Search

Your search keyword '"Saavedra-Pellitero, M"' showing total 3 results
Start Over Author "Saavedra-Pellitero, M" Publication Year Range This year
3 results on '"Saavedra-Pellitero, M"'

1. Late Miocene to Early Pliocene paleoceanographic evolution of the Central South Pacific: A deep-sea benthic foraminiferal perspective

Author

Das, S, Mahanta, N, Sahoo, B, Singh, R, Alvarez Zarikian, C, Tiwari, M, Vats, N, Nihal, Lamy, F, Winckler, G, Middleton, J, Arz, H, Gottschalk, J, Basak, C, Brombacher, A, Esper, O, Farmer, J, Herbert, L, Iwasaki, S, Lembke-Jene, L, Lawson, V, Lo, L, Malinverno, E, Michel, E, Moretti, S, Moy, C, Ravelo, A, Riesselman, C, Saavedra-Pellitero, M, Seo, I, Smith, R, Souza, A, Stoner, J, de Oliveira, I, Wan, S, Zhao, X, Das S. K., Mahanta N., Sahoo B., Singh R. K., Alvarez Zarikian C. A., Tiwari M., Vats N., Lamy F., Winckler G., Middleton J. L., Arz H. W., Gottschalk J., Basak C., Brombacher A., Esper O. M., Farmer J. R., Herbert L. C., Iwasaki S., Lembke-Jene L., Lawson V. J., Lo L., Malinverno E., Michel E., Moretti S., Moy C. M., Ravelo A. C., Riesselman C. R., Saavedra-Pellitero M., Seo I., Smith R. A., Souza A. L., Stoner J. S., de Oliveira I. V. M. P., Wan S., Zhao X., Das, S, Mahanta, N, Sahoo, B, Singh, R, Alvarez Zarikian, C, Tiwari, M, Vats, N, Nihal, Lamy, F, Winckler, G, Middleton, J, Arz, H, Gottschalk, J, Basak, C, Brombacher, A, Esper, O, Farmer, J, Herbert, L, Iwasaki, S, Lembke-Jene, L, Lawson, V, Lo, L, Malinverno, E, Michel, E, Moretti, S, Moy, C, Ravelo, A, Riesselman, C, Saavedra-Pellitero, M, Seo, I, Smith, R, Souza, A, Stoner, J, de Oliveira, I, Wan, S, Zhao, X, Das S. K., Mahanta N., Sahoo B., Singh R. K., Alvarez Zarikian C. A., Tiwari M., Vats N., Lamy F., Winckler G., Middleton J. L., Arz H. W., Gottschalk J., Basak C., Brombacher A., Esper O. M., Farmer J. R., Herbert L. C., Iwasaki S., Lembke-Jene L., Lawson V. J., Lo L., Malinverno E., Michel E., Moretti S., Moy C. M., Ravelo A. C., Riesselman C. R., Saavedra-Pellitero M., Seo I., Smith R. A., Souza A. L., Stoner J. S., de Oliveira I. V. M. P., Wan S., and Zhao X.

Abstract

The bottom water conditions in the Central South Pacific (CSP) and associated changes in the Lower Circumpolar Deep Water (LCDW) and Antarctic Bottom Water (AABW) under warmer-than-present conditions need to be better understood. These water masses transfer their properties to the major ocean basins. We analyzed Late Miocene to Early Pliocene (5.6–3.6 Ma) marine sediment core sections from the CSP for benthic foraminifera, ice rafted debris (IRD), Ostracoda, planktic foraminifera Orbulina universa abundance, and organic geochemical proxies to assess the bottom water characteristics under warmer-than-present day conditions. A significant increase in IRD abundance between 5.3 and 4.9 Ma marks the Early Pliocene warm phase. The benthic foraminiferal assemblages indicate shifts in bottom water conditions over time in the CSP region. Between 5.6 and 5.3 Ma, predominantly oxygenated bottom water with moderate organic matter flux prevailed. This shifted to suboxic conditions with increased organic matter flux from 5.3 to 4.9 Ma. Subsequently, between 4.9 and 4.4 Ma, bottom water conditions alternated frequently between oxic and suboxic states. Enhanced bottom water formation and inflow of LCDW and AABW in the CSP during 4.4–4.0 Ma promoted oxygenated conditions, accompanied by low organic export flux. However, sluggish bottom water circulation from 4.0 to 3.6 Ma reverted to suboxic conditions, associated with increased carbon burial. Notably, productivity peaked intermittently between 5.3 and 3.6 Ma, as indicated by the occurrence of suboxic species assemblages and increase in the abundance of Orbulina universa, benthic microfauna (ostracods), and other paleoproductivity indicators.

