title: Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity.
abstract: The transport of moisture in the tropics is a critical process for the global energy budget and on geologic timescales, has markedly influenced continental landscapes, migratory pathways, and biological evolution. Here we present a continuous, first-of-its-kind 1.3-My record of continental hydroclimate and lake-level variability derived from drill core data from Lake Malawi, East Africa (9-15° S). Over the Quaternary, we observe dramatic shifts in effective moisture, resulting in large-scale changes in one of the world's largest lakes and most diverse freshwater ecosystems. Results show evidence for 24 lake level drops of more than 200 m during the Late Quaternary, including 15 lowstands when water levels were more than 400 m lower than modern. A dramatic shift is observed at the Mid-Pleistocene Transition (MPT), consistent with far-field climate forcing, which separates vastly different hydroclimate regimes before and after ∼800,000 years ago. Before 800 ka, lake levels were lower, indicating a climate drier than today, and water levels changed frequently. Following the MPT high-amplitude lake level variations dominate the record. From 800 to 100 ka, a deep, often overfilled lake occupied the basin, indicating a wetter climate, but these highstands were interrupted by prolonged intervals of extreme drought. Periods of high lake level are observed during times of high eccentricity. The extreme hydroclimate variability exerted a profound influence on the Lake Malawi endemic cichlid fish species flock; the geographically extensive habitat reconfiguration provided novel ecological opportunities, enabling new populations to differentiate rapidly to distinct species.
authors.affiliation: Department of Earth Sciences, Syracuse University, Syracuse, NY 13244;
authors.forename: Robert P
authors.initials: RP
authors.lastname: Lyons
authors.affiliation: Department of Earth Sciences, Syracuse University, Syracuse, NY 13244; cascholz@syr.edu.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Scholz
authors.affiliation: Department of Geosciences, University of Arizona, Tucson, AZ 85721;
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Cohen
authors.affiliation: Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882;
authors.forename: John W
authors.initials: JW
authors.lastname: King
authors.affiliation: Large Lakes Observatory and Department of Earth and Environmental Sciences, University of Minnesota, Duluth, MN 55812;
authors.forename: Erik T
authors.initials: ET
authors.lastname: Brown
authors.affiliation: Institute at Brown for the Study of the Environment and Society, Brown University, Providence, RI 02912;
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Ivory
authors.affiliation: Large Lakes Observatory and Department of Earth and Environmental Sciences, University of Minnesota, Duluth, MN 55812;
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Johnson
authors.affiliation: Berkeley Geochronology Center, Berkeley, CA 94709;
authors.forename: Alan L
authors.initials: AL
authors.lastname: Deino
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721;
authors.forename: Peter N
authors.initials: PN
authors.lastname: Reinthal
authors.affiliation: Department of Earth and Environmental Sciences, University of Kentucky, Lexington, KY 40506.
authors.forename: Michael M
authors.initials: MM
authors.lastname: McGlue
authors.affiliation: Department of Geosciences, University of Arizona, Tucson, AZ 85721;
authors.forename: Margaret W
authors.initials: MW
authors.lastname: Blome
mesh_terms: D000351:Africa, Eastern; D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D023681:Cichlids; D002980:Climate; D057231:Climate Change / Q000266:history; D017753:Ecosystem; D049690:History, Ancient; D060106:Lakes; D010163:Paleontology; D013997:Time Factors
keywords: East African rift; Lake Malawi; cichlid fish; quaternary; tropical paleoclimatology