9J (2015-2016): Collaborative Research: Grounding Line Dynamics: Crary Ice Rise Revisited

• Central Washington University, United States of America

Our overarching goal is to understand how small-scale obstructions such as ice rises and ice rumples influence large-scale ice-shelf flow and discharge of inland ice. Here we propose to revisit CIR (Fig. 2) with new tools (radars and seismic instruments, and high-precision GPS) and make targeted geophysical measurements both on the ice rise, and where possible, across the grounding line. Our measurements, together with data collected during IGY, RIGGS, SCP, as well as new data collected recently by others from the Whillans ice plain, and satellite-derived products (patterns of thinning/thickening from ICESat, and surface velocities), will be used to validate and develop models of the evolution of grounding line dynamics of the Ross Sea Embayment. The models will be used to address the following: 1. What dynamical effect does the presence/absence of CIR have on discharge of inland ice through the Ross ice streams today? In particular, is it contributing to the observed slow-down of Whillans Ice Stream? What is its influence on Mercer and Kamb Ice Streams? 2. What caused CIR to freeze to the bed 1100 years ago? Was it a response to changes in discharge of the ice streams, or was it in response to regional relative sea-level lowering caused by glacial isostatic adjustment? How does the timing of freeze-on relate to the observations that indicate grounding-line retreat in the Ross Embayment stopped ~2000 years ago? 3. What history of ice dynamics is preserved in the radar-detected internal stratigraphy? 4. How has CIR evolved over timescales ranging from: the past 35 years since the last major field campaigns; the past millennia after the freeze-on of CIR; through the deglaciation. 5. How will CIR respond to future possible environmental changes such as sea-level rise and/or ocean warming? Will it be subsumed when the grounding line advances, or will it vanish, as occurred recently to an ice rumple when the shelf in front of Pine Island Glacier melted and thinned.

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