The role of melt water on glacier behaviour

Prof Jane K. Hart jhart@soton.ac.uk, Prof Jadu Dash j.dash@soton.ac.uk
Rationale: 

The subglacial hydrological system modulates ice dynamics and is a vital component in understanding how glaciers respond to climate change and its corresponding impact on global sea level [1]. In particular, the ice streams of Antarctica (which rest on unconsolidated beds) are predicted to rapidly retreat in the immediate future. Rising temperatures will lead to increased surface melting of the glacier, and there are currently two contrasting models predicting the response of glaciers to this melt increase. The first argues that increased melt will cause more water to flow to the glacier bed, which promotes basal sliding, more crevassing, and allows the glacier to flow faster. This brings more ice into the lower altitudes, which in turn promotes more melting. In contrast, the second model postulates that the glacier can accommodate the increase in meltwater and so additional surface melt water has little effect [3]. In Greenland it has been suggested that early in the summer the glacier speeds up with increased melt, but during later summer the extra melt is accommodated, however it is not clear whether this leads to velocity increases over an annual timescale; nor whether this model is universally applicable. Advances in remote sensing (both increases in spatial and temporal resolution) now allow these models to be tested.

These contrasting models will be tested in Iceland (which is a smaller scale analogue for the Antarctica ice streams, as the glaciers are also resting on unconsolidated bed). These will be tested by using a variety of techniques including the use of ‘Planet Lab’ images to carry out offset (or intensity) tracking, a well-established method for deriving displacements from repeat imagery to calculate velocity, estimate lake depth changes, and ice marginal geomorphological changes throughout the season.

 

Methodology: 

There will be number of techniques used to investigate changes in glacier behavior throughout the year: 1) 3 hourly data sent back via a smart dGPS tracker installed on the glacier; 2) Daily Planet optical imagery and Sentinel 1 and 2 imagery will be used to assess short-term changes in glacier velocity. We will also assess changes in the surface elevation of the glaciers and compute geodetic mass balances. This will be done by comparing multi-temporal DEMs, both pre-processed (such as the Arctic DEM, and the national LiDAR DEMs of Iceland); 3) use Planet optical imagery to track relative discharge changes (via lake area measurements) and changes in marginal position related to extreme weather (very hot and/or high rain fall events) during both summer and winter. We can also examine older imagery for longer term changes.

 

Location: 
University of Southampton
Training: 

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the School of Geography and Environmental Science. Specific training will include: glaciology, landscape change, remote sensing.

 

Eligibility & Funding Details: 

Please check https://inspire-dtp.ac.uk/how-apply for details.  

 

Background Reading: 
  1. Hart, J.K., Martinez, K., Basford, P.J., Clayton, A.I., Robson, B.A. and Young, D.S., 2019. Surface melt driven summer diurnal and winter multi-day stick-slip motion and till sedimentology. Nature communications, 10(1), p.1599.
  2. Zwally, H.J., Abdalati, W., Herring, T., Larson, K., Saba, J. and Steffen, K., 2002. Surface melt-induced acceleration of Greenland ice-sheet flow. Science, 297(5579), pp.218-222.
  3. Sundal, A.V., Shepherd, A., Nienow, P., Hanna, E., Palmer, S. and Huybrechts, P., 2011. Melt-induced speed-up of Greenland ice sheet offset by efficient subglacial drainage. Nature, 469(7331), p.521.

 

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