazon Basin and equatorial Atlantic. However, we demonstrate that the final desiccation of the Bodélé Basin occurred around 1 ka. Consequently, the present-day mode and scale of dust production from the Bodélé Basin cannot have occurred before 1 ka, suggesting that its role in fertilizing marine and terrestrial ecosystems is either overstated or geologically recent.
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Paleoenvironmental context of the Middle Stone Age record from Karungu, Lake Victoria Basin, Kenya, and its implications for human and faunal dispersals in East Africa. J Hum Evol 2015; 83:28-45. [DOI: 10.1016/j.jhevol.2015.03.004] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 03/11/2015] [Accepted: 03/12/2015] [Indexed: 01/12/2023]
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Marcott SA, Bauska TK, Buizert C, Steig EJ, Rosen JL, Cuffey KM, Fudge TJ, Severinghaus JP, Ahn J, Kalk ML, McConnell JR, Sowers T, Taylor KC, White JWC, Brook EJ. Centennial-scale changes in the global carbon cycle during the last deglaciation. Nature 2014; 514:616-9. [PMID: 25355363 DOI: 10.1038/nature13799] [Citation(s) in RCA: 319] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 08/27/2014] [Indexed: 11/09/2022]
Abstract
Global climate and the concentration of atmospheric carbon dioxide (CO2) are correlated over recent glacial cycles. The combination of processes responsible for a rise in atmospheric CO2 at the last glacial termination (23,000 to 9,000 years ago), however, remains uncertain. Establishing the timing and rate of CO2 changes in the past provides critical insight into the mechanisms that influence the carbon cycle and helps put present and future anthropogenic emissions in context. Here we present CO2 and methane (CH4) records of the last deglaciation from a new high-accumulation West Antarctic ice core with unprecedented temporal resolution and precise chronology. We show that although low-frequency CO2 variations parallel changes in Antarctic temperature, abrupt CO2 changes occur that have a clear relationship with abrupt climate changes in the Northern Hemisphere. A significant proportion of the direct radiative forcing associated with the rise in atmospheric CO2 occurred in three sudden steps, each of 10 to 15 parts per million. Every step took place in less than two centuries and was followed by no notable change in atmospheric CO2 for about 1,000 to 1,500 years. Slow, millennial-scale ventilation of Southern Ocean CO2-rich, deep-ocean water masses is thought to have been fundamental to the rise in atmospheric CO2 associated with the glacial termination, given the strong covariance of CO2 levels and Antarctic temperatures. Our data establish a contribution from an abrupt, centennial-scale mode of CO2 variability that is not directly related to Antarctic temperature. We suggest that processes operating on centennial timescales, probably involving the Atlantic meridional overturning circulation, seem to be influencing global carbon-cycle dynamics and are at present not widely considered in Earth system models.
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Affiliation(s)
- Shaun A Marcott
- 1] College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA [2] Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Thomas K Bauska
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
| | - Christo Buizert
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
| | - Eric J Steig
- Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA
| | - Julia L Rosen
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
| | - Kurt M Cuffey
- Department of Geography, University of California, Berkeley, California 94720, USA
| | - T J Fudge
- Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA
| | - Jeffery P Severinghaus
- Scripps Institution of Oceanography, University of California, San Diego, California 92037, USA
| | - Jinho Ahn
- School of Earth and Environmental Sciences, Seoul National University, Seoul 151-742, South Korea
| | - Michael L Kalk
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
| | - Joseph R McConnell
- Desert Research Institute, Nevada System of Higher Education, Reno, Nevada 89512, USA
| | - Todd Sowers
- Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Kendrick C Taylor
- Desert Research Institute, Nevada System of Higher Education, Reno, Nevada 89512, USA
| | - James W C White
- INSTAAR, University of Colorado, Boulder, Colorado 80309, USA
| | - Edward J Brook
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA
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Abstract
Heinrich Events, the abrupt changes in the Laurentide Ice Sheet that cause the appearance of the well-observed Heinrich Layers, are thought to have a strong effect on the global climate. The focus of most studies that have looked at the climate's response to these events has been the freshwater flux that results from melting icebergs. However, there is the possibility that the varying height of the ice sheet could force a change in the climate. In this study, we present results from a newly developed coupled climate/ice sheet model to show what effect this topographic change has both on its own and in concert with the flux of freshwater from melting icebergs. We show that the topographic forcing can explain a number of the climate changes that are observed during Heinrich Events, such as the warming and wettening in Florida and the warm sea surface temperatures in the central North Atlantic, which freshwater forcing alone cannot. We also find regions, for example the tropical Atlantic, where the response is a mixture of the two: Here observations may help disentangle the relative importance of each mechanism. These results suggest that the simple paradigm of a Heinrich Event causing climate change via freshwater inputs into the North Atlantic needs to be revised.
