Early 20th-century Arctic warming intensified by Pacific and Atlantic multidecadal variability
Early 20th-century Arctic warming intensified by Pacific and Atlantic multidecadal variability
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DOI：
10.1073/pnas.1615880114
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发表时间：
2017-05
期刊：
影响因子：
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通讯作者：
H. Tokinaga;S. Xie;H. Mukougawa
中科院分区：
文献类型：
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作者：
H. Tokinaga;S. Xie;H. Mukougawa
重要意义北极放大是气候对全球变暖反应的一个强有力的特征，对生态系统和社会有很大影响。一个长期存在的谜团是，北极显著变暖发生在20世纪初，当时辐射强迫的年代际变化速度比现在弱得多。在这里，我们利用观测和模式实验表明，内部产生的太平洋和大西洋年代际变化的综合效应在20世纪初加剧了北极陆地变暖。太平洋-大西洋同步变暖极大地改变了北半球行星尺度的大气环流，将暖空气输送到北极。我们的结果突出了区域海洋表面温度变化对北极气候的重要性，并限制了这一重要区域的模式预测。随着全球变暖的加剧和创纪录的海冰减少，北极是全球变暖的金丝雀。人们对历史上的北极变暖知之甚少，限制了我们对模型预测的信心。具体地说，北极地表气温在20世纪初迅速上升，速度与近几十年相当，尽管温室气体强迫要弱得多。在这里，我们表明，太平洋和大西洋年代际变化模式的同时相移是20世纪初北极迅速变暖的主要驱动因素。当海洋表面温度的年代际变率(SST)被适当规定时，大气模式模拟成功地再现了北极早期变暖。20世纪初北极变暖与热带和北大西洋SST正异常和太平洋SST模式有关，太平洋SST模式使人联想到太平洋年代际振荡的正阶段。大气环流变化是20世纪初北极变暖的重要原因。赤道太平洋变暖加深了阿留申低压，将暖空气平流到北美北极地区。温带北大西洋和北太平洋海温变暖加强了欧亚大陆北部的地面西风，加剧了那里的变暖。耦合的海洋-大气模拟支持太平洋和大西洋年代际模式同时从负到正的相移，从而建设性地加剧北极变暖。我们的结果有助于将历史上的北极变暖归因于此，从而限制了这一重要地区预计的放大变暖。
Significance Arctic amplification is a robust feature of climate response to global warming, with large impacts on ecosystems and societies. A long-standing mystery is that a pronounced Arctic warming occurred during the early 20th century when the rate of interdecadal change in radiative forcing was much weaker than at present. Here, using observations and model experiments, we show that the combined effect of internally generated Pacific and Atlantic interdecadal variabilities intensified the Arctic land warming in the early 20th century. The synchronized Pacific–Atlantic warming drastically alters planetary-scale atmospheric circulations over the Northern Hemisphere that transport warm air into the Arctic. Our results highlight the importance of regional sea surface temperature changes for Arctic climate and constrain model projections in this important region. With amplified warming and record sea ice loss, the Arctic is the canary of global warming. The historical Arctic warming is poorly understood, limiting our confidence in model projections. Specifically, Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing. Here, we show that the concurrent phase shift of Pacific and Atlantic interdecadal variability modes is the major driver for the rapid early 20th-century Arctic warming. Atmospheric model simulations successfully reproduce the early Arctic warming when the interdecadal variability of sea surface temperature (SST) is properly prescribed. The early 20th-century Arctic warming is associated with positive SST anomalies over the tropical and North Atlantic and a Pacific SST pattern reminiscent of the positive phase of the Pacific decadal oscillation. Atmospheric circulation changes are important for the early 20th-century Arctic warming. The equatorial Pacific warming deepens the Aleutian low, advecting warm air into the North American Arctic. The extratropical North Atlantic and North Pacific SST warming strengthens surface westerly winds over northern Eurasia, intensifying the warming there. Coupled ocean–atmosphere simulations support the constructive intensification of Arctic warming by a concurrent, negative-to-positive phase shift of the Pacific and Atlantic interdecadal modes. Our results aid attributing the historical Arctic warming and thereby constrain the amplified warming projected for this important region.