Purpose of Review

The observed substantial loss of Arctic sea ice has raised prospects of a seasonally ice-free Arctic Ocean within the foreseeable future. In this review, we summarize our current understanding of the most likely trajectory of the Arctic sea-ice cover towards this state.

Recent Findings

The future trajectory of the Arctic sea-ice cover can be described through a deterministic component arising primarily from future greenhouse gas emissions, and a chaotic component arising from internal variability. The deterministic component is expected to cause a largely ice-free Arctic Ocean during summer for less than 2 ^∘C global warming relative to pre-industrial levels. To keep chances below 5 % that the Arctic Ocean will largely be ice free in a given year, total future CO₂ emissions must remain below 500 Gt.

Summary

The Arctic Ocean will become ice free during summer before mid-century unless greenhouse gas emissions are rapidly reduced.

中文翻译：

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通往季节性无冰北冰洋的轨迹。

审查目的

观察到的北冰洋海冰大量减少，在可预见的未来提出了季节性无冰北冰洋的前景。在这篇综述中，我们总结了我们目前对北极海冰覆盖最有可能走向这一状态的轨迹的理解。

最近的发现

北极海冰覆盖的未来轨迹可以通过主要由未来温室气体排放产生的确定性成分和由内部变化引起的混沌成分来描述。预计确定性成分将在夏季导致北冰洋基本无冰，相对于工业化前水平，全球变暖低于 2 ^{∘ C。}为使北冰洋在特定年份基本无冰的可能性保持在 5% 以下，未来的 CO ₂总排放量必须保持在 500 Gt 以下。

概括

除非迅速减少温室气体排放，否则北冰洋将在本世纪中叶之前的夏季变得无冰。