Academic Affiliation: Community College of Denver [currently at Metro State University]
Beth Schaeffer was recently reintroduced to her love for geology and science in general during camping trips with her family. She currently attends Metro State University of Denver where she studies applied geology and geographic information systems. In her spare time she enjoys hiking, spending time with her family, and watching volcano documentaries
Exploring the Mechanisms and Causes of High-Elevation Crevasses in the Interior of the Greenland Ice Sheet
Greenland ice-sheet flow is expected to accelerate in the 21st century as it experiences increased rates of melting and ice flow, including the introduction of meltwater to the bed of the ice sheet. As lakes and rivers form at higher elevations on the surface, the potential for meltwater to reach the bed through new moulins is of primary concern for future ice-sheet flow. Previous studies have concluded that moulins are unlikely to form in the high elevation interior above 1600 m above sea level (asl) because strain rates are too low for fracturing to occur. During Greenland’s record-breaking melt season of 2012, enough snow melted to expose dozens of narrow cracks at elevations up to 1900 m asl in southwest Greenland, with reports of individual cracks reaching as high as 2100 m asl. Five differential GPS stations were installed near the KAN-U station at 1870 m asl in Southwest Greenland, from spring 2017 to spring 2018, to provide an introductory study into the causes of these surface crevasses. Several hypotheses were investigated. Our data provide a strong indication that ice flow is accelerating at the KAN-U station with annual speeds now exceeding 55 m yr-1, a 7.5% increase since 2009. Longitudinal strain rates remain quite low at 0.1% yr-1 or less, only 20% of the 0.5% yr-1 critical strain rate traditionally cited to open surface crevasses in the warm ice of Greenland’s wet-snow zone. Crevasse locations correlate strongly with local topography. We suggest that increasing volumes of refrozen meltwater may be causing the surface to become more brittle than traditional near-surface stratigraphic layers made purely of firn. The brittle surface ice may allow fractures to form under increasingly smaller strain rates. Though these appear to be the main mechanisms at play, we cannot rule out the interplay of several hydrological and geophysical components which may contribute to the formation of such high-elevation crevasses. Future research will further examine the mechanisms of high elevation crevasses, explore what interactions they may have with subglacial drainage systems and moulins, and assess the possible implications to high elevation ice flow acceleration.