Bohoyo, B.

Escutia, C.

García-García, M. (Margarita)

IODP382Scientists, x

Martos, Y.

Pérez, L.F.

Raymo, M.

Weber, M.

Williams, T.

English

IODP 382 Scientists

Repositorio Institucional Digital del IEO

Geodynamic and paleoceanographic evolution of the Scotia Sea. IODP EXPEDITION 3821 Instituto Español de Oceanografía, Centro de Cádiz. 11006, Cádiz. marga.garcia@ieo.es2 Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR). Armilla (Granada); cescutia@ugr.es 3 British Antarctic Survey. Cambridge CB3 0ET (Reino Unido). larrez@bas.ac.uk4 NASA Goddard Space Flight Center (MD, EEUU), yasmina.martos@nasa.gov5 Steinmann-Institute, University of Bonn. 53115, Bonn (Alemania), mike.weber@uni-bonn.de6 Lamont Doherty Earth Observatory, Columbia University, NY 10964 (EEUU), raymo@ldeo.columbia.edu1,2 3 4 5 6 7 8 2M. García , L.F. Pérez , Y. Martos , M. Weber , M. Raymo , T. Williams , F. Bohoyo , C. Escutia  and IODP Exp382 Scientists*7 International Ocean Discovery Program, Texas A&M University (EEUU), williams@iodp.tamu.edu8 Instituto Geológico y Minero de España. 28760 Tres Cantos (Madrid), f.bohoyo@igme.es* IODP Exp382 Scientists: L. Armbrecht, I. Bailey, S. Brachfeld, Z. Du, G. Fauth, A. Glud̈er, M. Guitard, M. Gutjahr, S. Hemming, I. Hernandez-Almeida, F. Snilsveit Hoem, J.-H. Hwang, M. Iizuka, Y. Kato, B. Lee, S. O'Connell, V. Peck, B. Reilly, T. Ronge, O. Seki, L. Tauxe, S. Tripathi, J. Warnock, X. ZhengThe Study AreaIODP 382 Expedition “Iceberg Alley” Specific Scientific ObjectivesDecipher past Antarctic Ice Sheet (AIS) behaviorReconstruct atmospheric circulation and dust transportDrake Passage throughflow and paleoceanograhic changeSpecific time slices: Deglaciation, LIG, MIS12, MIS31, MPT, Pliocene, MioceneEstablish the time frame with bio-, magneto-, and tephrostratigraphy, stable isotopes, paleointensity, and dust tuningVariability in and sources of AIS mass loss (provenance studies)Relationship between AIS mass loss and global sea levelEffects of water-mass changes and ocean thermal forcing on ice-mass loss (SST temperature, alkenones, TEX 86; ℇNd)Dust-climate couplings and dust sources, as well as potential effect on iron fertilization and glacial CO2 drawdownGlacial-to-interglacial changes in the frontal systems and associated sea-ice shifts (HBIs) and the carbon cycleChanges in sea-ice extent and interaction with the Antarctic Circumpolar Current and the Southern Hemisphere westerlies Paleoceanographic changes of the Drake Passage and thermal isolation of Antarctica (d30Si, d18O on diatoms)Role of sea-icePhysical property measurements were made during Expedition 382 for lithostratigraphic characterization, stratigraphic correlation and to tie core descriptions to downhole data and main seismic reflectors. Physical property data were key to generating first high-resolution and continuous data sets for hole-to-hole and site-to-site stratigraphic correlation, detection of discontinuities and inhomogeneities, obtaining information about differences in the composition and texture of sediment, identification of major seismic reflectors, and construction of synthetic seismic profiles. The thermal properties of the recovered material were also measured and combined with downhole temperature measurements to estimate geothermal heat flow. Different techniques and methods were used to characterize Expedition 382 cores on whole-round, split section-half, and discrete samples.Physical properties from coresThis work is based on geophysical databases collected on board the RV Hesperides during the SCAN cruises since 1997, including swath bathymetry and very high-resolution seismic reflection data. Swath bathymetric data were obtained with EM 12 and EM 120 SIMRAD™ systems. The equipment was operated at a frequency of 12 kHz and a swath aperture of 120ｰ, obtaining seafloor coverage of about 3.5 times the water depth. Multibeam files were postprocessed with NEPTUNE™ and CARIS™ software. Datasets have been displayed and interpreted using Fledermaus™ and Global Mapper™ software. Regional bathymetric data have been obtained from compilations of global seafloor bathymetry (Smith and Sandwell, 1997; Ryan et al., 2009). High-resolution seismic profiles were simultaneously obtained with a TOPAS PS 18 (TOpographic PArameter Sonar) system, which operated in high-penetration (chirp) mode with a primary frequency of 18 kHz and up to 30 kW power. This provided a maximum penetration of about 100 m into the subsurface seafloor sediments with a resolution of 0.5–1 m. Pulse lenght was 25 ms and the shot interval ranged between 5000 and 7000 ms. Signal processing included: band-pass filter, swell filter, deconvolution, time variable gain, muting, and delay correction