Ice-margin change (advance/recession) at the terrestrial, lacustrine and marine margins of the south-western sector of the Greenland Ice Sheet between 1987 and 2015
A dataset of ice-margin change (advance/recession) at the south-western sector of the Greenland Ice Sheet, comprising data from 3325 terrestrial, 439 lacustrine and 35 marine ice-margins respectively. The dataset also comprises measures of ice-marginal lake parameters including area and intersect (l...
| Main Authors: | , , , |
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| Format: | Dataset |
| Language: | English |
| Published: |
NERC EDS UK Polar Data Centre
2021
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| Subjects: | |
| Online Access: | https://dx.doi.org/10.5285/ebfbbe88-902b-4c74-9b62-07101d89e509 https://data.bas.ac.uk/full-record.php?id=GB/NERC/BAS/PDC/01498 |
| Summary: | A dataset of ice-margin change (advance/recession) at the south-western sector of the Greenland Ice Sheet, comprising data from 3325 terrestrial, 439 lacustrine and 35 marine ice-margins respectively. The dataset also comprises measures of ice-marginal lake parameters including area and intersect (length of the lake - ice-margin interface). Measurements were made at approximately five year intervals (epochs) from 1987 to 2015. The ice sheet margin and adjacent ice-marginal lakes were delineated by applying the Normalised Difference Snow Index (NDSI) and the Normalised Difference Water Index (NDWI) respectively to Landsat TM, ETM+ and OLI scenes. Ice-margin changes were measured relative to a series of fixed reference points. The dataset was generated to facilitate comparison of changes at the disparate ice-marginal environments of the ice sheet and investigate temporal patterns of ice-margin recession. The dataset was created and processed by researchers in the School of Geography at the University of Leeds and the Institute of Integrative Biology at the University of Liverpool. : Measurements of ice-margin change were recorded by applying the Normalised Difference Snow Index (NDSI) to the Landsat TM, ETM+ and OLI archive to delineate the ice sheet margin and measure changes relative to a series of fixed reference points at approximately 5-year intervals (epochs) between 1987 and 2015. Rates of ice-margin advance or recession were calculated by differencing the mean distance values between the fixed reference points and the ice-margin in successive epochs, and subsequently dividing by the interval duration. Note that positive and negative values of mean ice-margin change and mean annual change represent ice-margin advance and recession respectively. Lake areas and intersects (length of the lake - ice-margin interface) were also derived at the same 5-year intervals by applying the Normalised Difference Water Index (NDWI) to the same Landsat scenes. The lake persistence parameter provides a quantitative measure of the presence of a lake in each of the respective epochs. The latitudes and altitudes of the fixed reference points were extracted from a 1985 DEM of the region. Full details of the satellite scenes used and the associated processing and data extraction in ENVI and ArcMap can be found in the publication listed below under References. : Scenes from the Landsat TM, ETM+ and OLI sensors were processed in ENVI v.5.2 and Esri ArcMap v.10.3.1. : The delineation of ice-margin and lake extent is assumed to be accurate to within ±1 pixel (30 m) of the true ice-margin/lake perimeter. Given the regional aggregation of measurements, it is assumed that any over-estimation of the ice-margin position is cancelled out by an equal and opposite under-estimation, and uncertainty in the ice-margin positions is therefore not specifically assessed for these bulk figures. In addition, the absolute error associated with each lake area measurement was dependent on lake size and planform, and thus resulted in a declining power law relationship whereby the greatest errors were associated with the smallest lakes. For example, lakes measuring 0.5 km2 had an area uncertainty of ~9 %, whilst lakes measuring > 5 km2 had an uncertainty of < 3 %. Rates of change at lacustrine margins were only generated when a lake was present in two or more successive epochs. Measurements of ice-margin change between 1987 and 1992 at the southernmost latitudes of the survey area are absent due to the unavailability of Landsat TM scenes for this region in the years 1985-1988. |
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