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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities
 

Lead Supervisor: Helen Williams, Earth Sciences

Co-Supervisor: Emily Stevenson, Earth Sciences; Stephen Roberts, British Antarctic Survey; Sasha Turchyn, Earth Sciences & Kate Hendry, Department of Earth Sciences, University of Bristol

Brief summary: 
In polar regions, climate warming is accelerating glacier retreat and associated weathering processes and the goal of this project is to understand how this could influence the export of an important nutrient, iron, from subglacial continental regions to the oceans
Importance of the area of research concerned: 
Iron is essential to life and the fourth most abundant element in the Earth’s crust. In sediments iron is bound in clay minerals, highly crystalline minerals such as magnetite, or is completely sulfurized to pyrite in organic sediments. However, it is only found in trace concentration in the oceans. Iron is transferred from the continents to the oceans in both particulate and soluble (bioavailable) forms generated through physical and chemical weathering processes. In polar regions, climate warming is accelerating glacial retreat, permafrost thaw and thermokarst collapse, processes that expose fresh and highly-reactive minerals in sediments to weathering and riverine transport. Recent studies suggest that polar regions represent more than 10% of the total global sediment delivery from the continents to the oceans. As the Earth’s climate continues to warm, it is becoming increasingly important to understand the role that glacial chemical and physical weathering processes play in mediating global iron, carbon and sulfur cycles. However, to date only a few studies have compared Fe exports from different glacial fluvial and runoff systems. This is the overall goal of this project.
Project summary : 
This project will use Fe stable isotopes to study temporal changes in the export and reactivity of Fe during glacial weathering in polar regions, using river water and bedload sediment samples collected in Arctic field campaigns coupled with archive lake core samples from Antarctica. The Arctic samples were collected over several field seasons and can be used to relate weathering fluxes to changes in seasonal conditions and events such as outburst floods. They provide a complementary record to the Antarctic lake cores, which represent high-temporal resolution archives of events such as glacier retreat and/or growth. These records will be compared to better understand the processes controlling the chemical cycling of glacial Fe over different timescales, and further refine our estimates of glacial Fe delivery to the oceans and predictions for how this might change in a warming world.
What will the student do?: 
The project presents an exciting opportunity to use novel stable isotopes to unravel the roles that glacial hydrological events play in Fe release, transformation and transport. Iron stable isotopes respond to changes in Fe bonding environment and oxidation state and can be used to trace iron input and output fluxes and chemical transformations (e.g. sulfide oxidation and breakdown, Fe adsorption onto oxyhydroxide particles). The student will study river water and bedload sediment samples collected in recent Arctic field campaigns and will combine these samples with archive lake cores from Antarctica. There may also be the possibility of fieldwork, if so, the student would collect samples of melt water, river water and bedload sediments in a well-characterised glacial catchment for analysis. The student will carry out Fe analyses of water samples and bulk and fraction-specific (e.g. for mobile, crystalline, silicate Fe forms) analyses of selected sediment samples. They will combine these with other geochemical data and ancillary parameters to determine temporal variations in Fe fluxes and reaction pathways and develop quantitative models for Fe export from glacial catchments.
References - references should provide further reading about the project: 
Henkel, Susann, Sabine Kasten, Jan F. Hartmann, Adrián Silva-Busso, and Michael Staubwasser. Iron cycling and stable Fe isotope fractionation in Antarctic shelf sediments, King George Island. Geochimica et Cosmochimica Acta 237 (2018): 320-338.
Hawley, S. M., von Strandmann, P. A. P., Burton, K. W., Williams, H. M., & Gíslason, S. R. (2017). Continental weathering and terrestrial (oxyhydr) oxide export: comparing glacial and non-glacial catchments in Iceland. Chemical Geology, 462, 55-66.
Zhang, R., John, S. G., Zhang, J., Ren, J., Wu, Y., Zhu, Z., ... & Wenger, F. (2015). Transport and reaction of iron and iron stable isotopes in glacial meltwaters on Svalbard near Kongsfjorden: From rivers to estuary to ocean. Earth and Planetary Science Letters, 424, 201-211.
Applying
You can find out about applying for this project on the Department of Earth Sciences page.
Dr Helen Williams
Dr Alexandra (Sasha) Turchyn
Department of Earth Sciences Graduate Administrator