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Dr Tom Cowton

[Tom Cowton]
  • Postdoctoral Research Associate
  • School of Geosciences, University of Edinburgh, EH8 9XP
  • Email: tom.cowton [at] ed.ac.uk
  • Tel: 0131 650 9140
  • Research group website: Edinburgh Glaciology and Cryosphere

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Research

Modelling fjord circulation

I am presently employed at the University of Edinburgh as a PDRA on the three-year NERC funded project Investigating controls on flow variabiility in Greenland's tidewater glaciers: the impact of runoff on fjord circulation and termini melt rates. In this role, my work is centred on the use of a numerical general circulation model, MITgcm, to examine and quantify the processes controlling the delivery of oceanic heat to Greenland's marine-terminating outlet glaciers.

Many of Greenland's marine-terminating outlet glaciers have undergone a dramatic retreat since the late 1990s, far exceeding the rate of change observed at neighbouring land-terminating glaciers. This contrast in behaviour between marine and land terminating glaciers indicates that the recent warming of ocean waters around Greenland may be a key factor driving the loss of mass from the ice sheet. However, the extent to which oceanic warming is experienced by the glaciers, which are typically separated from the open ocean by lengthy fjords, remains unclear.

The runoff of meltwater from the glaciers may be important for stimulating circulation of the fjords, drawing in warm water from the ocean. To investigate this, I have modified MITgcm to allow the input of glacial runoff to be incorporated in simulations of fjord circulation. I am now in the process of using this capability to assess how runoff affects the heat transport from the ocean to Greenland's marine terminating glaciers.

Hydrology and dynamics of the Greenland Ice Sheet

In 2013, I completed my PhD at the University of Edinburgh on The hydrology of a land-terminating Greenlandic outlet glacier. This work was undertaken as part of a larger NERC funded investigation into the influence of meltwater runoff on the dynamics of the Greenland Ice Sheet.

Meltwater forming on the surface of the ice sheet during the summer months is able to penetrate to the ice sheet bed, where it then influences the sliding motion of the overlying ice. If the greater volumes of meltwater produced in warmer summers result in the ice sheet sliding faster, then this could lead to the ice sheet wasting more rapidly as the climate warms.

To investigate this hypothesis, we undertook several lengthy field campaigns to obtain high resolution observations of the hydrology and dynamics of Leverett Glacier, a land-terminating outlet glacier on the western margin of the Greenland Ice Sheet. One of my main roles was to use tracing experiments to determine the form of the subglacial drainage pathways, work which provided the first direct evidence of efficient subglacial drainage channels beneath the Greenland Ice Sheet. Following this, I undertook hydrological modelling experiments to examine the relationship between meltwater runoff, subglacial water pressure and recorded ice motion, concluding that the largest fluctuations in ice motion occurred due to the expansion of water filled cavities at the bed at times when meltwater runoff was increasing.

As a whole, our findings indicate that while the input of meltwater increases average ice velocities during the summer months, this is offset by a subsequent decrease in ice velocity during the autumn and early winter, resulting in little net variation in ice motion from one year to the next.

Glacial erosion and geomorphology

As part of our investigation into the hydrology of Leverett Glacier, we collected several years of sediment flux data from the proglacial driver. This provided a unique opportunity to assess the erosive power of Greenland's outlet glaciers. The calculated erosion rates indicate that Greenland's outlet glaciers are capable of eroding their bed 1-2 orders of magnitude faster than was widely assumed, allowing new insight into the rapid rate at which ice sheets are capable of modifying the landscape.

My first publication was also focussed on glacial geomorphology, using relic landforms and sediments to reconstruct a former ice cap in the Sanabria mountains in of northwest Spain. This proved to be one of the largest relic ice caps south of the Pyrenees, and has subsequently attracted attention from those investigating the climate of this region during the Last Glacial Maximum.

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Publications

  • Cowton, T, D Slater, A Sole, D Goldberg, P Nienow (2015), Modeling the impact of glacial runoff on fjord circulation and submarine melt rate using a new parameterization for glacial plumes. Journal of Geophysical Research: Oceans, v. 120, p. 796-812
  • Slater, D, P Nienow, T Cowton, D Golderg, A Sole (2015), Effect of near terminus subglacial hydrology on tidewater glacier submarine melt rates. Geophysical Research Letters, 42(8), p2861-2868
  • Hawkings, J, J Wadham, M Tranter, E Lawson, A Sole, T Cowton, A Tedstone, I Bartholomew, P Nienow and D Chandler (2015), The effect of warming climate on nutrient and solute export from the Greenland Ice Sheet. Geochemical Perspectives Letters, v.1, p. 94-10
  • Cowton, T, P Nienow, A Sole, J Wadham, G Lis, I Bartholomew, D Mair, D Chandler (2013), Evolution of drainage system morphology at a land-terminating Greenlandic outlet glacier. Journal of Geophysical Research (Earth Surface), v. 118.
  • Chandler, D, J Wadham, G Lis, T Cowton, A Sole, I Bartholomew, J Telling, P Nienow, E Bagshaw, D Mair, S Vinen and A Hubbard (2013), Evolution of the subglacial drainage system beneath the Greenland Ice Sheet revealed by tracers. Nature Geoscience.
  • Sole, A, P Nienow, I Bartholomew, D Mair, T Cowton, A Tedstone and M King (2013), Winter motion mediates dynamic response of the Greenland Ice Sheet to warmer summers. Geophysical Research Letters, v. 40, p. 1-5
  • Tedstone, A, P Nienow, A Sole, D Mair, T Cowton, I Bartholomew, M King (2013), Greenland Ice Sheet motion insensitive to exceptional meltwater forcing. Proceedings of the National Academy of Sciences, v. 110, p. 19719-19724
  • Bartholomew, I, P Nienow, A Sole, D Mair, T Cowton, M King (2012), Short-term variability in Greenland Ice Sheet motion forced by time-varying meltwater drainage: Implications for the relationship between subglacial drainage system behavior and ice velocity. Journal of Geophysical Research (Earth Surface), v. 117, F03002.
  • Cowton, T, P Nienow, I Bartholomew, A Sole, D Mair (2012), Rapid erosion beneath the Greenland ice sheet. Geology, v. 40, p. 343-346
  • Bartholomew, I, P Nienow, A Sole, D Mair, T Cowton, M King (2011), Seasonal variation in Greenland Ice Sheet motion: inland extent and behaviour at higher elevations. Earth and Planetary Science Letters, v. 307, p. 271-278.
  • Bartholomew, I, P Nienow, A Sole, D Mair, T Cowton, S Palmer and J Wadham (2011), Supraglacial forcing of subglacial drainage in the ablation zone of the Greenland ice sheet. Geophysical Research Letters, v. 38, p. L08502.
  • Cowton, T, P Hughes, P Gibbard (2009), Palaeoglaciation of Parque Natural Lago de Sanabria, northwest Spain. Geomorphology 108 p. 282-291.

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