Using Landsat to Reconstruct Past Glacial Lake Outburst Floods at Mammoth Glacier, Wyoming

Abstract

The Central Rocky Mountains in the United States has many alpine environments with active glaciers such as the Wind River Mountain Range of Wyoming. Increased temperatures have caused glacial retreat in the Wind River Range resulting in multiple glacial lake outburst floods (GLOFs). Notably a GLOF at Grasshopper Glacier in September 2003 released 3.2 million cubic meters. Less documented GLOFs have occurred at nearby Mammoth Glacier as recently as 1996 despite the glacier being responsible for a catastrophic GLOF ~260 years before present (yr B.P.). The ~260 yr B.P. GLOF partially breached moraine controlled Scott Lake, creating a ~2.2 million cubic meter flood, illustrating the natural hazards GLOFs present. Landsat series of satellites have been collecting earth observation data since 1972 in the visible and invisible regions of the spectrum. Using Landsat data, this study examines changes in water extents using NDWI (Normalized Difference Water Index) of the dammed glacial lake responsible for the Mammoth Glacier GLOFs. NDWI is a widely used spectral index for distinguishing surface water extent in satellite images. Combining water extent with elevation datasets can reconstruct the volume released during the 1994 and 1996 GLOFs, giving insight into the scale and mechanisms of the catastrophic GLOF ~260 yr B.P. Understanding GLOFs helps protect downstream residents, agriculture, and infrastructure.