DOCSLIB.ORG

West African Monsoon Dynamics Inferred from Abrupt Fluctuations of Lake Mega-Chad

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
West African Monsoon Dynamics Inferred from Abrupt Fluctuations of Lake Mega-Chad West African monsoon dynamics inferred from abrupt fluctuations of Lake Mega-Chad Simon J. Armitagea,1, Charlie S. Bristowb, and Nick A. Drakec aCentre for Quaternary Research, Department of Geography, Royal Holloway University of London, Egham, Surrey, TW20 0EX, United Kingdom; bDepartment of Earth and Planetary Sciences, Birkbeck College, University of London, London, WC1E 7HX, United Kingdom; and cDepartment of Geography, King’s College London, Strand, London, WC2R 2LS, United Kingdom Edited by Thomas Dunne, University of California, Santa Barbara, CA, and approved May 11, 2015 (received for review September 12, 2014) From the deglacial period to the mid-Holocene, North Africa was decrease in humidity since the LGM (6). These three scenarios, characterized by much wetter conditions than today. The broad timing (i) abrupt onset and termination, (ii) gradual change, and (iii)abroad of this period, termed the African Humid Period, is well known. trend with shorter-term variability, are supported to a greater or However, the rapidity of the onset and termination of the African lesser extent by climate models in which an enhanced WAM is linked Humid Period are contested, with strong evidence for both abrupt and to summer-season insolation in the Northern Hemisphere, which gradual change. We use optically stimulated luminescence dating of peaked around 10 ka and then gradually declined (7–9). Abrupt dunes, shorelines, and fluviolacustrine deposits to reconstruct the changes in North African climate can be simulated by biogeophysical fluctuations of Lake Mega-Chad, which was the largest pluvial lake in feedbacks (7), whereas a gradual change in rainfall is simulated by a Africa. Humid conditions first occur at ∼15 ka, and by 11.5 ka, Lake coupled transient simulation model (9), where vegetation feedbacks Mega-Chad had reached a highstand, which persisted until 5.0 ka. Lake are muted and more localized. Alternatively, a “flickering switch” levels fell rapidly at ∼5 ka, indicating abrupt aridification across the may be simulated, in which the climate system and ecosystems in entire Lake Mega-Chad Basin. This record provides strong terrestrial North Africa have two stable configurations, a green state and a evidence that the African Humid Period ended abruptly, supporting desert state, with strong centennial-scale fluctuations across the the hypothesis that the African monsoon responds to insolation forcing transition due to nonlinear biogeophysical feedback (10). In addition, in a markedly nonlinear manner. In addition, Lake Mega-Chad exerts many studies attribute arid–humid (humid–arid) transitions at strong control on global biogeochemical cycles because the northern individual sites to the northward (southward) migration of the EARTH, ATMOSPHERIC, ’ (Bodélé) basin is currently the world s greatest single dust source and intertropical convergence zone (ITCZ) in response to preces- AND PLANETARY SCIENCES possibly an important source of limiting nutrients for both the Amazon sionally driven increases (decreases) in summer-season insolation Basin and equatorial Atlantic. However, we demonstrate that the final amounts in the northern low latitudes. However, several recent desiccation of the Bodélé Basin occurred around 1 ka. Consequently, studies have indicated that at least some arid phases observed in the present-day mode and scale of dust production from the Bodélé the African paleoclimate record are due to in situ weakening of Basin cannot have occurred before 1 ka, suggesting that its role in rainfall associated with the ITCZ (11–13) or contraction of this fertilizing marine and terrestrial ecosystems is either overstated or rainfall band in an interhemispherically symmetric manner (14). geologically recent. Although existing proxy and climate model data yield important insights into the drivers and mechanisms governing WAM African monsoon | Lake Chad | dust | African Humid Period strength, the paucity of regional-scale terrestrial records inhibits the evaluation of competing theories (15). he West African monsoon (WAM) is key to our understanding We present a regional-scale record of north central African Tof the African climate system and the impacts of future climate moisture balance, derived by optically stimulated luminescence change upon its population. Climatically, the WAM is a major (OSL) dating sedimentary deposits associated with the rise and component of the global monsoon belt, which regulates moisture fall of Lake Chad and its earlier incarnation, paleolake Mega- availability in the low latitudes and is sensitive to climate dynamics Chad. The latter was the largest freshwater lake in Africa and in both the high latitudes and the tropics. From a human per- spective, the WAM represents the dominant control upon agri- Significance cultural productivity in a densely populated region that is heavily reliant on subsistence agriculture (1). The broad pattern of WAM – dynamics