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Surface and Basal Hydrology of the Greenland Ice Sheet

Surface and Basal Hydrology of the Greenland Ice Sheet

The Greenland Ice Sheet is now the main cryospheric contributor to global sea level change, with its contribution rising from 0.6 mm per year in 2000-2010, to over 1mm per year since 2010. This change has been driven partly by accelerating melt, but also by dynamic changes within the ice sheet, with accelerating ice flow delivering more ice from the interiors to the melting or calving margins. Ice sheet hydrology, both surface and at the bed, has been strongly implicated as one of the drivers of these changes.

Ongoing research at the Scott Polar Research Institute is investigating the behaviour of the supraglacial lakes which form every summer on the ice sheet, some of which drain rapidly to the bed, injecting very large volumes of water into the ice sheet which cause the ice to accelerate. This research has been based around the ongoing development of numerical models of supraglacial hydrology, including slow and fast lake drainage and water drainage into crevasses and moulins, linking the output of this model to an advanced model of basal hydrology, and most recently, to a higher-order ice flow model in order to investigate the possible impact of lake drainage events on ice flow.

We are also developing novel ways of using high temporal resolution satellite data to track lake evolution throughout summer melt seasons across large areas of the ice sheet, and of using newly available date from other satellite sensors, such as the new European Sentinel satellites, to investigate both water storage in lakes, and within the surface snowpack and firn layers.

Publications

Papers stemming from this project so far:

  • Miles, K., Willis, I., Benedek, C., Williamson, A. and Tedesco, M. 2017. Towards monitoring surface and subsurface lakes on the Greenland Ice Sheet using Sentinel-1 SAR and Landsat-8 OLI imagery. Frontiers in Earth Science - Cryospheric Sciences. doi: 10.3389/feart.2017.00058
  • Williamson, A.G., Arnold, N.S., Banwell, A.F. and Willis, I.C. In Review. A Fully Automated Supraglacial lake area and volume Tracking (FAST) algorithm: development and application using MODIS imagery of West Greenland. Remote Sensing of Environment. doi:10.1016/j.rse.2017.04.032.
  • Kozoil, C., Arnold, N., Pope, A., and Colgan, W. 2017. Quantifying supraglacial meltwater pathways in the Paakitsoq region, West Greenland. Journal of Glaciology. doi:10.1017/jog.2017.5.
  • Banwell, A., Hewitt, I., Willis, I. and Arnold, N., 2016. Moulin density controls drainage development beneath the Greenland ice sheet. Journal of Geophysical Research: Earth Surface, v. 121, p.2248-2269. doi:10.1002/2015JF003801.
  • Arnold, N.S., Banwell, A.F. and Willis, I.C., 2014. High-resolution modelling of the seasonal evolution of surface water storage on the Greenland Ice Sheet. Cryosphere, v. 8, p.1149-1160. doi:10.5194/tc-8-1149-2014.
  • Banwell, A.F., Caballero, M., Arnold, N.S., Glasser, N.F., Cathles, L.M. and MacAyeal, D.R., 2014. Supraglacial lakes on the Larsen B ice shelf, Antarctica, and at Paakitsoq, West Greenland: A comparative study. Annals of Glaciology, v. 55, p.1-8. doi:10.3189/2014AoG66A049.
  • Mayaud, J.R., Banwell, A.F., Arnold, N.S. and Willis, I.C., 2014. Modeling the response of subglacial drainage at Paakitsoq, west Greenland, to 21st century climate change. Journal of Geophysical Research F: Earth Surface, v. 119, p.2619-2634. doi:10.1002/2014JF003271.
  • Banwell, A.F., Willis, I.C. and Arnold, N.S., 2013. Modeling subglacial water routing at Paakitsoq, W Greenland. Journal of Geophysical Research: Earth Surface, v. 118, p.n/a-n/a. doi:10.1002/jgrf.20093.
  • Tedesco, M., Willis, I.C., Hoffman, M.J., Banwell, A.F., Alexander, P. and Arnold, N.S., 2013. Ice dynamic response to two modes of surface lake drainage on the Greenland ice sheet. Environmental Research Letters, v. 8, p.034007-034007. doi:10.1088/1748-9326/8/3/034007.
  • Banwell, A.F., Arnold, N.S., Willis, I.C., Tedesco, M. and Ahlstrom, A.P., 2012. Modelling surface routing and lake filling on the Greenland Ice Sheet. Journal of Geophysical Research-Earth Surface, v. 117, p.n/a-n/a. doi:10.1029/2012JF002393.
  • Banwell, A.F., Willis, I.C., Arnold, N.S., Messerli, A., Rye, C.J., Tedesco, M. and Ahlstrøm, A.P., 2012. Calibration and evaluation of a high resolution surface mass balance model for Paakitsoq, west Greenland. Journal of Glaciology, v. 58, p.1047-1062. doi:10.3189/2012JoG12J034.
  • Tedesco, M., Lthje, M., Steffen, K., Steiner, N., Fettweis, X., Willis, I., Bayou, N. and Banwell, A., 2012. Measurement and modeling of ablation of the bottom of supraglacial lakes in western Greenland. Geophysical Research Letters, v. 39, doi:10.1029/2011GL049882.

