Reconstructing deglacial ocean ventilation using radiocarbon : data and inverse modeling
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2017 Significant changes occurred during the last deglaciation (roughly 10-20 thousand years (ka) before pres...
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Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
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ftwhoas:oai:darchive.mblwhoilibrary.org:1912/8685 2023-05-15T17:32:02+02:00 Reconstructing deglacial ocean ventilation using radiocarbon : data and inverse modeling Zhao, Ning 2017-02 https://hdl.handle.net/1912/8685 en_US eng Massachusetts Institute of Technology and Woods Hole Oceanographic Institution WHOI Theses https://hdl.handle.net/1912/8685 doi:10.1575/1912/8685 doi:10.1575/1912/8685 Climatology Climatic changes Glaciers Carbon dioxide Thesis 2017 ftwhoas https://doi.org/10.1575/1912/8685 2022-05-28T22:59:50Z Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2017 Significant changes occurred during the last deglaciation (roughly 10-20 thousand years (ka) before present) throughout the climate system. The ocean is a large reservoir of carbon and heat, however, its role during the deglaciation is still not well understood. In this thesis, I rely on radiocarbon measurements on fossil biogenic carbonates sampled from the seafloor to constrain deglacial ocean ventilation rates, using new data, an extensive data compilation, and inverse modeling. First, based on a sediment core that is absolutely dated from wooden remains, I argue that the deglacial 14C reservoir age of the upper East Equatorial Pacific was not very different from today. Combined with stable carbon isotope data, the results suggest that the deglacial atmospheric CO2 rise was probably due to CO2 released directly from the ocean (e.g., in the Southern Ocean) to the atmosphere rather than first mixed through the upper ocean. Then using a high-deposition-rate sediment core located close to deep water formation regions in the western North Atlantic, I show that compared to today, the mid-depth water production in the North Atlantic was probably stronger during the Younger Dryas cold episode, and weaker during other intervals of the late deglaciation. However, the change was not as large as suggested by previous studies. Finally, I compile published and unpublished deep ocean 14C data, and find that the 14C activity of the deep ocean mirrors that of the atmosphere during the past 25 ka. A box model of modern ocean circulation is fit to the compiled data using an inverse method. I find that the residuals of the fit can generally be explained by the data uncertainties, implying that the compiled data jointly do not provide strong evidence for basin-scale ventilation changes. Overall, this thesis suggests that, although deep ... Thesis North Atlantic Southern Ocean Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) Pacific Southern Ocean Woods Hole, MA |
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Open Polar |
collection |
Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) |
op_collection_id |
ftwhoas |
language |
English |
topic |
Climatology Climatic changes Glaciers Carbon dioxide |
spellingShingle |
Climatology Climatic changes Glaciers Carbon dioxide Zhao, Ning Reconstructing deglacial ocean ventilation using radiocarbon : data and inverse modeling |
topic_facet |
Climatology Climatic changes Glaciers Carbon dioxide |
description |
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2017 Significant changes occurred during the last deglaciation (roughly 10-20 thousand years (ka) before present) throughout the climate system. The ocean is a large reservoir of carbon and heat, however, its role during the deglaciation is still not well understood. In this thesis, I rely on radiocarbon measurements on fossil biogenic carbonates sampled from the seafloor to constrain deglacial ocean ventilation rates, using new data, an extensive data compilation, and inverse modeling. First, based on a sediment core that is absolutely dated from wooden remains, I argue that the deglacial 14C reservoir age of the upper East Equatorial Pacific was not very different from today. Combined with stable carbon isotope data, the results suggest that the deglacial atmospheric CO2 rise was probably due to CO2 released directly from the ocean (e.g., in the Southern Ocean) to the atmosphere rather than first mixed through the upper ocean. Then using a high-deposition-rate sediment core located close to deep water formation regions in the western North Atlantic, I show that compared to today, the mid-depth water production in the North Atlantic was probably stronger during the Younger Dryas cold episode, and weaker during other intervals of the late deglaciation. However, the change was not as large as suggested by previous studies. Finally, I compile published and unpublished deep ocean 14C data, and find that the 14C activity of the deep ocean mirrors that of the atmosphere during the past 25 ka. A box model of modern ocean circulation is fit to the compiled data using an inverse method. I find that the residuals of the fit can generally be explained by the data uncertainties, implying that the compiled data jointly do not provide strong evidence for basin-scale ventilation changes. Overall, this thesis suggests that, although deep ... |
format |
Thesis |
author |
Zhao, Ning |
author_facet |
Zhao, Ning |
author_sort |
Zhao, Ning |
title |
Reconstructing deglacial ocean ventilation using radiocarbon : data and inverse modeling |
title_short |
Reconstructing deglacial ocean ventilation using radiocarbon : data and inverse modeling |
title_full |
Reconstructing deglacial ocean ventilation using radiocarbon : data and inverse modeling |
title_fullStr |
Reconstructing deglacial ocean ventilation using radiocarbon : data and inverse modeling |
title_full_unstemmed |
Reconstructing deglacial ocean ventilation using radiocarbon : data and inverse modeling |
title_sort |
reconstructing deglacial ocean ventilation using radiocarbon : data and inverse modeling |
publisher |
Massachusetts Institute of Technology and Woods Hole Oceanographic Institution |
publishDate |
2017 |
url |
https://hdl.handle.net/1912/8685 |
geographic |
Pacific Southern Ocean |
geographic_facet |
Pacific Southern Ocean |
genre |
North Atlantic Southern Ocean |
genre_facet |
North Atlantic Southern Ocean |
op_source |
doi:10.1575/1912/8685 |
op_relation |
WHOI Theses https://hdl.handle.net/1912/8685 doi:10.1575/1912/8685 |
op_doi |
https://doi.org/10.1575/1912/8685 |
op_publisher_place |
Woods Hole, MA |
_version_ |
1766129950846353408 |