Characteristics of the sticky spot of Kamb Ice Stream, West Antarctica. Issue 3 (21st March 2017)

• Record Type: Journal Article
• Authors: Luthra, Tarun; Peters, Leo E.; Anandakrishnan, Sridhar; Alley, Richard B.; Holschuh, Nicholas; Smith, Andrew M.
• Is Part Of: Journal of geophysical research. Volume 122:Issue 3(2017)
• Page Start: 641
• Page End: 653
• Publication Date: 2017-03-21
• Subjects: West Antarctic Ice Sheet -- glaciology -- geophysics -- sticky spot -- Kamb Ice Stream -- reflection seismology; Geomorphology -- Periodicals; 551.3
• DOI: 10.1002/2016JF004181
• Languages: English
• ISSNs: 2169-9003

Abstract

Abstract: Amplitude analysis of reflection seismic data reveals the presence of highly variable bed conditions under the main sticky spot and adjacent regions of the Kamb Ice Stream (formerly ice stream C). The sticky spot, which is a zone of bed that imparts high basal resistance to ice flow, is situated on a local topographic high composed of consolidated sediments or sedimentary rock. Any meltwater draining from upglacier along the base of the ice is routed around the sticky spot. The ice over the sticky spot includes, in at least some places, a seismically detectable basal layer containing a low concentration of debris, which locally thickens to 40 m over a topographic low in the bed. The ice‐contact basal material ranges from dilated and highly porous to more‐compacted and stiff, and perhaps locally frozen. The softer material is preferentially in topographic lows, but there is not a one‐to‐one correspondence between basal character and basal topography. We speculate that the 40 m thick frozen‐on debris layer formed by glaciohydraulic supercooling of lake‐drainage events along a basal channel during the former, active phase of the ice stream. We also speculate that loss of lubricating water, perhaps from piracy upstream, contributed to the slowdown of the ice stream, with drag from the sticky spot playing an important role, and with the basal heterogeneity greatly increasing after the slowdown of the ice stream. Key Points: Hydropotential suggests that upstream water would route around the sticky spot which lies on a local topographic high Bed conditions vary from soft deformable till at topographic lows to more consolidated stiffer till Observation of a debris‐rich frozen‐on ice 40 m above a basal channel