since the Last Glacial Maximum (LGM) is well known, North Africa was wetter 15,000 5,000 years ago than today, with with initially arid conditions being replaced by a more humid wetlands and lakes formed in the Sahara due to an enhanced monsoon. We reconstruct the lake-level history of Lake Mega- phase, sometimes termed the African Humid Period (AHP), Chad, when it was the largest African lake, and demonstrate that which lasted from the deglacial period to the mid-Holocene. this humid period ended abruptly 5,000 years ago, indicating that However, paleoclimate proxy data from North Africa and adjacent the African monsoon exhibits a nonlinear response to insolation areas of the Atlantic provide contrasting evidence for the rate and forcing. The northern basin of Lake Mega-Chad, currently the timing of these changes, leading to uncertainty over the controls world’s greatest dust source, became dry around 1,000 years ago. upon WAM dynamics. Prior to that time dust output from the northern basin would West African Monsoon Dynamics have been limited, and suggestions that this dust plays an im- portant role in fertilizing Atlantic and Amazonian ecosystems are The widely cited terrigenous dust record from Ocean Drilling either overstated or only true for the last thousand years. Program (ODP) site 658C indicates abrupt onset and termination of the AHP at 14.8 and 5.5 ka, respectively (2). In contrast, records Author contributions: S.J.A., C.S.B., and N.A.D. designed research, performed research, from Lake Yoa within the Sahara (3–5) and the Gulf of Guinea analyzed data, and wrote the paper. (1) are interpreted to indicate gradual aridification over the past The authors declare no conflict of interest. 6 ka, with pollen data suggesting the onset of full desert conditions This article is a PNAS Direct Submission. at 2.7 ka. Reviews of lake-level change within the southern Sahara 1To whom correspondence should be addressed. Email: [email protected]. and Sahel indicate additional millennial to centennial changes This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. superimposed on the broad pattern of increase and subsequent 1073/pnas.1417655112/-/DCSupplemental. www.pnas.org/cgi/doi/10.1073/pnas.1417655112 PNAS | July 14, 2015 | vol. 112 | no. 28 | 8543–8548 Downloaded by guest on September 30, 2021 probably the largest pluvial lake on Earth. During the Early to samples below 287 m only constrain lake levels in the basin mid-Holocene wet phase, Lake Mega-Chad attained an area where they were collected, except that the lakes in both basins of 361,000 km2 (16–18) and a depth of up to 160 m (Fig. 1). must be below the elevation of the BEG sill at that time. Both Paleolake Mega-Chad has the potential to provide an important basins contain (formerly) submerged aeolian dunes, extensive record of WAM dynamics because it is (i) sensitive to changing relict shorelines, and fluviolacustrine sediments indicative of past moisture balance due to its shallow depth and large surface area; lake fluctuations. We used OSL and radiocarbon dating of these (ii) dominated by fluvial inputs, unlike smaller North African deposits combined with existing records from the basin to doc- lakes where groundwater can dominate; and (iii) Located in ument the fluctuations of Lake Chad and construct a regional- north central Africa, thereby integrating moisture from tropical scale record of WAM variability. and desert latitudes (Fig. 1 A and B). In addition, Lake Chad potentially acts as a climate driver in itself, projecting tropical Fluctuations of Paleolake Mega-Chad moisture ∼1,000 km northward during humid periods, thereby A reconstruction of Lake Mega-Chad levels, based upon new providing an efficient moisture source in the absence of long- and published OSL and radiocarbon ages (sample details are range atmospheric moisture delivery (19) and allowing dust provided in SI Appendix, Table S1), is presented in Fig. 2. Sus- production in the Bodélé Depression during arid periods (20, tained aridity in the period immediately after the LGM is evident 21). This dust production may further enhance aridity by sup- in both basins. Transverse dunes are preserved in the Chad Basin pressing rainfall (22). This dual role as alternate moisture and between 19 and 16 ka (NG33-36), whereas barchan dunes are dust source is made possible by the geography of the paleolake preserved under freshwater diatomite in the Bodélé date from 17 Mega-Chad catchment, which feeds two interlinked basins (Fig. to 15 ka (CH16, 22, and 51). The transverse dunes on the bed of 1C). The southern (Chad) basin contains present-day Lake Chad Lake Chad are indicative of drier than present-day conditions in and is fed primarily by the tropical catchments of the Chari the Chari catchment before ∼16 ka. A single age of 19 ± 2ka River. The northern (Bodélé) basin is presently hyperarid and is (NG41) for fluvial sands at Dalori Quarters in the Chad Basin fed either by Saharan catchments or by overflow from the Chad suggests elevated lake levels at that time. There are no analytical Basin via the Bahr el Ghazal (BEG) sill at an elevation of 287 m reasons for doubting the accuracy of this age.
