Bereichsbild

Sedimentology & Marine Paleoenvironmental Dynamics

 

PD Dr. André Bahr



Address:

                

 

 

Institute of Earth Sciences

Ruprecht-Karls-Universität Heidelberg

Im Neuenheimer Feld 234

D-69120 Heidelberg

Room:

211

Phone:

Fax:

+49 (0)6221-54 6062

+49 (0)6221-54 5503

E-mail:

andre.bahr@geow.uni-heidelberg.de

Bahr Profilbild 2

 


 

Research Focus:

Earth has cycled between warm and cold climatic states and these serve as a model to help us to understand Earth's likely future. The ocean plays a pivotal role in climate change due to its function as a global heat pump. Hence, it is of utmost importance to understand the dynamics of ocean circulation and its role in the regulation of global climate, particularly in light of the ongoing climate change debate.

My research focuses on intervals of Earth history that serve as analogues for possible environmental changes in the future. These include the massive climatic and environmental fluctuations seen in the last glaciation and the orbitally forced climate-cycles of the Neogene, as well as episodes of global warmth found in Pleistocene interglacials and hyperthermals of the Mesozoic and Cenozoic. I aim to reconstruct the feedbacks between ocean circulation and continental environmental conditions. My overarching question is, how does the ocean control changes in terrestrial climate and vice versa?  

My core questions are:

  • How and on what time scales do changes in ocean circulation affect continental climate?
  • Do changes in the terrestrial environment, such as the amount of precipitation, exert any influence on oceanic circulation? If so, what are these influences?
  • Are there systematic leads and lags between marine and terrestrial climate changes that reveal how the climate system works?

I make use of a combination of geochemical and biotic techniques:

  • foraminiferal geochemistry: temperature and salinity of surface and bottom water;
  • proxy calibration: Ba/Ca and Mg/Ca analyses on planktic foraminifera combined with faunal methods;
  • sedimentary geochemistry: sediment provenance, weathering intensity in the hinterland of rivers, reconstruction of marine bottom currents;
  •  grain-size analysis: investigation of sediment transport (e.g. eolian vs. fluviatile) and bottom current velocity.

 

Ongoing projects:

 

1) Dynamics of the South American Monsoon during the Pleistocene and Holocene

Monsoonal rainfall determines water availability over large parts of South America, however, its temporal and spatial dynamics are poorly understood. I am studying (with German Research Foundation, DFG support) the history of run-off of major rivers (e.g. Orinoco, Amazon, Sao Francisco) as an indicator of the moisture availability in the South American interior on decadal to orbital time scales. The combination of terrestrial climate indicators (e.g. Ba/Ca on planktic foraminifera as a river water tracer) with marine proxies (e.g. Mg/Ca-temperatures in planktic foraminifera) reveals the dynamics of terrestrial and oceanic feedbacks in the monsoon cycle.

 

2) Role of the Subtropical Gyre in ice sheet growth during the mid-Pleistocene

The mid-Pleistocene (ca. 1400–500 ka) is characterized by persistent growth of continental glaciers. We hypothesize that evaporation from the North Atlantic subtropical gyre contributed moisture for ice sheet growth in the high latitudes. This DFG-funded project investigates the spatial extent and strength of gyre circulation during the mid-Pleistocene via Mg/Ca analyses on shallow and deep-dwelling planktic foraminifera. The samples sites cover the western (Ocean Drilling Program Site 1058), northern (International Ocean Discovery Program, IODP, Site U1313) and eastern (IODP Site 1385) boundary of the gyre. This permits an in-depth view of the heat and moisture-transport from the North Atlantic into northern and central Europe during a critical phase of glacier advance.

 

3) Mediterranean Outflow Water dynamics since the mid-Pleistocene.

The Mediterranean Outflow Water (MOW) plays a pivotal role in Earth's climate as a source of salty water that helps drive the North Atlantic overturning circulation. Changes in the Zr/Al ratios within sediment cores retrieved from the Gulf of Cadiz (IODP Expedition 339) show the long-term contribution of MOW to the salt inventory in the Atlantic. This DFG-funded projects aims to understand what controls MOW-dynamics and assess how MOW production affects the ease of deep convection in the North Atlantic. We have found that variations in the East African Monsoon affect Nile discharge and this freshwater influences formation of the MOW in the eastern Mediterranean – a prime example for the direct coupling of oceanic and continental environmental processes.

