Evidence for the Drainage of a Superglacial Lake as the Source of Seismic Waves Recorded at a Regional Distance

• Main Author: Orantes, Erik J
• Format: Thesis
• Language: English
• Published: CUNY Academic Works 2016
• Subjects: Glaciers; Seismicity; Greenland; Atmospheric Sciences; Climate; Earth Sciences; Oceanography and Atmospheric Sciences and Meteorology; Physical Sciences and Mathematics; Ice Sheet
• Online Access: https://academicworks.cuny.edu/cc_etds_theses/681; https://academicworks.cuny.edu/cgi/viewcontent.cgi?article=1681&context=cc_etds_theses

Surface melting during the summer leads to the formation of lakes on the Greenland Ice Sheet surface, known as supraglacial lakes. Some of these lakes drain through cracks in their beds and release the water into the ice sheet. Previous studies suggest that some of the water reaches the bedrock, enabling basal sliding, which could potentially increase glacial discharge (Sundal et al., 2009). Das et al. (2008) showed that supraglacial lake drainage can be accompanied by seismic activity, but little work has been done on the regional detection of such waves. The present study analyzes seismic data for the period coincident with the drainage of a supraglacial lake, an event that was documented by a team of researchers (Tedesco, et al., 2013). The study uses all available high frequency seismic data from the Greenland Ice Sheet Monitoring Network (GLISN) for the time around the onset of sudden drainage on June 19, 2011. Linear trends from a plot of seismic arrival times vs. distance from the lake location indicate seismic wave velocities of 292 and 378 m/s. These velocities are too slow for waves to be traveling through either rock or solid ice. Our current hypothesis is that they are traveling in a low-velocity channel of till underneath the ice. This would be consistent with the low attenuation required for the propagation of high frequency energy over regional distances. This research is relevant because it has become increasingly important to study how the surface-to-base interaction affects ice sheet discharge and therefore, sea level rise.