Scott Hawley


Assessing the Influence of Glacial Weathering on Marine Iron (Fe) Inputs Using Fe Stable Isotopes

Advisors; Kevin Burton, Helen Williams (Durham University), Philip Pogge von Strandmann (University College London), Sigurður Gislason (University of Iceland), Sigurður H. Markússon (Landsvirkjun)

My research is driven by two questions:

  • What effect does glacial retreat/advance have on the planet’s climate?
  • Do glaciers help moderate Earth’s climate?

Traditional thinking holds that glacial ice and Earth’s climate are linked via the albedo effect and sea level changes leading to a positive climate feedback cycle between global temperatures and glacial ice. In other words the loss of glaciers is thought to promote further warming on the planet while increases in glacial ice are thought to drive future global cooling. However this traditional view does not take into account the role the solid Earth plays in determining changes to Earth’s climate.

Over short geologic time scales climate change is driven by fluctuations in the exchange rates of material between Earth’s atmosphere and geosphere. The burning of fossil fuels, which transfers carbon from the geosphere to the atmosphere, is at the core of modern climate change. However carbon burial, the process which removes atmospheric carbon back into the geosphere, needs to be considered alongside anthropogenic activity to fully understand how the atmosphere and climate are and will continue to change. Carbon burial is a dynamic process and certain forms of iron, known as reactive iron species, enhance carbon burial through a process known as the ‘Rusty Carbon Sink’ (Lalonde et al 2012).   As a result any process which changes reactive iron formation/transport is expected to change carbon burial and by extension the rate at which carbon is removed from Earth’s atmosphere. This links back into modern climate change because reactive iron formation is dictated by terrestrial weathering processes which are in themselves climatically sensitive. Glaciers weather rocks in a unique way that means that their presents/absents may significantly affect reactive iron formation and transport.

To investigate the direction and magnitude of the interplay between climate, reactive iron and carbon burial I analyze the iron stable isotope composition of glacial and precipitation fed river waters and riverine sediments from Iceland and Greenland. Iron stable isotope fractionation provides a powerful novel method and facilitates the analysis of samples which previously could not be measured for reactive iron.

Durham University Department of Earth Sciences: