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

摘要

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 km~2 (±1σ), with maximum melt-lake area increasing at an average rate of 0.032 km~2 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±20m (±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℃ 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.