Constraining Respired Carbon Storage in the Eastern Tropical Pacific Over the Last 25 Thousand Years Using Benthic Foraminiferal Boron/Calcium Ratios

<p>The storage of inorganic carbon in the deep Pacific Ocean is thought to play an important role in regulating both glacial-interglacial and millennial-scale atmospheric CO₂ concentrations (Broecker and Barker 2007; Sigman et al., 2010). A recent study by Loveley et al. (2017) showed that sedimentary authigenic uranium (aU) concentrations, a proxy for suboxic bottom-water conditions, increased significantly in the Eastern Equatorial Pacific (EEP) during the Last Glacial Maximum (LGM, 18 kyr – 23 kyr). If this is correct, the low-oxygen, CO_2-rich waters would also have a lower pH and a lower carbonate ion concentration ([CO₃^2-]). Yu and Elderfield (2007) showed that the boron to calcium (B/Ca) ratio in the benthic foraminifera <em>C. wuellerstorfi</em> is a reliable proxy for reconstructing bottom water [CO₃^2-]. Here I present new constraints on deep ocean carbon storage over the last 25 kyr in the EEP using new benthic foraminiferal B/Ca-[CO₃^2-] reconstructions from four cores at a range of depths from within and outside the Panama Basin. These four new records all reveal lower glacial [CO₃^2-], with the largest LGM-Holocene difference coming from core MV1014-02-17JC (17JC) (00<strong>°</strong>10.83’S, 85<strong>°</strong>52.00’W; 2.9 km water depth) inside the Panama Basin. New depth profiles of glacial carbon storage in the region show that respired CO₂ storage outside the Panama Basin was relatively homogenous while inside the basin there was a gradient of increasing CO₂ storage with depth from 2.2 km down to 2.9 km. A new sub-millennial scale record shows that during the last deglaciation (18 kyr - 11 kyr), waters inside the Panama Basin experienced two large increases in respired CO₂ storage during Heinrich Stadial 1 and the Younger Dryas. Finally, intra-core proxy comparisons of²³²Th (a dust flux proxy), excess barium (a paleoproductivity proxy), and aU from 17JC and MV1014-02-8JC (8JC) (6<strong>°</strong>14’N, 86<strong>°</strong>2’W; 2 km water depth) illustrate that two different mechanisms likely influenced CO₂ storage in the region. For 8JC, a poorly ventilated Pacific wide water mass was likely the source for the lower glacial [CO₃^2-] at its core location. While for 17JC, in addition to the previously noted poorly ventilated water mass influence, respired CO₂ storage at this core location was further enhanced by millennial scale increases in export production. By sequestering carbon away from the atmosphere and surface ocean, deep waters in the Panama Basin and in the greater EEP region likely played an important role in lowering glacial atmospheric CO₂.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Ocean & Earth Sciences

Year dc:date.available

2020

Author dc:creator

• Close, Brian James

Contributors dc:contributor

• Matthew Schmidt
• David Burdige
• Peter Sedwick

• Carbon storage
• Eastern Pacific
• Fe fertilization
• Paleoceanography
• Paleoclimatology
• Geology
• Paleontology

Statement dc:rights

• <p>In Copyright. URI: <a href="http://rightsstatements.org/vocab/InC/1.0/">http://rightsstatements.org/vocab/InC/1.0/</a> This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).</p>

Identifier

9798557052993

OAI identifier oai:identifier

oai:digitalcommons.odu.edu:oeas_etds-1175