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Mediterranean Outflow Water dynamics across the middle Pleistocene transition based on a 1.3 million-year benthic foraminiferal record off the Portuguese margin

Publication . Guo, Qimei; Li, Baohua; Voelker, Antje; Kim, Jin-Kyoung

Reconstruction of the Mediterranean Outflow Water (MOW) dynamics in the geologic past contributes to exploring its influence on the North Atlantic Ocean circulation and global climate. The middle Pleistocene transition (MPT) is one of the most important characteristics of Quaternary climate change, but until now, research on the MOW variability during this time interval has been limited. To decipher the MOW variability over the last 1.3 myr, this work presents the first continuous and high-resolution (similar to 2 kyr) foraminiferal stable oxygen and carbon isotopes and benthic foraminiferal records from Integrated Ocean Drilling Program (IODP) Site U1391, which was drilled off the Portuguese margin in the Northeast Atlantic Ocean and is currently bathed by the lower MOW core. Based on spectral analysis results of the foraminiferal delta O-18 record, the MPT peaked from 0.9 to 0.7 Ma. The 'epibenthos group' was previously found attached to elevated substrates only within the MOW current and more abundant at higher current velocities, so the relative abundance of the 'elevated epibenthos group' was adopted as an indicator of MOW strength in this study. The MOW indicator suggests that the MOW strengthened during MIS 1, MIS 5, MIS 7, MIS 9, MIS 11, MIS 13, MIS 15, MIS 17, early MIS 18 to late MIS 19, MIS 21, MISs 23-25, MISs 28-30, early MIS 34 to MIS 35, early MIS 36 to late MIS 37 and MIS 40 with a similar to 100 kyr cycle. Superimposed on the long-term variability of the MOW current, the similar to 41-kyr and similar to 20-kyr cyclic fluctuations are also evident, whereby the similar to 41-kyr cycle is more significant. The results of cross-spectral analyses indicate that the similar to 20-kyr cyclic variation in the MOW intensity was drived by the precession forcing; the similar to 41-kyr cyclic variation in the pre- MPT MOW dynamics and the similar to 100-kyr cyclic variation in the post-MPT MOW dynamics were strongly controlled by the Earth's obliquity. The variation in the abundance of the elevated epibenthos group was dominated by the similar to 41-kyr cycle prior to the MPT and by the similar to 100-kyr cycle after the MPT, which suggested there was a MPT-related shift in the MOW dynamics. Benthic delta C-13 record of the last 0.56 myr shows precessional (23-kyr) and glacial-interglacial (similar to 100 kyr) cycles, indicating cyclic variations in bottom water ventilation. Enhanced ventilation coincides with precession maxima and reduced ventilation with precession minima. Bottom water was well ventilated by MOW during the interglacial periods and by GNAIW during the glacial periods, and pooly ventilated during the glaical terminations. (C) 2020 Elsevier Ltd. All rights reserved.

2020-11Journal article

Restricted

Mediterranean Outflow and surface water variability off southern Portugal during the early Pleistocene: A snapshot at Marine Isotope Stages 29 to 34 (1020-1135 ka)

Publication . Voelker, Antje H. L.; Salgueiro, Emilia; Rodrigues, Teresa; Jiménez-Espejo, Francisco J.; Bahr, Andre; Alberto, Ana; Loureiro, Isabel; Padilha, Maria; Rebotim, Andreia; Roehl, Ursula

Centennial-to-millennial scale records from IODP Site U1387, drilled during IODP Expedition 339 into the Faro Drift at 558 m water depth, now allow evaluating the climatic history of the upper core of the Mediterranean Outflow (MOW) and of the surface waters in the northern Gulf of Cadiz during the early Pleistocene. This study focuses on the period from Marine Isotope Stages (MIS) 29 to 34, i.e. the interval surrounding extreme interglacial MIS 31. Conditions in the upper MOW reflect obliquity, precession and millennial-scale variations. The benthic delta O-18 signal follows obliquity with the exception of an additional, smaller delta O-18 peak that marks the MIS 32/31 transition. Insolation maxima (precession minima) led to poor ventilation and a sluggish upper MOW core, whereas insolation minima were associated with enhanced ventilation and often also increased bottom current velocity. Millennial-scale periods of colder sea-surface temperatures (SST) were associated with short-term maxima in flow velocity and better ventilation, reminiscent of conditions known from MIS 3.A prominent contourite layer, coinciding with insolation cycle 100, was formed during MIS 31 and represents one of the few contourites developing within an interglacial period. MIS 31 surface water conditions were characterized by an extended period (1065-1091 ka) of warm SST, but SST were not much warmer than during MIS 33. Interglacial to glacial transitions experienced 2 to 3 stadial/interstadial cycles, just like their mid-to-late Pleistocene counterparts. Glacial MIS 30 and 32 recorded periods of extremely cold (<12 degrees C) SST that in their climatic impact were comparable with the Heinrich events of the mid and late Pleistocene. Glacial MIS 34, on the other hand, was a relative warm glacial period off southern Portugal. Overall, surface water and MOW conditions at Site U1387 show a strong congruence with Mediterranean climate, whereas millennial-scale variations are closely linked to North Atlantic circulation changes. (C) 2015 Elsevier B.V. All rights reserved.

