BRITICE-CHRONO: Constraining rates and style of marine influenced ice sheet decay

最近对地球极地冰盖的卫星测量强调，冰的范围和厚度的变化速度远远高于预期。研究人员面临的挑战是将这些观测结果置于更长期的背景下，并建立计算机模型（“冰盖预测”），以可靠地预测本世纪及以后冰盖的命运。尽管远离人类居住，极地冰盖却影响着全球海平面。融化加剧和冰山崩解造成的退缩导致海平面上升，人们担心海平面可能上升数米，使数百万人及其生计离开沿海家园。在这个时间点上，不可能研究目前南极或格陵兰冰盖的完整生命周期，因为它们仍在演变和经历大规模的变化。相反，我们将使用现已完全消退的冰盖；在最后一个冰河时期，覆盖了英国、爱尔兰和北海大部分地区的冰盖。大约在2.5万年前，最后一次不列颠-爱尔兰冰盖的最大覆盖面积达到了100万平方公里，以全球标准来看相对较小。然而，它的特征、环境和行为与现代南极西部和格陵兰冰盖有惊人的相似之处。英国-爱尔兰冰盖的大部分地区受到海洋的影响，就像今天的南极洲西部一样；无数湍急的冰流带走了大部分的冰块，就像今天的格陵兰冰盖一样。这三者都是或曾经是高度动态的，在气候敏感地区，有海洋部门、海洋终端边缘和陆地冰川。所有这些共同因素使英爱冰原成为了解冰原在一系列时间尺度上的动态变化的一个强有力的类比，在现在和未来都是如此。该联盟成员最近的工作揭示了曾经覆盖不列颠群岛的冰盖退缩的模式，正如终碛和其他冰川地貌所记录的那样。该联盟成员的其他工作是使用复杂的计算机模型来模拟上一个冰河时代结束时冰盖对气候变化的反应。然而，这些模型只能与它们所依据的地质数据一样好，而且这种模式在时间上的约束很差。我们需要更多地了解过去气候变化对冰盖消融的方式、速率和时间的影响。这些知识使我们能够进一步完善计算机模型，以便做出更好的预测。因此，该项目的主要重点是收集覆盖不列颠群岛的最后一个冰原沉积的沉积物和岩石，并利用这些沉积物和有机残留物，到目前为止（例如通过放射性碳分析）冰原边缘的退缩。为了实现这一目标，该项目将使用200多个精心挑选的地点，对大约800个样本进行测年。在海上，将使用从科考船降至海底的取芯装置提取样本，在陆上则通过人工采样和使用小型钻井平台提取样本。一旦样品确定了年代，并与地形提供的模式信息相结合，就可以绘制出冰盖萎缩的地图。这将提供关于整个冰盖变化的时间和速度的关键信息。英国-爱尔兰冰原将成为世界上最受约束的冰原，并将成为未来冰原模型改进和测试的基准。关于不列颠群岛周围海底沉积物的特征和年龄的知识对许多工业、考古和遗产应用也很有用。因此，该项目与感兴趣的合作伙伴密切相关，例如，定位海上风电场，英国和爱尔兰之间的电缆，以及旨在保护海上考古遗迹的遗产机构。

Recent satellite measurements of the Earth's polar ice sheets highlight that changes in ice extent and thickness are occurring at rates far higher than expected. The challenge for researchers is to place these observations into a longer-term context and produce computer models ('ice sheet forecasts') that reliably predict the fate of ice sheets over this century and beyond. Although remote from habitation, the polar ice sheets influence global sea level. Retreat by increased melting and iceberg calving produces higher sea levels and concerns exist that sea level may rise by metres displacing many millions of people, and their livelihoods, from their coastal homes. At this point in time, it is not possible to study the full life cycle of the present Antarctic or Greenland ice sheets as they are still evolving and undergoing large-scale changes. Instead, we will use an ice sheet that has now fully retreated; the ice sheet that covered most of Britain, Ireland and the North Sea during the last ice age. The last British-Irish ice sheet covered up to 1,000,000 km2 at its maximum size, around 25,000 yrs ago, and was relatively small by global standards. However, its character, setting and behaviour have striking parallels with both the modern West Antarctic and Greenland Ice Sheets. Large parts of the British-Irish Ice Sheet were marine-influenced just like in west Antarctica today; and numerous fast-flowing ice streams carried much of its mass, just like in the Greenland Ice Sheet today. All three are or were highly dynamic, in climatically sensitive regions, with marine sectors, ocean-terminating margins and land-based glaciers. All these common factors make the British-Irish Ice Sheet a powerful analogue for understanding ice sheet dynamics on a range of timescales, operating now and in the future.Recent work by members of this consortium has revealed the pattern of ice sheet retreat that once covered the British Isles, as recorded by end moraines and other glacial landforms. Other work by members of this consortium has used sophisticated computer models to simulate the ice sheet's response to climate change at the end of the last Ice Age. However, these models can only be as good as the geological data on which they are based, and the pattern is poorly constrained in time. We need to know more about the style, rate and timing of ice sheet decay in response to past climate change. Such knowledge allows us to further refine computer modelling so that better predictions can be made. The main focus of the project therefore, is to collect sediments and rocks deposited by the last ice sheet that covered the British Isles, and use these, along with organic remains, to date (e.g. by radiocarbon analyses) the retreat of the ice sheet margins. The project will use over 200 carefully chosen sites, dating some 800 samples in order to achieve this. Offshore, samples will be extracted using coring devices lowered from a research ship to the seabed, and onshore by manual sampling and by use of small drilling rigs. Once the samples are dated and added to the pattern information provided by the landforms, maps of the shrinking ice sheet will be produced. These will provide crucial information on the timing and rates of change across the whole ice sheet. The British-Irish Ice Sheet will become the best constrained anywhere in the world and be the benchmark against which ice sheet models are improved and tested in the future.Knowledge on the character and age of the seafloor sediments surrounding the British Isles is also useful for many industrial, archaeological and heritage applications. Accordingly, the project is closely linked to partners interested, for example, in locating offshore windfarms, electricity cables between Britain and Ireland, and heritage bodies aiming to preserve offshore archaeological remains.