Date of Award

Fall 12-2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean/Earth/Atmos Sciences

Program/Concentration

Ocean and Earth Sciences

Committee Director

Matthew Schmidt

Committee Member

David Burdige

Committee Member

Peter Sedwick

Abstract

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, CO2-rich waters would also have a lower pH and a lower carbonate ion concentration ([CO32-]). Yu and Elderfield (2007) showed that the boron to calcium (B/Ca) ratio in the benthic foraminifera C. wuellerstorfi is a reliable proxy for reconstructing bottom water [CO32-]. Here I present new constraints on deep ocean carbon storage over the last 25 kyr in the EEP using new benthic foraminiferal B/Ca-[CO32-] reconstructions from four cores at a range of depths from within and outside the Panama Basin. These four new records all reveal lower glacial [CO32-], with the largest LGM-Holocene difference coming from core MV1014-02-17JC (17JC) (00°10.83’S, 85°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 of 232Th (a dust flux proxy), excess barium (a paleoproductivity proxy), and aU from 17JC and MV1014-02-8JC (8JC) (6°14’N, 86°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 [CO32-] 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.

DOI

10.25777/568q-b132

ISBN

9798557052993

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