The future of Arctic sea ice

人为的气候变化正在破坏北极海冰覆盖。冰的损失是不稳定的（可变的），但科学家们一致认为，北极常年的冰盖将在本世纪消失。海冰覆盖部分地阻碍了上面的空气和海洋之间的热、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，并通过改变低纬度地区（欧洲）大气和海洋的热量和动量交换来影响极端天气和全球气候。使用复杂气候模式生成的气候预测表明，北冰洋在未来几十年将成为季节性无冰区。然而，这些模式低估了极地变暖和海冰损失之间联系的强度；他们只能在不切实际的极地变暖中达到观测到的冰损失率。近年来，对北极的观测有所改善，新卫星如IceSat-2和CryoSat-2从空间测量海冰特性，以及实地实验，如MOSAiC提供海冰物理过程的详细测量。这些数据表明，北极海冰正在变得更薄、范围更小、碎片化程度更高、季节性更强。海冰物理的气候模型是建立在常年冰期的，不能充分反映新出现冰盖的季节性和破碎性。我们将结合不同的卫星数据产品，提供当地海冰质量预算的估计。这些测量结果将被用于对海冰模型进行前所未有的严格测试。我们将通过结合在季节性冰盖物理中观测到的重要物理过程的表征来增强我们的海冰模型，例如不断变化的浮冰大小分布和巴西冰的先进表征，这两者已经被认为在更具季节性的南大洋海冰覆盖中发挥了主导作用。该项目将导致对北极海冰模型表示的必要升级。新的海冰物理学将被纳入一个完整的气候模型，该模型将用于探索它们对过去几十年冰盖的影响，以及它们对十年预测的影响。我们对气候模拟的分析将利用我们在更简单、更理想化的模型和对以前气候模型模拟的分析中探索过的想法。我们的目标是在我们接近一个季节性无冰的北冰洋时，对最近的过去和不久的将来的北极海冰趋势和变化进行更真实的模拟。该项目将：(i)结合观测到的北极变暖速率，模拟观测到的北极海冰损失率；（ii）更严格地限制北冰洋何时成为季节性无冰；（iii）验证气候模式在海冰损失率和北极变暖之间的不匹配是现代北极海冰覆盖的物理表征不足的结果这一假设。

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.