VEGETATION GROWTH AND SNOW RETREAT IN SOUTHERN GREENLAND OBSERVED WITH LANDSAT SATELLITE IMAGES FROM THE PAST 15 YEARS

Landsat 8 orbits earth collecting scenes every 16 days to monitor environmental changes. These environmental changes are particularly evident when reviewing images from Greenland over the past two decades, both in regards to growth of vegetation and retreat of ice. Scenes of Greenland, collected by the 11 bands that compose Landsat 8, range from February 2013 to the present. Landsat 7 has been collecting data since April 1999 to the present. Landsat 5 adds limited imagery starting in 1992. Failure of the Scan Line Corrector (SLC) on Landsat 7 in 2003 lowers the quality of the images, but does not interfere with NDVI (normalized difference vegetation index) and NDSI (normalized difference snow index) statistics. In addition, the high latitude provides coverage with two looks in every 16 day cycle, improving the odds of cloud free coverage and allowing duplicate computation of statistics. Vegetation growth and snow/ice retreat were detected using normalized difference indexes. These indexes show contrast in the images, differentiating between vegetation and ice, and snow, rock, and soil. When comparing images from the early 1990’s to the present, a noticeable change in ice coverage is evident in southern Greenland, between latitudes 60N to 62N and longitudes 44W to 48W, near Qaqortoq. Concurrently, vegetation growth increased over time, especially on the southernmost coast. A total of ten scenes, ranging from May to late September, 1999-2014, were collected and analyzed in detail. These months were chosen due to the lack of shadows interfering with the landscape images and the consistency of ice, regardless of the severity of the previous winter, from one month in one year to that month in a latter year. The highest NDVI and NDSI values were computed and compared. The NDVI values were consistently lower in the earlier images, and far greater in the later images. The NDSI values were lower in the later images and greater in the earlier ones. Finally, we can trace the loss of ice cover with the retreat of the glacier termini.