Arctic sea ice and bifurcations in a hierarchy of simplemodels (tentative)

在我的博士学位中，我将研究北冰洋海冰系统中存在哪些分叉以及控制它们的过程。我的项目将特别关注季节性在分叉中所起的作用，并研究夏季和常年海冰的分叉。学术文献分叉的外部通常被称为“临界点”，指的是系统中控制参数的微小变化会导致系统质量行为的突变。北极的气候主要是由太阳辐射驱动的，由于其高反照率，海冰对北极的能量输入有很大影响。进一步的影响包括表面温度逆温的形成、海洋的热屏蔽和对当地大气循环的影响(Liu等人，2016)。海冰的增长和融化也会影响全球大气和海洋循环(Semmler等人，2016)。海冰对北极生态也至关重要--它为许多动物提供了栖息地，它的生长和融化循环在海洋中的营养循环中发挥着重要作用。因此，由于夏季和常年海冰对北极和更广泛的世界都有很大的影响，因此研究它们进入和离开有夏季和常年海冰的国家是非常有兴趣的。此外，北冰洋海冰的减少是衡量气候变化进程的常用指标，因此提高对其进程的理解是很有意义的。我的项目将考察一系列模型，以确定模型预测北冰洋海冰分叉的条件。我将集中讨论大气中二氧化碳浓度变化对分叉的控制。这将有助于提高对在不久的将来出现分叉可能性的理解，但更重要的是，将澄清北极气候的不同组成部分在日益复杂的模型中如何相互作用。更好的海冰在强迫下的行为概念模型也将有助于为海冰在GCM中的表现提供新的基准。我还希望展望未来，考虑在其他强迫情况下存在分叉--特别是在冰川-间冰旋回期间的轨道强迫下。

In my PhD I will look at the question of what bifurcations exist in the Arctic sea ice system and what processes control them. My project will in particular focus on the role seasonality plays in bifurcations and look at bifurcations in both summer and perennial sea ice.Outside of academic literature bifurcations are commonly called 'tipping points' and refer to points in a system where a small variation of a control parameter leads to an abrupt shift in the qualitative behaviour of a system.The climate of the Arctic is primarily driven by solar radiation, and due to its high albedo sea ice greatly impacts the energy input to the Arctic. Further effects include the formation of surface temperature inversions, thermal shielding of the ocean and impacts on local atmospheric circulation(Liu et al., 2016). Growth and melt of sea ice can also affect global atmospheric and ocean circulation(Semmler et al., 2016). Sea ice is also vital for Arctic ecology - it provides a habitat for many animals, and its growth and melt cycles play an important role in circulating nutrients in the oceans. As such, study into transitions in and out of states with summer and perennial sea ice is of great interest due to the large impacts they have both on the Arctic and wider world. Moreover, Arctic sea ice decline is a common measure for the progress of climate change so it is of interest to improve understanding of its progression.My project will look at a hierarchy of models to identify which conditions models predict bifurcations in Arctic sea ice in. I will focus on bifurcations controlled by changing of atmospheric CO2concentrations. This will help improve the understanding of the likelihood of a bifurcation looming in the near future, but more importantly will clarify how different components of Arctic climate interact in models of increasing complexity. Better conceptual models of how sea ice behaves under forcing will also help provide new benchmarks for sea ice representation in GCMs.I also hope to look beyond the near future and consider the existence of bifurcations under other forcing situations - in particular under orbital forcing during glacial-interglacial cycles.