Investigating Grounding Zones by RAGEing WISSARDs

The latest IPCC report recognized that the greatest uncertainties in assessing future global sea-level change stem from a poor understanding of ice sheet dynamics and vulnerability to oceanic and atmospheric warming. Ice stream grounding zones (GZs) of West Antarctic Ice Sheet (WAIS) are seen as high priority targets to investigate as they may be perturbed by internal ice stream dynamics, increased thermal ocean forcing, subglacial sediment flux, and/or filling/draining cycles of subglacial lakes. A new interdisciplinary study to assess the stability of WAIS and Ross Ice Shelf (RIS), RAGES (Robotic Access to Grounding-zones for Exploration and Science) has been initiated as part of a larger project, WISSARD (Whillans Ice Stream Subglacial Access Research Drilling). Three main science goals for RAGES are to assess: (a) WAIS stability, (b) the degree to which grounding-zone sedimentary systems house important records of past WAIS dynamics, and (c) the importance of microbial activity and subglacial geochemical weathering in supplying nutrients to WAIS grounding zone, RIS cavity and Southern Ocean to influence global biogeochemical cycles. The proposed field plan integrates surface geophysical surveys; samples of subglacial water, sediments, and basal ice for biological, geochemical, glaciological, sedimentological, and micropaleontological analyses; measurements of subglacial and sub-ice-shelf cavity physical and chemical conditions and their spatial variability; and data on sediment types and character, state and change of subglacial water discharge, oceanography and basal ice at the grounding line and within the nearby sub-ice-shelf cavity using a multi-sensor Sub-Ice ROVer (SIR) and long-term, sub-ice oceanographic moorings.