Load more

Recommended publications
  • 100,000 Years of African Monsoon Variability Recorded in Sediments of the Nile Margin
    Quaternary Science Reviews 29 (2010) 1342–1362 Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev 100,000 Years of African monsoon variability recorded in sediments of the Nile margin Marie Revel a,*, E. Ducassou b, F.E. Grousset b, S.M. Bernasconi c, S. Migeon a, S. Revillon d, J. Mascle a, A. Murat e, S. Zaragosi b, D. Bosch f a Geosciences Azur, Observatoire Oce´anologique, La Darse, B.P. 48 06235 Villefranche/Mer, France b Universite´ Bordeaux 1, CNRS, UMR 5805-EPOC, avenue des faculte´s, 33405 Talence cedex, France c ETH Zurich, Geologisches Institut, 8092 Zurich, Switzerland d IFREMER, De´partement Ge´osciences Marines, BP70, 29280, Plouzane´, France e Cnam-Intechmer, BP324, 50103 Cherbourg, France f Laboratoire de Tectonophysique, Universite´ de Montpellier II, 34095 Montpellier, France article info abstract Article history: Multiproxy analyses were performed on core MS27PT recovered in hemipelagic sediments deposited on Received 20 April 2009 the Nile margin in order to reconstruct Nile River palaeohydrological fluctuations during the last 100,000 Received in revised form years. The strontium and neodymium isotope composition of the terrigenous fraction and the major 17 December 2009 element distribution reveal large and abrupt changes in source, oscillating between a dominant aeolian Accepted 4 February 2010 Saharan contribution during arid periods and a dominant Nile River contribution during pluvial periods. Iron content shows a strong correlation with strontium and neodymium isotopes. This allows the use of a high-resolution continuous Fe record as a proxy of Blue Nile sediment input over the last 100,000 years.
    [Show full text]
  • Neanderthal Extinction by Competitive Exclusion William E
    Neanderthal Extinction by Competitive Exclusion William E. Banks, Francesco d’Errico, A. Townsend Peterson, M. Kageyama, Sima Adriana, M. F. Sánchez Goñi To cite this version: William E. Banks, Francesco d’Errico, A. Townsend Peterson, M. Kageyama, Sima Adriana, et al.. Neanderthal Extinction by Competitive Exclusion. PLoS ONE, Public Library of Science, 2008, 3 (12), pp.e3972. 10.1371/journal.pone.0003972. halshs-00453393 HAL Id: halshs-00453393 https://halshs.archives-ouvertes.fr/halshs-00453393 Submitted on 28 Oct 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Neanderthal Extinction by Competitive Exclusion William E. Banks1*, Francesco d’Errico1,2, A. Townsend Peterson3, Masa Kageyama4, Adriana Sima4, Maria-Fernanda Sa´nchez-Gon˜ i5 1 Institut de Pre´histoire et de Ge´ologie du Quaternaire, UMR 5199-PACEA, Universite´ Bordeaux 1, CNRS, Talence, France, 2 Institute for Human Evolution, University of Witwatersrand, Johannesburg, South Africa, 3 Natural History Museum and Biodiversity Research Center, The University of Kansas, Lawrence, Kansas, United States of America, 4 Laboratoire des Sciences du Climat et de l’Environnement/IPSL, UMR 1572, CEA/CNRS/UVSQ, CE Saclay, L’Orme des Merisiers, Gif-sur-Yvette, France, 5 EPHE, UMR5805-EPOC, Universite´ Bordeaux 1, CNRS, Talence, France Abstract Background: Despite a long history of investigation, considerable debate revolves around whether Neanderthals became extinct because of climate change or competition with anatomically modern humans (AMH).
