EAGER: An Operational System to Measure Surface Mass Balance Deep in the Interior of the Antarctic Ice Sheet

非技术描述：南极冰盖内部的积雪以及多少雪被风重新分配是南极洲气候系统的重要组成部分，但在很大程度上仍是未知的。由于在南极洲发现了极端的气象条件，对降雪和相关天气的直接观测很少，在该大陆的区域气候记录中留下了空白。南极冰盖上的积雪是评估南极对海平面上升的贡献的一个关键组成部分，并且需要精确的测量来评估区域气候模式的结果，这些模式用于重建整个冰盖最近的气候趋势。由于南极洲本身的面积，地表积雪总量的微小波动对冰盖的质量收支产生重大影响，从而对全球海平面产生重大影响。在这项工作中，将开发一套用于部署在南极洲南极研究站的仪器。监测站将配备最先进的传感器，记录积雪层内的天气、积雪量和结构状况。该自主系统将在地球上最寒冷、最黑暗的冬天进行测试，并将首次提供冰盖内部积雪过程的连续测量，这将用于验证大气和区域气候模型。技术描述：提出的工作的总体目标是提高我们对冰盖表面质量平衡和雪层内致密率的时空变异性的理解，雪层大约100米厚，由尚未致密成固体冰的掩埋和压实的雪组成。为此，我们将A)为南极洲设计并安装一个成本效益高、可靠且易于部署的地面质量平衡和土壤监测系统；B)使系统适应在最恶劣的气象条件下长时间自主运行；C)利用观测资料评价大气再分析和区域气候模式模拟的地表物质平衡；D)测量地表质量平衡、地表密度和冰雪压实率，得出低冰动力地区的冰盖表面高程变化。监测站设置的独特之处在于，它能够分别监测由地表质量平衡变率和绝对地表质量平衡引起的高度变化，后者以水当量为单位，两者的区分对于理解地表过程在冰盖质量平衡中的作用至关重要。安装的声波探测仪将每小时测量一次由于积雪引起的地表高度变化。地表高度变化本身不足以评估地表质量平衡的大气模式，地表质量平衡是以质量为单位测量的；缺少的一个关键变量是密度。为了克服这个问题，该系统将配备一个SnowFox传感器，该传感器能够捕获表面质量平衡随时间的变化。结合高度变化和质量变化将使我们能够确定材料的密度，这对于将观察到的由于表面过程引起的高度变化转换为质量变化非常重要。因此，我们的目标是更好地评估由于地表质量平衡而引起的地表高度和质量波动的短期变化，以提高我们对总质量变化的理解，并评估通常用于全冰盖质量平衡研究的大气模式。

Non-Technical Description: Snow accumulation in the interior of the Antarctic Ice Sheet, and how much snow is redistributed by wind are important components of the climate system of Antarctica, yet remain largely unknown. Because of the extreme meteorological conditions found in Antarctica, direct observations of snowfall and related weather are few, leaving a gap in the regional climate records in the continent. Snow accumulation across the Antarctic Ice Sheet is a critical component for the assessment of the contribution of Antarctica to sea level rise, and accurate measurements are required to evaluate results from regional climate models, used to reconstruct climate trends of the recent past for the whole ice sheet. Owing to the size of Antarctica alone, small fluctuations in the total snow accumulation at the surface have a significant effect on the mass budget of the ice sheet and thus on global sea level. In this work will develop an instrument suite for deployment at the South Pole research station in Antarctica. The monitoring station will have new state-of-the-art sensors will record measurements of weather, snow accumulation, and structural conditions within the layer of packed snow. The autonomous system will be tested in the coldest and darkest winter on the planet, and will provide the first continuous measurements of snow accumulation processes in the interior of the ice sheet, which will be used to validate atmospheric and regional climate models. Technical Description: The overarching goal of the proposed work is to improve our understanding of the spatiotemporal variability in ice-sheet surface mass balance and densification rates within the layer of firn, a layer roughly 100 m thick consisting of the buried and compacted snow that has yet to densify into solid ice. For this, we will A) design and install a cost-efficient, reliable, and easily deployable surface mass balance and firn monitoring system for Antarctica; B) adapt the system to operate autonomously for long periods of time under the harshest meteorological conditions; C) use observations for evaluation of surface mass balance simulated by atmospheric reanalyzes and regional climate model; and D) measure the surface mass balance, surface density, and firn compaction rates to derive ice sheet surface elevation change in areas with low ice dynamics. The set up of the monitoring station is unique in that it is able to monitor separately height change due to surface mass balance variability and absolute surface mass balance, the latter in units of water equivalence, and differentiation of the two is crucial for understanding the role of surface processes in ice sheet mass balance. An installed sonic ranger will provide hourly measurements of surface height change that is due to snow accumulation. Surface height change alone is not sufficient to evaluate atmospheric models of surface mass balance, which is measured in in units of mass; a key variable missing is density. To overcome this, the system will be equipped with a SnowFox sensor that is able to capture the variations in surface mass balance in terms of mass through time. Combining the height change with mass change will allow us to determine the density of the material as well, which is very important for conversion of observed height changes due to surface processes into mass changes. Therefore, we aim to better evaluate the short-term variability in surface height and mass fluctuations due to surface mass balance to improve our understanding of the total mass change and to evaluate atmospheric models, which are typically used for ice sheet-wide mass balance studies.