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Shirai K, Inomata N, Mizoiri S, Aibara M, Terai Y, Okada N, Tachida H. High prevalence of non-synonymous substitutions in mtDNA of cichlid fishes from Lake Victoria. Gene 2014; 552:239-45. [PMID: 25241383 DOI: 10.1016/j.gene.2014.09.039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Revised: 08/28/2014] [Accepted: 09/17/2014] [Indexed: 10/24/2022]
Abstract
When a population size is reduced, genetic drift may fix slightly deleterious mutations, and an increase in nonsynonymous substitution is expected. It has been suggested that past aridity has seriously affected and decreased the populations of cichlid fishes in Lake Victoria, while geographical studies have shown that the water levels in Lake Tanganyika and Lake Malawi have remained fairly constant. The comparably stable environments in the latter two lakes might have kept the populations of cichlid fishes large enough to remove slightly deleterious mutations. The difference in the stability of cichlid fish population sizes between Lake Victoria and the Lakes Tanganyika and Malawi is expected to have caused differences in the nonsynonymous/synonymous ratio, ω (=dN/dS), of the evolutionary rate. Here, we estimated ω and compared it between the cichlids of the three lakes for 13 mitochondrial protein-coding genes using maximum likelihood methods. We found that the lineages of the cichlids in Lake Victoria had a significantly higher ω for several mitochondrial loci. Moreover, positive selection was indicated for several codons in the mtDNA of the Lake Victoria cichlid lineage. Our results indicate that both adaptive and slightly deleterious molecular evolution has taken place in the Lake Victoria cichlids' mtDNA genes, whose nonsynonymous sites are generally conserved.
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Affiliation(s)
- Kazumasa Shirai
- Graduate School of Systems Life Sciences, Kyushu University, Fukuoka, Japan
| | - Nobuyuki Inomata
- International College of Arts and Sciences, Fukuoka Women's University, Fukuoka, Japan
| | | | - Mitsuto Aibara
- Foundation for Advancement of International Science, Tsukuba, Japan
| | - Yohey Terai
- The Graduate University for Advanced Studies, Kanagawa, Japan
| | - Norihiro Okada
- Foundation for Advancement of International Science, Tsukuba, Japan; Department of Life Sciences, National Cheng Kung University, Tainan 701, Taiwan
| | - Hidenori Tachida
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan.
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Rapid interhemispheric climate links via the Australasian monsoon during the last deglaciation. Nat Commun 2014; 4:2908. [PMID: 24309539 DOI: 10.1038/ncomms3908] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 11/08/2013] [Indexed: 11/08/2022] Open
Abstract
Recent studies have proposed that millennial-scale reorganization of the ocean-atmosphere circulation drives increased upwelling in the Southern Ocean, leading to rising atmospheric carbon dioxide levels and ice age terminations. Southward migration of the global monsoon is thought to link the hemispheres during deglaciation, but vital evidence from the southern sector of the vast Australasian monsoon system is yet to emerge. Here we present a 230thorium-dated stalagmite oxygen isotope record of millennial-scale changes in Australian-Indonesian monsoon rainfall over the last 31,000 years. The record shows that abrupt southward shifts of the Australian-Indonesian monsoon were synchronous with North Atlantic cold intervals 17,600-11,500 years ago. The most prominent southward shift occurred in lock-step with Heinrich Stadial 1 (17,600-14,600 years ago), and rising atmospheric carbon dioxide. Our findings show that millennial-scale climate change was transmitted rapidly across Australasia and lend support to the idea that the 3,000-year-long Heinrich 1 interval could have been critical in driving the last deglaciation.
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North Atlantic forcing of tropical Indian Ocean climate. Nature 2014; 509:76-80. [PMID: 24784218 DOI: 10.1038/nature13196] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2013] [Accepted: 02/28/2014] [Indexed: 11/09/2022]
Abstract
The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells, but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well-dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic circulation slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during North Atlantic cold spells.
