Towards a marginal Arctic sea ice cover

最近观察到的北极变化已经成为全球气候变化的“典型代表”，特别是因为夏季海冰范围在过去35年中迅速缩小。海冰的消退导致了跨北极航运的增长，以及从海底提取矿物和化石燃料的计划。政府间气候变化专门委员会（气候专委会）的最新评估得出结论，假设温室气体排放继续增加，到2050年北极可能会可靠地成为无冰地区。然而，IPCC使用的气候模拟往往无法真实地捕捉北极海冰的大尺度特性，如范围，变化和最近的趋势。因此，有必要改进北极海冰的模拟，以便更好地了解最近观察到的变化和对未来的可信预测，帮助评估风险和机会，并为关于适应和减缓的重要政策决定提供信息。近年来，随着新卫星从太空测量海冰特性，对北极的观测有所改善。这些卫星不仅揭示了北极冰盖的范围和厚度在所有季节都在减少，而且边缘冰区（MIZ），一个由相对分散的小浮冰组成的低冰区集中区域，已经增长。模型预测表明，到2050年，MIZ将从夏季海冰覆盖的10%左右增长到80%，将迄今为止相对平静的北冰洋暴露在大气中。空气、冰和海洋之间的非线性相互作用放大或缩小了变化，即所谓的反馈，与海冰覆盖面积减少和边缘化有关，这种作用将在未来几年出现或占据主导地位。许多这些反馈要么完全没有，要么在当前的模型中没有充分捕捉到。例如，不包括的是反馈，从而产生较小的浮冰由于冰融化或海洋波浪应力下的分裂促进进一步的横向融化和波的传播更深的包，进一步扩大MIZ。由于现有的气候模型过度简化了这些反馈，它们在理解和预测北极变化和变化方面的效用受到了损害。由于纬向大气和海洋环流的误差以及北极的冰输出，这也导致低纬度气候模型的准确性受损。我们将使用现有的和新的观测结果来研究控制MIZ演变的过程。我们将包括物理波冰相互作用，冰破裂和融化，浮冰碰撞到冰，海洋和气候模型。我们将使用这些模型，约束和验证新的观测，探索海冰，海洋和大气之间的反馈使用一系列的数值实验。我们将量化MIZ的增加对北极物理气候的影响，并探索导致北极海冰预计损失的过程。

Recent observed changes in the Arctic have become a 'poster child' for global climatic changes, particularly because the summer sea ice extent has shrunk rapidly over the past 35 years. This retreat of the sea ice has led to growth of trans-Arctic shipping and plans to extract minerals and fossil fuels from the ocean floor. The latest assessment of the Intergovernmental Panel on Climate Change (IPCC) concluded that it was likely that the Arctic would become reliably ice-free by 2050 assuming greenhouse gas emissions continue to increase. However, the climate simulations used by the IPCC often fail to realistically capture large scale properties of the Arctic sea ice, such as the extent, variability and recent trends. Therefore, there is a need to improve simulations of Arctic sea ice to provide better understanding of the recent observed changes and credible projections of the future to help assess risks and opportunities and inform important policy decisions about adaptation and mitigation. Observations of the Arctic have improved in recent years with new satellites measuring sea ice properties from space. These satellites reveal not only that the extent and thickness of the Arctic ice cover is reducing in all seasons but that the Marginal Ice Zone (MIZ), a region of low ice area concentration consisting of a relatively disperse collection of small floes, has grown.Model projections indicate the MIZ will grow from around 10% to 80% of the summer sea ice cover by 2050, exposing a hitherto relatively quiescent Arctic Ocean to the atmosphere. Nonlinear interactions between the air, ice, and ocean that magnify or diminish change, known as feedbacks, associated with a reduced and marginal sea ice cover will emerge or assume dominance in the coming years. Many of these feedbacks are either entirely absent or inadequately captured in current models. For example, not included is the feedback whereby the creation of smaller floes due to ice melt or breakup under ocean wave stress promotes further lateral melt and propagation of waves deeper into the pack, further enlarging the MIZ. Because existing climate models oversimplify these feedbacks, their utility for understanding and predicting variability and change in the Arctic is compromised. This leads to impairment of climate model accuracy at lower latitudes also, due to errors in meridional atmospheric and oceanic circulations as well as ice export from the Arctic. We will investigate processes controlling evolution of the MIZ using existing and new observations. We will include physics of wave-ice interaction, ice breakup and melt, and floe collisions into ice, ocean, and climate models. We will use these models, constrained and verified with new observations, to explore feedbacks between the sea ice, ocean, and atmosphere using a series of numerical experiments. We will quantify the impact of the increase in the MIZ on the Arctic physical climate, and explore the processes responsible for the projected loss of Arctic sea ice.