Generating a supraglacial melt-lake inventory near Jakobshavn, West Greenland, using a new semi-automated lake-mapping technique

ABSTRACT We analyze Landsat-7 imagery spanning a 13-year period (2000–2012) for the Jakobshavn Ablation Region (JAR) along the west coast of Greenland. In addition, we introduce a new semi-automated technique for the mapping of melt-lakes using FoveaPro image-processing software (plug-in to Adobe Photoshop™), greatly simplifying the process, and resulting in more-precise spatial melt-lake statistics over existing manual methods. We found a total mean melt-lake area of 0.30 ± 0.12 km2 (±1σ), with maximum melt-lake area increasing at an average rate of 0.032 km2 d−1 across the study periods. Additionally, we note a yearly seasonal increase (∼1.8 m d−1) in the overall mean lake elevation (∼200 m per season) as well as an optimal elevation of the largest-area melt-lakes of ∼1320 ± 20 m (±1σ). We also found an increase in the maximum average melt-lake elevation (MAME) of ∼3.8 m a−1 (∼50 m). Based on data recorded at nearby automated weather stations, the mean seasonal temperature increased ∼1.6°C over the 13-year period at an average rate of 0.125°C a−1. Although temperature is a driver for meltwater production, we conclude that mechanisms related to the surface topography are more likely modulating the spatial pattern and characteristics of melt lakes in the ablation zone.