EGU2020-2209
https://doi.org/10.5194/egusphere-egu2020-2209
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Pliocene ocean and climate dynamics in the eastern Indian Ocean and their implications for the global climate state.

David De Vleeschouwer1, Angelina Füllberg1, Rebecca Smith2, Gerald Auer3, Benjamin Petrick4, Isla Castañeda2, and Beth Christensen5
David De Vleeschouwer et al.
  • 1Universität Bremen, MARUM, MARUM, Bremen, Germany (ddevleeschouwer@marum.de)
  • 2Department of Geosciences, University of Massachusetts at Amherst, Amherst, USA
  • 3Department of Biogeochemistry, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Kanagawa, Japan
  • 4Max-Planck-Institut für Chemie, Mainz, Germany
  • 5Rowan University, USA

The Indonesian Throughflow (ITF) operates as an important link in global thermohaline circulation and is often considered a modulator of global past climate changes, with effects as far as Africa or the Atlantic Ocean. Yet, to what extent ITF variability accounted for oceanographic change along the west Australian coast remains controversial. A tectonically reduced ITF has been invoked to explain the short, but intense Pliocene glaciation Marine Isotope Stage (MIS) M2 (3.3 Ma). The hypothesis hinges on a reduced equator-to-pole heat transfer in the Indian Ocean, in response to low connectivity with the Indo-Pacific warm pool. To clarify links between regional oceanographic change and global climate, we present a two-site multiproxy reconstruction from the Perth (U1459) and the Carnarvon (U1463) Basin. These sites provide the opportunity to unravel the Pliocene history of the Leeuwin Current (LC). We use the LC as a proxy for ITF connectivity, as the ITF is the source for the warm, low-salinity, nutrient-deficient LC. A U1459-U1463 comparison thus allows for investigating the possible relationship between mid-Pliocene glaciations and ITF heat flux. We show that the LC was active throughout the Pliocene, albeit with fluctuations in intensity and scope. We identify three main factors that controlled LC strength. First, a tectonic ITF reorganization caused an abrupt and permanent LC reduction at 3.7 Ma, coeval with the remarkably intense Pliocene glacial MIS Gi4. On shorter timescales, eustatic sea level and direct orbital forcing of wind patterns hampered or promoted the LC. At 3.3 Ma, LC intensity plunged in response to a eustatic ITF restriction. MIS M2 caused the latitudinal U1463–U1459 planktonic oxygen isotope gradient to steepen from 1.2 to 2.0‰ and the TEX86 sea surface temperatures gradient to increase from 3 to 6°C. Yet, comparison with Exmouth Plateau Site 763 shows that the LC did not shut down completely during MIS M2: The ITF heat flux dwindled but did not cease. Weakened ITF connectivity led to a significant drop in Indian Ocean poleward heat transport and thus constitutes a positive feedback mechanism that contributed to the relative intensity of MIS M2 and the thermal isolation of Antarctica. This positive feedback mechanism is ultimately driven by orbital-scale changes in relative sea level in the ITF region.

How to cite: De Vleeschouwer, D., Füllberg, A., Smith, R., Auer, G., Petrick, B., Castañeda, I., and Christensen, B.: Pliocene ocean and climate dynamics in the eastern Indian Ocean and their implications for the global climate state., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2209, https://doi.org/10.5194/egusphere-egu2020-2209, 2020

Comments on the presentation

AC: Author Comment | CC: Community Comment | Report abuse

Presentation version 2 – uploaded on 29 Apr 2020
Use Full Screen Slide Show to hear recorded Narrations
  • CC1: Comment on EGU2020-2209, Elwyn de la Vega, 05 May 2020

    Hi David, interesting work. I would be interested to see more about the timing between, d18O/temperature gradients of your W Australians cores and sea-levels relative to the LR04 benthic stack, during the M2 glaciation. I can't really tell form the figures, how is the phasing? Have you noticed any leads or lags? I'm trying to link that to a new CO2 record I have produced accross this interval that show some dephasing and it appears sea-level from Rohling et al (red sea) also lags d18O. 

    • AC1: Reply to Elwyn, David De Vleeschouwer, 05 May 2020

      Dear Elwyn,

      Thank you for your interesting question. 

      The isotopic Δδ18O gradient between U1459 (Perth Basin) and U1463 (Northwest shelf of Australia) is obliquity-dominated, just as the LR04 stack. However, the amplitude of the obliquity imprint is more constant compared to the LR04 stack, which has very expressed as well as much subdued obliquity cycles. 

      You can download the isotopic gradient time-series here: https://www.dropbox.com/s/t461pfrqs7ha3ty/D_d18O_U1459_U1463_for_Elwyn.xlsx?dl=0

      Proxy series at face-value are stored on PANGAEA:

      You can use those for your purposes by citing De Vleeschouwer et al., 2019, Geophysical Research Letters. 

      Let me know if you have further questions.

      David.

      • CC2: Reply to AC1, Elwyn de la Vega, 05 May 2020

        Great, thank you so much for sending the data along! Will plot up these with my stuff along with the references you mentioned in your presentation. Thanks again!

Presentation version 1 – uploaded on 28 Apr 2020 , no comments