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Mid-latitude interhemispheric hydrologic seesaw over the past 550,000 years. Nature 2014; 508:378-82. [PMID: 24695222 DOI: 10.1038/nature13076] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 01/22/2014] [Indexed: 11/08/2022]
Abstract
An interhemispheric hydrologic seesaw--in which latitudinal migrations of the Intertropical Convergence Zone (ITCZ) produce simultaneous wetting (increased precipitation) in one hemisphere and drying in the other--has been discovered in some tropical and subtropical regions. For instance, Chinese and Brazilian subtropical speleothem (cave formations such as stalactites and stalagmites) records show opposite trends in time series of oxygen isotopes (a proxy for precipitation variability) at millennial to orbital timescales, suggesting that hydrologic cycles were antiphased in the northerly versus southerly subtropics. This tropical to subtropical hydrologic phenomenon is likely to be an initial and important climatic response to orbital forcing. The impacts of such an interhemispheric hydrologic seesaw on higher-latitude regions and the global climate system, however, are unknown. Here we show that the antiphasing seen in the tropical records is also present in both hemispheres of the mid-latitude western Pacific Ocean. Our results are based on a new 550,000-year record of the growth frequency of speleothems from the Korean peninsula, which we compare to Southern Hemisphere equivalents. The Korean data are discontinuous and derived from 24 separate speleothems, but still allow the identification of periods of peak speleothem growth and, thus, precipitation. The clear hemispheric antiphasing indicates that the sphere of influence of the interhemispheric hydrologic seesaw over the past 550,000 years extended at least to the mid-latitudes, such as northeast Asia, and that orbital-timescale ITCZ shifts can have serious effects on temperate climate systems. Furthermore, our result implies that insolation-driven ITCZ dynamics may provoke water vapour and vegetation feedbacks in northern mid-latitude regions and could have regulated global climate conditions throughout the late Quaternary ice age cycles.
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Abstract
The Indo-Pacific warm pool houses the largest zone of deep atmospheric convection on Earth and plays a critical role in global climate variations. Despite the region's importance, changes in Indo-Pacific hydroclimate on orbital timescales remain poorly constrained. Here we present high-resolution geochemical records of surface runoff and vegetation from sediment cores from Lake Towuti, on the island of Sulawesi in central Indonesia, that continuously span the past 60,000 y. We show that wet conditions and rainforest ecosystems on Sulawesi present during marine isotope stage 3 (MIS3) and the Holocene were interrupted by severe drying between ∼33,000 and 16,000 y B.P. when Northern Hemisphere ice sheets expanded and global temperatures cooled. Our record reveals little direct influence of precessional orbital forcing on regional climate, and the similarity between MIS3 and Holocene climates observed in Lake Towuti suggests that exposure of the Sunda Shelf has a weaker influence on regional hydroclimate and terrestrial ecosystems than suggested previously. We infer that hydrological variability in this part of Indonesia varies strongly in response to high-latitude climate forcing, likely through reorganizations of the monsoons and the position of the intertropical convergence zone. These findings suggest an important role for the tropical western Pacific in amplifying glacial-interglacial climate variability.
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Development of Middle Stone Age innovation linked to rapid climate change. Nat Commun 2013; 4:1905. [PMID: 23695699 PMCID: PMC4354264 DOI: 10.1038/ncomms2897] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 04/16/2013] [Indexed: 12/04/2022] Open
Abstract
The development of modernity in early human populations has been linked to pulsed phases of technological and behavioural innovation within the Middle Stone Age of South Africa. However, the trigger for these intermittent pulses of technological innovation is an enigma. Here we show that, contrary to some previous studies, the occurrence of innovation was tightly linked to abrupt climate change. Major innovational pulses occurred at times when South African climate changed rapidly towards more humid conditions, while northern sub-Saharan Africa experienced widespread droughts, as the Northern Hemisphere entered phases of extreme cooling. These millennial-scale teleconnections resulted from the bipolar seesaw behaviour of the Atlantic Ocean related to changes in the ocean circulation. These conditions led to humid pulses in South Africa and potentially to the creation of favourable environmental conditions. This strongly implies that innovational pulses of early modern human behaviour were climatically influenced and linked to the adoption of refugia. The South African archaeological record contains evidence of the early flourishing of the human mind. Ziegler et al. provide new paleoclimate reconstructions, which suggest that rapid fluctuations in global climate have played a key role in the evolution of these early human cultures.
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Tierney JE, deMenocal PB. Abrupt shifts in Horn of Africa hydroclimate since the Last Glacial Maximum. Science 2013; 342:843-6. [PMID: 24114782 DOI: 10.1126/science.1240411] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The timing and abruptness of the initiation and termination of the Early Holocene African Humid Period are subjects of ongoing debate, with direct consequences for our understanding of abrupt climate change, paleoenvironments, and early human cultural development. Here, we provide proxy evidence from the Horn of Africa region that documents abrupt transitions into and out of the African Humid Period in northeast Africa. Similar and generally synchronous abrupt transitions at other East African sites suggest that rapid shifts in hydroclimate are a regionally coherent feature. Our analysis suggests that the termination of the African Humid Period in the Horn of Africa occurred within centuries, underscoring the nonlinearity of the region's hydroclimate.
