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001 AAI10805663
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008 181022s2017 xx sbm 000 0 eng d
020 9780355825558
035 (MiAaPQ)AAI10805663
040 MiAaPQ|beng|cMiAaPQ|dNTU
100 1 Komar, Nemanja
245 10 Biogeochemical Responses of the Earth System to Massive
Carbon Cycle Perturbations and the Cenozoic Long-Term
Evolution of Climate :|bA Modeling Perspective
264 0 |c2017
300 1 online resource (207 pages)
336 text|btxt|2rdacontent
337 computer|bc|2rdamedia
338 online resource|bcr|2rdacarrier
500 Source: Dissertation Abstracts International, Volume: 79-
08(E), Section: B
502 Thesis (Ph.D.)--University of Hawai'i at Manoa, 2017
504 Includes bibliographical references
520 Both short-term and long-term changes in climate and
carbon cycling are reflected in oxygen (delta18O) and
carbon (delta 13C) isotope fluctuations in the geological
record, often indicating a highly dynamic nature and close
connection between climate and carbon cycling through the
ocean-atmosphere-biosphere system. When used in
conjunction with mathematical models, stable carbon and
oxygen isotopes provide a powerful tool for deciphering
magnitude and rate of past environmental perturbations. In
this study, we focus on two transient global warming
events and a multi-million-year evolution of climate: (1)
the end-Permian (̃252 Ma), (2) the Paleocene Eocene
Thermal Maximum (PETM; ̃56 Ma), and (3) climatic and ocean
chemistry variations across the Cenozoic. The transient
events (1) and (2) are both accompanied by a massive
introduction of isotopically light carbon into the ocean-
atmosphere system, as indicated by prominent negative
excursions of both delta 13C and delta18O. We use a
combination of the well-established GEOCARB III and LOSCAR
models to examine feedbacks between the calcium and carbon
cycle during massive and rapid CO2 release events, and
feedbacks between biological production and the cycles of
carbon, oxygen and phosphorus (C-O-P feedback). The
coupled GEOCARB-LOSCAR model enables simulation of marine
carbonate chemistry, delta13C, the calcite compensation
depth (CCD) and organic carbon burial rates across
different time scales. The results of the coupled carbon-
calcium model (LOSCAR only model) suggest that ocean
acidification, which arises due to large and rapid carbon
input, is not reflected in the calcium isotope record
during the end-Permian, contrary to the claims of previous
studies. The observed changes in calcium isotopes arise
due to 12,000 Pg C emitted by Siberian Trap volcanism, the
consequent extinction of the open ocean primary producers,
and variable v calcium isotope fractionation. The results
presented in Chapter 3 indicate that the C-O-P mechanism
may act as a negative feedback during high CO2 emission
events such as the PETM, restoring atmospheric CO2 through
increased organic carbon burial as a consequence of an
accelerated nutrient delivery to the surface ocean and
enhanced organic carbon export. Our results indicate that
the feedback was triggered by an initial carbon pulse of 3,
000 Pg C followed by an additional carbon leak of 2,500 Pg
C. Through the C-O-P feedback, ̃2,000 Pg C could be
sequestered during the recovery phase of the PETM but only
if CaCO3 export remained constant. Regarding long-term
Cenozoic changes (Chapter 4), we propose that the
temperature effect on metabolic rates played an important
role in controlling the evolution of ocean chemistry and
climate across multi-million-year time scales by altering
organic carbon burial rates. Model predicted organic
carbon burial rates combined with the ability to simulate
the CCD changes imposes a critical constraint on the
carbon cycle and aids in a better understanding carbon
cycling during the Cenozoic. Our results suggest that the
observed CCD trends over the past 60 million years were
decoupled from the continental carbonate and silicate
weathering rates. We identify two dominant mechanisms for
the decoupling: (a) shelf-basin carbonate burial
fractionation and (b) decreasing respiration of organic
matter at intermediate water depths as the Earth
transitioned from the greenhouse conditions of the Eocene
to the colder temperatures of the Oligocene
533 Electronic reproduction.|bAnn Arbor, Mich. :|cProQuest,
|d2018
538 Mode of access: World Wide Web
650 4 Chemical oceanography
650 4 Geochemistry
650 4 Paleoclimate science
655 7 Electronic books.|2local
690 0403
690 0996
690 0653
710 2 ProQuest Information and Learning Co
710 2 University of Hawai'i at Manoa.|bOceanography
773 0 |tDissertation Abstracts International|g79-08B(E)
856 40 |uhttps://pqdd.sinica.edu.tw/twdaoapp/servlet/
advanced?query=10805663|zclick for full text (PQDT)
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