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159 results on '"Jimenez Espejo, Francisco J."'

1. A Neanderthal's specialised burning structure compatible with tar obtention

Author

Ochando, Juan, Jiménez-Espejo, Francisco J., Giles-Guzmán, Francisco, Neto de Carvalho, Carlos, Carrión, Jose S., Muñiz, Fernando, Rubiales, Juan Manuel, Cura, Pedro, Belo, João, Finlayson, Stewart, Martrat, Belen, van Drooge, Barend L., Jiménez-Moreno, Gonzalo, García-Alix, Antonio, Lozano Rodríguez, Jose Antonio, Albert, Rosa María, Ohkouchi, Naohiko, Ogawa, Nanako, Suga, Hisami, Camuera, Jon, Martínez-Ruiz, Francisca, Villanueva, Joan, Teruel, Oriol, Davtian, Nina, Moreira, Noel, Belaústegui, Zain, Rodríguez-Vidal, Joaquín, Munuera, Manuel, Menez, Alex, Finlayson, Geraldine, and Finlayson, Clive

Published
2024
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16. Fossils in Iberian prehistory: A review of the palaeozoological evidence

Author

Cortés-Sánchez, Miguel, Simón-Vallejo, María D., Corral, José-Carmelo, Lozano-Francisco, María del Carmen, Vera-Peláez, José Luis, Jiménez-Espejo, Francisco J., García-Alix, Antonio, Heras, Carmen de las, Sánchez, Rafael Martínez, Bretones García, María Dolores, Barandiarán-Maestu, Ignacio, and Morales-Muñiz, Arturo

Published
2020
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19. Sea-level and monsoonal control on the Maldives carbonate platform (Indian Ocean) over the last 1.3 million years

Author

Alonso-Garcia, Montserrat, primary, Reolid, Jesus, additional, Jimenez-Espejo, Francisco J., additional, Bialik, Or M., additional, Alvarez Zarikian, Carlos A., additional, Laya, Juan Carlos, additional, Carrasquiera, Igor, additional, Jovane, Luigi, additional, Reijmer, John J. G., additional, Eberli, Gregor P., additional, and Betzler, Christian, additional

Published
2024
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23. Sedimentology of lower Pliocene to Upper Pleistocene diamictons from IODP Site U1358, Wilkes Land margin, and implications for East Antarctic Ice Sheet dynamics

Author

Orejola, Nadine, Passchier, Sandra, Brinkhuis, Hendrik, Escutia Dotti, Carlota, Klaus, Adam, Fehr, Annick, Williams, Trevor, Bendle, James AP, Bijl, Peter K, Bohaty, Steven M, Carr, Stephanie A, Dunbar, Robert B, Flores, Jose-Abel, Gonzalez, Jhon J, Hayden, Travis G, Iwai, Masao, Jimenez-Espejo, Francisco J, Katsuki, Kota, Kong, Gee Soo, McKay, Robert M, Nakai, Mutsumi, Olney, Matthew P, Pekar, Stephen F, Pross, Joerg, Riesselman, Christina, Roehl, Ursula, Sakai, Toyosaburo, Shrivastava, Prakash Kumar, Stickley, Catherine E, Sugisaki, Saiko, Tauxe, Lisa, Tuo, Shouting, van de Flierdt, Tina, Welsh, Kevin, Yamane, Masako, and Scientists, Iodp Expedition 318

Subjects
continental shelf, geochemistry, heavy minerals, particle size, provenance, Marine Biology & Hydrobiology, Environmental Sciences, Biological Sciences, Earth Sciences
Abstract