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Affiliation(s)
- Jessica E Tierney
- Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02540, USA
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Faith JT, Tryon CA, Peppe DJ, Beverly EJ, Blegen N. Biogeographic and Evolutionary Implications of an Extinct Late Pleistocene Impala from the Lake Victoria Basin, Kenya. J MAMM EVOL 2013. [DOI: 10.1007/s10914-013-9238-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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The impact of the geologic history and paleoclimate on the diversification of East african cichlids. INTERNATIONAL JOURNAL OF EVOLUTIONARY BIOLOGY 2012; 2012:574851. [PMID: 22888465 PMCID: PMC3408716 DOI: 10.1155/2012/574851] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 03/26/2012] [Accepted: 05/09/2012] [Indexed: 11/25/2022]
Abstract
The cichlid fishes of the East African Great Lakes are the largest extant vertebrate radiation identified to date. These lakes and their surrounding waters support over 2,000 species of cichlid fish, many of which are descended from a single common ancestor within the past 10 Ma. The extraordinary East African cichlid diversity is intricately linked to the highly variable geologic and paleoclimatic history of this region. Greater than 10 Ma, the western arm of the East African rift system began to separate, thereby creating a series of rift basins that would come to contain several water bodies, including the extremely deep Lakes Tanganyika and Malawi. Uplifting associated with this rifting backponded many rivers and created the extremely large, but shallow Lake Victoria. Since their creation, the size, shape, and existence of these lakes have changed dramatically which has, in turn, significantly influenced the evolutionary history of the lakes' cichlids. This paper reviews the geologic history and paleoclimate of the East African Great Lakes and the impact of these forces on the region's endemic cichlid flocks.
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Blome MW, Cohen AS, Tryon CA, Brooks AS, Russell J. The environmental context for the origins of modern human diversity: A synthesis of regional variability in African climate 150,000–30,000 years ago. J Hum Evol 2012; 62:563-92. [DOI: 10.1016/j.jhevol.2012.01.011] [Citation(s) in RCA: 202] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 12/02/2011] [Accepted: 01/24/2012] [Indexed: 11/27/2022]
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Dutilleul P, Cumming BF, Lontoc-Roy M. Autocorrelogram and Periodogram Analyses of Palaeolimnological Temporal-Series from Lakes in Central and Western North America to Assess Shifts in Drought Conditions. TRACKING ENVIRONMENTAL CHANGE USING LAKE SEDIMENTS 2012. [DOI: 10.1007/978-94-007-2745-8_16] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Forcing of wet phases in southeast Africa over the past 17,000 years. Nature 2011; 480:509-12. [PMID: 22193106 DOI: 10.1038/nature10685] [Citation(s) in RCA: 204] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 10/27/2011] [Indexed: 11/08/2022]
Abstract
Intense debate persists about the climatic mechanisms governing hydrologic changes in tropical and subtropical southeast Africa since the Last Glacial Maximum, about 20,000 years ago. In particular, the relative importance of atmospheric and oceanic processes is not firmly established. Southward shifts of the intertropical convergence zone (ITCZ) driven by high-latitude climate changes have been suggested as a primary forcing, whereas other studies infer a predominant influence of Indian Ocean sea surface temperatures on regional rainfall changes. To address this question, a continuous record representing an integrated signal of regional climate variability is required, but has until now been missing. Here we show that remote atmospheric forcing by cold events in the northern high latitudes appears to have been the main driver of hydro-climatology in southeast Africa during rapid climate changes over the past 17,000 years. Our results are based on a reconstruction of precipitation and river discharge changes, as recorded in a marine sediment core off the mouth of the Zambezi River, near the southern boundary of the modern seasonal ITCZ migration. Indian Ocean sea surface temperatures did not exert a primary control over southeast African hydrologic variability. Instead, phases of high precipitation and terrestrial discharge occurred when the ITCZ was forced southwards during Northern Hemisphere cold events, such as Heinrich stadial 1 (around 16,000 years ago) and the Younger Dryas (around 12,000 years ago), or when local summer insolation was high in the late Holocene, that is, during the past 4,000 years.
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Soares P, Alshamali F, Pereira JB, Fernandes V, Silva NM, Afonso C, Costa MD, Musilova E, Macaulay V, Richards MB, Cerny V, Pereira L. The Expansion of mtDNA Haplogroup L3 within and out of Africa. Mol Biol Evol 2011; 29:915-27. [DOI: 10.1093/molbev/msr245] [Citation(s) in RCA: 193] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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