| Summary: | Based on drainage divides, we have identified eight separate glaciers that feed Nuup Kangerlua (Godsthåbfjord): three are marine-terminating and five land-terminating. To assess the amount of ice lost from these glaciers during recent decades, we analyzed 1985 aerial photos acquired by the Danish National Survey and Cadastre (KMS) and derived a high-quality 25 m grid digital elevation model (DEM). We also obtained a 2008 40 m grid SPOT DEM covering the same region. Comparison of the two DEMs over glacier areas is limited by the boundary of the 1985 DEM: ground control was only available for adjacent land areas, limiting its coverage of inland ice. Comparison of the two DEMs over the contiguous area of overlap (1800 km2) revealed a total volume loss over the 23 year period of 31.5 km3, equivalent to an average specific mass balance of –0.8 m a–1. Although each glacier lost ice, one glacier in particular, Kangiata Nunaata Sermia (KNS), accounted for 45% of total ice loss. KNS is a tidewater glacier at the head of Nuup Kangerlua and has retreated 22 km from its Little Ice Age (LIA) maximum, with post-LIA drawdown of 550 m at its present terminus. In contrast, the terminus of upfjord tidewater glacier Narsap Sermia (NS) has remained relatively stable at its LIA extent until quite recently. Comparison of Laser Vegetation Imaging Sensor (LVIS) data (flown May 2011) to the 2008 DEM indicates that KNS continues to thin at rates of 1–5 m a–1 below 800 m, but has been stable at higher elevations. The calving retreat of NS began in 2000 and accelerated after 2009: LVIS data indicate a drawdown of over 80 m in the NS terminus region since 2008 and Landsat images show a retreat of about 0.5 km.
|
|---|