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Brandon Bell MS thesis final.pdf (4.76 MB)

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Eastern equatorial Pacific export production and micronutrient delivery during the middle Miocene Climate Optimum

Bell, Brandon Blake
http://orcid.org/0000-0002-6243-8505
http://rave.ohiolink.edu/etdc/view?acc_num=osu1650546504070897

Abstract Details

2022, Master of Science, Ohio State University, Earth Sciences.
Equatorial upwelling makes the eastern equatorial Pacific (EEP) one of the largest source regions of CO2 to the atmosphere today, but primary production is limited by scarce micronutrients. This pattern of upwelling was likely present during the middle Miocene Climate Optimum (mMCO; 16.9 – 14.7 Ma), a warmer interval that is a potential analogue for near-future conditions, although productivity variations are less well known. Here I examined whether variations in micronutrient flux impacted productivity in the EEP in response to orbital eccentricity cycles (100 and 400 k.y.) during the mMCO. Eccentricity has a well-noted impact on middle Miocene climate, as seen by nine short-term positive benthic δ13C maxima (CM) events occurring at 400 k.y. eccentricity minima as well as bottom water warming and cooling at 100 k.y. eccentricity. A new marine pelagic barite record spanning 16.94 -14.0 Ma at International Ocean Discovery Program Site U1337 was produced and is compared to published XRF paleoproductivity and micronutrient data from the same site. Within the first ~ 500 k.y. interval of this study (16.94 – 16.46 Ma), extraterrestrial (ET) 3He and terrestrial 4He concentrations were measured to better constrain accumulation rates. During this interval, there is no consistent association between barite accumulation and 100 k.y. eccentricity, suggesting variability in barite is due primarily to carbonate dissolution. However, corresponding increases in the ET 3He-normalized barite and terrestrial proxies (Ti, Al, Fe) occurred during these first two CM events. Increases in upwelled micronutrient iron in the EEP during these CM events likely stimulated and increased export production in the early mMCO. However, because carbonate accumulation increased more than opal or barite during one of these events, the EEP did not likely contribute to net carbon sequestration at this time. Instead, a stimulated carbonate counterpump may have expanded the EEP’s role as a carbon source, acting as a negative feedback on cooling during this early CM event in contrast to its potential role as a carbon sink during CM6.
Elizabeth Griffith (Advisor)
Lonnie Thompson (Committee Member)
Jill Leonard-Pingel (Committee Member)
138 p.
Geochemistry; Geology; Paleoclimate Science
paleoclimate; paleoceanography; carbon cycle; marine sediment; equatorial Pacific; eastern equatorial Pacific; IODP; Site U1337

Recommended Citations

Citations

  • Bell, B. B. (2022). Eastern equatorial Pacific export production and micronutrient delivery during the middle Miocene Climate Optimum [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1650546504070897

    APA Style (7th edition)

  • Bell, Brandon. Eastern equatorial Pacific export production and micronutrient delivery during the middle Miocene Climate Optimum. 2022. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1650546504070897.

    MLA Style (8th edition)

  • Bell, Brandon. "Eastern equatorial Pacific export production and micronutrient delivery during the middle Miocene Climate Optimum." Master's thesis, Ohio State University, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=osu1650546504070897

    Chicago Manual of Style (17th edition)

osu1650546504070897
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