Collaborative Research: A new radiostratigraphy of the Greenland Ice Sheet and critical boundary conditions for the next generation of ice-sheet models

Predictive ice-sheet models are our best tools for understanding the cumulative effects of forcings and feedbacks upon the Greenland Ice Sheet (GIS). However, these models lack detail concerning the GIS basal boundary condition, which is a critical control upon ice flow. They also do not take advantage of the wealth of information contained in its internal radiostratigraphy, but that could become a key component of their validation and application as predictive tools. To address this need for new constraints on ice-sheet models, funds are provided to develop, validate, and analyze a new radiostratigraphic database of the GIS. The database will be derived from past (e.g., PARCA, CReSIS) and ongoing (e.g., IceBridge) airborne radar-sounding campaigns. The research objectives are three-fold: 1. Development of novel automated layer-picking techniques. Picking widespread layers in radar data is often a time-intensive process. Recent advances permit dramatic improvements in automated layer picking, which will yield both insights into the nature of ice-sheet radiostratigraphy and accelerate a more precise study of ice-flow history from it. 2. Holocene surface and basal mass balance of the GIS. The picked radiostratigraphy will be combined with strain-rate modeling to map both Holocene surface-accumulation and basal melt rates across the GIS. This proven method will be extended beyond its previous application to northern Greenland, with uncertainties quantified using their knowledge of past ice-flow conditions. This study will both inform understanding of Greenland?s subglacial geology and provide key boundary conditions for ice-flow models of the GIS. 3. LAYERMAP: A dated radiostratigraphic model of the GIS. The radiostratigraphic database will be gridded in a manner similar to that for bed elevation underneath ice sheets. LAYERMAP will contribute to the advancement of IPCC-level ice-sheet models of the GIS, whose projections of its future evolution will hinge on data validation of its modern state. In addition, LAYERMAP will provide a means of mapping basal conditions and englacial drainage features across the GIS. Observations suggest a recent acceleration of the contribution of a degrading Greenland Ice Sheet to global sea level rise. Present projections of the rate of sea level rise are bounded by broad error bars, preventing accurate assessment of the response necessary to mitigate the impact of sea level rise. This project will develop data sets needed to validate and constrain models of the Greenland Ice Sheets contribution to future sea level.