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第51期出刊日：2022.04.15

不同二氧化碳濃度作用下北極暖化加強及其季節性變化

Arctic Amplification, and its Seasonal Migration, Over a Wide Range of Abrupt CO2 Forcing

文 / Yu-Chiao Liang (梁禹喬); Lorenzo M. Polvani; Ivan Mitevski

The Arctic amplification - specifically referring to the outpace of the near-surface air temperature increases within the Arctic relative to the weaker global temperature increases – is one of the most prominent features as a consequence of the anthropogenic global warming in observations and climate model simulations (Figures 1a and b). However, larger model-to-model difference (Figure 1c) indicates that more studies are needed to improve our understanding of the drivers. This international cooperation research led by the Department of Atmospheric Sciences, College of Science, National Taiwan University, examines the Arctic amplification and its seasonality response to varying CO2 forcing in a suite of climate model experiments. International cooperators include scientists from Columbia University in the City of New York. This study has been accepted in npj Climate and Atmospheric Science under Nature Publisher in December, 2021. The online version will be available in early January, 2022.

The causes and effects of Arctic amplification have been extensively attracted climate scientists’ interest in understanding the underlying mechanisms. This study uses well-designed global climate model experiments to show that the increasing CO2 concentrations give rise to stronger Arctic warming but weaker Arctic amplification, due to relatively weaker warming of the Arctic in comparison with the rest of the globe due to weaker sea-ice loss and atmosphere-ocean heat fluxes at higher CO2 levels. Researchers further find that the seasonal peaks in Arctic warming and Arctic amplification shift gradually from November to January as CO2 increases (Figure 2). The results suggest that the changes in the magnitude and seasonality of Arctic amplification may have important ecological and socio-economic implications.

北極暖化加強是指北極近地表溫度增加比全世界近地表溫度上升強兩至五倍的現象，此現象是全球氣候暖化下最顯著的氣候表徵之一。本研究利用全球模式實驗加入不同二氧化碳濃度來探討北極暖化加強現象以及其季節性的變化，我們發現北極暖化加強的幅度隨著二氧化碳濃度的增加而減少，同時一年當中北極暖化加強的最大值會逐漸從晚秋(November)移到晚冬(January)，這樣的改變和北極的海冰融化程度和海洋大氣間的熱量傳送有著密不可分的關係。由於北極暖化加強的現象對全球氣候以及經濟可能會產生顯著的影響，因此本研究的結果可以提供生態系及社會經濟層面對應此劇烈變化的參考依據。

References：

Yu-Chiao Liang, Lorenzo M. Polvani, and Ivan Mitevski (2022) Arctic amplification, and its seasonal migration, over a wide range of abrupt CO2 forcing. npj Climate and Atmospheric Science, 5, 14 (2022). https://doi.org/10.1038/s41612-022-00228-8.

Hansen, J., R. Ruedy, M. Sato, and K. Lo (2010) Global surface temperature change. Review Geophysics, 48, RG4004.

Lenssen, N., G. Schmidt, J. Hansen, M. Menne, A. Persin, R. Ruedy, and D. Zyss (2019) Improvements in the GISTEMP uncertainty model. Journal of Geophysical Research Atmosphere, 124, 6307-6326.

Figure 1. (a) Linear trend map of global near-surface air temperatures during 1979-2014 period based on the observational estimate from NASA Surface Temperature Analysis version 4 (GISTEMP v4) [Hansen et al. 2010; Lenssen et al. 2019, https://data.giss.nasa.gov/gistemp/]. (b) Multi-model mean trend map of global near-surface air temperatures during 1979-2014 period from 50 CMIP6 models. (c) Standard deviation map of the global near-surface air temperature trends across 50 CMIP6 models. Figure courtesy of Mr. You-Ting Wu at National Taiwan University.
圖一。(a) 1979-2014近地表溫度線性趨勢地圖。(b) 50組CMIP6氣侯模式模擬的近地表溫度線性趨勢圖。(c) 50組CMIP6氣候模式模擬之進地表溫度線性趨勢圖的標準差。感謝台大吳宥廷同學幫忙繪製圖一。

Figure 2. Seasonal evolutions of the Arctic surface air temperature (SAT) response, and AAFs in the CO2 forcing experiments. (a) The evolution of Arctic SAT responses for 2x to 8xCO2. (b) Similar as a but for Arctic amplification factor, defined as the Arctic SAT change divided by global SAT change. Values in (a) are referenced to July values. This figure is adapted from Liang et al. (2022).
圖二。(a) 每個月份近地表溫度隨著不同強度二氧化碳濃度的變化。(b) 同圖(a)，但表示北極暖化加強因子隨著不同二氧化碳濃度的變化。