    [Show full text]
  • Geomorphology, Stratigraphy, and Paleohydrology of the Aeolis Dorsa Region, Mars, with Insights from Modern and Ancient Terrestrial Analogs
    University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 12-2016 Geomorphology, Stratigraphy, and Paleohydrology of the Aeolis Dorsa region, Mars, with Insights from Modern and Ancient Terrestrial Analogs Robert Eric Jacobsen II University of Tennessee, Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Geology Commons Recommended Citation Jacobsen, Robert Eric II, "Geomorphology, Stratigraphy, and Paleohydrology of the Aeolis Dorsa region, Mars, with Insights from Modern and Ancient Terrestrial Analogs. " PhD diss., University of Tennessee, 2016. https://trace.tennessee.edu/utk_graddiss/4098 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Robert Eric Jacobsen II entitled "Geomorphology, Stratigraphy, and Paleohydrology of the Aeolis Dorsa region, Mars, with Insights from Modern and Ancient Terrestrial Analogs." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Geology. Devon M. Burr,
    [Show full text]
  • Geologic Site of the Month: Why Is Sebago Lake So Deep?
    Why is Sebago Lake so deep? Maine Geological Survey Maine Geologic Facts and Localities February, 1999 Why is Sebago Lake so deep? 43° 51‘ 13.36“ N, 70° 33‘ 43.98“ W Text by Robert A. Johnston Maine Geological Survey, Department of Agriculture, Conservation & Forestry 1 Why is Sebago Lake so deep? Maine Geological Survey Introduction Modern geophysical equipment allows geologists to investigate previously unmapped environments, including ocean and lake floors. Recent geophysical research studied the types, composition, areal extent, and thickness of sediments on the bottom of Sebago Lake in southwestern Maine. Geologists used side- scan sonar and seismic reflection profiling to map the bottom of the lake. Approximately 58 percent of the lake bottom was imaged with side-scan sonar and over 60 miles of seismic reflection profiles were collected. This web site will discuss the findings of the seismic reflection profiling. Maine Geological Survey, Department of Agriculture, Conservation & Forestry 2 Why is Sebago Lake so deep? Maine Geological Survey Physiographic setting Sebago Lake, although second in surface area to Moosehead Lake, is Maine's deepest lake. With a water depth of 316 feet, its deepest part is 49 feet below sea level! Sebago Lake is located in southwestern Maine 20 miles northwest of Portland and 50 miles southeast of the White Mountains. It lies along the transition between the Central Highlands and the Coastal Lowlands physiographic regions of New England (Figure 1). The abrupt change in landscape can be seen in panoramic views from several vantage points near Sebago Lake. Denny, 1982 Denny, Maine Geological Survey From From Figure 1.
    [Show full text]
  • Implications for Management AFRICAN GREAT LAKES
    AFRICAN GREAT LAKES CONFERENCE 2nd – 5th MAY 2017, ENTEBBE, UGANDA Dynamics of Fish Stocks of Commercial Importance in Lake Victoria, East Africa: Implications for Management Robert Kayanda, Anton Taabu-Munyaho, Dismas Mbabazi, Hillary Mrosso, and Chrisphine Nyamweya INTRODUCTION • Lake Victoria with a surface area of 68,800 sqkm is the world’s second largest freshwater body • It supports one of the world’s most productive inland fisheries with the estimated total fish landings from the lake for the period of 2011 to 2014 have been about 1 million tons with a beach value increasing from about US$ 550 Million in 2011 to about US$ 840 million in 2014. • It supports about 220,000 fishers (Frame Survey 2016) • The fish stocks of Lake Victoria have changed dramatically since the introduction of Nile perch Lates niloticus during the late 1950s and early 1960s Fishery Haplochromines The Original Fish Fauna Brycinus sp Protopterus Rastrineobola Mormyrus spp Barbus spp Bagrus docmac Labeo Schilbe intermedius Oreochromis variabilis Clarias gariepinus Mormyrus spp Synodontis victoriae Oreochromis leucostictus INTRODUCTION Currently, the fisheries is dominated by four major commercial important species, these are; •Nile perch •Dagaa •Nile tilapia •Haplochromis Apart from Nile tilapia only estimated through trawl and catch surveys, the other 3 are estimated through trawl, acoustics, and catch INTRODUCTION This paper summarizes current knowledge of the status of the fish stocks and reviews the need for species specific management plans for the major commercial important fish species of Lake Victoria (Nile perch, Nile tilapia, dagaa and haplochromines). Methods • Fisheries dependent – Frame surveys – Catch assessment surveys • Fisheries independent – Acoustic – Bottom trawl Biomass and relative abundance • Total biomass from the surveys 3500 remained fairly stable over time.
