MONITORING MENDENHALL GLACIER MASS LOSS AND RETREAT AND SUBSEQUENT MENDENHALL LAKE EXPANSION USING GEOINFORMATICS

The Mendenhall Glacier retreat and subsequent Mendenhall Lake expansion are indicators of local climate change in Juneau, Alaska. On-going monitoring of climate change effects includes glacial mass balance, terminus position, lake size, and real-time weather and photographs of the glacier. The Mendenhall Glacier lost an average of 1.44 ma^-1 water equivalent from 2001-2007. Mass balance was measured two ways: 1) in-situ via ablation wires and snow depth/snow density profiles, and 2) via repeat laser altimetry profiles. Differential GPS was used to track mass balance markers and terminus location. The glacier terminus retreated 4.7 km since the Little Ice Age extent of the 1760’s and 517 m recently (1997-2008) and will likely retreat ~180 m out of Mendenhall Lake in the next several years. Mendenhall Lake, a proglacial lake formed circa 1910 as the glacier retreated, now encompasses 3.7 km² and has a volume of 0.19km³. Since 2004 the glacier retreated from its deep lake basin, ~81.7 m below mean sea level, to ~77 m below mean sea level in 2008. A depth sounder coupled with a DGPS mounted to a skiff was used for monitoring lake expansion. Repeated bathymetric surveys are important for monitoring lake depth at the glacier terminus, understanding calving dynamics, and for analysis of lake morphology and sedimentation rates as the glacier and glacial streams deposit rock and sediment. Real-time automatic weather station data near the terminus- temperature, precipitation, wind speed and direction- and photographs of the terminus, continue to serve as additional climate change monitoring tools accessible to researchers, the general public, and visitors to the Mendenhall Glacier Visitors Center.