AbstractDuring the early Pliocene a dynamic marine-based ice sheet retreated from the Wilkes Land margin with periodic ice advances beyond Last Glacial Maximum position. A change in sand provenance is indicative of a more stable Mertz Glacier system during the Late Pleistocene. East Antarctic Ice Sheet (EAIS) dynamics were evaluated through the analysis of marine diamictons from Integrated Ocean Drilling Program (IODP) site U1358 on the Adélie Land continental shelf. The warmer than present conditions of the early Pliocene coupled with the site's proximity to the landward sloping Wilkes Subglacial Basin provided the rationale for the investigations at this site. Based on visual core descriptions, particle size distributions, and major and trace element ratios, we interpret the origin of lower Pliocene strata by intermittent glaciomarine sedimentation with open-marine conditions and extensive glacial advances to the outer shelf. Heavy mineral analyses show that sand-sized detritus in the lower Pliocene strata was sourced from local intermediate to high-grade metamorphic rocks near Mertz Glacier. In contrast, Pleistocene diamictons exhibit a larger contribution from a prehnite-pumpellyite greenschist facies suggesting supply via iceberg rafting from northern Victoria Land. From this sedimentological evidence, we postulate a shift from a dynamic EAIS margin in the early Pliocene to possible stabilization in the Pleistocene.

Published
2014

26. Dynamic behaviour of the East Antarctic ice sheet during Pliocene warmth

Author

Cook, Carys P, van de Flierdt, Tina, Williams, Trevor, Hemming, Sidney R, Iwai, Masao, Kobayashi, Munemasa, Jimenez-Espejo, Francisco J, Escutia, Carlota, González, Jhon Jairo, Khim, Boo-Keun, McKay, Robert M, Passchier, Sandra, Bohaty, Steven M, Riesselman, Christina R, Tauxe, Lisa, Sugisaki, Saiko, Galindo, Alberto Lopez, Patterson, Molly O, Sangiorgi, Francesca, Pierce, Elizabeth L, Brinkhuis, Henk, Klaus, Adam, Fehr, Annick, Bendle, James A. P, Bijl, Peter K, Carr, Stephanie A, Dunbar, Robert B, Flores, José Abel, Hayden, Travis G, Katsuki, Kota, Kong, Gee Soo, Nakai, Mutsumi, Olney, Matthew P, Pekar, Stephen F, Pross, Jörg, Röhl, Ursula, Sakai, Toyosaburo, Shrivastava, Prakash K, Stickley, Catherine E, Tuo, Shouting, Welsh, Kevin, and Yamane, Masako

Published
2013

27. Sea-level and monsoonal control on the Maldives carbonate platform (Indian Ocean) over the last 1.3 million years

Author

Alonso-Garcia, Montserrat, primary, Reolid, Jesus, additional, Jimenez-Espejo, Francisco J., additional, Bialik, Or M., additional, Alvarez Zarikian, Carlos A., additional, Laya, Juan C., additional, Carrasquiera, Igor, additional, Jovane, Luigi, additional, Reijmer, John J. G., additional, Betzler, Christian, additional, and Eberli, Gregor P., additional

Published
2023
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33. A two-million-year-long hydroclimatic context for hominin evolution in southeastern Africa

Author

Caley, Thibaut, Extier, Thomas, Collins, James A., Schefuß, Enno, Dupont, Lydie, Malaizé, Bruno, Rossignol, Linda, Souron, Antoine, McClymont, Erin L., Jimenez-Espejo, Francisco J., García-Comas, Carmen, Eynaud, Frédérique, Martinez, Philippe, Roche, Didier M., Jorry, Stephan J., Charlier, Karine, Wary, Mélanie, Gourves, Pierre-Yves, Billy, Isabelle, and Giraudeau, Jacques

Published
2018
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38. Sea-level and monsoonal control on the Maldives carbonate platform (Indian Ocean) over the last 1.3 million years.

Author

Alonso-Garcia, Montserrat, Reolid, Jesus, Jimenez-Espejo, Francisco J., Bialik, Or M., Alvarez Zarikian, Carlos A., Laya, Juan Carlos, Carrasquiera, Igor, Jovane, Luigi, Reijmer, John J. G., Betzler, Christian, and Eberli, Gregor P.

