Seismic observations of a complex firn structure across the Amery Ice Shelf, East Antarctica

• Published in: Journal of Glaciology
• Main Authors: Hollmann, H, Treverrow, A, Peters, LE, Reading, AM, Kulessa, B
• Format: Article in Journal/Newspaper
• Language: English
• Published: Int Glaciol Soc 2021
• Subjects: polar firn; seismics; snow mechanics; Antarctic; The Antarctic; East Antarctica; Amery; Amery Ice Shelf; Lambert Glacier; Mawson Escarpment; Antarc*; Antarctica; Antarctica Journal; Ice Sheet; Ice Shelf; Journal of Glaciology
• Online Access: https://eprints.utas.edu.au/45696/; https://eprints.utas.edu.au/45696/1/147933%20-%20Seismic%20observations%20of%20a%20complex%20firn%20structure.pdf

We use seismic refraction data to investigate the firn structure across a suture zone on the AmeryIce Shelf, East Antarctica, and the possible role of glacier dynamics in firn evolution. In the downstreamdirection, the data reveal decreasing compressional-wave velocities and increasing penetrationdepth of the propagating wave in the firn layer, consistent with ~1m firn thickeningevery 6 km. The boundary between the Lambert Glacier unit to the west and a major suturezone and the Mawson Escarpment Ice Stream unit to the east, is marked by differences in firnthicknesses, compressional-wave velocities and seismic anisotropy in the across-flow direction.The latter does not contradict the presence of a single-maximum crystal orientation fabricoriented 45–90◦ away from the flow direction. This is consistent with the presence of transversesimple shear governing the region’s underlying ice flow regime, in association with elevated strainalong the suture zone. The confirmation and quantification of the implied dynamic couplingbetween firn and the underlying ice requires integration of future seismic refraction, coringand modelling studies. Because firn is estimated to cover ~ 98% of the Antarctic continent anysuch coupling may have widespread relevance to ice-sheet evolution and flow.