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Ballalai, João M; Santos, Thiago Pereira dos; Lessa, Douglas Villela de Oliveira; Venancio, Igor Martins; Chiessi, Cristiano Mazur; Johnstone, Heather J H; Kuhnert, Henning; Claudio, Marcela R; Toledo, Felipe Antonio de L; Costa, Karen B; Albuquerque, Ana Luiza Spadano (2018): Thermocline temperature and seawater δ18O reconstruction during Termination II and the Last Interglacial for the core GL-1090, in the western South Atlantic [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.896152, Supplement to: Ballalai, JM et al. (2019): Tracking spread of the Agulhas Leakage into the western South Atlantic and its northward transmission during the Last Interglacial. Paleoceanography and Paleoclimatology, https://doi.org/10.1029/2019PA003653

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Abstract:
Thermocline temperature and seawater d18O reconstruction during Termination II and the Last Interglacial for the core GL-1090, in the western South Atlantic.
The intensification of the Agulhas Leakage (AL) during glacial Terminations has long been proposed as a necessary mechanism to return the Atlantic Meridional Overturning Circulation (AMOC) to its interglacial mode. However, the lack of records showing the downstream evolution of the AL signal and the substantial temporal differences between AL intensification and resumption of deep-water convection cast doubt on the importance of this mechanism to the overturning. Here, we analyze a combination of new and previously published data related to Mg/Ca-derived temperatures and ice volume-corrected seawater δ18O records (δ18OIVC-SW as a proxy for ocean relative salinity changes) that demonstrate the propagation of the AL signal via surface and thermocline waters to the western South Atlantic (Santos Basin) during glacial Termination II and the early Last Interglacial. The saline AL waters were temporally stored in the upper subtropical South Atlantic until they were abruptly released in two steps into the North Atlantic via the surface and thermocline at ca. 129 and 123 ka BP, respectively. Within age uncertainties, these two steps are coeval with the resumption of convection in the Labrador and Nordic Seas during the Last Interglacial. We propose a mechanism whereby both an active AL and a favorable ocean-atmosphere configuration in the tropical Atlantic were required to allow the flux of AL waters into the North Atlantic, where they then contributed to enhancing the AMOC during the Last Interglacial period. Our results provide a framework that connects AL strengthening to the AMOC intensifications that follow glaciations.
Keyword(s):
Agulhas rings; Atlantic meridional overturning circulation; Brazil Current; Subtropical gyre; Termination II
Source:
Santos, Thiago Pereira dos; Lessa, Douglas Villela de Oliveira; Venancio, Igor Martins; Chiessi, Cristiano Mazur; Mulitza, Stefan; Kuhnert, Henning; Albuquerque, Ana Luiza Spadano (2017): Oxygen isotope composition of surface, thermocline and mid-depth western South Atlantic during Termination I and II. PANGAEA, https://doi.org/10.1594/PANGAEA.884584
Santos, Thiago Pereira dos; Lessa, Douglas Villela de Oliveira; Venancio, Igor Martins; Chiessi, Cristiano Mazur; Mulitza, Stefan; Kuhnert, Henning; Albuquerque, Ana Luiza Spadano (2017): The impact of the AMOC resumption in the Western South Atlantic thermocline at the onset of the last interglacial. Geophysical Research Letters, 44(22), 11,547-1,554, https://doi.org/10.1002/2017GL074457
Santos, Thiago Pereira dos; Lessa, Douglas Villela de Oliveira; Venancio, Igor Martins; Chiessi, Cristiano Mazur; Mulitza, Stefan; Kuhnert, Henning; Govin, Aline; Machado, Thiago; Costa, Karen Badaraco; Toledo, Felipe Antonio de L; Dias, Bruna Borba; Albuquerque, Ana Luiza Spadano (2017): Mg/Ca sea surface temperature and seawater δ¹⁸O of sediment core GL1090 from subtropical western South Atlantic for the last 185 kyr. PANGAEA, https://doi.org/10.1594/PANGAEA.871874
Santos, Thiago Pereira dos; Lessa, Douglas Villela de Oliveira; Venancio, Igor Martins; Chiessi, Cristiano Mazur; Mulitza, Stefan; Kuhnert, Henning; Govin, Aline; Machado, Thiago; Costa, Karen Badaraco; Toledo, Felipe Antonio de L; Dias, Bruna Borba; Albuquerque, Ana Luiza Spadano (2017): Prolonged warming of the Brazil Current precedes deglaciations. Earth and Planetary Science Letters, 463, 1-12, https://doi.org/10.1016/j.epsl.2017.01.014
Further details:
Cléroux, Caroline; Cortijo, Elsa; Anand, Pallavi; Labeyrie, Laurent D; Bassinot, Franck C; Caillon, Nicolas; Duplessy, Jean-Claude (2008): Mg/Ca and Sr/Ca ratios in planktonic foraminifera: Proxies for upper water column temperature reconstruction. Paleoceanography, 23(3), PA3214, https://doi.org/10.1029/2007PA001505
Shackleton, Nicholas J (1974): Attainment of isotopic equilibrium between ocean water and the benthonic foraminifera genus Uvigerina: isotopic changes in the ocean during the last glacial. In: Labeyrie, L. (ed.) Les méthodes quantitatives d'etude des variation du climat au cours du Pléistocène. Colloques Internationaux du C.N.R.S (Centre Nationale de la Recherche Scientifique), 219, 203–209, hdl:10013/epic.41396.d001
Coverage:
Latitude: -24.920000 * Longitude: -42.510000
Minimum DEPTH, sediment/rock: 13.28 m * Maximum DEPTH, sediment/rock: 16.53 m
Event(s):
GL1090 (GL-1090) * Latitude: -24.920000 * Longitude: -42.510000 * Elevation: -2225.0 m * Location: western South Atlantic * Comment: collected by the Petrobras oil company
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1 DEPTH, sediment/rockDepth sedmBallalai, João MGeocode
2 AGEAgeka BPBallalai, João MGeocode
3 Globorotalia inflata, δ18OG. inflata δ18O‰ PDBBallalai, João Msee Santos et al. (2017b)from Santos et al., 2017b (doi:10.1016/j.epsl.2017.01.014 and doi:10.1594/PANGAEA.884584)
4 Globorotalia inflata, Magnesium/Calcium ratioG. inflata Mg/Cammol/molBallalai, João Mthis study
5 Temperature, calculatedT cal°CBallalai, João Mthis study - derived from eq Cleroux et al 2008
6 δ18O, seawater, reconstructedδ18Osw‰ SMOWBallalai, João MThermocline (to VSMOW - this study - derived from eq Shackleton, 1974)
7 δ18O, seawater, reconstructedδ18Osw‰ SMOWBallalai, João Msee Santos et al. (2017a)Surface (to VSMOW - this study - from Santos et al., 2017a doi:10.1016/j.epsl.2017.01.014 and doi:10.1594/PANGAEA.871874 on the revised age model)
License:
Creative Commons Attribution 4.0 International (CC-BY-4.0)
Size:
335 data points

Data

Download dataset as tab-delimited text — use the following character encoding:

1 
Depth sed [m]		2 
Age [ka BP]		3 
G. inflata δ18O [‰ PDB]
(from Santos et al., 2017b (do...)		4 
G. inflata Mg/Ca [mmol/mol]
(this study)		5 
T cal [°C]
(this study - derived from eq ...)		6 
δ18Osw [‰ SMOW]
(Thermocline (to VSMOW - this ...)		7 
δ18Osw [‰ SMOW]
(Surface (to VSMOW - this stud...)
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