ScotIce - How fast could ice caps collapse?

在上个世纪，地球上的平均地表气温一直在上升，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地区冰川的萎缩和海冰的显著减少，而北极地区是大气变暖最明显的地区。海冰融化不会导致海平面上升，但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。冰川和冰帽融化的速度有多快？它们是会在几十年内消失，将所有的水迅速注入海洋，还是会在更长的时间跨度内融化，速度较慢，但最终海平面上升的幅度相同。对于生活在涨潮1米以内的1.5亿人，以及那些关心维护全球价值数万亿英镑的沿海基础设施的人来说，回答冰川和冰盖融化并导致海平面上升的速度有多快，是很重要的。ScotIce将通过分析大约11600年前存在于苏格兰的冰盖的崩塌来确定冰盖融化的速度，这些冰盖在气温上升8摄氏度的时候消失了，这与北极到2100年的温度上升预测相同。通过测量冰盖消失的速度，我们将了解到今天同等大小的冰块受到类似变暖的影响会消失多快，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塌的速度，我们需要能够确定以前冰块的变化率。我们将利用宇宙射线在岩石中的矿物石英中产生的宇宙核素10Be和26Al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层融化时地貌暴露时间的技术。我们将测量这些核素在冰川磨损和脱落的岩石表面以及冰川运输的巨石中的浓度，这些岩石表面位于冰盖的最大、中间和最小范围。因为我们知道宇宙形成核素在石英中产生的速度有多快，我们可以使用测量的宇宙形成核素浓度来确定样品岩石表面何时从冰下暴露出来。换句话说，我们可以确定冰从采样点消失的时间。最大和最小冰面积之间的年龄差提供了退缩率，将与独立定年的气候代理档案相结合，以寻找因果关系。为了能够测试苏格兰冰盖快速崩塌的假设，我们首先需要改进地表暴露年代测定技术，从目前常规的2-3%提高到1%，或者提高10Be和26Al的测量精度。目前用于测量10Be和26Al的加速器质谱（AMS）的分析改进将使我们能够解决冰盖崩塌的速度。然而，有一些问题AMS不太可能提供必要的精度。为了确定冰盖的下降是稳定的还是偶然的，苏格兰大学环境研究中心（SUERC）率先开发了一种全新的方法，通过正离子质谱法（PIMS）测量26Al。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的速率和日期景观的范式转变。ScotIce关于冰盖崩塌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有可能彻底改变地表暴露年代测定，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.