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How the Central American Seaway alters large-scale ocean circulation, climate and marine biogeochemistry

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Title
How the Central American Seaway alters large-scale ocean circulation, climate and marine biogeochemistry
Name (type = personal)
NamePart (type = family)
Sentman
NamePart (type = given)
Lori
NamePart (type = date)
1975-
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Lori Sentman
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RoleTerm (authority = RULIB)
author
Name (type = personal)
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Broccoli
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Anthony J
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Anthony J Broccoli
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Advisory Committee
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chair
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NamePart (type = family)
Miller
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James R
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James R Miller
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Advisory Committee
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internal member
Name (type = personal)
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Curchitser
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Enrique
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Enrique Curchitser
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Advisory Committee
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internal member
Name (type = personal)
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Dunne
NamePart (type = given)
John P.
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John P. Dunne
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Advisory Committee
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outside member
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Rutgers University
Role
RoleTerm (authority = RULIB)
degree grantor
Name (type = corporate)
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School of Graduate Studies
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RoleTerm (authority = RULIB)
school
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Text
Genre (authority = marcgt)
theses
OriginInfo
DateCreated (qualifier = exact)
2018
DateOther (qualifier = exact); (type = degree)
2018-01
Place
PlaceTerm (type = code)
xx
Language
LanguageTerm (authority = ISO639-2b); (type = code)
eng
Abstract (type = abstract)
The study of past climates using climate models and paleoclimate proxy records is helpful for understanding how the Earth system responds to external natural forcing on time scales longer than the current instrumental records. The Central American Seaway (CAS) was an important ocean gateway connecting the Pacific and Atlantic Oceans until its gradual shoaling and final closure near the end of the Pliocene (5.3-2.6 Ma), when paleoclimate proxy records indicate a major reorganization in large-scale ocean circulation and shifting spatial patterns in global climate and marine biogeochemistry. Climate models are not consistent in reconciling the impact of the seaway on global deep-water circulation, tropical Pacific and Southern Hemisphere physical mean state, and interannual tropical Pacific climate variability, and have not been able to explore the coupled impacts on ocean biogeochemistry or sediment calcium carbonate (CaCO3) long-term burial. For the first time, as far as this author knows, a suite of four idealized experiments, including a very narrow (109 km-wide) single meridional grid point channel, are performed for multi-millennial scale simulations using the Geophysical Fluid Dynamics Laboratory Earth System Model, GFDL-ESM2G, with high ocean spatial resolution to explore the mechanistic role of changing topography – varying only seaway widths and sill depths – associated with the various stages of seaway constriction and shoaling on global ocean circulation, climate and marine biogeochemistry compared to “preindustrial” 1860 climate. Model output is combined with an uncoupled box model to obtain the first sediment CaCO3 (as calcite) long-term burial estimates and atmosphere pCO2 concentrations associated with a very narrow seaway for comparison with proxy records. Independent of the CAS configuration in GFDL-ESM2G, the open CAS alters ocean physical mean state and deep water properties globally, driven by the direct impacts of the seaway on global mass, heat and salt transports. Net mass transport from the Pacific through the CAS into the Caribbean is 20.5-23.1 Sv with the 2000-m deep seaways, but only 14.1 Sv for the 200-m shallow seaway. The CAS provided a shortcut for southern sourced Pacific water mass transport, warming the South Atlantic and reducing Indonesian Throughflow mass transport by 59-82%. The CAS suppressed Antarctic Bottom Water northward extent, allowing North Atlantic Deep Water to deepen ~500 m and slightly strengthen (~2Sv), in contrast to preindustrial observational estimates and previous studies with an open CAS using climate models. Global mean climate and tropical Pacific interannual variability are sensitive