Southern Ocean bottom water cooling and ice sheet expansion during the middle Miocene climate transition
The middle Miocene climate transition (MMCT, ~14.5–13.0 Ma) was associated with a significant expansion of Antarctic ice, but the mechanisms triggering the event remain enigmatic. We present a new clumped isotope (∆ 47 ) bottom water temperature (BWT) record from 16.0 Ma to 12.2 Ma from Ocean Drilli...
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ftcopernicus:oai:publications.copernicus.org:cpd91700 2023-05-15T13:31:39+02:00 Southern Ocean bottom water cooling and ice sheet expansion during the middle Miocene climate transition Leutert, Thomas J. Modestou, Sevasti Bernasconi, Stefano M. Meckler, A. Nele 2020-12-18 application/pdf https://doi.org/10.5194/cp-2020-157 https://cp.copernicus.org/preprints/cp-2020-157/ eng eng doi:10.5194/cp-2020-157 https://cp.copernicus.org/preprints/cp-2020-157/ eISSN: 1814-9332 Text 2020 ftcopernicus https://doi.org/10.5194/cp-2020-157 2020-12-21T17:22:13Z The middle Miocene climate transition (MMCT, ~14.5–13.0 Ma) was associated with a significant expansion of Antarctic ice, but the mechanisms triggering the event remain enigmatic. We present a new clumped isotope (∆ 47 ) bottom water temperature (BWT) record from 16.0 Ma to 12.2 Ma from Ocean Drilling Program (ODP) Site 747 in the Southern Ocean, and compare it to existing BWT records. We show that BWTs in the Southern Ocean were ~8–10 °C during the middle Miocene greenhouse, and thus considerably warmer than today. Nonetheless, bottom water δ 18 O (calculated from foraminiferal δ 18 O and ∆ 47 ) suggests substantial amounts of land ice throughout the interval of the study. Our dataset demonstrates that BWTs at Site 747 decreased by ~3–5 °C across the MMCT. This cooling preceded the stepped main increase in global ice volume, and appears to have been followed by a transient bottom water warming starting during or slightly after the main ice volume increase. We speculate that a regional freshening of the upper water column at this time may have increased stratification and reduced bottom water heat loss to the atmosphere, counteracting global cooling in the bottom waters of the Southern Ocean and possibly even at larger scales. Additional processes and feedbacks required for substantial ice growth may have contributed to the observed decoupling of Southern Ocean BWT and global ice volume. Text Antarc* Antarctic Ice Sheet Southern Ocean Copernicus Publications: E-Journals Antarctic Southern Ocean |
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Copernicus Publications: E-Journals |
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ftcopernicus |
language |
English |
description |
The middle Miocene climate transition (MMCT, ~14.5–13.0 Ma) was associated with a significant expansion of Antarctic ice, but the mechanisms triggering the event remain enigmatic. We present a new clumped isotope (∆ 47 ) bottom water temperature (BWT) record from 16.0 Ma to 12.2 Ma from Ocean Drilling Program (ODP) Site 747 in the Southern Ocean, and compare it to existing BWT records. We show that BWTs in the Southern Ocean were ~8–10 °C during the middle Miocene greenhouse, and thus considerably warmer than today. Nonetheless, bottom water δ 18 O (calculated from foraminiferal δ 18 O and ∆ 47 ) suggests substantial amounts of land ice throughout the interval of the study. Our dataset demonstrates that BWTs at Site 747 decreased by ~3–5 °C across the MMCT. This cooling preceded the stepped main increase in global ice volume, and appears to have been followed by a transient bottom water warming starting during or slightly after the main ice volume increase. We speculate that a regional freshening of the upper water column at this time may have increased stratification and reduced bottom water heat loss to the atmosphere, counteracting global cooling in the bottom waters of the Southern Ocean and possibly even at larger scales. Additional processes and feedbacks required for substantial ice growth may have contributed to the observed decoupling of Southern Ocean BWT and global ice volume. |
format |
Text |
author |
Leutert, Thomas J. Modestou, Sevasti Bernasconi, Stefano M. Meckler, A. Nele |
spellingShingle |
Leutert, Thomas J. Modestou, Sevasti Bernasconi, Stefano M. Meckler, A. Nele Southern Ocean bottom water cooling and ice sheet expansion during the middle Miocene climate transition |
author_facet |
Leutert, Thomas J. Modestou, Sevasti Bernasconi, Stefano M. Meckler, A. Nele |
author_sort |
Leutert, Thomas J. |
title |
Southern Ocean bottom water cooling and ice sheet expansion during the middle Miocene climate transition |
title_short |
Southern Ocean bottom water cooling and ice sheet expansion during the middle Miocene climate transition |
title_full |
Southern Ocean bottom water cooling and ice sheet expansion during the middle Miocene climate transition |
title_fullStr |
Southern Ocean bottom water cooling and ice sheet expansion during the middle Miocene climate transition |
title_full_unstemmed |
Southern Ocean bottom water cooling and ice sheet expansion during the middle Miocene climate transition |
title_sort |
southern ocean bottom water cooling and ice sheet expansion during the middle miocene climate transition |
publishDate |
2020 |
url |
https://doi.org/10.5194/cp-2020-157 https://cp.copernicus.org/preprints/cp-2020-157/ |
geographic |
Antarctic Southern Ocean |
geographic_facet |
Antarctic Southern Ocean |
genre |
Antarc* Antarctic Ice Sheet Southern Ocean |
genre_facet |
Antarc* Antarctic Ice Sheet Southern Ocean |
op_source |
eISSN: 1814-9332 |
op_relation |
doi:10.5194/cp-2020-157 https://cp.copernicus.org/preprints/cp-2020-157/ |
op_doi |
https://doi.org/10.5194/cp-2020-157 |
_version_ |
1766019902817173504 |