Abstract

Changes in sea-level are linked to glacial-interglacial variability and have been claimed as the main factor controlling the production of carbonate platform factories. The Maldives archipelago (Indian Ocean), composed of two rows of atolls that enclose an inner sea, is a very sensitive region to sea-level changes. The sediments of the Inner Sea, offer an excellent study site to explore the impact of sea-level changes on carbonate platforms. Elemental geochemical composition records, obtained by X-ray fluorescence (XRF) core-scanning, from the Maldives Inner Sea (IODP Site U1467), have been used in this work to evaluate the influence of orbitally-driven sea-level fluctuations on the carbonate production and export from the neritic environment into the Maldives Inner Sea over the last 1.3 million years. High Sr aragonite-rich carbonates (HSAC) from neritic settings are deposited in the Maldives Inner Sea during sea-level highstand intervals, increasing the values of the Sr/Ca ratio. In contrast, during sea-level lowstand periods large areas of the atolls were exposed or unable to grow and the demise in the carbonate production and sediment export is reflected as low Sr/Ca values in the Inner Sea. However, we propose that sea level is not the only factor controlling the production of HSAC during sea-level highstands since several interglacial periods before and after the Mid-Brunhes event (MBE, ~430 ka) indicate high carbonate production (high Sr/Ca). The intensity of the summer monsoon and the Indian Ocean Dipole probably modulated the production at the atolls. Marine Isotope Stage 11 stands out as a period with high sea-level and rather high carbonate production in the Maldives platform. This extraordinary carbonate production in the Maldives atolls (and in other low latitude carbonate platforms) probably contributed to the Mid-Brunhes dissolution event through a strong shelf-to-basin fractionation of carbonate deposition. [ABSTRACT FROM AUTHOR]

Published
2023
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40. Environmental conditions and geomorphologic changes during the Middle–Upper Paleolithic in the southern Iberian Peninsula

Author

Jiménez-Espejo, Francisco J., Rodríguez-Vidal, Joaquín, Finlayson, Clive, Martínez-Ruiz, Francisca, Carrión, José S., García-Alix, Antonio, Paytan, Adina, Giles Pacheco, Francisco, Fa, Darren A., Finlayson, Geraldine, Cortés-Sánchez, Miguel, Rodrigo Gámiz, Marta, González-Donoso, José M., Linares, M. Dolores, Cáceres, Luis M., Fernández, Santiago, Iijima, Koichi, and Martínez Aguirre, Aranzazu

Published
2013
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41. The Mesolithic–Neolithic transition in southern Iberia

Author

Cortés Sánchez, Miguel, Jiménez Espejo, Francisco J., Simón Vallejo, María D., Gibaja Bao, Juan F., Carvalho, António Faustino, Martinez-Ruiz, Francisca, Gamiz, Marta Rodrigo, Flores, José-Abel, Paytan, Adina, López Sáez, José A., Peña-Chocarro, Leonor, Carrión, José S., Morales Muñiz, Arturo, Roselló Izquierdo, Eufrasia, Riquelme Cantal, José A., Dean, Rebecca M., Salgueiro, Emília, Martínez Sánchez, Rafael M., De la Rubia de Gracia, Juan J., Lozano Francisco, María C., Vera Peláez, José L., Rodríguez, Laura Llorente, and Bicho, Nuno F.

Published
2012
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42. Sensitivity of the West Antarctic Ice Sheet to +2 °C (SWAIS 2C)

