Geodetic Monitoring Networks: GNSS-Derived Glacier Surface Velocities at the Global Change Observatory Inylchek (Kyrgyzstan)

Abstract

The German Research Centre for Geosciences (GFZ, Potsdam, Germany) and the Central-Asian Institute for Applied Geosciences (CAIAG, Bishkek, Kyrgyzstan) jointly established the Global Change Observatory “Gottfried Merzbacher” at the Inylchek Glacier in eastern Kyrgyzstan which is one of the largest non-polar glaciers of the world and consists of two glacier streams. The flow of melt-water from the northern tributary forms a lake (Lake Merzbacher) that is dammed by the calving ice front of the southern Inylchek Glacier. At least once a year a glacial lake outburst flood (GLOF) occurs and the complete water of the Lake Merzbacher drains through sub-glacial channels. To monitor the glacier dynamics including the post-drainage ice dam response, a small network of remotely operated multi-parameter stations (ROMPS) was installed at different locations at the glacier. Directly located near the ice dam, a continuously measuring kinematic GNSS station provides precise long-term data of variations in the dynamics of the ice dam for the years 2010, 2011 and 2012. While the station reflects the horizontal motion of the ice dam towards the Lake Merzbacher, the vertical component shows a clear loss of elevation as a “long-term” response after the GLOF lasting for several weeks instead of only a few days. In correspondence to the elevation decrease, the surface velocity has a higher variability due to a relaxing process of the ice dam but changes significantly to a nearly constant velocity during the winter time.