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

在我的博士论文中，我将研究北极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中的分叉。在学术文献之外，分叉通常被称为“临界点”，指的是系统中控制参数的微小变化导致系统定性行为突然转变的点。北极的气候主要由太阳辐射驱动，由于北极海冰的高度密集，极大地影响了北极的能源输入。进一步的影响包括形成表面温度逆温、海洋的热屏蔽和对当地大气环流的影响（Liu等人，2016）。海冰的增长和融化也会影响全球大气和海洋环流（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，其生长和融化周期在海洋中的营养循环中发挥着重要作用。因此，研究夏季和常年海冰状态的转换非常有趣，因为它们对北极和更广泛的世界都有很大的影响。此外，北极海冰下降是气候变化进展的一个常见指标，因此提高对其进展的理解是有意义的。我的项目将研究模型的层次结构，以确定哪些条件模型预测北极海冰的分叉。我将重点关注由大气CO2浓度变化控制的分叉。这将有助于更好地理解在不久的将来出现分叉的可能性，但更重要的是，将澄清北极气候的不同组成部分如何在日益复杂的模型中相互作用。更好的概念模型下海冰的行为强迫也将有助于提供新的基准海冰表示在GCMs.I还希望看到在不久的将来，并考虑在其他强迫情况下的分叉的存在-特别是在轨道强迫在冰川间冰期周期。

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.