Author

Patterson, Molly O., Levy, Richard H., Kulhanek, Denise K., van de Flierdt, Tina, Horgan, Huw, Dunbar, Gavin B., Naish, Timothy R., Ash, Jeanine, Pyne, Alex, Mandeno, Darcy, Winberry, Paul, Harwood, David M., Florindo, Fabio, Jimenez-Espejo, Francisco J., Läufer, Andreas, Yoo, Kyu-Cheul, Seki, Osamu, Stocchi, Paolo, Klages, Johann P., Lee, Jae Il, Colleoni, Florence, Suganuma, Yusuke, Gasson, Edward, Ohneiser, Christian, Flores, José-Abel, Try, David, Kirkman, Rachel, Koch, Daleen, Science Team, SWAIS 2C inc., Sime, Louise, Smith, James, Patterson, Molly O., Levy, Richard H., Kulhanek, Denise K., van de Flierdt, Tina, Horgan, Huw, Dunbar, Gavin B., Naish, Timothy R., Ash, Jeanine, Pyne, Alex, Mandeno, Darcy, Winberry, Paul, Harwood, David M., Florindo, Fabio, Jimenez-Espejo, Francisco J., Läufer, Andreas, Yoo, Kyu-Cheul, Seki, Osamu, Stocchi, Paolo, Klages, Johann P., Lee, Jae Il, Colleoni, Florence, Suganuma, Yusuke, Gasson, Edward, Ohneiser, Christian, Flores, José-Abel, Try, David, Kirkman, Rachel, Koch, Daleen, Science Team, SWAIS 2C inc., Sime, Louise, and Smith, James

Abstract

The West Antarctic Ice Sheet (WAIS) presently holds enough ice to raise global sea level by 4.3 m if completely melted. The unknown response of the WAIS to future warming remains a significant challenge for numerical models in quantifying predictions of future sea level rise. Sea level rise is one of the clearest planet-wide signals of human-induced climate change. The Sensitivity of the West Antarctic Ice Sheet to a Warming of 2 ∘C (SWAIS 2C) Project aims to understand past and current drivers and thresholds of WAIS dynamics to improve projections of the rate and size of ice sheet changes under a range of elevated greenhouse gas levels in the atmosphere as well as the associated average global temperature scenarios to and beyond the +2 ∘C target of the Paris Climate Agreement. Despite efforts through previous land and ship-based drilling on and along the Antarctic margin, unequivocal evidence of major WAIS retreat or collapse and its causes has remained elusive. To evaluate and plan for the interdisciplinary scientific opportunities and engineering challenges that an International Continental Drilling Program (ICDP) project along the Siple coast near the grounding zone of the WAIS could offer (Fig. 1), researchers, engineers, and logistics providers representing 10 countries held a virtual workshop in October 2020. This international partnership comprised of geologists, glaciologists, oceanographers, geophysicists, microbiologists, climate and ice sheet modelers, and engineers outlined specific research objectives and logistical challenges associated with the recovery of Neogene and Quaternary geological records from the West Antarctic interior adjacent to the Kamb Ice Stream and at Crary Ice Rise. New geophysical surveys at these locations have identified drilling targets in which new drilling technologies will allow for the recovery of up to 200 m of sediments beneath the ice sheet. Sub-ice-shelf records have so far proven difficult to obtain but are critical to

Published
2022

44. Southern Hemisphere Westerly Winds have modulated the formation of laminations in sediments in Lago Fagnano (Tierra del Fuego, Argentina) over the past 6.3 ka.

Author

Vizcaino, Alexis, Jimenez‐Espejo, Francisco J., Dunbar, Robert B., Mucciarone, David, García‐Alix, Antonio, Neugebauer, Ina, and Ariztegui, Daniel

Subjects
*WESTERLIES, *SOUTHERN oscillation, *SEDIMENTS, *ANALYTICAL geochemistry, *ATMOSPHERIC carbon dioxide, *WINTER
Abstract

Tierra del Fuego in Argentina is a unique location to examine past Holocene wind variability since it intersects the core of the Southern Hemisphere Westerly Winds (SHWW). The SHWW are the most powerful prevailing winds on Earth. Their variation plays a role in regulating atmospheric CO2 levels and rainfall amounts and distribution, both today and in the past. We obtained a piston core (LF06‐PC8) from Bahía Grande, a protected sub‐basin at the southern margin of Lago Fagnano, the largest lake in Tierra del Fuego. This article focuses on the uppermost 185 cm of this core, corresponding to laminated sediment from the last ~6.3 ka. Laminations consist of millimetre‐scale paired dark and light layers. Previous studies and new geochemical analysis show that the dark and light layers are characterized by differing concentrations of Mn and Fe. We attribute the distribution of Mn and Fe to episodic hypolimnic oxic–anoxic variations. The age model suggests an approximately bidecadal timescale for the formation of each layer pair. We propose a new model of these redox changes with the SHWW variations. The most likely phenomenon to produce complete water‐column mixing is thermobaric instability, which occurs in colder winters with low‐intensity SHWW (El Niño‐like conditions). In contrast, windier winters are characterized by higher temperatures and reduced mixing in the water column, facilitating a decline in oxygen concentration. Laminations, and the inferred presence of periodic hypolimnion redox changes, are common features of the past ~6.3 ka. Geochemical proxy variability is compatible with an intensification of El Niño/Southern Oscillation activity during the past ~2 ka. [ABSTRACT FROM AUTHOR]

