James A Collins
University of Bremen
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Featured researches published by James A Collins.
Nature | 2010
Stefan Mulitza; David Heslop; Daniela Pittauerova; Helmut W Fischer; Inka Meyer; Jan-Berend W Stuut; Matthias Zabel; Gesine Mollenhauer; James A Collins; Henning Kuhnert; Michael Schulz
The Sahara Desert is the largest source of mineral dust in the world. Emissions of African dust increased sharply in the early 1970s (ref. 2), a change that has been attributed mainly to drought in the Sahara/Sahel region caused by changes in the global distribution of sea surface temperature. The human contribution to land degradation and dust mobilization in this region remains poorly understood, owing to the paucity of data that would allow the identification of long-term trends in desertification. Direct measurements of airborne African dust concentrations only became available in the mid-1960s from a station on Barbados and subsequently from satellite imagery since the late 1970s: they do not cover the onset of commercial agriculture in the Sahel region ∼170 years ago. Here we construct a 3,200-year record of dust deposition off northwest Africa by investigating the chemistry and grain-size distribution of terrigenous sediments deposited at a marine site located directly under the West African dust plume. With the help of our dust record and a proxy record for West African precipitation we find that, on the century scale, dust deposition is related to precipitation in tropical West Africa until the seventeenth century. At the beginning of the nineteenth century, a sharp increase in dust deposition parallels the advent of commercial agriculture in the Sahel region. Our findings suggest that human-induced dust emissions from the Sahel region have contributed to the atmospheric dust load for about 200 years.
Nature Communications | 2017
James A Collins; Matthias Prange; Thibaut Caley; Luis Gimeno; Britta Beckmann; Stefan Mulitza; Charlotte Skonieczny; Didier M. Roche; Enno Schefuß
The rapidity and synchrony of the African Humid Period (AHP) termination at around 5.5 ka are debated, and it is unclear what caused a rapid hydroclimate response. Here we analysed the hydrogen isotopic composition of sedimentary leaf-waxes (δDwax) from the Gulf of Guinea, a proxy for regional precipitation in Cameroon and the central Sahel-Sahara. Our record indicates high precipitation during the AHP followed by a rapid decrease at 5.8–4.8 ka. The similarity with a δDwax record from northern East Africa suggests a large-scale atmospheric mechanism. We show that northern high- and mid-latitude cooling weakened the Tropical Easterly Jet and, through feedbacks, strengthened the African Easterly Jet. The associated decrease in precipitation triggered the AHP termination and combined with biogeophysical feedbacks to result in aridification. Our findings suggest that extratropical temperature changes, albeit smaller than during the glacial and deglacial, were important in triggering rapid African aridification during the Holocene.The synchrony, spatial distribution and causes of the African Humid Period termination at 5.5 ka remain debated. Here, the authors show that rapid aridification in Cameroon and the central Sahel-Sahara took place between 5.8–4.8 ka and was likely triggered by high- and mid-latitude cooling.
Supplement to: Collins, JA et al. (2013): Abrupt shifts of the Sahara-Sahel boundary during Heinrich stadials. Climate of the Past, 9(3), 1181-1191, https://doi.org/10.5194/cp-9-1181-2013 | 2013
James A Collins; Aline Govin; Stefan Mulitza; David Heslop; Matthias Zabel; Jens Hartmann; Ursula Röhl; Gerold Wefer
J. A. Collins, A. Govin, S. Mulitza, D. Heslop, M. Zabel, J. Hartmann, U. Röhl, and G. Wefer MARUM – Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, 28359 Bremen, Germany Research School of Earth Sciences, The Australian National University, Canberra ACT 0200, Australia Institute for Biogeochemistry and Marine Chemistry, University of Hamburg, Bundesstraße 55, 20146 Hamburg, Germany
Geochemistry Geophysics Geosystems | 2012
Aline Govin; Ulrike Holzwarth; David Heslop; Lara Ford Keeling; Matthias Zabel; Stefan Mulitza; James A Collins; Cristiano Mazur Chiessi
Nature Geoscience | 2011
James A Collins; Enno Schefuß; David Heslop; Stefan Mulitza; Matthias Prange; Matthias Zabel; Rik Tjallingii; Trond Dokken; Enqing Huang; Andreas Mackensen; Michael Schulz; Jun Tian; Michelle Zarriess; Gerold Wefer
Sedimentary Geology | 2012
M.R. Bloemsma; Matthias Zabel; Jan-Berend W Stuut; Rik Tjallingii; James A Collins; Gert Jan Weltje
Quaternary Science Reviews | 2013
James A Collins; Enno Schefuß; Stefan Mulitza; Matthias Prange; Martin Werner; Thejna Tharammal; André Paul; Gerold Wefer
Climate of The Past | 2013
James A Collins; Aline Govin; Stefan Mulitza; David Heslop; Matthias Zabel; Jens Hartmann; Ursula Röhl; Gerold Wefer
Earth and Planetary Science Letters | 2014
James A Collins; Enno Schefuß; Aline Govin; Stefan Mulitza; Ralf Tiedemann
Geochemistry Geophysics Geosystems | 2012
Aline Govin; Ulrike Holzwarth; David Heslop; Lara Ford Keeling; Matthias Zabel; Stefan Mulitza; James A Collins; Cristiano Mazur Chiessi