Abstract
AbstractCrary Ice Rise formed after the Ross Ice Shelf re-grounded ~1 kyr BP. We present new ice-penetrating radar data from two systems operating at center frequencies of 7 and 750 MHz that confirm the ice rise is composed of a former ice shelf buried by subsequent accumulation. Stacks of englacial diffraction hyperbolas are present almost everywhere across the central ice rise and extend up to ~350 m above the bed. In many cases, bed reflections beneath the diffraction hyperbolas are obscured for distances up to 1 km. Waveform modeling indicates that the diffraction hyperbolas are likely caused by marine ice deposits in former basal crevasses and rifts. The in-filling of rifts and basal crevasses may have strengthened the connection between the ice rise and the surrounding ice shelf, which could have influenced local and regional ice dynamics. Three internal reflection horizons mark the upper limit of disturbed ice and diffraction hyperbolas in different sections of the ice rise, indicating at least three stages of flow stabilization across the ice rise. A surface lineation visible in MODIS imagery corresponds spatially to deepening and strong deformation of these layers, consistent with the characteristics of former grounding lines observed elsewhere in Antarctica.
Highlights
Ice rises are locally grounded regions within ice shelves that provide a stabilizing resistance to ice flow (Thomas and others, 1979; MacAyeal and others, 1987; Favier and Pattyn, 2015; Matsuoka and others, 2015)
Crary Ice Rise (CIR) is a grounded promontory within the Ross Ice Shelf (Fig. 1) that provides roughly half the resistance to flow from Whillans and Mercer Ice Streams, and reduces ice-shelf spreading rates by an order of magnitude (MacAyeal and others, 1987, 1989; Still and others, 2018)
Our radar surveys reveal that CIR contains abundant marine ice, which likely accreted within rifts and basal crevasses in the Ross Ice Shelf shortly after it re-grounded at this site
Summary
Ice rises are locally grounded regions within ice shelves that provide a stabilizing resistance to ice flow (Thomas and others, 1979; MacAyeal and others, 1987; Favier and Pattyn, 2015; Matsuoka and others, 2015). We present new observations that provide insight into the formation and evolution of an ice rise. Borehole thermometry data and thermal modeling indicate that the ice rise formed in at least two stages, when the ice shelf re-grounded ∼1 kyr and ∼600 yr BP (Bindschadler and others, 1990). It is not known whether the re-grounding was a result of increased discharge from the Siple Coast ice streams (Bindschadler, 1993), isostatic rebound (e.g. Kingslake and others, 2018) or a combination of the two. We model radar waveforms to test hypotheses about the origin of the radar-detected structures we observe
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