Published
2023
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45. Antarctic icebergs reorganize ocean circulation during Pleistocene glacials

Author

Starr, Aidan, Hall, Ian R., Barker, Stephen, Rackow, Thomas, Zhang, Xu, Hemming, Sidney R., van der Lubbe, H. J.L., Knorr, Gregor, Berke, Melissa A., Bigg, Grant R., Cartagena-Sierra, Alejandra, Jiménez-Espejo, Francisco J., Gong, Xun, Gruetzner, Jens, Lathika, Nambiyathodi, LeVay, Leah J., Robinson, Rebecca S., Ziegler, Martin, Brentegani, Luna, Caley, Thibaut, Charles, Christopher D., Coenen, Jason J., Crespin, Julien G., Franzese, Allison M., Han, Xibin, Hines, Sophia K.V., Jimenez Espejo, Francisco J., Just, Janna, Koutsodendris, Andreas, Kubota, Kaoru, Norris, Richard D., dos Santos, Thiago Pereira, Rolison, John M., Simon, Margit H., Tangunan, Deborah, Yamane, Masako, Zhang, Hucai, Ministerio de Ciencia e Innovación (España), Natural Environment Research Council (UK), National Key Research and Development Program (China), Helmholtz Association, European Commission, and Geology and Geochemistry

Subjects
Atlantic hurricane, Oceanic circulation, Multidisciplinary, 010504 meteorology & atmospheric sciences, Pleistocene, Global climate, North Atlantic Deep Water, Ocean current, 010502 geochemistry & geophysics, 01 natural sciences, Iceberg, Oceanography, SDG 14 - Life Below Water, Glacial period, General, Atlantic Ocean, Geology, 0105 earth and related environmental sciences, Teleconnection
Abstract

The dominant feature of large-scale mass transfer in the modern ocean is the Atlantic meridional overturning circulation (AMOC). The geometry and vigour of this circulation influences global climate on various timescales. Palaeoceanographic evidence suggests that during glacial periods of the past 1.5 million years the AMOC had markedly different features from today; in the Atlantic basin, deep waters of Southern Ocean origin increased in volume while above them the core of the North Atlantic Deep Water (NADW) shoaled. An absence of evidence on the origin of this phenomenon means that the sequence of events leading to global glacial conditions remains unclear. Here we present multi-proxy evidence showing that northward shifts in Antarctic iceberg melt in the Indian–Atlantic Southern Ocean (0–50° E) systematically preceded deep-water mass reorganizations by one to two thousand years during Pleistocene-era glaciations. With the aid of iceberg-trajectory model experiments, we demonstrate that such a shift in iceberg trajectories during glacial periods can result in a considerable redistribution of freshwater in the Southern Ocean. We suggest that this, in concert with increased sea-ice cover, enabled positive buoyancy anomalies to ‘escape’ into the upper limb of the AMOC, providing a teleconnection between surface Southern Ocean conditions and the formation of NADW. The magnitude and pacing of this mechanism evolved substantially across the mid-Pleistocene transition, and the coeval increase in magnitude of the ‘southern escape’ and deep circulation perturbations implicate this mechanism as a key feedback in the transition to the ‘100-kyr world’, in which glacial–interglacial cycles occur at roughly 100,000-year periods., Acknowledgements This research used samples and/or data provided by the International Ocean Discovery Program (IODP). Funding for this research was provided by The Natural Environmental Research Council GW4+ Doctoral Training Partnership (A.S.) and NERC grant NE/P000037/1 (I.R.H.). A.S. acknowledges further funding through the Antarctic Science International Bursary. X.Z. acknowledges funding from Lanzhou University (number 225000-830006) and National Key R&D programme of China (number 2018YFA0606403). F.J.J.-E. acknowledges funding through Spanish Ministry of Science and Innovation (grant CTM2017-89711-C2-1-P), co-funded by the European Union through FEDER funds. G.K. acknowledges funding by the German Helmholtz national REKLIM initiative and the BMBF project PalMod. L. Owen, S. Slater, A. Nedebragt and D. Muir are thanked for laboratory assistance.

