A HIGH-RESOLUTION DEM TIMESERIES TO MEASURE GLACIER MASS BALANCE, DYNAMICS, AND VARIABILITY AT MOUNT BAKER, WA USA

Mount Baker is an active stratovolcano covered by ~39 km² of glacier ice. Despite mean annual precipitation of >4-6 meters of water equivalent (m.w.e.), negative mass balance estimates of -0.5 to -0.7 m.w.e./yr are obtained from 1990-2010, which translates to cumulative ice loss of ~10-20% and thinning of ~10-11 m (Pelto and Brown, 2012). Such long-term observations of glacier mass balance are important for understanding regional climate trends and variability, as well as informing water resources and fisheries management. Traditional measurement approaches involve extended field campaigns to obtain sparse in situ data for a subset of glaciers. Here, we explore the application of repeat, high-resolution topographic surveys from digital images as an inexpensive, complementary approach to measure regional snowpack thickness, surface mass balance, and glacier dynamics/variability.

We present a preliminary 2013-2014 timeseries of high-resolution digital elevation models (DEMs) derived from oblique aerial Structure from Motion (SfM) surveys, small UAV SfM surveys, ground-based SfM surveys, and WorldView along-track stereo satellite imagery. The baseline DEM for Mount Baker (9/10/13) was generated from 506 oblique photos acquired from a single-engine airplane with a handheld 36 Megapixel camera. Automated SfM software was used to produce a 1.3 meter per pixel (m/px) DEM and 0.3 m/px orthomosaic, both with areal coverage of ~105 km². Standard error of ~0.5 m and RMSE of ~2.7 m are estimated from comparisons with 13 USGS GPS sites. Photographs acquired by compact cameras on small, low altitude, UAV platforms allow us to produce DEM and orthoimage products with cm-scale resolution over ~1-5 km². Finally, we use WorldView satellite stereo imagery to generate ~2.0 m/px DEMs over ~250-300 km². Cloud-free stereopairs are available from 9/11/13, 9/13/13 and 5/14/14, with additional acquisitions planned for 9/1/14-10/15/14.

We will use this DEM timeseries to produce seasonal and interannual volume/mass change estimates for Mount Baker. Future comparisons with in situ measurements and similar DEM timeseries throughout the Cascades will offer new insights for regional mass balance estimates, while also establishing baselines for other dynamic geologic processes (e.g., volcanic deformation, mass wasting).