Supervisor: Luke Skinner (Earth Sciences)
Importance of the area of research:
The distribution of dissolved oxygen in the ocean interior is intimately connected to the biological cycling of organic carbon and atmosphere-ocean gas exchange. As such it has a direct bearing on the marine carbon cycle, including in particular the balance of pre-formed versus remineralised nutrients in the ocean interior, which is expected to exert a primary control on atmospheric CO2 on millennial- and glacial-interglacial timescales [Ito and Follows, 2005; Sigman et al., 2010]. The reconstruction of past oxygenation has long been a major challenge in palaeoceanography. However, recent analytical developments (for example using laser-ablation micro-analysis techniques) have opened up new opportunities for the investigation of past redox conditions. If new insights into the past oxygenation of the ocean interior can indeed be obtained, our understanding of the ocean’s role in past atmospheric CO2 variability may be greatly improved.
This project will make use of a set of newly recovered and pristine multi-core and gravity/piston core sediments, as well as pore-fluid and seawater samples, from the Iberian Margin (Northeast Atlantic) to investigate modern controls on a set of complimentary ‘ventilation’ and oxygenation proxies including benthic fauna, redox-sensitive metal concentrations, infaunal versus epifaunal benthic foraminifer stable carbon isotope ratios and radiocarbon. Using sediment cores from a range of water depths on the Iberian and Namibian Margins, these proxies will also be used to reconstruct the evolution of North Atlantic and South Atlantic water-column oxygenation across the last deglaciation. The project thus seeks to derive new insights into our proxies for past ocean interior oxygenation, and to investigate the implications of novel palaeo-oxygenation reconstructions for our understanding of the glacial-interglacial carbon cycling.
What the student will do:
The student will perform geochemical measurements on core-top sediment samples and foraminifera from these samples, as well as pore fluid and seawater samples, with the aim of refining our understanding of a host of possible seawater and pore-water redox proxies. The student will also assess the microhabitat preferences and variable abundances of key benthic foraminifer indicator species, in particular as these relate to their stable isotope and trace-element geochemistry. The student will need to consider a range of water-column and pore-water processes that may affect the oxygenation proxies under consideration, as well as microhabitat effects on benthic foraminifer geochemistry. Insights gained from this modern-process study will then be applied to a series of down-core investigations, targeting the marine carbon cycle, and its role in atmospheric CO2 variability during/since the last glacial period.
Please contact the lead supervisor directly for further information relating to what the successful applicant will be expected to do, training to be provided, and any specific educational background requirements.
Boiteau, R., Greaves, M., and Elderfield, H., 2012. Authigenic uranium in foraminiferal coatings: A proxy for ocean redox chemistry: Paleoceanography, vol. 27.
Jaccard, S. L., and Galbraith, E., 2012. Large climate-driven changes of oceanic oxygen concentrations during the last deglaciation: Nature Geoscience, vol. 5, pp. 151-156.
Gottschalk, J., Skinner, L.C., Lippold, J., Vogel, H., Frank, N., Jaccard, S.L., Waelbroeck, C., 2016. Biological and physical controls in the Southern Ocean on past millennial-scale atmospheric CO2 changes. Nature Communications 7, 11539.
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