Ice elevation changes in the Shackleton Range Weddell Sea embayment, Antarctica

南极洲韦德尔海海湾沙克尔顿山脉的冰海拔变化：我们的目标是用突出在南极冰盖中的山脉作为过去冰层厚度和体积变化的标尺。我们将重点关注沙克尔顿山脉，该山脉位于浮动的费尔奇纳冰架和大陆冰交界处的敏感位置，并建立最后一次冰盛期的冰厚度和过去10,000年来变薄的轨迹。在一个正在变暖的世界里，知道南极冰盖将会发生什么是很重要的。例如，在IPCC的报告中，科学家们的共识是，全球变暖对南极冰盖体积的影响将接近中性。两个截然不同的过程将相互抵消。一方面，气温的升高会增加大气的持水能力，从而导致降雪，导致冰层厚度增加。另一方面，南极洲周围温暖的海水温度可能会增加漂浮冰架的融化，并导致外围地区变薄。卫星观测记录了这两个过程，但令人惊讶的是，西南极部分地区正在发生融化和变薄的速度。有一种风险是，变薄可能会蔓延到西南极冰盖的大部分，这些冰盖固定在海平面以下，并导致海平面上升至多5米。提高认识的一个步骤是建立近数千年来冰盖变化的轨迹。这将确定冰盖的所有部分是否以类似的方式对全球变暖和海平面上升等外部强迫做出反应，或者不同部门是否对由于当地条件而导致的冰川动态的周期性变化做出反应。此外，变化记录将是检验冰盖模型预测能力的一种方式。如果这些模型能够复制过去冰量的波动，那么我们就可以更有信心地相信它们预测未来情景的能力。人们对韦德尔海地区冰盖变化的历史知之甚少，特别是在沙克尔顿山脉地区，那里的边界冰流占到菲尔什纳-罗恩冰架总流入的三分之一。我们建议通过对山脉中不稳定的巨石和基岩进行宇宙成因的同位素分析来纠正这一点。这项技术测量了岩石表面暴露在宇宙射线下的时间长度。如果冰一直在变薄，那么较高海拔的岩石表面暴露的时间将比较低海拔的岩石表面暴露的时间更长，这将被岩石表层中的宇宙成因核素吸收。在现实中，这种模式往往更有趣，因为反复无常的表面和基岩表面可能在覆盖的冰下完好无损地存活下来，并反映了几次冰川的历史。通过使用三种同位素10Be、26Al和21Ne，我们可以拾取它，甚至重建相当复杂的历史，然后用它来开发更好的冰盖模型。这项工作将减少我们对西南极冰盖构成的风险的理解中的不确定性。这也将提高我们对自上一次冰盛期以来海平面上升的了解，因为目前还没有确凿的证据来估计威德尔海部分的冰量损失。

Ice elevation changes in the Shackleton Range, Weddell Sea embayment, Antarctica: summary Our aim is to use mountains protruding through the Antarctic Ice Sheets as dipsticks of past changes in ice thickness and volume. We will focus on the Shackleton Range which is situated in a sensitive location at the junction between the floating Filchner Ice Shelf and continental ice and establish the thickness of ice at the Last Glacial Maximum and the trajectory of thinning over the last 10,000 years. It is important to know what will happen to the Antarctic Ice Sheet in a world that is warming. The consensus among scientists, for example in the IPCC reports, is that the effect of global warming on the volume of the Antarctic Ice Sheet will be close to neutral. Two contrasting processes will cancel each other out. On the one hand the increase in air temperatures will increase the water-holding capacity of the atmosphere, and thus snowfall, causing an increase in ice thickness. On the other hand, warmer sea water temperatures around Antarctica may increase melting of floating ice shelves and cause thinning of peripheral areas. Satellite observations record both such processes, but a surprise is the speed with which melting and thinning is occurring in parts of West Antarctica. There is a risk that the thinning may spread to much of the West Antarctic Ice sheet that is grounded below sea level and lead to a sea-level rise of up to 5m. One step in improving understanding is to establish the trajectory of change of the ice sheet over recent millennia. This will establish whether all parts of the ice sheet are responding in a similar way to external forcing such as global warming and sea level rise, or whether different sectors are responding to cyclic changes in glacier dynamics as a result of local conditions. In addition the record of change will be a way of testing the predictive power of ice-sheet models. If the models can replicate the past fluctuations in ice volume, then we can have more confidence in their ability to forecast future scenarios. The history of ice sheet changes in the Weddell Sea sector is poorly understood, especially in the Shackleton Range area where bounding ice streams accounts for one third the total inflow into the Filchner-Ronne Ice Shelf. We propose to remedy this by using cosmogenic isotope analysis on erratic boulders and bedrock in the mountains. The technique measures the length of time that a rock surface has been exposed to cosmic rays. If the ice has been thinning then rock surfaces at higher altitudes will have been exposed for longer than those at lower altitudes and this will be picked up by the cosmogenic nuclides in the surface layer of the rock. In reality the pattern is often more interesting in that erratics and bedrock surfaces may have survived intact beneath overriding ice and reflect a history of several glaciations. By using three isotopes 10Be, 26Al and 21Ne, we can pick this up and even reconstruct quite complicated histories which will then be used to develop better ice sheet models. The work will reduce the uncertainties in our understanding of the risk posed by the West Antarctic Ice Sheet. It will also improve our knowledge of sea-level rise since the Last Glacial Maximum, since at the moment there is no firm evidence on which to base estimates of ice volume loss from the Weddell Sea sector.