Using Seismicity to Monitor and Quantify Glacier Dynamics
Open Access
- Author:
- Kluskiewicz, Daniel
- Area of Honors:
- Geosciences
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Andrew Arnold Nyblade, Thesis Supervisor
Andrew Arnold Nyblade, Thesis Supervisor
Peter J Heaney, Thesis Honors Advisor - Keywords:
- Glacier
Ice Quake
Seismology
Glaciology
Climate - Abstract:
- Observations of accelerated flow in both temperate tidewater glaciers and their polar counterparts underlie a need for an improved understanding of glacier dynamics. Among the tools that could help develop this understanding is a proxy of ice discharge at glacier termini. Based on data from a network of seismometers around Yahtse Glacier in southcentral Alaska, we explore relationships between ice discharge and seismicity for calving events at a glacier’s terminus. Yahtse’s current state of advance gives us an opportunity to study a unique phase of the tidewater glacier cycle that has received little attention in contemporary research. Terminus dynamics in this phase are characterized by frequent, small sub-aerial calving events as opposed to large submarine events that generally account for most ice discharge in a retreating glacier. Consistent with previous observations of calving seismicity at other (retreating) glaciers, we observe characteristic 1-3 Hz seismic signals during calving events. We demonstrate that these signals are mimicked by other seismic sources that include upstream ice collapse and calving at nearby Guyot Glacier. The prevalence of these alternate sources among the 1-3 Hz signals provides a motivation to further characterize calving seismicity such that it can be distinguished from other events with similar seismicity. In this pursuit, we observe the seismicity from long (70s) period standing waves (seiche) that occur in the glacier’s fjord subsequent to large sub-aerial calving events, and demonstrate a method for detecting these signals automatically. Based on these detections, we show that seiche signals can be used to differentiate large sub-aerial calving from other types of terminus events (sub-marine calving, fracture, ice-collapse behind terminus wall) and calving from Guyot Glacier, and demonstrate a strong correlation between the amount of ice discharged in such an event and the amplitude of the associated seiche seismicity. These results suggest that seiche seismicity could contribute to a refined seismic proxy of glacier terminus ice-discharge. Preliminary application of these methods suggests a 3.6 day periodicity to calving at Yahtse’s terminus.