Spatial and temporal variations in lakes on the Greenland Ice Sheet

Johansson, A. Malin; Jansson, Peter; Brown, Ian A.

doi:10.1016/j.jhydrol.2012.10.045

Cited by 30 publications

(35 citation statements)

References 33 publications

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“…Our results and work by others [ Johansson et al , ] show that at low elevations (below ~1300 m; Figures a–d), lakes are typically empty by the end of the melt season, draining either rapidly through hydrofractures [ Krawczynski et al , ] or more slowly through short (local) overflow streams. By contrast, higher‐elevation lakes tend to drain incompletely (Figures e and f) through long overflow streams that carry the melt to distant (nonlocal) moulins (Figure a and Figure S1 in the supporting information) [ Johansson et al , ].…”

Section: Discussionmentioning

confidence: 99%

“…These cracks can either (a) initiate directly beneath the lake water within the basin or (b) exist outside the basin. In the former case, it is sometimes assumed that when a certain energy threshold or melt volume is reached, a lake can self‐generate the crack necessary for drainage [ Georgiou et al , ; Johansson et al , ]. However, whether lakes drain is not well correlated to their volume [ Fitzpatrick et al , ], implying that some other drainage initiation mechanism is required [ Selmes et al , ].…”

Section: Variation Of Strain Rate With Elevationmentioning

confidence: 99%

See 1 more Smart Citation

Limits to future expansion of surface‐melt‐enhanced ice flow into the interior of western Greenland

Poinar

Joughin

Das

et al. 2015

Geophysical Research Letters

176

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Moulins are important conduits for surface meltwater to reach the bed of the Greenland Ice Sheet. It has been proposed that in a warming climate, newly formed moulins associated with the inland migration of supraglacial lakes could introduce surface melt to new regions of the bed, introducing or enhancing sliding there. By examining surface strain rates, we found that the upper limit to where crevasses, and therefore moulins, are likely to form is ~1600 m. This is also roughly the elevation above which lakes do not drain completely. Thus, meltwater above this elevation will largely flow tens of kilometers through surface streams into existing moulins downstream. Furthermore, results from a thermal ice sheet model indicate that the ~1600 m crevassing limit is well below the wet‐frozen basal transition (~2000 m). Together, these data sets suggest that new supraglacial lakes will have a limited effect on the inland expansion of melt‐induced seasonal acceleration.

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Section: Discussionmentioning

confidence: 99%

Section: Variation Of Strain Rate With Elevationmentioning

confidence: 99%

Limits to future expansion of surface‐melt‐enhanced ice flow into the interior of western Greenland

Poinar

Joughin

Das

et al. 2015

Geophysical Research Letters

176

View full text Add to dashboard Cite

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“…In the Landsat imagery, freeze-through was detected manually for each lake when it appeared optically similar to the surrounding ice surface (cf. Johansson et al, 2013;Selmes et al, 2013;Luckman et al, 2014). If a lake had not frozen at the end of the available imagery, a freeze-through date was not recorded.…”

Section: Lake Freeze-throughmentioning

confidence: 99%

Toward Monitoring Surface and Subsurface Lakes on the Greenland Ice Sheet Using Sentinel-1 SAR and Landsat-8 OLI Imagery

et al. 2017

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Supraglacial lakes are an important component of the Greenland Ice Sheet's mass balance and hydrology, with their drainage affecting ice dynamics. This study uses imagery from the recently launched Sentinel-1A Synthetic Aperture Radar (SAR) satellite to investigate supraglacial lakes in West Greenland. A semi-automated algorithm is developed to detect surface lakes from Sentinel-1 images during the 2015 summer. A combined Landsat-8 and Sentinel-1 dataset, which has a comparable temporal resolution to MODIS (3 days vs. daily) but a higher spatial resolution (25-40 vs. 250-500 m), is then used together with a fully automated lake drainage detection algorithm. Rapid (<4 days) and slow (>4 days) drainages are investigated for both small (<0.125 km 2 , the minimum size detectable by MODIS) and large (≥0.125 km 2 ) lakes through the summer. Drainage events of small lakes occur at lower elevations (mean 159 m), and slightly earlier (mean 4.5 days) in the melt season than those of large lakes. The analysis is extended manually into the early winter to calculate the dates and elevations of lake freeze-through more precisely than is possible with optical imagery (mean 30 August; 1,270 m mean elevation). Finally, the Sentinel-1 imagery is used to detect subsurface lakes and, for the first time, their dates of appearance and freeze-through (mean 9 August and 7 October, respectively). These subsurface lakes occur at higher elevations than the surface lakes detected in this study (mean 1,593 and 1,185 m, respectively). Sentinel-1 imagery therefore provides great potential for tracking melting, water movement and freezing within both the firn zone and ablation area of the Greenland Ice Sheet.

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“…Scenes covering the entire melt season were obtained from 2002 to 2012 from day of year (DOY) 121 (1 May) to DOY 274 (30 September). Previous studies classified supraglacial lakes in MODIS imagery using manual digitisation (McMillan et al, 2007;Lampkin and Vanderberg, 2011), band thresholds (Box and Ski, 2007;Liang et al, 2012), and object-orientated approaches (Sundal et al, 2009;Johansson et al, 2013). Here, we opted for a semi-automatic strategy to classify SGL extents, using a modified normalized difference water index (NDWI) (Huggel et al, 2002;Yang and Smith, 2013, Eq.…”

Section: Calculating Lake Extentmentioning

confidence: 99%

A decade (2002–2012) of supraglacial lake volume estimates across Russell Glacier, West Greenland

et al. 2014

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Abstract. Supraglacial lakes represent an ephemeral storage buffer for meltwater runoff and lead to significant, yet shortlived, episodes of ice-flow acceleration by decanting large meltwater and energy fluxes into the ice sheet's hydrological system. Here, a methodology for calculating lake volume is used to quantify storage and drainage across Russell Glacier, West Greenland, between 2002 and 2012. Using 502 MODIS scenes, water volume at ∼ 200 seasonally occurring lakes was derived using a depth-reflectance relationship, which was independently calibrated and field validated against lake bathymetry. The inland expansion of lakes is strongly correlated with air temperature: during the record melt years of 2010 and 2012, lakes formed and drained earlier, attaining their maximum volume 38 and 20 days earlier than the 11 yr mean, as well as occupying a greater area and forming at higher elevations (> 1800 m) than previously. Despite occupying under 2 % of the study area, lakes delay the transmission of up to 7-13 % of the bulk meltwater discharged. Although the results are subject to an observational bias caused by periods of cloud cover, we estimate that across Russell Glacier, 28 % of supraglacial lakes drain rapidly (< 4 days). Clustering of such events in space and time suggests a synoptic trigger mechanism. Further, we find no evidence to support a unifying critical size or depth-dependent drainage threshold.

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Spatial and temporal variations in lakes on the Greenland Ice Sheet

Cited by 30 publications

References 33 publications

Limits to future expansion of surface‐melt‐enhanced ice flow into the interior of western Greenland

Limits to future expansion of surface‐melt‐enhanced ice flow into the interior of western Greenland

Toward Monitoring Surface and Subsurface Lakes on the Greenland Ice Sheet Using Sentinel-1 SAR and Landsat-8 OLI Imagery

A decade (2002–2012) of supraglacial lake volume estimates across Russell Glacier, West Greenland

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