Investigating basal conditions and flow dynamics on Vestfonna Ice Cap, Svalbard

越来越多的科学证据表明，人类活动对全球气候造成了重大影响，公众的担忧突显出，需要更好地评估北极等地区的当代环境变化。尽管地球上绝大多数的冰储存在格陵兰岛和南极洲，但重要的是要记住，冰冻圈对20世纪海平面上升的贡献中，有70%归因于山脉冰川和冰帽的消退。北极冰块是全球变化的一个重要组成部分，特别是在北极气温上升速度几乎是全球平均水平的两倍的情况下。该项目的重点是斯瓦尔巴群岛东北部的维斯特凡纳冰帽。这个北极冰盖特别令人感兴趣，因为它的北部冰缘终止于陆地，而南部边缘包含一系列潮水出口冰川，可与那些排干格陵兰冰盖的冰川相媲美。斯科特极地研究所1983年和1986年收集的空中无线电回波探测数据显示，维斯特凡纳冰帽的体积约为500千米3。航空照片和卫星图像随后显示，南潮水冰川的水流速度为每年几百米。这比周围的冰快了一个数量级，是计算出的平衡速度的两倍多。有人认为，这种物质平衡的负状态是短暂的冰川涌动的结果。然而，维斯特凡纳冰帽内部的冰高原今天正在经历广泛的渐进式减薄，这要么是由于区域气候动态的变化，要么是因为出口冰川的流量增加。该项目建议对维斯特凡纳冰帽进行冰川学研究，目的是量化气候动力学和冰流之间的联系。拟议的调查包括收集横跨冰盖和两个指定研究区域的无线电回波探测数据，一个在北部冰缘，另一个在南部潮水冰川。雷达数据提供了一种测量冰层厚度和检查冰床性质的手段，例如融化和冻结的分布以及作为润滑剂的水的存在。我们将在Frazerbreen冰川的终点附近安装两台数码相机，这是一座潮水冰川，这样我们就可以监测它正在融化的冰锋的位置。总共六个GPS接收器将安装在冰上，以监测在18个月内每小时一次的水平和垂直运动。通过将GPS数据与数字延时图像相结合，并从自动气象站输出，我们将能够了解冰盖中的力是如何平衡的，这将使我们能够研究冰块在不同气候和海洋条件下的行为。通过应用三维数值冰流模式，我们将能够研究冰盖对全球变暖的响应，并预测其对海平面变化的贡献。

The body of scientific evidence for significant anthropogenic impacts on the global climate is growing and public concern underscores a need for better assessments of contemporary environmental changes in regions such as the Arctic. Although the vast majority of ice on Earth is stored in Greenland and Antarctica, it is important to keep in mind that 70% of the cryospheric contribution to 20th century sea-level rise was attributed to the retreat of mountain glaciers and ice caps. Arctic ice masses are an important component of global change, especially as Arctic temperatures are increasing at almost twice the global average. This project focuses on Vestfonna Ice Cap in northeast Svalbard. This Arctic ice cap is of particular interest because its northern ice margin terminates on land while the southern margin contains a series of tidewater outlet glaciers, comparable to those draining the Greenland Ice Sheet. Airborne radio-echo sounding data collected in 1983 and 1986 by Scott Polar Research Institute showed that the volume of Vestfonna Ice Cap was about 500 km3. Aerial photographs and satellite imagery subsequently showed that flow speeds on the southern tidewater glaciers were several hundred metres per year. This was an order of magnitude faster than the surrounding ice and more than double the calculated balance velocities. It was suggested that this negative state of mass balance was a result of short-lived glacier surges. However, the interior ice plateau on Vestfonna Ice Cap is today experiencing widespread progressive thinning, either as a result of changing regional climate dynamics or enhanced discharge from outlet glaciers. This project proposes glaciological investigations on Vestfonna Ice Cap with the aim to quantify the link between climate dynamics and ice flow. The proposed investigations include the collection of radio-echo sounding data in a traverse across the ice cap and in two designated study areas, one on the northern ice margin and one on a southern tidewater glacier. The radar data provide a means to measure ice thickness and examine the nature of the bed, e.g. the distribution of melting and freezing and the presence of water, which serves as a lubricant. We will install two digital cameras near the terminus of Frazerbreen, which is a tidewater glacier, so that we can monitor the position of its calving ice front. A total of six GPS receivers will be installed on the ice to monitor horizontal and vertical motion on a sub-hourly timescale during an 18-month period. By combining GPS data with digital time-lapsed imagery, and output from an automatic weather station, we will be able to understand how forces are balanced in the ice cap and this will enable us to examine how the ice mass behaves under different climatic and oceanographic conditions. With the application of a 3D numerical ice-flow model, we will be able to study the response of the ice cap to global warming and predict its contribution to sea level change.