Published
2021
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46. Data report: evaluation of shipboard magnetostratigraphy by alternating field demagnetization of discrete samples, Expedition 361, Site U1475

Author

Just, J., Hall, Ian R., Hemming, Sidney R., LeVay, Leah J., Barker, Stephen R., Berke, Melissa A., Brentegani, Luna, Caley, Thibaut, Catagena-Sierra, Alejandra, Charles, Christopher D., Coenen, Jason J., Crespin, Julien G., Franzese, Allison M., Gruetzner, Jens, Han, Xibin, Hines, Sophia K. V., Jimenez Espejo, Francisco J., Just, Janna, Koutsodendris, Andreas, Kubota, Kaoru, Lathika, Nambiyathodi, Norris, Richard D., dos Santos, Thiago Pereira, Robinson, Rebecca, Rolison, John M., Simon, Margit H., Tangunan, Deborah, van der Lubbe, Jeroen J. L., Yamane, Masako, Zhang, Hucai, and Rooks-Cast, Nina

Abstract

The paleomagnetic shipboard data of International Ocean Discovery Program Site U1475, with a record reaching back to approximately 7 Ma, allowed for the identification of major magnetic polarity chrons and subchrons back to ~3.5 Ma. However, the natural remanent magnetization (NRM) was very weak, and transitional intervals with unclear polarity were as thick as several meters. The midpoints of these transitional intervals were reported in the shipboard results without decimal places because of the poor data quality. To evaluate and possibly refine the shipboard magnetostratigraphy, subsampling was performed across the polarity transitions. Detailed alternating field (AF) demagnetization experiments were conducted on these discrete samples and were complemented by anhysteretic remanent magnetization acquisition measurements and subsequent demagnetization. AF demagnetization data of NRM were analyzed using anchored principal component analysis (PCA) to obtain the characteristic remanent magnetization. These PCA results generally confirm the smoothed signal across polarity transitions at Site U1475. However, the midpoint depths of the top of the Keana Subchron, the Gauss-Matuyama and Matuyama-Brunhes boundaries, and the base of the Olduvai Subchron were adjusted.

Published
2020

47. The interglacial-glacial sequence of events at the Agulhas Plateau: Antarctic icebergs lead ocean circulation into ice ages and across the Mid-Pleistocene Transition

Author

Starr, Aidan, Hall, Ian R., Barker, Stephen, Hemming, Sidney R., Rackow, Thomas, Zhang, Xu, van der Lubbe, J.J.L., Knorr, Gregor, Berke, Melissa A., Bigg, Grant R., Cartagena-Sierra, Alejandra, Jimenez-Espejo, Francisco J., Gong, Xun, Gruetzner, Jens, Lathika, Nambiyathodi, LeVay, Leah J., Ziegler, Martin, Starr, Aidan, Hall, Ian R., Barker, Stephen, Hemming, Sidney R., Rackow, Thomas, Zhang, Xu, van der Lubbe, J.J.L., Knorr, Gregor, Berke, Melissa A., Bigg, Grant R., Cartagena-Sierra, Alejandra, Jimenez-Espejo, Francisco J., Gong, Xun, Gruetzner, Jens, Lathika, Nambiyathodi, LeVay, Leah J., and Ziegler, Martin

