Observations of seasonal and diurnal glacier velocities at Mount Rainier, Washington, using terrestrial radar interferometry

Abstract

Abstract. We present surface velocity maps derived from repeat terrestrial radar interferometry (TRI) measurements and use these time series to examine seasonal and diurnal dynamics of alpine glaciers at Mount Rainier, Washington. We show that the Nisqually and Emmons glaciers have small slope-parallel velocities near the summit (< 0.2 m day −1 ), high velocities over their upper and central regions (1.0-1.5 m day −1 ), and stagnant debris-covered regions near the terminus (< 0.05 m day −1 ). Velocity uncertainties are as low as ±0.02-0.08 m day −1 . We document a large seasonal velocity decrease of 0.2-0.7 m day −1 (−25 to −50 %) from July to November for most of the Nisqually Glacier, excluding the icefall, suggesting significant seasonal subglacial water storage under most of the glacier. We did not detect diurnal variability above the noise level. Simple 2-D ice flow modeling using TRI velocities suggests that sliding accounts for 91 and 99 % of the July velocity field for the Emmons and Nisqually glaciers with possible ranges of 60-97 and 93-99.5 %, respectively, when considering model uncertainty. We validate our observations against recent in situ velocity measurements and examine the long-term evolution of Nisqually Glacier dynamics through comparisons with historical velocity data. This study shows that repeat TRI measurements with > 10 km range can be used to investigate spatial and temporal variability of alpine glacier dynamics over large areas, including hazardous and inaccessible areas.

A Low-Cost Optical Remote Sensing Application for Glacier Deformation Monitoring in an Alpine Environment

“…The data have been processed by the author using an interferometric approach [10,11,45]. The time separation between consecutive acquisitions is 16 min.…”

Monitoring Alpine glacier surface deformations with GB-SAR

“…Second, the interferograms with high noise and significant unwrapping errors are excluded from the stack of the interferograms (Allstadt et al 2015). In the case at hand, the huge number of radar images necessitates the definition of a criterion for identifying the interferograms to be rejected.…”

“…More recently, in Strozzi et al (2012) and Riesen et al (2011), the authors focused on monitoring a short-term surface ice motion linked to the fast drainage of an adjacent lake. In Allstadt et al (2015) the results of a radar survey were used as validation of a glacier deformation model. Although this novel technique is able to provide only a partial estimate of the actual ice flow, displacement maps of glaciers of some square kilometres in size, from 3-4 km distances and entirely remotely sensed, can be obtained.…”

Assessing the Risk of Glacial Outburst Floods From Emmons Glacier, Mt. Rainier, Washington

“…. 2016 Satellite Imagery of Emmons glacier debris-covered ablation zone, with icesurface velocities (Allstadt et al, 2015;Digital Globe, 2017).…”