to the presence of the CAS, with the largest sensitivity occurring in the Southern Hemisphere for the relatively wide (1308 km) and 2000-m deep CAS. In response to the global ocean reorganization associated with the CAS opened to various shoaling stages, global mean surface air temperatures warm 0.4-0.7°C with a bipolar, asymmetric response of Northern Hemisphere cooling up to ~2°C in the northwest Pacific and Southern Hemisphere warming up to ~8°C near the Ross Sea, in contrast to global mean cooling in climate models. In the tropical Pacific, opening the CAS leads to a global mean warming 0.4-0.8°C in the top 300 m, increased equatorial sea surface temperature gradient in the central and east Pacific, decreased meridional sea surface temperature asymmetry about the equator at 110°W, and the thermocline deepens 5-11 m. Opening the CAS leads to larger El Niño-Southern Oscillation (ENSO) amplitude with more La Niña or cold events, a weaker annual cycle, and ~3 months earlier development. Opening the CAS results in stronger ventilation and a reduction in the sequestration efficiency of the biological pump, allowing respired CO2 to escape to the atmosphere via increased ocean CO2 outgassing. The loss of dissolved inorganic carbon increases the deep ocean carbonate (CO32-) leading to a short-term (< 500 kyr) increase in global CaCO3 burial of 0.002 PgC a-1 corresponding to large long-term increases in the global sediment CaCO3 pool (~200 PgC over 105 years) and a net migration of ~150 PgC from the spatial distribution of CaCO3 in the active layer of 10 cm surface sediment, providing the upper limit on the decrease in ocean alkalinity (~300 PgC), in which alkalinity and DIC are removed in a 2:1 ratio. The enhanced burial of CaCO3 leads to an additional release of 237.9 ppmv (506.8 PgC) to the atmosphere from the partitioning of carbon species implying short-term warming of 0.4-1.0 K in the Pliocene with a very narrow CAS. Overall, this paleoclimate application has broad implications for the sensitivity of coupled ocean-atmosphere dynamics and ocean biogeochemistry to changing ocean circulation with far-reaching, long-term climate, ENSO, marine ecosystem, ocean biogeochemical, and atmosphere pCO2 impacts.
Subject (authority = RUETD)
Topic
Atmospheric Science
RelatedItem (type = host)
TitleInfo
Title
Rutgers University Electronic Theses and Dissertations
Identifier (type = RULIB)
ETD
Identifier
ETD_8572
PhysicalDescription
Form (authority = gmd)
electronic resource
InternetMediaType
application/pdf
InternetMediaType
text/xml
Extent
1 online resource (xxix, 177 p. : ill.)
Note (type = degree)
Ph.D.
Note (type = bibliography)
Includes bibliographical references
Subject (authority = ETD-LCSH)
Topic
Ocean circulation
Note (type = statement of responsibility)
by Lori Sentman
RelatedItem (type = host)
TitleInfo
Title
School of Graduate Studies Electronic Theses and Dissertations
Identifier (type = local)
rucore10001600001
Location
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NjNbRU
Identifier (type = doi)
doi:10.7282/T3JW8J31
Genre (authority = ExL-Esploro)
ETD doctoral
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The author owns the copyright to this work.
RightsHolder (type = personal)
Name
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Sentman
GivenName
Lori
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Copyright Holder
RightsEvent
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Permission or license
DateTime (encoding = w3cdtf); (qualifier = exact); (point = start)
2017-12-18 14:53:23
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Name
Lori Sentman
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Affiliation
Rutgers University. School of Graduate Studies
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I hereby grant to the Rutgers University Libraries and to my school the non-exclusive right to archive, reproduce and distribute my thesis or dissertation, in whole or in part, and/or my abstract, in whole or in part, in and from an electronic format, subject to the release date subsequently stipulated in this submittal form and approved by my school. I represent and stipulate that the thesis or dissertation and its abstract are my original work, that they do not infringe or violate any rights of others, and that I make these grants as the sole owner of the rights to my thesis or dissertation and its abstract. I represent that I have obtained written permissions, when necessary, from the owner(s) of each third party copyrighted matter to be included in my thesis or dissertation and will supply copies of such upon request by my school. I acknowledge that RU ETD and my school will not distribute my thesis or dissertation or its abstract if, in their reasonable judgment, they believe all such rights have not been secured. I acknowledge that I retain ownership rights to the copyright of my work. I also retain the right to use all or part of this thesis or dissertation in future works, such as articles or books.
Copyright
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Availability
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Open
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Permission or license
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