THE ROLE OF AGULHAS LEAKAGE IN PLIOCENE CLIMATE CHANGE
The late Pliocene (2.6-3.3 Myr) was an epoch of gradual cooling, with expanding Antarctic ice sheets and sea ice preceding a general Northern Hemisphere glaciation. A decline in the strength of the Atlantic Meridional Circulation (AMOC) in the late Pliocene may have decreased Southern Hemisphere oce...
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ftunivmassamh:oai:scholarworks.umass.edu:dissertations_2-2854 2024-04-28T07:59:32+00:00 THE ROLE OF AGULHAS LEAKAGE IN PLIOCENE CLIMATE CHANGE Patel, Neil 2019-10-30T15:32:59Z application/pdf https://scholarworks.umass.edu/dissertations_2/1740 https://doi.org/10.7275/15243692 https://scholarworks.umass.edu/context/dissertations_2/article/2854/viewcontent/thesis_neil_patel_corrected.pdf unknown ScholarWorks@UMass Amherst https://scholarworks.umass.edu/dissertations_2/1740 doi:10.7275/15243692 https://scholarworks.umass.edu/context/dissertations_2/article/2854/viewcontent/thesis_neil_patel_corrected.pdf Doctoral Dissertations Pliocene Agulhas Leakage Ocean Modeling Past Climate Change Climate Oceanography text 2019 ftunivmassamh https://doi.org/10.7275/15243692 2024-04-03T14:49:41Z The late Pliocene (2.6-3.3 Myr) was an epoch of gradual cooling, with expanding Antarctic ice sheets and sea ice preceding a general Northern Hemisphere glaciation. A decline in the strength of the Atlantic Meridional Circulation (AMOC) in the late Pliocene may have decreased Southern Hemisphere oceanic heat transport into the Northern Hemisphere; pre-conditioning it for glaciation. A common explanation for a weakening of the AMOC in paleoclimate is freshwater forcing into the North Atlantic. In this thesis, I posit that a northward shift in the Southern Hemisphere westerlies in the late Pliocene, due to an expanded Antarctic ice sheet, weakens the Agulhas Leakage — a narrow current flowing past the Cape of Good Hope that connects the Indian and Atlantic Ocean basins. Since the Agulhas Leakage transports relatively salty waters from the Indian Ocean into the South Atlantic, it could alter the AMOC by changing the density stratification in North Atlantic deep-water formation sites. To test this hypothesis, I use a high-resolution (1/6°) ocean model, the MITgcm, with passive and Lagrangian particle-based tracers to quantify changes in Agulhas Current leakage. Following a spin-up simulation, I run two experiments, an experiment with a prescribed 6° northward shift in the southern westerlies and a control experiment with unchanged winds, both run for 58 model-years. I found a quick (< 10 year) decline in Agulhas Leakage volume in the northward wind perturbation experiment that, by the experiment end, led to changes in North Atlantic surface densities, including in areas of North Atlantic deep water formation (NADW), with an increase in vertical stratification in the perturbation experiment suggesting a weakening of the NADW. The findings from my research indicate that Agulhas Leakage water has a pathway into the North Atlantic and that the northward wind perturbation decreased the influx of Agulhas water into the North Atlantic, with corresponding implications for salt and heat transport. A northward shift in ... Text Antarc* Antarctic Ice Sheet NADW North Atlantic Deep Water North Atlantic Sea ice University of Massachusetts: ScholarWorks@UMass Amherst |
institution |
Open Polar |
collection |
University of Massachusetts: ScholarWorks@UMass Amherst |
op_collection_id |
ftunivmassamh |
language |
unknown |
topic |
Pliocene Agulhas Leakage Ocean Modeling Past Climate Change Climate Oceanography |
spellingShingle |
Pliocene Agulhas Leakage Ocean Modeling Past Climate Change Climate Oceanography Patel, Neil THE ROLE OF AGULHAS LEAKAGE IN PLIOCENE CLIMATE CHANGE |
topic_facet |
Pliocene Agulhas Leakage Ocean Modeling Past Climate Change Climate Oceanography |
description |
The late Pliocene (2.6-3.3 Myr) was an epoch of gradual cooling, with expanding Antarctic ice sheets and sea ice preceding a general Northern Hemisphere glaciation. A decline in the strength of the Atlantic Meridional Circulation (AMOC) in the late Pliocene may have decreased Southern Hemisphere oceanic heat transport into the Northern Hemisphere; pre-conditioning it for glaciation. A common explanation for a weakening of the AMOC in paleoclimate is freshwater forcing into the North Atlantic. In this thesis, I posit that a northward shift in the Southern Hemisphere westerlies in the late Pliocene, due to an expanded Antarctic ice sheet, weakens the Agulhas Leakage — a narrow current flowing past the Cape of Good Hope that connects the Indian and Atlantic Ocean basins. Since the Agulhas Leakage transports relatively salty waters from the Indian Ocean into the South Atlantic, it could alter the AMOC by changing the density stratification in North Atlantic deep-water formation sites. To test this hypothesis, I use a high-resolution (1/6°) ocean model, the MITgcm, with passive and Lagrangian particle-based tracers to quantify changes in Agulhas Current leakage. Following a spin-up simulation, I run two experiments, an experiment with a prescribed 6° northward shift in the southern westerlies and a control experiment with unchanged winds, both run for 58 model-years. I found a quick (< 10 year) decline in Agulhas Leakage volume in the northward wind perturbation experiment that, by the experiment end, led to changes in North Atlantic surface densities, including in areas of North Atlantic deep water formation (NADW), with an increase in vertical stratification in the perturbation experiment suggesting a weakening of the NADW. The findings from my research indicate that Agulhas Leakage water has a pathway into the North Atlantic and that the northward wind perturbation decreased the influx of Agulhas water into the North Atlantic, with corresponding implications for salt and heat transport. A northward shift in ... |
format |
Text |
author |
Patel, Neil |
author_facet |
Patel, Neil |
author_sort |
Patel, Neil |
title |
THE ROLE OF AGULHAS LEAKAGE IN PLIOCENE CLIMATE CHANGE |
title_short |
THE ROLE OF AGULHAS LEAKAGE IN PLIOCENE CLIMATE CHANGE |
title_full |
THE ROLE OF AGULHAS LEAKAGE IN PLIOCENE CLIMATE CHANGE |
title_fullStr |
THE ROLE OF AGULHAS LEAKAGE IN PLIOCENE CLIMATE CHANGE |
title_full_unstemmed |
THE ROLE OF AGULHAS LEAKAGE IN PLIOCENE CLIMATE CHANGE |
title_sort |
role of agulhas leakage in pliocene climate change |
publisher |
ScholarWorks@UMass Amherst |
publishDate |
2019 |
url |
https://scholarworks.umass.edu/dissertations_2/1740 https://doi.org/10.7275/15243692 https://scholarworks.umass.edu/context/dissertations_2/article/2854/viewcontent/thesis_neil_patel_corrected.pdf |
genre |
Antarc* Antarctic Ice Sheet NADW North Atlantic Deep Water North Atlantic Sea ice |
genre_facet |
Antarc* Antarctic Ice Sheet NADW North Atlantic Deep Water North Atlantic Sea ice |
op_source |
Doctoral Dissertations |
op_relation |
https://scholarworks.umass.edu/dissertations_2/1740 doi:10.7275/15243692 https://scholarworks.umass.edu/context/dissertations_2/article/2854/viewcontent/thesis_neil_patel_corrected.pdf |
op_doi |
https://doi.org/10.7275/15243692 |
_version_ |
1797572223656001536 |