Anthropogenic Forcing of Antarctic Ice Loss (AnthroFAIL)

冰盖融化被广泛认为是人为全球变暖的例证。地球上最大的冰块-南极洲-正在失去冰，到2100年可能会对全球海平面造成1米或更多的影响。然而，目前还不清楚这种冰层流失是由人类活动造成的。相反，这块冰盖可能只是对气候系统中的自然变化做出了反应。南极冰层的消失主要是由于海洋增加了冰盖的融化。然而，目前还不知道为什么这种融化会发生变化。融化了西南极冰盖的深海海水已经在深海中埋藏了几个世纪，而不仅仅是与其他气候一起变暖。相反，风的变化被认为改变了这些温暖的海水向南极洲的运输。这导致了南极洲正在融化冰的两种主要可能性。首先，温室气体和/或臭氧空洞引起的风的人为变化可能逐渐增加了向冰盖供应温暖的水。或者，风的自然变异性可能导致了一段时间的高度融化，引发了自我维持的冰盖后退。现在我们迫切需要了解人类活动是否加剧了南极洲的海洋融化。如果冰的流失是由人类活动造成的，我们必须确定将未来变化降至最低的最佳策略。如果冰层的消失是自然的和不可避免的，我们必须为海平面上升做好准备，海平面上升将在未来几个世纪上演。该项目将通过对西南极周围海洋的计算机模拟，仔细分析自然和人类影响的影响。我们将首先使用气候模型中的历史风来驱动一组海洋模拟，这些模拟包括我们对1920年以来在各种自然和人为因素作用下南极洲海洋融化的真实历史的最佳猜测。这些模拟将与来自船舶、自动驾驶车辆和海洋沉积物岩心的可用历史观测进行测试。一旦我们有了这个模型历史，我们就会计算出它是如何受到每一种不同的作用力的影响的。我们将在有或没有人类温室气体、臭氧空洞和自然气候变异性的情况下进行大量的海洋模拟。这些模拟将告诉我们每个作用力对西南极冰盖海洋融化的贡献。当我们对历史力量的作用有了很好的了解后，我们就有能力评估未来力量的影响。臭氧空洞预计将在2100年之前恢复，因此问题是，未来的温室气体排放将在多大程度上压倒这种恢复，并在此后继续不受控制。这项研究将解决人类是否导致南极冰川消失的根本问题，以及我们现在是否可以对此做些什么。迫切需要这些问题的答案，以澄清我们防止或适应未来海平面上升的各种选择。

Melting ice caps are widely viewed as illustrative of anthropogenic global warming. The largest ice mass on Earth - Antarctica - is losing ice, and may contribute 1 metre or more to global sea level by 2100. However, it is not clear that this ice loss has been caused by human activities. Instead, this ice sheet may be simply responding to natural variability in the climate system.Antarctic ice loss is primarily caused by increased melting of the ice sheet by the ocean. However, it is not known why this melting has changed. The deep ocean waters melting the West Antarctic Ice Sheet have been buried in the deep ocean for centuries, and have not simply warmed alongside the rest of the climate. Instead, changes in the winds are thought to have altered the transport of these warm waters towards Antarctica.This leads to two main possibilities for why Antarctica is losing ice. Firstly, anthropogenic changes in the winds, caused by greenhouse gases and/or the ozone hole, may have gradually increased the supply of warm water towards the ice sheet. Alternatively, natural variability of the winds may have caused a period of high melting that triggered a self-sustaining ice sheet retreat.It is now urgent that we understand whether human activities have increased the ocean melting of Antarctica. If the ice loss is caused by human activities, we must identify the best strategy for minimising future change. If the ice loss is natural and inevitable, we must prepare for the sea-level rise that will play out over the coming centuries. This project will carefully unpick the contributions of natural and human influences using computer simulations of the ocean surrounding West Antarctica. We will first use historical winds from climate models to drive a set of ocean simulations that comprise our 'best guess' of the real history of ocean melting of Antarctica since 1920, under all natural and human forcings. These simulations will be tested against available historical observations from ships, autonomous vehicles, and ocean sediment cores.Once we have this model history, we will work out how it has been influenced by each of the different forcings. We will perform large sets of ocean simulations with and without human greenhouse gases, the ozone hole, and natural climate variability. These simulations will tell us the contribution of each forcing to the oceanic melting of the West Antarctic Ice Sheet. When we have a good understanding of the role of historical forcings, we will be equipped to assess the impact of future forcings. The ozone hole is expected to recover before 2100, so the question is to what extent future emissions of greenhouse gases will overwhelm this recovery, and continue unchecked thereafter. This research will address the fundamental questions of whether humans have caused Antarctic ice loss, and whether there is anything we can now do about it. The answers to these questions are urgently needed to clarify our options for preventing or adapting to future sea-level rise.