    [Show full text]
  • The End of the Holocene Humid Period in the Central Sahara and Thar Deserts: Societal Collapses Or New Opportunities? Andrea Zerboni1, S
    60 SCIENCE HIGHLIGHTS: CLIMATE CHANGE AND CULTURAL EVOLUTION doi: 10.22498/pages.24.2.60 The end of the Holocene Humid Period in the central Sahara and Thar deserts: societal collapses or new opportunities? Andrea Zerboni1, S. biagetti2,3,4, c. Lancelotti2,3 and M. Madella2,3,5 The end of the Holocene Humid Period heavily impacted on human societies, prompting the development of new forms of social complexity and strategies for food security. Yearly climatic oscillations played a role in enhancing the resilience of past societies. The Holocene Humid Period or Holocene settlements (Haryana, India), show a general changes in settlement pattern, rather than full- climatic Optimum (ca. 12–5 ka bP), in its local, trend towards desertification and higher fledged abandonment. monsoon-tuned variants of the African Humid evapotranspiration between 5.8 and 4.2 ka bP, Period (DeMenocal et al. 2000; Gasse 2000) followed by an abrupt increase in δ18O values In the SW Fazzan, the transition from the Late and the period of strong Asian southwest (or and relative abundance of carbonates, indic- Pastoral (5-3.5 ka bP) to the Final Pastoral summer) monsoon (Dixit et al. 2014), is one ative of a sudden decrease in Indian summer (3.5-2.7 ka bP) marks the ultimate adaptation of the best-studied climatic phases of the monsoon precipitations (Dixit et al. 2014). to hyperarid conditions and, later, the rise Holocene. Yet the ensuing trend towards arid- of the Garamantian kingdom (2.7-1.5 ka bP; ity, the surface processes shaping the pres- Aridification and cultural processes Mori et al.
    [Show full text]
  • Rice Lake Nature Area
    Rice Lake Nature Area Location: 4120 Bassett Creek Drive Nature Area Size: 9.23 Acres Description The Rice Lake Nature Area is located along the north side of Bassett Creek Drive. The nature area is within a residential neighborhood, although the woods and wetland provide more seclusion than expected for a small urban nature area. Access to the park is through a pedestrian bridge crossing of Bassett Creek, which flows from west to east. In this reach, Bassett Creek is within an incised channel and some bank erosion is present. The creek is bordered by mixed hardwood floodplain forest and hardwood swamp. Reed canary grass is present where there is sufficient clearing, but the understory can be sparse due to heavy shading. Tree removal would likely generate a flush of reed canary grass Rice Lake Nature Area can be accessed by walking an aggregate path, and a boardwalk leading to a floating dock. South Rice Pond, sometimes referred to as Rice Lake, is a shallow basin, with a wide emergent marsh fringe. Small, shallow ponds and lakes like South Rice, are somewhat unique, as they are successionally proceeding from deeper open water to wetland. That natural process can be observed from the Rice Lake Nature Area, by observing the existing habitat and surrounding areas. The Rice Lake Nature Area provides a unique opportunity to provide an unobstructed view of South Rice Pond. Because the park is dominated by wetland, access is limited to a raised trail and boardwalk. Forest and Woodlands The southern portion of the Rice Lake Nature Area is composed of a mixture of floodplain forest and hardwood swamp.
