Collaborative Research: Toward Dense Observation of Geothermal Fluxes in Antarctica Via Logistically Light Instrument Deployment

目前，在南极洲的研究受到在数千米冰内和冰下放置测量仪器的成本的严重限制。我们的目标是通过推进低成本冰融化探针技术的发展来部署仪器，从而实现密集、广泛的测量网络。融冰探测器利用电能在冰层表面几乎没有支撑结构的情况下穿过厚厚的冰层。我们正在扩展以前的技术，通过使用防冻剂来保持下降探头上方部分开放的融化孔，同时我们部署了一种新的光纤技术来测量冰的温度。冰温测量将揭示从冰下地球涌出的热量的空间模式，这反过来将极大地有助于寻找包含全球气候记录的古代冰，并了解冰流如何提高海平面。在这个为期一年的项目中，我们的直接目标是在威斯康星大学的一个15米高的冰柱上测试和完善我们的防冻方法，从而降低未来现场测试的技术风险。技术摘要：我们发展的总体目标是在南极冰盖内部和下方广泛、空间密集地部署仪器，进行各种调查，首先是观测冰盖底部的基础温度和地热通量。密集、广泛部署所需的后勤成本远低于目前的冰钻和取芯成本。我们的方法是扩展融冰探头技术（该技术本身就很轻，在物流上），允许在探头下降时从冰面逐步部署分布式温度传感（DTS）电缆，而不会大大增加物流成本。我们的扩展是基于在下降过程中，通过在探测器上方几米的地方注入防冻剂，特别是在温度接近0℃的乙醇，来阻止探测器上方融化孔（直径是电缆直径的几倍）的重新冻结。在液体乙醇/水柱与冰达到热平衡后，DTS测量得到冰盖温度的深度剖面，由此可以推断基底温度和（在冻结床上）地热通量。我们已经在一个冷室实验室对我们的方法进行了初步试验，但是仅基于这种小规模试验的实地工作仍可能涉及不必要的风险。因此，我们建议在威斯康星州麦迪逊的冰钻设计和操作（IDDO）设施进行进一步测试。新的试验将测试我们的融孔控制和探头回收方法，将测试电缆和电缆张力管理方法，这些方法更接近于在冰盖上工作所需的方法，并将在其现场配置中演示分布式温度传感。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical AbstractStudies in Antarctica are, at present, severely limited by the costs of placing measurement instruments within and beneath thousands of meters of ice. Our aim is to enable dense, widespread measurement-networks by advancing development of low-cost ice melt probe technology to deploy instruments. Ice melt probes use electrical energy to descend through thick ice with little support structure on the ice surface. We are extending previous technology by using anti-freeze to maintain a partially open melt-hole above a descending probe, deploying as we go a new a new fiber-optic technology to measure ice temperature. Ice temperature measurements will reveal spatial patterns of heat welling up from the Earth beneath the ice, which in turn will contribute greatly to finding ancient ice that contains global climate records, and to understanding how ice flow may raise sea levels. Our immediate objective in this 1-year project is to test and refine our anti-freeze-based method in a 15 meter-tall ice column at the University of Wisconsin, so as to reduce technical risk in future field tests. Technical AbstractThe overarching aim of our development is to enable widespread, spatially dense deployments of instruments within and beneath the Antarctic Ice Sheet for a variety of investigations, beginning with observations of basal temperature and geothermal flux at the base of the ice sheet. Dense, widespread deployment requires logistical costs far below current costs for ice drilling and coring. Our approach is to extend ice melt probe technology (which is inherently light, logistically) to allow the progressive deployment of cable for Distributed Temperature Sensing (DTS) from the ice surface as the probe descends, without greatly increasing logistical costs. Our extension is based on arresting refreezing of the melt-hole above the probe (at a diameter a few times the cable diameter) by injecting anti-freeze - specifically, ethanol at temperature near 0C - a few meters above the probe during descent. After thermal equilibration of the liquid ethanol/water column with the ice, DTS measurements yield the depth-profile of ice sheet temperature, from which basal temperature and (over frozen beds) geothermal flux can be inferred. We have carried out initial trials of our approach in a cold-room laboratory, but field work based only on such small-scale tests may still involve unnecessary risk. We therefore propose further testing at a facility of the Ice Drilling Design and Operations (IDDO) facility in Madison, WI. The new trials will test our approaches to melt-hole control and probe recovery in the taller column, will test cable and cable-tension-management methods more nearly approximating those needed to work on ice sheets, and will demonstrate the Distributed Temperature Sensing in its field configuration.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.