by using TOPAS™ and Radexpro™ softwares. The resulting SEG-Y files were imported into Kingdom Suite™ software for interpretation.U1538U1537U1536U1536 and U1537, Dove BasinBathymetry and sub-bottom profilesDatasets and methodsThe objective of this work is to decipher the main changes in the tectonic, climatic and paleoceanographic conditions that led to major shifts in the depositional/erosional sedimentary processes recorded in high-resolution seismic profiles that can offer a regional perspective of the South Scotia Sea sub-basins. The sites are strategically located in two areas of Iceberg Alley, the major Antarctic gateway to lower latitudes, where nearly all Antarctic icebergs exit to the Southern Ocean, allowing for the first spatially integrated and longterm reconstruction of AIS variability and its relation to sea level and climate change. A recent proof-of-concept revealed that, at least for the Late Pleistocene, the sites are highly resolved and capable of deciphering rapid climate and ice-sheet changes on decadal-to-centennial timescales, including the discovery of substantial and repeated deglacial increase in iceberg discharge within decades (Weber et al., 2014), which has fundamental implications for projections of future AIS behavior in a warming world.Reflector-a' marks the predominance of oceanographic control over the sedimentation in the Scotia Sea, at about 0.6-0.4 Ma, within the time interval of Marine Isotope Stage (MIS) 11 (Pérez et al., 2021). The change in the physical properties of the Scotia Sea records is likely associated with the increased amplitude of the glacial-interglacial oscillations occurring after the Mid-Brunhes Transition (Barth etal., 2018). A generally high WSDW outflow through Scotia Sea after Reflector-a' would be consistent with the high sedimentation rates, and only supported with relative diminution of AABW volume limited to extreme interglacials (Barth etal., 2018). In turn, a recent study reported lack of WSDW export into the Atlantic sector of the Southern Ocean during the last two glacial maxima (Huang etal., 2020). The ACC and WSDW flows would have been maintained by dynamic AMOC.DiscussionCorrelation of the regional stratigraphic discontinuities of the Scotia Sea with the megasplice of benthic δ18O global records as published by De Vleeschouwer etal. (2017). After Pérez et al (2021). U1538, Pirie BasinBarth, A.et al., 2018. Climate evolution across the mid-brunhes transition. Clim. Past, 2071–2087; Huang, H., et al., 2020. No detectable Weddell Sea Antarctic bottom water export during the last and penultimate glacial maxi-mum. Nat. Commun.11, 424; Pérez, L.F., et al., 2021. Miocene to present oceanographic variability in the Scotia Sea and Antarctic ice sheets dynamics: Insights from revised seismic-stratigraphy following IODP Expedition 382. Earth and Planetary Science Letters, 2021, https://doi.org/10.1016/j.epsl.2020.116657; Weber, M.E., et al, 2021. Iceberg Alley and Subantarctic Ice and Ocean Dynamics. Proceedings of the International Ocean Discovery Program, 382: College Station, TX (Interna-tional Ocean Discovery Program). https://doi .org /10 .14379 /diop .proc .382 .2021.De Vleeschouwer, D., et al., 2017. Alternating Southern and Northern Hemisphere climate response to astronomical forcing during the past 35 m.y. Geology45, 375–378; These results and the correlation with the age models established in the IODP 382 Expedition place the high-resolution data in the time interval following the mid-Pleistocene (Weber etal., 2021). Reflector-a has an age of ∼1.7 Ma. Above, magnetic susceptibility and natural gamma radiation decrease, pointing to bottom current controlled sedimentation. A decrease in sediment input from the continental shelf is also suggested by abundant diatom ooze sedimentation above Reflector-a. In Pirie Basin, a sharp increase in the sedimentation rate above this reflector suggests fast growth of the contourite drifts from the Mid-Pleistocene to the present, that may result from more vigorous Pacific Overturning Circulation. The development of Reflector-a at ∼1.7 Ma most likely reflects the regional Southern Hemisphere expression of major global climatic changes such as ice sheet advance over continental shelves, cold trends in different regions and sea level drop (Pérez et al., 2021).Results: core-seismic correlation

Geodynamic and paleoceanographic evolution of the Scotia Sea. IODP EXPEDITION 382

García-García, Margarita

Digital.CSIC

http://www.repositorio.ieo.es/e-ieo/bitstream/10508/12363/1/MGarcia_etal_CGE_IODP_Poster_compressed.pdf

Geodynamic and paleoceanographic evolution of the Scotia Sea. IODP EXPEDITION 382

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