2015-10Journal article

Open Access

The GEOTRACES Intermediate Data Product 2014

Publication . Mawji, Edward; Schlitzer, Reiner; Dodas, Elena Masferrer; Abadie, Cyril; Abouchami, Wafa; Anderson, Robert F.; Baars, Oliver; Bakker, Karel; Baskaran, Mark; Bates, Nicholas R.; Bluhm, Katrin; Kretschmer, Sven; Kumamoto, Yuichiro; Laan, Patrick; Labatut, Marie; Lacan, Francois; Lam, Phoebe J. Lam; Lannuzel, Delphine; le Moigne, Frederique; Lechtenfeld, Oliver J.; Lohan, Maeve C.; Saito, Mak A.; Lu, Yanbin; Masqué, Pere; McClain, Charles R.; Measures, Christopher; Middag, Rob; Moffett, James; Navidad, Alicia; Nishioka, Jun; Noble, Abigail; Obata, Hajime; Roshan, Saeed; Ohnemus, Daniel C.; Owens, Stephanie; Planchon, Frédéri; Pradoux, Catherine; Puigcorbé, Viena; Quay, Paul; Radic, Amandine; Obata; Rehkämper, Mark; Remenyi, Tomas; Salt, Lesley; Rijkenberg, Micha J. A.; Rintoul, Stephen; Robinson, Laura F.; Roeske, Tobias; Rosenberg, Mark; van der Loeff, Michiel Rutgers; Ryabenko, Evgenia; Sarthou, Géraldine; Schauer, Ursula; Scott, Peter; Sedwick, Peter N.; Sha, Lijuan; Shiller, Alan M.; Sigman, Daniel M.; Bowie, Andrew; Smethie, William; Smith, Geoffrey J; Sohrin, Yoshiki; Speich, Sabrina; Stichel, Torben; Stutsman, Johnny; Swif, James H; Tagliabue, Alessandro; Thomas, Alexander; Tsunogai, Urumu; Bown, Johann; Twining, Benjamin S.; van Aken, Hendrik M.; van Heuven, Steven; van Ooijen, Jan; van Weerlee, Evaline; Venchiarutti, Celia; Voelker, Antje; Wake, Bronwyn; Warner, Mark J.; Woodward, E. Malcolm S. W; Boye, Marie; Wu, Jingfeng Wu; Wyatt, Neil; Yoshikawa, Hisayuki; Zheng, Xin-Yuan; Xue, Zichen; Zieringer, Moritz; Zimmer, Louise A.; Boyle, Edward A.; Branellec, Pierre; Bruland, Kenneth W.; Brzezinski, Mark A.; Bucciarelli, Eva; Buesseler, Ken; Butler, Edward; Cai, Pinghe; Cardinal, Damien; Casciotti, Karen; Chaves, Joaquin; Cheng, Hai; Chever, Fanny; Church, Thomas M.; Colman, Albert S.; Conway, Tim M.; Croot, Peter L.; Cutter, Gregory A.; de Baar, Hein J.W.; Souza, Gregory F. de; Dehairs, Frank; Deng, Feifei; Thi Dieu, Huong; Dulaquais, Gabriel; Echegoyen-Sanz, Yolanda; Edwards, R. Lawrence; Fahrbach, Eberhard; Fitzsimmons, Jessica; Martin, Fleisher; Frank, Martin; Friedrich, Jana; Fripiat, François; Galer, Stephen J. G.; Gamo, Toshitaka; Solsona, Ester Garcia; Gerringa, Loes J. A.; Godoy, José Marcus; Gonzalez, Santiago; Grossteffan, Emilie; Hatta, Mariko; Hayes, Christopher T.; Heller, Maija Iris; Henderson, Gideon Henderson; Huang, Kuo-Fang; Jeandel, Catherine; Jenkins, William J.; Seth, John; Kenna, Timothy C.; Klunder, Maarten

The GEOTRACES Intermediate Data Product 2014 (IDP2014) is the first publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2013. It consists of two parts: (1) a compilation of digital data for more than 200 trace elements and isotopes (TEIs) as well as classical hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing a strongly inter-linked on-line atlas including more than 300 section plots and 90 animated 3D scenes. The IDP2014 covers the Atlantic, Arctic, and Indian oceans, exhibiting highest data density in the Atlantic. The TEI data in the IDP2014 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at cross-over stations. The digital data are provided in several formats, including ASCII spreadsheet, Excel spreadsheet, netCDF, and Ocean Data View collection. In addition to the actual data values the IDP2014 also contains data quality flags and 1-σ data error values where available. Quality flags and error values are useful for data filtering. Metadata about data originators, analytical methods and original publications related to the data are linked to the data in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2014 data providing section plots and a new kind of animated 3D scenes. The basin-wide 3D scenes allow for viewing of data from many cruises at the same time, thereby providing quick overviews of large-scale tracer distributions. In addition, the 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of observed tracer plumes, as well as for making inferences about controlling processes.

2015-12Journal article

Open Access