Bering Glacier surge 2011: analysis of laser altimeter data

The Bering Glacier–Bagley Icefield system in Alaska is currently surging (2011). Large-scale elevation changes and small-scale elevation-change characteristics are investigated to understand surge progression, especially mass transport from the pre-surge reservoir area to the receiving area and propagation of the kinematic surge wave as manifested in heavy crevassing characteristic of rapid, brittle deformation. This analysis is based on airborne laser altimeter data collected over Bering Glacier in September 2011. Results include the following: (1) Maximal crevasse depth is 60m, reached in a rift that separates two deformation domains, indicative of two different flow regimes. Otherwise surge crevasse depth reaches 20–30m. (2) Characteristic parameters of structural provinces are derived by application of geostatistical classification. Parameters include significance and spacing of crevasses, surface roughness and crevasse-edge curvature (indicative of crevasse age). A classification based on these parameters serves to objectively discriminate structural provinces, indicative of surge progression down-glacier and up-glacier. (3) Elevation changes from 2011 and 2010 altimetry show 40–70m surface lowering in the reservoir area in lower central Bering Glacier and 20–40m thickening near the front in Tashalich arm. Combining elevation changes with results of crevasse profilometry and pattern analysis, the rapid progression of the surge can be mathematically–physically reconstructed.