Abstract
Abstract. We present a new method of modelling the growth of supraglacial lakes at the western margin of the Greenland ice sheet, based on routing runoff estimated by a regional climate model across a digital elevation model (DEM) of the ice sheet surface. Using data acquired during the 2003 melt season, we demonstrate that the model is 19 times more likely to correctly predict the presence (or absence) of lakes than it is to make incorrect predictions, within an elevation range of 1100 to 1700 metres above sea level (m a.s.l.), when compared with MODIS satellite imagery. Of the 66% of observed lake locations which the model correctly reproduces, the simulated lake onset day is found to be correlated with that observed with a Pearson correlation coefficient of 0.76. Our model accurately simulates maximum cumulative lake area with only a 1.5% overestimate. However, because our model does not simulate processes leading to lake stagnation or decay, such as refreezing or drainage, at present we do not simulate absolute daily lake area. We find that the maximum potential lake-covered ice sheet area is limited by topography to 6.4%. We estimate that this corresponds to a volume of 1.49 km3, 12% of the runoff produced in 2003. This can be taken as an upper bound given uncertainty in the DEM. This study has proved a good first step towards capturing the variability of supraglacial lake evolution with a numerical model. These initial results are promising and suggest that the model is a useful tool for use in analysing the behaviour of supraglacial lakes on the Greenland ice sheet in the present day and potentially beyond.
Highlights
Supraglacial lakes (SGLs) have been observed to form during the summer melt season across much of the ablation zone of the Greenland ice sheet (GrIS) (McMillan et al, 2007; Sundal et al, 2009; Sneed and Hamilton, 2007; Selmes et al, 2011). Observations show that they form in the same locations each year (Echelmeyer et al, 1991), in depressions that are controlled by the underlying bedrock topography and by spatial variations in the degree of basal ice lubrication (Gudmundsson, 2003)
We assess the skill of the model in predicting lake location on a lake-by-lake and on a cell-wise basis across our study area
There are simulated and observed lakes that are in close proximity, but that are not coincident
Summary
Supraglacial lakes (SGLs) have been observed to form during the summer melt season across much of the ablation zone of the Greenland ice sheet (GrIS) (McMillan et al, 2007; Sundal et al, 2009; Sneed and Hamilton, 2007; Selmes et al, 2011). Supraglacial lakes impact upon the mass balance of the ice sheet in several different ways; melt ponds have been shown to reduce the albedo of large areas of ice (Perovich et al, 2002), thereby promoting additional melting. They are temporary water storage sites, which can modify the rate at which runoff leaves the ice sheet.
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