 

 

Scientific Career and Education:

since 10/2014

Scientific assistant („Akademischer Rat“), Institute of Earth Sciences (Heidelberg)

12/2009-09/2014

Scientific assistant, Institute of Geosciences (Frankfurt)

01/2008-11/2009

Postdoc, GEOMAR, (Kiel)

08/2007-12/2007

Postdoc, MARUM (Bremen)

02/2007-08/2007

Postdoc, NIOZ (den Burg, Texel, The Netherlands)

02/2006-02/2007

Postdoc, MARUM (Bremen)

10/2002-12/2005

Doktorand, MARUM (Bremen)

10/1995-02/2002

Studies of Geology and Paleontology, University Hamburg

 

Publications:

(as of 11/2016)

in press

  • Lofi, J., Voelker, A., Ducassou, E., Hernández-Molina, F., Sierro, F., Bahr, A., Galvani, A., Lourens, L., Pardo-Igúzquiza, E. and Rodríguez-Tovar, F.,in press. Quaternary chronostratigraphic framework and sedimentary processes for the Gulf of Cadiz and Portuguese Contourite Depositional Systems derived from Natural Gamma Ray records. Marine Geology, doi: 10.1016/j.margeo.2015.12.005.

2016

  • Bahr, A., Spadano Albuquerque, A.L., Ardenghi, N., Batenburg, S.J., Bayer, M., Catunda, M.C., Conforti, A., Dias, B., Díaz Ramos, R., Egger, L.M., Evers, F., Fischer, T., Hatsukano, K., Hennrich, B., Hoffmann, J., Jivcov, S., Kusch, S., Munz, P., Niedermeyer, E., Osborne, A., Raddatz, J., Raeke, A.W., Reissig, S., Sebastian, U., Taniguchi, N., Martins Venancio, I., Voigt, S., Wachholz, A., 2016. South American Hydrological Balance and Paleoceanography during the Late Pleistocene and Holocene (SAMBA) - Cruise No. M125 - March 21 - April 15, 2016 - Rio de Janeiro (Brazil) - Fortaleza (Brazil). METEOR-Berichte, M125, 1-47.
  • Jakob, K.A., Wilson, P.A., Bahr, A., Bolton, C.T., Pross, J., Fiebig, J., Friedrich, O., 2016. Glacial-interglacial productivity changes in the eastern equatorial Pacific upwelling system and its response to Plio-Pleistocene ice-sheet dynamics. Paleoceanography, 31, 453-470.
  • Jiménez-Espejo, F., Pardos-Gené, M., Martínez-Ruiz, F., García-Alix, A., van de Flierdt, T., Toyofuku, T., Bahr, A., and Kreissig, K., 2016. Geochemical evidence for intermediate water circulation in the westernmost Mediterranean over the last 20 ky cal BP and its impact on the Mediterranean outflow. Global and Planetary Change.

2015

  • Bahr, A., Kaboth, S., Jiménez-Espejo, F., Sierro, F., Voelker, A., Lourens, L., Röhl, U., Reichart, G., Escutia, C., Hernández-Molina, F., Pross, J., and Friedrich, O., 2015. Persistent monsoonal forcing of Mediterranean Outflow Water dynamics during the late Pleistocene. Geology, p. G37013. Link to paper
  • Kaboth, S., Bahr, A., Reichart, G.-J., Jacobs, B., and Lourens, L. J., in press. New insights into upper MOW variability over the last 150 kyr from IODP 339 Site U1386 in the Gulf of Cadiz. Marine Geology, doi: 10.1016/j.margeo.2015.08.014.
  • Voelker, A. H., Salgueiro, E., Rodrigues, T., Jiménez-Espejo, F. J., Bahr, A., Alberto, A., Loureiro, I., Padilha, M., Rebotim, A., and Röhl, U., 2015. Mediterranean Outflow and surface water variability off southern Portugal during the early Pleistocene: A snapshot at Marine Isotope Stages 29 to 34 (1020–1135ka). Global and Planetary Change, 133, 223-237.
  • McCormack, J.M., Bahr, A., Gerdes, A., Tütken, T., and Prinz-Grimm, P., 2015. Preservation of successive diagenetic stages in Middle Triassic bonebeds: Evidence from in situ trace element and strontium isotope analysis of vertebrate fossils. Chemical Geology, 410, 108-123.
  • Nürnberg, D., Bahr, A., Mildner, T., Eden, C., and Kujau, A., 2015. Loop Current variability - its relation to meridional overturning circulation and the impact of Mississippi discharge, in Integrated Analysis of Interglacial Climate Dynamics, edited by M. Schulz and A. Paul, Springer, 55-62.

