The future of Arctic sea ice

人为气候变化正在破坏北冰洋的海冰覆盖。冰的消失是不稳定的(可变的)，但科学家们一致认为，常年的北极冰盖将不会在本世纪幸存下来。海冰覆盖部分阻碍了上面的空气和漂浮的海洋之间的热量、水和动量的交换。海冰的减少正在并预计将继续对当地气候和生态产生主要影响，并通过改变(欧洲)较低纬度大气和海洋中的热量和动量交换来影响极端天气和全球气候。使用复杂气候模型产生的气候预测表明，北冰洋在未来几十年将成为季节性无冰的。然而，这些模型低估了极地变暖和海冰减少之间的联系的强度；它们只能在不切实际的极地变暖的情况下获得观测到的冰消失率。近年来，随着新的卫星，如IceSat-2和CryoSat-2，从空间测量海冰的性质，以及马赛克等实地实验提供海冰物理过程的详细测量，对北极的观测有所改进。这些表明，北冰洋海冰正在变薄、变小、变得更加碎片化、变得更具季节性。海冰物理的气候模型建立在常年结冰的时代，不能充分反映正在形成的冰盖的季节性和碎片化的性质。我们将结合不同的卫星数据产品，提供对当地海冰质量预算的估计。这些测量以及其他测量将被用于对海冰模型进行前所未有的严格测试。我们将通过纳入在季节性冰盖物理中观察到的重要物理过程的表示来增强我们的海冰模型，例如不断演变的浮冰大小分布和脆弱冰的高级表示，这两个过程都已被视为在更具季节性的南大洋海冰覆盖中发挥主导作用。该项目将对北极海冰的模式表示进行必要的升级。新的海冰物理将被纳入一个完整的气候模式，用于探讨它们对过去几十年冰盖的影响，以及它们对年代际预测的影响。我们对气候模拟的分析将利用我们在更简单、更理想化的模型中探索的想法，以及对以前气候模型模拟的分析。我们的目标是在我们接近季节性无冰的北冰洋时，对最近过去和不久的将来的北冰洋海冰趋势和变化进行更现实的模拟。该项目将：(I)结合观测到的北极变暖速率模拟北冰洋海冰融化的观测速率；(Ii)更严格地限制北冰洋何时实现季节性无冰；以及(Iii)检验这样一种假设，即气候模型中海冰消融速率与北极变暖速率之间的不匹配是由于现代北冰洋海冰复盖的物理表现不充分造成的。

Anthropogenic climate change is destroying the Arctic sea ice cover. The ice loss is erratic (variable), but scientists agree the perennial Arctic ice cover will not survive this century. The sea ice cover is a partial barrier to exchanges of heat, water, and momentum between the air above and the ocean on which it floats. The reduction in sea ice is having, and is expected to continue to have, a dominant impact on local climate and ecology, and to affect extreme weather and global climate by modification of exchanges of heat and momentum in the atmosphere and ocean with lower (European) latitudes.Climate projections, generated using complex climate models, indicate that the Arctic Ocean will become seasonally ice free in the coming decades. However, these models underestimate the strength of the link between polar warming and sea ice loss; they only achieve observed rates of ice loss with unrealistic polar warming. Observations of the Arctic have improved in recent years with new satellites, e.g. IceSat-2 and CryoSat-2, measuring sea ice properties from space, and field experiments such as MOSAiC providing detailed measurements of sea ice physical processes. These show that Arctic sea ice is becoming thinner, less extensive, more fragmented, and more seasonal. Climate models of sea ice physics, built in a time of perennial ice, inadequately represent the seasonal, fragmented nature of the emerging ice cover. We will combine different satellite data products to provide estimates of the local sea ice mass budget. These measurements, among others, will be used to provide an unprecedently stringent test of sea ice models. We will enhance our sea ice models through the incorporation of representations of physical processes observed to be important in the seasonal ice cover physics, such as an evolving floe size distribution and advanced representation of frazil ice, both of which are already seen to play a leading role in the, more seasonal, Southern Ocean sea ice cover. This project will result in a necessary upgrade to model representation of Arctic sea ice.The new sea ice physics will be brought into a full climate model, which will be used to explore their impact on the ice cover of the past few decades, and their impact on decadal predictions. Our analysis of the climate simulations will utilise ideas we have explored in simpler, more idealised models and analysis of previous climate model simulations. Our aim is to produce more realistic simulations of Arctic sea ice trends and variability in the recent past and near future, as we approach a seasonally ice-free Arctic Ocean. This project will: (i) simulate the observed rates of Arctic sea ice loss in combination with the observed rates of Arctic warming; (ii) more tightly constrain when the Arctic Ocean will become seasonally ice free; and (iii) test the hypothesis that climate models' mismatch between rates of sea ice loss and Arctic warming is a consequence of inadequate physical representation of the modern Arctic sea ice cover.