ScotIce - How fast could ice caps collapse?

在上个世纪，地球上所有地方的平均地表气温都在上升，预计至少在下个世纪还会继续上升。气候变暖最明显的迹象之一是北极冰川的萎缩和海冰的显著减少，那里的大气变暖最为明显。海冰融化不会导致海平面上升，但来自陆地冰川和冰盖的融水最终流入海洋，是海平面上升的主要原因。冰川和冰盖融化的速度有多快？它们会在几十年内消失，将所有的水迅速加入海洋，还是会在更长的时间内融化，虽然速度较慢，但最终海平面上升的幅度相同。对于生活在离涨潮1米以内的1.5亿人，以及那些关心维护价值数万亿英镑的全球沿海基础设施的人来说，回答冰川和冰帽融化的速度以及导致海平面上升的速度是很重要的。苏格兰冰将通过分析大约11600年前存在于苏格兰并消失的冰帽的崩溃来确定冰帽融化的速度当时气温上升了8摄氏度，与2100年北极气温上升的预测相同。通过测量冰帽消失的速度，我们将了解到在类似变暖的情况下，现今同等大小的冰体消失的速度，从而为海平面上升模型提供所需的数据，以做出更明智的预测。为了量化苏格兰冰帽崩溃的速度，我们需要能够确定前冰体的变化率。我们将使用宇宙射线在岩石中的矿物石英中产生的宇宙成因核素10 Be和26 Al的表面暴露测年，即当岩石暴露在天空中时。相反，当岩石被几米厚的冰覆盖时，石英中的核素的产生就停止了。地表暴露年代测定法是唯一可以直接测定冰融化时地貌暴露年代的技术。我们将测量这些核素的浓度在冰川磨损和拔出的岩石表面和冰川搬运巨石，位于最大，中间和最小范围的冰帽。因为我们知道宇宙成因核素在石英中产生的速度有多快，所以我们可以使用测得的宇宙成因核素浓度来确定岩石表面样品何时从冰下暴露出来。换句话说，我们可以确定冰是何时从样本地点消失的。最大和最小的冰范围之间的年龄差提供的撤退率，这将是集成与独立日期的气候代理档案，以寻找因果关系。为了能够测试假设的快速崩溃的苏格兰冰帽，我们首先需要提高表面暴露测年技术从目前的常规2-3%到1%或更好的测量精度为10 Be和26 Al。对目前用于测量10 Be和26 Al的加速器质谱仪（AMS）的分析改进将使我们能够解决冰盖崩溃的速度。然而，对于某些问题，AMS不太可能提供必要的精确度。为了解决冰盖的下降是稳定的还是偶发的，需要开发一种全新的方法来测量26铝，该方法由苏格兰大学环境研究中心（SUERC）率先采用的正离子质谱法（PIMS）。开发Al PIMS有可能导致地球和环境科学家如何确定自然过程和日期景观速率的范式转变。ScotIce关于冰盖崩溃的经验数据将为预测海平面模型提供信息，而改进的AMS精度和新的Al-PIMS有可能彻底改变表面暴露年代测定，并为英国和国际科学界开辟新的研究领域。

Average surface air temperatures have been rising everywhere on Earth over the last century and are predicted to continue to rise for at least the next century. One of the clearest indicators of this warming is the shrinking of glaciers and the marked reduction of sea ice in the Arctic, where atmospheric warming is most pronounced. Melting of sea ice does not contribute to sea level rise, but meltwater from land-based glaciers and ice caps ends up in the oceans and is a major contributor to sea level rise. How fast will glaciers and ice caps melt? Will they disappear in decades, adding all of their water rapidly to the oceans, or will the melting occur over a longer time span, with a less rapid but ultimately the same amount of sea level rise. For the 150 million people living within 1 m of high tide, and those concerned about maintaining trillions of pounds worth of global coastal infrastructure, answering the question of how fast glaciers and ice caps will melt and contribute to sea level rise is important.ScotIce will determine how fast ice caps can melt by analysing the collapse of the ice cap that existed in Scotland about 11600 years ago and disappeared at a time when temperatures rose by 8C, the same as the temperature rise predicted for the Arctic by 2100. By measuring how quickly the ice cap disappeared we will learn how fast present day equivalent sized ice masses subjected to similar warming could disappear, thus providing data needed for sea level rise models to make more informed predictions.To quantify how fast the Scottish ice cap collapsed we need to be able to determine the rate of change of the former ice mass. We will use surface exposure dating with the cosmogenic nuclides 10Be and 26Al produced in the mineral quartz in rock by cosmic rays, that is, when the rock is exposed to the sky. Conversely, the production of the nuclides in quartz stops when the rocks are covered by a few metres of ice. Surface exposure dating is the only technique available to directly date when landforms become exposed as ice melts. We will measure the concentration of these nuclides in glacially abraded and plucked rock surfaces and glacially transported boulders, located at the maximum, intermediate and minimum extent of the ice cap. Because we know how fast the cosmogenic nuclides are produced in quartz, we can use the measured cosmogenic nuclide concentration to determine when the sampled rock surface became exposed from under the ice. In other words, we can determine when the ice disappeared from the sample site. The age difference between the maximum and minimum ice extent provides the retreat rate which will be integrated with independently dated climate proxy archives to look for causal relationships.To be able to test the hypothesised rapid collapse of the Scottish ice cap we first need to improve the surface exposure dating technique from the current routine 2-3% to 1% or better measurement precision for 10Be and 26Al. Analytical improvements to the accelerator mass spectrometry (AMS) that is currently used to measure 10Be and 26Al will allow us to resolve the rate of ice cap collapse. However, there are some questions for which AMS is unlikely to provide the necessary precision. To resolve if the decline of the ice cap was steady or episodic requires the development of an entirely new methodology for measuring 26Al by positive ion mass spectrometry (PIMS) being pioneered at the Scottish Universities Environmental Research Centre (SUERC). Developing Al PIMS has the potential for leading to a paradigm shift in how Earth and Environmental scientists determine the rate of natural processes and date landscapes. ScotIce empirical data on ice cap collapse will inform predictive sea level models, while improved AMS precision and new Al-PIMS has the potential to revolutionise surface exposure dating and open up new fields of research for the UK and international science community.