title: Century-Long Warming Trends in the Upper Water Column of Lake Tanganyika.
abstract: Lake Tanganyika, the deepest and most voluminous lake in Africa, has warmed over the last century in response to climate change. Separate analyses of surface warming rates estimated from in situ instruments, satellites, and a paleolimnological temperature proxy (TEX86) disagree, leaving uncertainty about the thermal sensitivity of Lake Tanganyika to climate change. Here, we use a comprehensive database of in situ temperature data from the top 100 meters of the water column that span the lake's seasonal range and lateral extent to demonstrate that long-term temperature trends in Lake Tanganyika depend strongly on depth, season, and latitude. The observed spatiotemporal variation in surface warming rates accounts for small differences between warming rate estimates from in situ instruments and satellite data. However, after accounting for spatiotemporal variation in temperature and warming rates, the TEX86 paleolimnological proxy yields lower surface temperatures (1.46 °C lower on average) and faster warming rates (by a factor of three) than in situ measurements. Based on the ecology of Thaumarchaeota (the microbes whose biomolecules are involved with generating the TEX86 proxy), we offer a reinterpretation of the TEX86 data from Lake Tanganyika as the temperature of the low-oxygen zone, rather than of the lake surface temperature as has been suggested previously. Our analyses provide a thorough accounting of spatiotemporal variation in warming rates, offering strong evidence that thermal and ecological shifts observed in this massive tropical lake over the last century are robust and in step with global climate change.
authors.affiliation: Center for Limnology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Kraemer
authors.affiliation: NASA Jet Propulsion Laboratory, Pasadena, California, United States of America.
authors.forename: Simon
authors.initials: S
authors.lastname: Hook
authors.affiliation: Finnish Environment Institute, Freshwater Centre, Jyväskylä, Finland.
authors.forename: Timo
authors.initials: T
authors.lastname: Huttula
authors.affiliation: Finnish Environment Institute, Marine Research Centre, Helsinki, Finland.
authors.forename: Pekka
authors.initials: P
authors.lastname: Kotilainen
authors.affiliation: Department of Geography-Geology, Illinois State University, Normal, Illinois, United States of America.
authors.forename: Catherine M
authors.initials: CM
authors.lastname: O'Reilly
authors.affiliation: Centre for Economic Development, Transport and the Environment for Pirkanmaa, Tampere, Finland.
authors.forename: Anu
authors.initials: A
authors.lastname: Peltonen
authors.affiliation: Royal Museum for Central Africa, Tervuren, Belgium.
authors.forename: Pierre-Denis
authors.initials: PD
authors.lastname: Plisnier
authors.affiliation: Department of Biology, University of Turku, Turku, Finland.
authors.forename: Jouko
authors.initials: J
authors.lastname: Sarvala
authors.affiliation: Department of Aquatic Sciences and Fisheries, University of Dar es Salaam, Dar es Salaam, Tanzania.
authors.forename: Rashid
authors.initials: R
authors.lastname: Tamatamah
authors.affiliation: Department of Biological Sciences, Wright State University, Dayton, Ohio, United States of America.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Vadeboncoeur
authors.affiliation: Surface Waters Department, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Kastanienbaum, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Wehrli
authors.affiliation: Center for Limnology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Peter B
authors.initials: PB
authors.lastname: McIntyre
mesh_terms: D001105:Archaea; D057232:Global Warming; D060106:Lakes / Q000382:microbiology*; D012621:Seasons; D014867:Water; D014871:Water Microbiology
chemical_list: D014867:Water