Abstract

Palaeoceanographic evidence suggests that glacial periods of the Mid to Late Pleistocene were characterized by markedly different global ocean circulation patterns to modern; in the Atlantic basin, deep waters of Southern Ocean origin increased in volume while above them the core of the North Atlantic Deep Water (NADW) shoaled. Whilst proxy records and modelling efforts continue to clarify this picture, an evidence alluding to the origin of this phenomenon remains elusive. Because of this, our understanding of the sequence of events leading to global glacial conditions remains incomplete. Here we present multi-proxy evidence showing that northward shifts in Antarctic iceberg melt in the Indian–Atlantic Southern Ocean (0–50°E) systematically preceded deep-water mass reorganizations by 1-2 thousand years during Pleistocene-era glaciations. With the aid of iceberg-trajectory model experiments, we demonstrate that such a shift in iceberg trajectories during glacial periods can result in a considerable redistribution of freshwater in the Southern Ocean. This, in concert with increased sea-ice cover, may have enabled positive buoyancy anomalies to effectively escape into the ‘upper’ Atlantic overturning circulation limb, providing a teleconnection between surface Southern Ocean conditions and the formation of NADW. Furthermore, we observe a distinct obliquity pacing of Antarctic iceberg melt both preceding and following the Mid-Pleistocene Transition, become obscured during this interval. With new and existing data we investigate the evolution of orbital forcing at the Agulhas Plateau, considering the implications for ‘Southern Escape’ of freshwater as a key feedback in the transition to the ‘100-kyr world’.

Published
2021

48. Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat

Author

Ashley, Kate E., McKay, Robert, Etourneau, Johan, Jimenez-Espejo, Francisco J., Condron, Alan, Albot, Anna, Crosta, Xavier, Riesselman, Christina, Seki, Osamu, Massé, Guillaume, Golledge, Nicholas, Gasson, Edward, Lowry, Daniel P., Barrand, Nicholas E., Johnson, Katelyn, Bertler, Nancy, Escutia, Carlota, Dunbar, Robert B., Bendle, James A., Ashley, Kate E., McKay, Robert, Etourneau, Johan, Jimenez-Espejo, Francisco J., Condron, Alan, Albot, Anna, Crosta, Xavier, Riesselman, Christina, Seki, Osamu, Massé, Guillaume, Golledge, Nicholas, Gasson, Edward, Lowry, Daniel P., Barrand, Nicholas E., Johnson, Katelyn, Bertler, Nancy, Escutia, Carlota, Dunbar, Robert B., and Bendle, James A.

Abstract

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ashley, K. E., McKay, R., Etourneau, J., Jimenez-Espejo, F. J., Condron, A., Albot, A., Crosta, X., Riesselman, C., Seki, O., Mass, G., Golledge, N. R., Gasson, E., Lowry, D. P., Barrand, N. E., Johnson, K., Bertler, N., Escutia, C., Dunbar, R., & Bendle, J. A. Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat. Climate of the Past, 17(1), (2021): 1-19, https://doi.org/10.5194/cp-17-1-2021., Over recent decades Antarctic sea-ice extent has increased, alongside widespread ice shelf thinning and freshening of waters along the Antarctic margin. In contrast, Earth system models generally simulate a decrease in sea ice. Circulation of water masses beneath large-cavity ice shelves is not included in current Earth System models and may be a driver of this phenomena. We examine a Holocene sediment core off East Antarctica that records the Neoglacial transition, the last major baseline shift of Antarctic sea ice, and part of a late-Holocene global cooling trend. We provide a multi-proxy record of Holocene glacial meltwater input, sediment transport, and sea-ice variability. Our record, supported by high-resolution ocean modelling, shows that a rapid Antarctic sea-ice increase during the mid-Holocene (∼ 4.5 ka) occurred against a backdrop of increasing glacial meltwater input and gradual climate warming. We suggest that mid-Holocene ice shelf cavity expansion led to cooling of surface waters and sea-ice growth that slowed basal ice shelf melting. Incorporating this feedback mechanism into global climate models will be important for future projections of Antarctic changes., This research has been supported by the Natural Environment Research Council (CENTA PhD; NE/L002493/1 and Standard Grant Ne/I00646X/1), Japanese Society for the Promotion of Science (JSPS/FF2/60 no. L-11523), NZ Marsden Fund (grant nos. 18-VUW-089 and 15-VUW-131), NSF (grant nos. PLR-1443347 and ACI-1548562), the U.S. Dept. of Energy (grant no. DE-SC0016105), ERC (StG ICEPROXY, 203441; ANR CLIMICE, FP7 Past4Future, 243908), L'Oréal-UNESCO New Zealand For Women in Science Fellowship, University of Otago Research Grant, the IODP U.S. Science Support Program, Spanish Ministry of Science and Innovation (grant no. CTM2017-89711-C2-1-P), and the European Union (FEDER).