Published
2024

2. Five million years of Antarctic Circumpolar Current strength variability

Author

Lamy, F, Winckler, G, Arz, H, Farmer, J, Gottschalk, J, Lembke-Jene, L, Middleton, J, van der Does, M, Tiedemann, R, Alvarez Zarikian, C, Basak, C, Brombacher, A, Dumm, L, Esper, O, Herbert, L, Iwasaki, S, Kreps, G, Lawson, V, Lo, L, Malinverno, E, Martinez-Garcia, A, Michel, E, Moretti, S, Moy, C, Ravelo, A, Riesselman, C, Saavedra-Pellitero, M, Sadatzki, H, Seo, I, Singh, R, Smith, R, Souza, A, Stoner, J, Toyos, M, de Oliveira, I, Wan, S, Wu, S, Zhao, X, Lamy F., Winckler G., Arz H. W., Farmer J. R., Gottschalk J., Lembke-Jene L., Middleton J. L., van der Does M., Tiedemann R., Alvarez Zarikian C., Basak C., Brombacher A., Dumm L., Esper O. M., Herbert L. C., Iwasaki S., Kreps G., Lawson V. J., Lo L., Malinverno E., Martinez-Garcia A., Michel E., Moretti S., Moy C. M., Ravelo A. C., Riesselman C. R., Saavedra-Pellitero M., Sadatzki H., Seo I., Singh R. K., Smith R. A., Souza A. L., Stoner J. S., Toyos M., de Oliveira I. M. V. P., Wan S., Wu S., Zhao X., Lamy, F, Winckler, G, Arz, H, Farmer, J, Gottschalk, J, Lembke-Jene, L, Middleton, J, van der Does, M, Tiedemann, R, Alvarez Zarikian, C, Basak, C, Brombacher, A, Dumm, L, Esper, O, Herbert, L, Iwasaki, S, Kreps, G, Lawson, V, Lo, L, Malinverno, E, Martinez-Garcia, A, Michel, E, Moretti, S, Moy, C, Ravelo, A, Riesselman, C, Saavedra-Pellitero, M, Sadatzki, H, Seo, I, Singh, R, Smith, R, Souza, A, Stoner, J, Toyos, M, de Oliveira, I, Wan, S, Wu, S, Zhao, X, Lamy F., Winckler G., Arz H. W., Farmer J. R., Gottschalk J., Lembke-Jene L., Middleton J. L., van der Does M., Tiedemann R., Alvarez Zarikian C., Basak C., Brombacher A., Dumm L., Esper O. M., Herbert L. C., Iwasaki S., Kreps G., Lawson V. J., Lo L., Malinverno E., Martinez-Garcia A., Michel E., Moretti S., Moy C. M., Ravelo A. C., Riesselman C. R., Saavedra-Pellitero M., Sadatzki H., Seo I., Singh R. K., Smith R. A., Souza A. L., Stoner J. S., Toyos M., de Oliveira I. M. V. P., Wan S., Wu S., and Zhao X.

Abstract

The Antarctic Circumpolar Current (ACC) represents the world’s largest ocean-current system and affects global ocean circulation, climate and Antarctic ice-sheet stability1–3. Today, ACC dynamics are controlled by atmospheric forcing, oceanic density gradients and eddy activity4. Whereas palaeoceanographic reconstructions exhibit regional heterogeneity in ACC position and strength over Pleistocene glacial–interglacial cycles5–8, the long-term evolution of the ACC is poorly known. Here we document changes in ACC strength from sediment cores in the Pacific Southern Ocean. We find no linear long-term trend in ACC flow since 5.3 million years ago (Ma), in contrast to global cooling9 and increasing global ice volume10. Instead, we observe a reversal on a million-year timescale, from increasing ACC strength during Pliocene global cooling to a subsequent decrease with further Early Pleistocene cooling. This shift in the ACC regime coincided with a Southern Ocean reconfiguration that altered the sensitivity of the ACC to atmospheric and oceanic forcings11–13. We find ACC strength changes to be closely linked to 400,000-year eccentricity cycles, probably originating from modulation of precessional changes in the South Pacific jet stream linked to tropical Pacific temperature variability14. A persistent link between weaker ACC flow, equatorward-shifted opal deposition and reduced atmospheric CO2 during glacial periods first emerged during the Mid-Pleistocene Transition (MPT). The strongest ACC flow occurred during warmer-than-present intervals of the Plio-Pleistocene, providing evidence of potentially increasing ACC flow with future climate warming.

Published
2024

3. Five million years of Antarctic Circumpolar Current strength variability.

Author

Lamy F, Winckler G, Arz HW, Farmer JR, Gottschalk J, Lembke-Jene L, Middleton JL, van der Does M, Tiedemann R, Alvarez Zarikian C, Basak C, Brombacher A, Dumm L, Esper OM, Herbert LC, Iwasaki S, Kreps G, Lawson VJ, Lo L, Malinverno E, Martinez-Garcia A, Michel E, Moretti S, Moy CM, Ravelo AC, Riesselman CR, Saavedra-Pellitero M, Sadatzki H, Seo I, Singh RK, Smith RA, Souza AL, Stoner JS, Toyos M, de Oliveira IMVP, Wan S, Wu S, and Zhao X

Abstract

The Antarctic Circumpolar Current (ACC) represents the world's largest ocean-current system and affects global ocean circulation, climate and Antarctic ice-sheet stability 1-3 . Today, ACC dynamics are controlled by atmospheric forcing, oceanic density gradients and eddy activity 4 . Whereas palaeoceanographic reconstructions exhibit regional heterogeneity in ACC position and strength over Pleistocene glacial-interglacial cycles 5-8 , the long-term evolution of the ACC is poorly known. Here we document changes in ACC strength from sediment cores in the Pacific Southern Ocean. We find no linear long-term trend in ACC flow since 5.3 million years ago (Ma), in contrast to global cooling 9 and increasing global ice volume 10 . Instead, we observe a reversal on a million-year timescale, from increasing ACC strength during Pliocene global cooling to a subsequent decrease with further Early Pleistocene cooling. This shift in the ACC regime coincided with a Southern Ocean reconfiguration that altered the sensitivity of the ACC to atmospheric and oceanic forcings 11-13 . We find ACC strength changes to be closely linked to 400,000-year eccentricity cycles, probably originating from modulation of precessional changes in the South Pacific jet stream linked to tropical Pacific temperature variability 14 . A persistent link between weaker ACC flow, equatorward-shifted opal deposition and reduced atmospheric CO 2 during glacial periods first emerged during the Mid-Pleistocene Transition (MPT). The strongest ACC flow occurred during warmer-than-present intervals of the Plio-Pleistocene, providing evidence of potentially increasing ACC flow with future climate warming., (© 2024. The Author(s).)

Published
2024
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results