Jacqueline Otto, Nina Kirchner
The annual distribution of supraglacial lakes on Ryder Glacier, Northern Greenland, was mapped for the peak of each year´s melt season (July and August) over the time period 1985 – 2020. Additionally, the mapped supraglacial lakes were classified according to their cessation mode over the course of the melt season.
The dataset consists of shapefiles for all studied years, each shapefile representing the annual lake mask consisting of all identified and delineated lakes of that year´s peak of the melt season. The years 1986, 1996, 2001, 2003 were excluded due to limited availability of required satellite imagery.
Supraglacial lakes are hydrological features that form on the ice surface when meltwater accumulates in surface depressions and numerously populate the margins of the Greenland Ice Sheet during every melt season. The dataset was developed for an analysis with two main objectives: (1) to identify possible trends of lake expansion over the most recent decades as a consequence of our currently warming climate, (2) to investigate if the drainage behavior and frequency have changed over the studied time period.
Download data
Citation
Jacqueline Otto, Nina Kirchner (2022) Annual distribution and behavior of supraglacial lakes on Ryder Glacier, Northern Greenland, 1985 – 2020. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/otto-2022-supraglacial-lakes-1
References
Otto J, Holmes FA, Kirchner N (2022) Supraglacial lake expansion, intensified lake drainage frequency, and first observation of coupled lake drainage, during 1985–2020 at Ryder Glacier, Northern Greenland. Frontiers in Earth Science 10:978137. https://doi.org/10.3389/feart.2022.978137
Morlighem M. et al. (2021, updated 2021). IceBridge BedMachine Greenland, Version 4. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. [Date Accessed: 2021-12-15]. https://doi.org/10.5067/VLJ5YXKCNGXO
Morlighem M. et al. (2017) BedMachine v3: Complete bed topography and ocean bathymetry mapping of Greenland from multi-beam echo sounding combined with mass conservation. Geophysical Research Letters. 44:11051 – 11061. https://doi.org/10.1002/2017GL074954
Data description
The dataset includes 32 lake drainage mode shapefiles (DrainageModeYEAR.shp), one file for each of the studied years between 1985 – 2020. Each shapefile represents the annual lake mask consisting of all identified and delineated lakes of that year´s peak of the melt season (July and August). The years 1986, 1996, 2001, 2003 were excluded from the analysis due to limited availability of required satellite imagery.
An annual lake mask was created by first applying the Normalized Difference Water Index (NDWI) with a threshold ranging between 0.15 – 0.5 to all available largely cloud-free Landsat satellite images for July and August, by this differentiating between (non)water-covered pixels representing lake surfaces, and then combining all resulting NDWI layers to one single annual lake mask. All lake features that were then delineated from the annual lake mask present the maximum lake extent of each identified lake during that melt season.
The attribute table of each shapefile contains the following information about the individual delineated lakes:
Lake area - the lake area in km², which was calculated according to the number and size of the image pixels identified as lake surface.
Drainage Mode - the classified mode of lake drainage/cessation over the course of the melt season. The classification is based on chronologically investigating satellite imagery from the onset to the end of the melt season (May – September). An attached xlsx spreadsheet file describes the classification key and all applied categories in detail.
Additionally, a shapefile of the study area extent for the here presented lake analyses is included in the dataset (RyderAOI.shp). Lake analysis was performed for the area of grounded ice, excluding the floating tongue of Ryder Glacier.
Each .shp file is accompanied by its associated complementary files defining additional formatting (.shx, .dbf, .prj etc.).