Latitudinal migrations of the subtropical front at the Agulhas Plateau through the Mid-Pleistocene transition
The meridional variability of the Subtropical Front (STF) in the Southern Hemisphere, linked to expansions or contractions of the Southern Ocean, may have played an important role in global ocean circulation by moderating the magnitude of water exchange at the Indian-Atlantic Ocean Gateway, so calle...
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| Main Authors: | , , , , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
23 June 2021
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| In: |
Paleoceanography and paleoclimatology
Year: 2021, Volume: 36, Pages: 1-17 |
| ISSN: | 2572-4525 |
| DOI: | 10.1029/2020PA004084 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1029/2020PA004084 Verlag, lizenzpflichtig, Volltext: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020PA004084 
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| Author Notes: | Alejandra Cartagena-Sierra, Melissa A. Berke, Rebecca S. Robinson, Basia Marcks, Isla S. Castañeda, Aidan Starr, Ian R. Hall, Sidney R. Hemming, Leah J. LeVay, and Expedition 361 scientific party |
| Summary: | The meridional variability of the Subtropical Front (STF) in the Southern Hemisphere, linked to expansions or contractions of the Southern Ocean, may have played an important role in global ocean circulation by moderating the magnitude of water exchange at the Indian-Atlantic Ocean Gateway, so called Agulhas Leakage. Here we present new biomarker records of upper water column temperature ( and ) and primary productivity (chlorins and alkenones) from marine sediments at IODP Site U1475 on the Agulhas Plateau, near the STF and within the Agulhas retroflection pathway. We use these multiproxy time-series records from 1.4 to 0.3 Ma to examine implied changes in the upper oceanographic conditions at the mid-Pleistocene transition (MPT, ca. 1.2-0.8 Ma). Our reconstructions, combined with prior evidence of migrations of the STF over the last 350 ka, suggest that in the Southwestern Indian Ocean the STF may have been further south from the Agulhas Plateau during the mid-Pleistocene Interim State (MPIS, MIS 23-12) and reached its northernmost position during MIS 34-24 and MIS 10. Comparison to a Globorotalia menardii-derived Agulhas Leakage reconstruction from the Cape Basin suggests that only the most extreme northward migrations of the STF are associated with reduced Agulhas Leakage. During the MPIS, STF migrations do not appear to control Agulhas Leakage variability, we suggest previously modeled shifting westerly winds may be responsible for the patterns observed. A detachment between STF migrations and Agulhas Leakage, in addition to invoking shifting westerly winds may also help explain changes in CO2 ventilation seen during the MPIS. |
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| Item Description: | Aus der Supporting information: Expedition 361 shipboard scientific party: Thibaut Caley, Stephen R. Barker, Christopher D. Charles, Janna Just, Jason J. Coenen, Julien G. Crespin, Allison M. Franzese, Jens Gruetzner, Deborah Tangunan, Richard D. Norris, Xibin Han, Sophia K.V. Hines, Francisco J. Jimenez Espejo, Andreas Koutsodendris, Kaoru Kubota, Nambiyathodi Lathika, Thiago Pereira dos Santos, John M. Rolison, Margit H. Simon, Jeroen J.L. van der Lubbe, Masako Yamane, and Hucai Zhang, Luna Brentegani Gesehen am 13.07.2021 |
| Physical Description: | Online Resource |
| ISSN: | 2572-4525 |
| DOI: | 10.1029/2020PA004084 |