Muddying the Waters
: Tracing Terrigenous Fluxes to the North Atlantic Ocean

  • George H Rowland

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


The flux of terrigenous material from the continents to the oceans both influences, and is dependent on, climate. To understand links with past and present climates, terrigenous fluxes in the ocean must be quantified. In the tropical Atlantic, the processes driving terrigenous fluxes are incompletely understood due to insufficient synthesis of existing data. At the west Greenland margin terrigenous fluxes may be important for phytoplankton but remain poorly constrained due to a lack of data.

I have analysed existing data from sediment cores in the tropical Atlantic to calculate spatial patterns of 230Th normalised 232Th fluxes. Using the patterns of 232Th fluxes I have determined the dominant terrigenous sources, the position of the tropical rain- belt and the strength of wind systems since the last glacial maximum (LGM). I have mapped the provenance of tropical Atlantic sediments using new analyses of n- alkane 13C/12C. I have used these data to highlight concurrent changes in vegetation and dust fluxes since the LGM. By combining 232Th and n-alkane data I have shown that the n-alkane/232Th ratio is sensitive to climate across different timescales, making the ratio a potential tracer of past environmental change. At the west Greenland margin I have quantified dissolved terrigenous fluxes reaching the ocean by analysing 232Th/230Th in seawater. I have found that lithogenic 232Th concentrations correlate with those of freshwater, implying a glacial source. I have shown that dissolved 232Th fluxes at the west Greenland margin remain elevated past the edge of the continental shelf and supply significant amounts of lithogenic nutrients to phytoplankton.

Collectively my results quantify the range of terrigenous fluxes reaching the tropical and high-latitude North Atlantic and demonstrate how fluxes are strongly modulated during periods of climatic change. The data I have presented can be used to assess the impact of terrigenous fluxes on climate.
Date of Award11 May 2021
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorKatharine Hendry (Supervisor) & Laura F Robinson (Supervisor)

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