2014

  • Bahr, A., Jiménez-Espejo, F.J., Kolasinac, N., Grunert, P., Hernández-Molina, F., Röhl, U., Voelker, A., Escutia, C., Stow, D.A.V., Hodell, D., and Alvarez Zarikian, C.A., 2014. Deciphering bottom current velocity and paleoclimate signals from contourite deposits in the Gulf of Cádiz during the last 140 kyr: an inorganic geochemical approach, Geochem. Geophys. Geosyst., 15(8), 3145-3160.
  • Hernández-Molina, F.J., Stow, D.A.V., Alvarez-Zarikian, C.A., Acton, G., Bahr, A., Balestra, B., Ducassou, E., Flood, R., Flores, J.-A., Furota, S., Grunert, P., Hodell, D., Jiménez-Espejo, F., Kim, J.K., Krissek, L., Kuroda, J., Li, B., Llave, E., Lofi, J., Lourens, L., Miller, M., Nanayama, F., Nishida, N., Richter, C., Roque, C., Pereira, H., Sanchez Goñi, M.F., Sierro, F.J., Singh, A.D., Sloss, C., Takashimizu, Y., Tzanova, A., Voelker, A., Williams, T., and Xuan, C., 2014. Onset of Mediterranean outflow into the North Atlantic, Science, 344(6189), 1244-1250.
  • Hoffmann, J., Bahr, A., Voigt, S., Schönfeld, J., Nürnberg, D., and Rethemeyer, J., 2014. Disentangling abrupt deglacial hydrological changes in northern South America: Insolation versus oceanic forcing, Geology, 42(7), 579-582.
  • Wacker, U., Fiebig, J., Schöne, B.R., Bahr, A., Friedrich, O., Tütken, T., Gischler, E., and Joachimski, M.M., 2014. Empirical calibration of the clumped isotope paleothermometer using calcites of various origins, Geochimica et Cosmochimica Acta, 141, 127-144.

2013

  • Bahr, A., Nürnberg, D., Karas, C., and Grützner, J., 2013. Millennial-scale versus long-term dynamics in the surface and subsurface of the western North Atlantic Subtropical Gyre during Marine Isotope Stage 5, Global and Planetary Change, 111(0), 77-87.
  • Bahr, A., Schönfeld, J., Hoffmann, J., Voigt, S., Aurahs, R., Kucera, M., Flögel, S., Jentzen, A., and Gerdes, A., 2013. Comparison of Ba/Ca and δ18OWATER as freshwater proxies: A multi-species core-top study on planktonic foraminifera from the vicinity of the Orinoco River mouth, Earth and Planetary Science Letters, 383, 45-57.

2012

  • Henkel, S., Mogollón, J.M., Nöthen, K., Franke, C., Bogus, K., Robin, E., Bahr, A., Blumenberg, M., Pape, T., Seifert, R., März, C., de Lange, G.J., and Kasten, S., 2012. Diagenetic barium cycling in Black Sea sediments – A case study for anoxic marine environments, Geochimica et Cosmochimica Acta, 88(0), 88-105.
  • Römer, M., Sahling, H., Pape, T., Bahr, A., Feseker, T., Wintersteller, P., and Bohrmann, G., 2012. Geological control and magnitude of methane ebullition from a high-flux seep area in the Black Sea – The Kerch Seep Area, Marine Geology, 319-322, 57-74.

2011

  • Bahr, A., Nürnberg, D., Schönfeld, J., and Garbe-Schönberg, D., 2011. Hydrological variability in Florida Straits during Marine Isotope Stage 5 cold events, Paleoceanography, 26(2), PA2214.
  • Pape, T., Bahr, A., Klapp, S.A., Abegg, F., and Bohrmann, G., 2011. High-intensity gas seepage causes rafting of shallow gas hydrates in the southeastern Black Sea, Earth and Planetary Science Letters, 307(1-2), 35-46.

