Abstract The piedmont lobe of San Quintín Glacier, the largest outlet of the Northern Patagonia Icefield, has recently entered a phase of rapid frontal retreat. We present results from a helicopter-borne ground-penetrating radar (GPR) survey conducted in May 2019 in the terminal zone of the glacier, combined with satellite-derived ice velocity, frontal position and surface elevation change data. GPR measurements along the flowline indicate ice thicknesses of 215–240 m in the lowermost 1400 m of the glacier. The inferred grounding line is located approximately 1500 m upstream from the 2019 calving front. Analysis of surface elevation change in 2017–19 shows mean thinning rates of -5.43 plus or minus $\pm$ ± 1.58 m a minus 1 $^{-1}$ − 1 upstream and -1.08 plus or minus $\pm$ ± 1.39 m a minus 1 $^{-1}$ − 1 near the terminus. Satellite-derived velocities reach up to 1050 m a minus 1 $^{-1}$ − 1 in the lower glacier, with higher values observed in the later part of the observation period. Residual bed reflection power derived from the GPR profiles indicates the presence of water at the glacier bed in the terminal zone. Taken together, these observations are consistent with the development of a semi-persistent floating terminus, where basal water and buoyancy modulate surface elevation change and control frontal stability and calving style. The results provide new observational constraints on the transient behaviour of floating termini at fast-flowing outlet glaciers in lacustrine settings.
This study developed a multi-process drilling system (MPDS) to extract 10 m subglacial bedrock samples beneath a 1000 m-thick region of the Antarctic ice sheet. The MPDS is made of five primary subsystems: drill rig, drill-rod module, air system, drilling fluid circulation system and generator. Each subsystem is modularly designed, allowing all components to be housed within a 20 foot container for efficient transportation across Antarctic ice sheets. The MPDS employs both compressed air and drilling fluid for ice cutting removal, utilising reverse circulation through a specially designed double-wall drill rod. A standard wireline coring drill is used to obtain subglacial bedrock samples. After fabrication and testing in China, the MPDS was sent to Antarctica in the 2024/25 season for preliminary testing. During field tests, a 110 m borehole was drilled, though no bedrock samples were retrieved. The tests identified several issues related to the drill bit, drill rig, air system, drilling fluid circulation system and the drilling fluid itself. Recommendations for future MPDS improvements have been proposed, with the expectation of obtaining subglacial bedrock cores from Antarctica within the next one to two seasons.
Abstract We located over one million icequakes that occurred during a 23 day period up-glacier of the grounding line of Rutford Ice Stream (RIS), West Antarctica. To investigate basal conditions and better understand the sliding process, we focused on sticky spots, spatially constrained clusters of regularly repeating basal icequakes. We developed a multistep workflow combining location and clustering to identify sticky spots with high confidence. The basal icequakes are consistent with low-angle slip in the ice-flow direction. Seismicity during our recording period showed weak tidal correlation and a minor sensitivity to atmospheric pressure, suggesting limited external forcing of basal processes. Icequake density was elevated on stoss sides of topographic highs likely characterized by exposed bedrock or compacted tills, and in low-lying moats eroded up-glacier of topographic highs, as well as in troughs extending down-glacier from the moats, likely reflecting hard beds that promote stick–slip. Local magnitudes followed a Gutenberg–Richter distribution with two distinct high (>2) b-values. Within sticky spots, repeating seismicity featured consistent waveforms and strong positive correlations between local magnitude and interevent time. During multihour active phases, seismic slip in sticky spots can fully accommodate ice flow, highlighting the role of stick–slip motion in basal sliding near the RIS grounding line. These results will help inform sliding relations used in numerical ice-flow models.