    [Show full text]
  • Tropical Climate and Vegetation Cover During Heinrich Event 1: Simulations with Coupled Climate- Vegetation Models
    Tropical climate and vegetation cover during Heinrich event 1: Simulations with coupled climate- vegetation models Dissertation zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften Dr. rer. nat. im Fachbereich 5 (Geowissenschaften) der Universität Bremen vorgelegt von Dian Noor Handiani Bremen, Oktober 2012 Erklärung Name: Dian Noor Handiani Anschrift: Woltmershauser straße 464, 28197 Bremen, Deutschland Hiermit versichere ich, dass ich 1. die Arbeit ohne unerlaubte fremde Hilfe angefertigt habe, 2. keine anderen als die von mir angegebenen Quellen und Hilfsmittel benutzt habe und 3. die den benutzten Werken wörtlich oder inhaltlich entnommenen Stellen als solche kenntlich gemacht habe. Bremen, Oktober 2012 (Unterschrift) Gutachter Prof. Dr. Michael Schulz Prof. Dr. Michal Kucera Promotionskolloquium: 20.12.2012 Mitglieder der Kommission: Herr Prof. Dr. Michael Schulz Herr Prof. Dr. Michal Kucera Herr Prof. Dr. Gerold Wefer Frau Prof. Dr. Gesine Mollenhauer Frau Dr. Lydie Dupont Frau Annegret Krandick Table of Content Acknowledgements i Summary iii Zusammenfassung v 1 Introduction 1 1.1 Motivation of study ………………………………………………………………… 1 1.2 Tropical climate and vegetation in the Heinrich events ……………….......... 3 1.3 Atlantic Meridional Overturning Circulation (AMOC) ………………………. 6 1.4 Research objectives ………………………………………………………………… 9 1.5 Research approach and chapter outline ………………………………………… 10 2 Methodology 11 2.1 The UVic ESCM ……………………………………………………………………. 11 2.1.1 The atmospheric model …………………………………………………….. 11 2.1.2 The ocean and sea-ice model ……………………………………………… 13 2.1.3 The land surface and dynamic vegetation models …………………….. 14 2.2 Plant functional types and biomes ………………………………………………. 15 2.3 A scheme of biome distribution estimation …………………………………….. 16 2.4 Experimental design ………………………………………………………………. 17 3 Tropical climate and vegetation changes during Heinrich event 1: 19 a model-data comparison 3.1 Abstract ……………………………………………………………………………… 19 3.2 Introduction ………………………………………………………………………….
    [Show full text]
  • Technical Note: Characterising and Comparing Different Palaeoclimates with Dynamical Systems Theory
    Clim. Past, 17, 545–563, 2021 https://doi.org/10.5194/cp-17-545-2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Technical note: Characterising and comparing different palaeoclimates with dynamical systems theory Gabriele Messori1,2,3,4 and Davide Faranda5,6,7 1Department of Earth Sciences, Uppsala University, Uppsala, Sweden 2Centre of Natural Hazards and Disaster Science (CNDS), Uppsala University, Uppsala, Sweden 3Department of Meteorology, Stockholm University, Stockholm, Sweden 4Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden 5Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Gif-sur-Yvette, France 6London Mathematical Laboratory, London, UK 7LMD/IPSL, Ecole Normale Superieure, PSL research University, Paris, France Correspondence: Gabriele Messori ([email protected]) Received: 30 July 2020 – Discussion started: 27 August 2020 Revised: 7 January 2021 – Accepted: 10 January 2021 – Published: 2 March 2021 Abstract. Numerical climate simulations produce vast At the same time, an appraisal of the framework’s limitations amounts of high-resolution data. This poses new challenges suggests that it should be viewed as a complement to more to the palaeoclimate community – and indeed to the broader conventional analyses, rather than as a wholesale substitute. climate community – in how to efficiently process and inter- pret model output. The palaeoclimate community also faces the additional challenge of having to characterise and com- 1 Motivation pare a much broader range of climates than encountered in other subfields of climate science. Here we propose an analy- Numerical climate models have enjoyed widespread use sis framework, grounded in dynamical systems theory, which in palaeoclimate studies, from early investigations based may contribute to overcoming these challenges.
    [Show full text]
  • The Last Glacial Maximum and Heinrich Event I on the Iberian Peninsula: a Regional Climate Modelling Study for Understanding Human Settlement Patterns
    Geophysical Research Abstracts Vol. 20, EGU2018-7848, 2018 EGU General Assembly 2018 © Author(s) 2018. CC Attribution 4.0 license. The Last Glacial Maximum and Heinrich Event I on the Iberian Peninsula: A regional climate modelling study for understanding human settlement patterns Patrick Ludwig (1,2), Yaping Shao (2), Martin Kehl (3), and Gerd-Christian Weniger (4) (1) Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Department Troposphere Research, Karlsruhe, Germany ([email protected]), (2) Institute for Geophysics and Meteorology, University of Cologne, Cologne, Germany, (3) Institute of Geography, University of Cologne, Cologne, Germany, (4) Neanderthal Museum, Mettmann, Germany The dating and spatial distribution of archaeological sites on the Iberian Peninsula (IP) suggest a poor occupation of the Southern IP by hunter-gatherers after the Last Glacial Maximum (LGM) and during Heinrich event 1 (H1) compared to Northern Iberia. The H1 was a period of cold and arid climate conditions and is assumed to have played an important role in the population dynamics in Europe at the end of the Pleistocene. In this study, the potential influence of climate change on the human settlement patterns on the IP is analysed based on regional paleoclimate modelling. The WRF model is used to simulate continuous time slices of 30 years of climate con- ditions representative for both the LGM and H1 at high spatial resolution (12.5 km). The model results indicate that, apart from a general decrease in temperature, a considerable decrease in precipitation over the southern IP occurred during the H1, that agrees with the available climate proxy data.
