Collaborative Research: Logistically Light Instrument Deployment for Estimation of Antarctic Basal Temperatures and Geothermal Heat Fluxes

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Title: Logistically Light Instrument Deployment for Estimation of Antarctic Basal Temperatures and Geothermal Heat FluxesNon-Technical Description: New observations of Antarctic ice sheet variables are essential for drill-site selection for climate records, for understanding how ice dynamics affect sea level, and for investigating the geologic history of the continent. Temperature depth-profiles are of particular current interest for estimating basal temperature and geothermal heat flux in Antarctica. Antarctic geothermal heat flux is presently poorly known except at recent drilling sites, and is the largest unknown in determining basal conditions. However, current logistical costs greatly limit drilling to acquire temperature profiles. Our long-term goal is the development, testing and commissioning of a new means of acquiring englacial temperature profiles at much lower costs than existing methods. To that end, we will undertake laboratory experiments and numerical modeling to develop to a new way to use ice melt probes, rather than traditional drilling, to deploy temperature measurement equipment to depths of a kilometer and greater. To use melt probes for this purpose, we must keep the melted ice above such probes from freezing completely, so that cable can be fed continually down to the probe as it descends. This development will also open the way toward recovering melt probes, so as to prevent environmental impacts and expense of equipment left in the field. Our initial experiments and modeling will test the validity of our approach and make it ready for further testing in the field.Technical Description: We will undertake laboratory and modeling work (1) to reduce the technical risk in our approach to melt-probe deployment of Raman Distributed Temperature Sensing (DTS) cables; and (2) to begin development of a recoverable ice melt probe. Specifically, we will use numerical modeling of the Stefan problem with cylindrical symmetry to guide detailed designs for cable-heating and anti-freeze injection, and will test and revise candidate designs by means of laboratory testing. We will test the long-term stability of ethanol-filled melt holes, to gauge their suitability for recoverable melt probe systems for temperature measurement (where months-long thermal equilibration after installation will be required). We will gain experience with Raman DTS methods by employing DTS to measure critical temperature data in our laboratory experiments, both within the melt hole and in adjacent ice. To address recoverability, we will design and test a new melt head for the upper end of our ice melt probe, and demonstrate upward travel through a partially refrozen melt hole. Finally, we will publish both modeling and experimental results in peer-reviewed publications, and will present the project to a broad public audience in a special event at a Seattle museum of science and technology. The result of this work will be demonstrated technical readiness for testing in a subsequent project at larger ice-drilling test facilities at the earliest opportunity (prospectively, at the University of Wisconsin, following soon after completion of this project) and, following that, in the field.