Thwaites Interdisciplinary Margin Evolution (TIME)

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The West Antarctic Ice Sheet (WAIS) contains 2 million cubic kilometers of ice. The global scientific community considers the it the most significant risk for coastal environments and cities, given its potential contribution to future sea-level rise. The risk posed by the WAIS is exacerbated because it is in direct contact with the warming ocean, and its bed slopes inland; this latter aspect makes the ice vulnerable to extensive and prolonged retreat. Although scientists have been aware of the precarious setting of the WAIS since the early 1970s, it is only now becoming apparent that the flow of ice in several large drainage basins is undergoing dynamic change, which is consistent with - although not certain to be - the beginning of a prolonged and potentially unstoppable disintegration. Two of the fundamental global challenges facing the scientific community today include understanding the controls on the stability of the WAIS, and enabling a more accurate prediction of sea-level rise through improved computer simulations of ice flow. In the TIME project, we directly address both challenges bya) using frontier technologies to observe rapidly deforming shear margins hypothesized to exert strong control on the future evolution of the Thwaites Glacier outlet of the WAIS, andb) using observational records to develop parameterizations for important processes which are not yet implemented in the ice sheet models used to predict the contribution of WAIS to sea level rise.TIME will test the key hypothesis that the future evolution of ice flow through the Thwaites Glacier Draining Basin is governed by the dynamics of its shear margin - the boundary at the edge of the glacier across which increased ice flow is observed. To test the hypothesis the team will set up an ice observatory at two sites on the eastern shear margin of Thwaites Glacier. The team argues that weak topographic control makes this shear margin susceptible to outward migration and, possibly, sudden jumps in response to the drawdown of inland ice when the grounding line of Thwaites retreats. The ice observatory is designed to produce new and comprehensive constraints on important englacial properties, which include ice deformation rates, ice crystal fabric, ice viscosity, ice temperature, ice liquid-water content and basal melt rates. The ice observatory will also establish basal conditions, including thickness and porosity of any subglacial sediment layer and the deeper marine sediments. Furthermore, the team will develop new knowledge with an unparalleled emphasis on the consequences of variations in these properties for ice flow, including a direct assessment of the spatial and temporal scales on which they vary. These knowledge will be obtained from three field-based geophysical platforms: - Active-source seismic surveys will be carried out in 2D and 3D, uniquely using wireless geophones, - A network of broadband seismometers, to identify the icequakes produced by crevassing and basal sliding, - Autonomous radar systems with phased arrays to produce sequential 3D images of rapidly deforming internal layers while potentially also revealing the geometry of a basal water system at the bed. Datasets will be incorporated into numerical models developed on different spatial scales. One will focus specifically on shear margin dynamics, the other on how shear margin dynamics can influence ice flow in the whole drainage basin. Upon completion, the project will have confirmed whether the eastern shear margin of Thwaites Glacier can migrate rapidly, as hypothesised, and if so what the impacts will be in terms of sea level rise in this century and beyond.