Unnatural Trend Detection of Arctic Amplification

Abstract The driving mechanism of Arctic amplification (AA) is so complex that no consistent and definitive conclusion has been formed yet. In particular, the natural or unnatural cause of AA has not yet been investigated and distinguished in clarity and depth. Given that the Arctic is more sensitive than other regions to greenhouse gases and other unnatural forcing, especially human activity, we are focusing on separating unnatural trend (caused by unnatural forcing) from the Arctic surface air temperature (SAT) changes during 1979–2017 to quantify the contribution of unnatural forcing on AA, with converting detection and attribution to probability statistics model. Compared to earlier studies, we find that the Arctic coast of the Siberian Great Plains, from the Barents Sea to the Kara Sea and eastward to the Bering Strait, has been warming most significantly, which is mainly dominated by unnatural trends. From 1979 to 2017, the minimum unnatural warming in most parts of the Arctic Ocean reached above 1.5℃, especially in the Kara Sea area, where the unnatural warming was significant, reaching 4℃. The Kara Sea is sensitive to unnatural forcing. In addition, the minimum unnatural contributions exceed 60% in most parts of the Arctic Circle, and was more than 80% in (75–90°N, 150–180°W). In 140°W-140°E Arctic region, the unnatural trend is the most remarkable with 0.82℃ per decade, accounting for 84.5% of the measured warming trend. Meanwhile, the unnatural trend changes most rapidly for the temporal evolution in this area (0-140°W, 60–90°N).