Collaborative Research: Grounding Line Dynamics: Crary Ice Rise Revisited

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.

本研究的核心目标为厘清冰隆（ice rises）与冰堆丘（ice rumples）这类小型障碍物，如何影响冰架的大规模流动与内陆冰的输出过程。
本研究拟借助新型探测设备（雷达、地震仪器与高精度全球定位系统（GPS））重访冰隆（CIR，见图2），并针对该冰隆区域及可行范围内的接地线（grounding line）开展针对性地球物理测量。
本次获取的测量数据，结合国际地球物理年（IGY）、RIGGS、SCP等项目收集的历史数据，以及近期其他团队从威兰斯冰原（Whillans ice plain）获取的新数据，再辅以卫星反演产品（来自ICESat的冰面厚薄变化图像与冰面流速数据），将用于验证并构建罗斯海海盆（Ross Sea Embayment）接地线动力学演化模型。
该模型将用于解答以下科学问题：
1. 当前罗斯冰流中，冰隆（CIR）的存在与否对内陆冰输出过程有何种动力学影响？具体而言，其是否促成了观测到的威兰斯冰流减速现象？它对默瑟冰流（Mercer Ice Streams）与坎布冰流（Kamb Ice Streams）又有何种影响？
2. 1100年前是什么原因导致冰隆（CIR）与冰床冻结？这一现象是对冰流输出量变化的响应，还是对冰川均衡调整（glacial isostatic adjustment）引发的区域相对海平面下降的响应？该冻结事件的发生时间，与罗斯海海盆接地线后退约于2000年前停止的观测结果之间存在何种关联？
3. 雷达探测到的冰内地层中，保存了何种冰动力学演化历史？
4. 冰隆（CIR）在不同时间尺度下的演化过程如何？包括自上一次大型野外作业以来的35年、冰隆冻结以来的千年尺度，以及整个冰消期（deglaciation）的演化历程。
5. 未来可能出现的环境变化（如海平面上升或海洋变暖）将对冰隆（CIR）产生何种影响？当地接线前进时，冰隆是否会被掩埋？或是像近期松岛冰川（Pine Island Glacier）前方冰架融化变薄导致一处冰堆丘消失那样，冰隆是否会完全消亡？