    [Show full text]
  • Le Maghreb a Conservé Des Traces De La Dernière Période Humide Africaine
    COMMUNIQUÉ DE PRESSE Mardi 2 mars 2021 LE MAGHREB A CONSERVÉ DES TRACES DE LA DERNIÈRE PÉRIODE HUMIDE AFRICAINE Une équipe franco-marocaine, comptant des chercheurs et chercheuses de l’Université Paul-Valéry Montpellier 3, du CNRS et des Universités de Rabat et d’Oujda vient de mettre en évidence au Maghreb des traces de l’African Humid Period (AHP). La formation de nombreuses zones humides dans les régions pré-désertiques, au nord du Sahara il y a 11 000 à 5 000 ans, a été enregistrée dans les archives sédimentaires des Hauts Plateaux et du bassin de la Moulouya, au Maroc. L’étude, qui vient de paraître le 1er mars dans la revue Quaternary Science Reviews, apporte les premiers éléments d’information sur l’AHP dans ces régions du Maroc oriental, sur leur sensibilité aux influences climatiques complexes (entre Méditerranée, Atlantique et Sahara), et montre par ailleurs qu’elles ont pu constituer des voies d’échanges privilégiées entre les sociétés sahariennes et méditerranéennes au cours de la Préhistoire récente. L’African Humid Period, communément appelée "Sahara Vert", correspond à l’installation de conditions humides en Afrique, via une intensification et un déplacement de la mousson vers le nord, rythmées par des paramètres orbitaux comme l’augmentation de l’ensoleillement. Loin d’être le désert que nous connaissons actuellement, le Sahara était alors parsemé de nombreux lacs et couvert d’une savane arborée. De nombreuses recherches ont été menées ces dernières décennies dans les régions équatoriales et sahéliennes, mais peu se sont intéressées aux bordures septentrionales du Sahara. L’étude qui vient de paraître, porte sur les archives sédimentaires alluviales du bassin de la Moulouya et des Hauts Plateaux du Maroc oriental.
    [Show full text]
  • Palaeoclimate: End of the African Humid Period
    news & views for aquatic ecosystems, but if we are to fully needed. Finally, we need to know what Chris Evans is at the Centre for Ecology understand the behaviour of countless rivers happens to the aged DOC in our rivers — and Hydrology, Environment Centre Wales, across the planet many more measurements in particular, whether it is reactive. The Deiniol Road, Bangor LL57 2UW, UK. are needed. Global land-use data sets do so-called active pipe theory of river carbon e-mail: [email protected] not yet allow us to distinguish the effects transport suggests that it is, with freshwaters of different kinds of human activities, and functioning as zones of active carbon cycling References we cannot conclusively rule out effects of rather than as passive conduits from land 1. Batjes, N. H. Eur. J. Soil Sci. 47, 151–163 (1996). 8 2. Smith, P. et al. in IPCC Climate Change 2014: Mitigation of intrinsic factors. For example, rivers that to ocean . But further work is needed to Climate Change Ch. 11 (Cambridge Univ. Press, 2014). export old DOC could also be also those quantify the influence of old carbon on the 3. Butman, D. E. et al. Nature Geosci. 8, 112–116 (2015). with dry, deep, permeable soils that have operation of aquatic ecosystems, and the 4. Raymond, P. A. et al. Glob. Biogeochem. Cycles 21, GB4011 (2007). proved conducive to human settlement. proportion of aged DOC that is ultimately 5. Evans, C. D. et al. Geophys. Res. Lett. 34, L07407 (2007). Experimental studies targeted on emitted to the atmosphere as CO2.
    [Show full text]