IRD heavy minerals as a provenance tool for ice coverage on Greenland

在过去150年左右的时间里，人类的工业化导致了地球气候的变化。这种变化的主要原因是我们燃烧化石燃料、砍伐森林和制造水泥所排放的二氧化碳（CO2）和甲烷（CH 4）等温室气体。到目前为止，温室变暖的幅度相对较小，年平均气温仅上升约1摄氏度。但由于这种变暖，大陆冰盖和山谷冰川已经开始融化，海洋已经热膨胀-两者都导致海平面上升约15厘米。到目前为止，这些变化相对较小，更令人担忧的是由于我们持续和以前的温室气体排放，即将到来的变暖程度以及随之而来的气候变化。为了更好地了解现代气候和预测未来的气候变化，人们开发了数值模型，试图模拟温室气体排放的影响。这些大气环流模式（GCM），虽然非常复杂，仍然是不完善的工具，需要验证。因此，对不同的古代气候系统的研究现在是向气候变化问题的决策者提供信息的一个组成部分。如果这些模型成功地再现了过去发生的大规模气候变化，这将使我们对它们对未来的预测更有信心。最具信息量的类似物是在最近的地质历史中，地理配置，洋流和生态系统与今天相似。上新世中期（大约300万年前）是地球历史上最近的一个时期，当时全球平均气温比今天高得多，如果我们继续以目前的速度燃烧化石燃料，气候将与本世纪末的预测相似。因此，有可能使用上新世中期作为未来全球变暖的模拟和测试气候模型的准确性。在我们对未来气候的预测方面，特别令人关切的是格陵兰岛和南极洲的大陆冰盖将在海平面变化中发挥的作用。例如，如果格陵兰岛上所有的冰融化，全球海平面将上升6-8米。在上新世中期，格陵兰岛上的冰可能比今天少，尽管我们目前还不知道岛上有多少被冰覆盖--和今天一样多吗？或者是明显更少？本提案的中心目的是解决这些问题，并首次确定上新世中期格陵兰冰盖的面积范围。我们将通过研究来自北大西洋300万年前深海沉积物中的沙子大小的颗粒来实现这一更大的理解。这些颗粒最初通过冰川侵蚀进入冰盖，被运送到冰缘，并在大约300万至330万年前冰山在开阔的海洋中融化时沉积下来。我们将首先测试现代谷物的化学和同位素组成以及年龄是否准确地反映了它们被侵蚀的格陵兰地区。然后，通过仔细观察大约300万年前沉积物中的颗粒，我们可以估计当时哪些地区被冰覆盖。然后可以将此重建与现有模型结果进行比较，以检查其性能。这将有助于我们了解他们对格陵兰冰盖未来行为的预测的信心程度。

Over the last 150 years or so the industrialisation of the human race has caused the climate of our planet to change. The principal causes of this change are our emissions of greenhouse gases such as carbon dioxide (CO2) and methane (CH4) due to burning fossil fuels, deforestation and cement making. So far the amount of greenhouse warming is relatively small, only ~1 degC increase in mean annual temperature. But as a consequence of this warming the continental ice sheets and valley glaciers are already beginning to melt and the oceans have thermally expanded - both leading to ~15 cm rise in sea level. Up to now these changes have been relatively minor, what is of more concern is the magnitude of the warming to come and the climate changes that will accompany it due to our continued and previous greenhouse gas emissions. In an effort to better understand modern climate and to predict future climate change, numerical models have been developed in an attempt to simulate the effects of greenhouse gas emissions. These General Circulation Models (GCM), though extraordinarily complex, remain imperfect tools that require validation. Therefore, the study of distinct ancient climate systems is now an integral part in informing policy makers on climate change issues. If these models successfully reproduce large-scale climate changes that occurred in the past, this will give us more confidence in their prediction for the future. The most informative analogues are in the recent geological past where geographical configurations, ocean currents and ecosystems are similar to today. The Mid-Pliocene (about 3 Myrs ago) is the most recent time in Earth's history when mean global temperatures were substantially warmer than today with a climate similar to that predicted for the end of this century if we continue to burn fossil fuels at the current rate. Thus, there is potential for using the Mid-Pliocene as an analogue for future global warming and testing the veracity of climate models. Of particular concern with respect to our prediction of future climate is the role the continental ice sheets of Greenland and Antarctica will play in changing sea level. For example, if all the ice on Greenland were to melt global sea level would be around 6-8 m higher. During the Mid-Pliocene it is likely that there was less ice on Greenland than today although we currently do not have a good idea about how much of the island was covered in ice - was it as much as today? Or was it significantly less? The central aim of this proposal is to address these questions and determine for the first time the areal extent of the Greenland ice sheet during the Mid-Pliocene. We will achieve this greater understanding by examining sand sized grains from 3 million year old deep ocean sediments from the North Atlantic. These grains were originally incorporated into the ice sheet by glacial erosion, transported to the ice margin, and incorporated into icebergs before being deposited as the iceberg melted in the open ocean around 3 to 3.3 million years ago. We will first test whether the chemical and isotopic composition and age of modern grains accurately reflect the region of Greenland from which they were eroded. Then, by carefully looking at grains from sediments from ~3 million years ago, we can get an estimate of which areas were covered in ice at that time. This reconstruction can then be compared to existing model results to examine their performance. This will help inform our level of confidence in their predictions of the behaviour of the Greenland ice sheet in the future.