Published
2021

49. Strong glacial-interglacial variability in upper ocean hydrodynamics, biogeochemistry, and productivity in the southern Indian Ocean

Author

Tangunan, Deborah, Berke, Melissa A., Cartagena-Sierra, Alejandra, Flores, José Abel, Gruetzner, Jens, Jiménez-Espejo, Francisco, LeVay, Leah J., Baumann, Karl Heinz, Romero, Oscar, Saavedra-Pellitero, Mariem, Coenen, Jason J., Starr, Aidan, Hemming, Sidney R., Hall, Ian R., Barker, Stephen, Brentegani, Luna, Caley, Thibaut, Charles, Christopher D., Crespin, Julien G., Franzese, Allison M., Han, Xibin, Hines, Sophia K.V., Jimenez Espejo, Francisco J., Just, Janna, Koutsodendris, Andreas, Kubota, Kaoru, Lathika, Nambiyathodi, Norris, Richard D., dos Santos, Thiago Pereira, Robinson, Rebecca S., Rolison, John M., Simon, Margit H., van der Lubbe, Jeroen J.L., Yamane, Masako, Zhang, Hucai, Tangunan, Deborah, Berke, Melissa A., Cartagena-Sierra, Alejandra, Flores, José Abel, Gruetzner, Jens, Jiménez-Espejo, Francisco, LeVay, Leah J., Baumann, Karl Heinz, Romero, Oscar, Saavedra-Pellitero, Mariem, Coenen, Jason J., Starr, Aidan, Hemming, Sidney R., Hall, Ian R., Barker, Stephen, Brentegani, Luna, Caley, Thibaut, Charles, Christopher D., Crespin, Julien G., Franzese, Allison M., Han, Xibin, Hines, Sophia K.V., Jimenez Espejo, Francisco J., Just, Janna, Koutsodendris, Andreas, Kubota, Kaoru, Lathika, Nambiyathodi, Norris, Richard D., dos Santos, Thiago Pereira, Robinson, Rebecca S., Rolison, John M., Simon, Margit H., van der Lubbe, Jeroen J.L., Yamane, Masako, and Zhang, Hucai

Abstract

In the southern Indian Ocean, the position of the subtropical front – the boundary between colder, fresher waters to the south and warmer, saltier waters to the north – has a strong influence on the upper ocean hydrodynamics and biogeochemistry. Here we analyse a sedimentary record from the Agulhas Plateau, located close to the modern position of the subtropical front and use alkenones and coccolith assemblages to reconstruct oceanographic conditions over the past 300,000 years. We identify a strong glacial-interglacial variability in sea surface temperature and productivity associated with subtropical front migration over the Agulhas Plateau, as well as shorter-term high frequency variability aligned with variations in high latitude insolation. Alkenone and coccolith abundances, in combination with diatom and organic carbon records indicate high glacial export productivity. We conclude that the biological pump was more efficient and strengthened during glacial periods, which could partly account for the reported reduction in atmospheric carbon dioxide concentrations.

Published
2021

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