2010

  • Bahr, A., Pape, T., Abegg, F., Bohrmann, G., van Weering, T.C.E., and Ivanov, M.K., 2010. Authigenic carbonates from the eastern Black Sea as an archive for shallow gas hydrate dynamics – results from the combination of CT imaging with mineralogical and stable isotope analyses, Marine and Petroleum Geology, 27, 1819-1829.
  • Kujau, A., Nürnberg, D., Zielhofer, C., Bahr, A., and Röhl, U., 2010. Mississippi River discharge over the last ~560,000 years - Indications from X-ray fluorescence core-scanning, Palaeogeography, Palaeoclimatology, Palaeoecology, 298(3-4), 311-318.
  • Pape, T., Kasten, S., Zabel, M., Bahr, A., Abegg, F., Hohnberg, H.-J., and Bohrmann, G., 2010. Gas hydrates in shallow deposits of the Amsterdam mud volcano, Anaximander Mountains, Northeastern Mediterranean Sea, Geo-Mar. Lett., 30, 187-206.
  • Pape, T., Bahr, A., Rethemeyer, J., Kessler, J.D., Sahling, H., Hinrichs, K.-U., Klapp, S.A., Reeburgh, W.S., and Bohrmann, G., 2010. Molecular and isotopic partitioning of low-molecular-weight hydrocarbons during migration and gas hydrate precipitation in deposits of a high-flux seepage site, Chemical Geology, 269(3-4), 350-363.

2009

  • Bahr, A., Pape, T., Bohrmann, G., Mazzini, A., Haeckel, M., Reitz, A., and Ivanov, M., 2009. Authigenic carbonate precipitates from the NE Black Sea: a mineralogical, geochemical, and lipid biomarker study, International Journal of Earth Sciences, 98, 677–695.
  • Kwiecien, O., Arz, H.W., Lamy, F., Plessen, B., Bahr, A., and Haug, G.H., 2009. North Atlantic control on precipitation pattern in the eastern Mediterranean/Black Sea region during the last glacial, Quaternary Research, 71(3), 375-384.
  • Sahling, H., Bohrmann, G., Artemov, Y.G., Bahr, A., Brüning, M., Klapp, S.A., Klaucke, I., Kozlova, E., Nikolovska, A., Pape, T., Reitz, A., and Wallmann, K., 2009. Vodyanitskii mud volcano, Sorokin trough, Black Sea: Geological characterization and quantification of gas bubble streams, Marine and Petroleum Geology, 26(9), 1799-1811.

2008

  • Bahr, A., Lamy, F., Arz, H.W., Major, C.O., Kwiecien, O., and Wefer, G., 2008. Abrupt changes of temperature and water chemistry in the late Pleistocene and early Holocene Black Sea, Geochemistry, Geophysics, Geosystems, 9(1), Q01004.
  • Bahr, A., Bohrmann, G., and Teichert, B.M.A., 2008. Data report: bulk mineralogical composition of Cascadia margin sediments, IODP Expedition 311, in Proceedings of the Integrated Drilling Program, edited by M. Riedel, et al., p. doi:10.2204/iodp.proc.2311.2201.2008, Integrated Ocean Drilling Program, College Station, TX, USA.
  • Kwiecien, O., Arz, H.W., Lamy, F., Wulf, S., Bahr, A., Röhl, U., and Haug, G.H., 2008. Estimated reservoir ages of the Black Sea since the last glacial, Radiocarbon, 50(1), 99–118.
  • Mazzini, A., Ivanov, M., Nermoen, A., Bahr, A., Bohrmann, G., Svensen, H., and Planke, S., 2008. Complex plumbing systems in the near subsurface: geometries of authigenic carbonates from Dolgovskoy Mound (Black Sea) constrained by analogue experiments, Marine and Petroleum Geology, 25, 457-472.

2006

  • Bahr, A., Arz, H.W., Lamy, F., and Wefer, G., 2006. Late glacial to Holocene paleoenvironmental evolution of the Black Sea, reconstructed with stable oxygen isotope records obtained on ostracod shells, Earth and Planetary Science Letters, 241(3-4), 863-875.
  • Lamy, F., Arz, H.W., Bond, G., Bahr, A., and Pätzold, J., 2006. Multicentennial-scale hydrological changes in the Black Sea and northern Red Sea during the Holocene and the Arctic/North Atlantic Oscillation, Paleoceanography, 21(PA1008).

2005

  • Bahr, A., Lamy, F., Arz, H., Kuhlmann, H., and Wefer, G. 2005. Late glacial to Holocene climate and sedimentation history in the NW Black Sea, Marine Geology, 214, 309-322.

2004

  • Bahr, A., Wong, H.K., Yim, W.W.-S., Huang, G., and Lüdmann, T., 2004. Stratigraphy of Quaternary inner-shelf sediments in Tai O Bay, Hong Kong, based on ground-truthed seismic profiles Geo-Mar. Lett., 25(1), 20-33.

 

Outreach:

Appearance in broadcast "Global" in SWRinfo Radio, 19 Nov 2015.

Editor: Email
Latest Revision: 2016-12-01
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