Figure

A lake on the surface of the Greenland Ice Sheet. The network of streams feeding water into the lake can be seen in the foreground, and the overflow stream can be seen in the background, together with several other lakes. Photo: Ian Willis.

Figure

The Paakitsoq region of W. Greenland. The detailed map shows a satellite image of the area, taken on 7 July 2002. Lakes on the ice surface area are clearly visible as blue patches, and the ice-free topography in front of the ice sheet margin can also be seen to the left. Contour lines for surface elevation are shown in blue, and the outline of depressions on the ice surface which could potentially fill with water as identified by our model are shown in red. Note that at high elevations, the depressions do not fill with water to form lakes as insufficient melt occurs. The presence of depressions in these areas suggests that lakes could form at higher elevations under possible warmer climate conditions in the future, however. From Arnold et al, 2014.

Figure

Model results showing predicted lake drainage events by date. The results clearly show that lakes higher on the ice sheet drain later in the summer, as they fill more slowly due to the colder temperatures and consequent lower melt rates at high elevations. From Arnold et al, 2014.

Figure

Bar chart showing partitioning of water into different drainage pathways (crevasses, moulins and via lake hydrofracture and the subsequent drainage) at different distance bands from the study site margin. The three charts correspond to each of the melt season intensities tested: (a) average melt year (2011), (b) elevated melt year (2011), (c) extreme melt year (2012). Black line in middle plot shows width-averaged elevation profile of the study area. Crevasses and moulins form the main method for surface water drainage near to the snout of the ice sheet, but drainage via lake hydrofracture and the subsequent inflow of water after the hydrofracture event itself become increasingly important at mid to high elevations. From Koziol et al, 2017.

Figure

Model results for a marginal catchment of the Paakitsoq region showing daily mean width-integrated subglacial water discharge (m2 s-1) (1st & 3rd columns) and daily mean water pressure / ice overburden pressure (Pw/Pi) (2nd & 4th columns) on a sequence of days through the 2005 melt season across the subglacial domain for a low moulin density scenario (columns 1 and 2) and a high moulin density scenario (columns 3 and 4). The solid black dots indicate moulins that are closed and do not input water and the open black circles indicate moulins that are open (i.e., those that are inputting water), with their size proportional to the surface water discharge entering the moulin. In the left columns, the intensity of blue shading represents the subglacial discharge, and the red contour lines indicate hydraulic equipotential. In the right columns, the intensity of red shows Pw/Pi, with Pw/Pi = 0 indicative of water at atmospheric pressure, and Pw/Pi = 1 indicative of water at ice overburden pressure. The number and location of moulins that deliver surface water to the base of the ice sheet affects the way in which the subglacial drainage system evolves through the summer with implications for subglacial water pressures (and therefore basal sliding). From Banwell et al, 2016.