Recent work published in Climate Dynamics by Professor Xiuqun Yang's group has unveiled the changes in wintertime poleward heat and moisture transport associated with Arctic amplification, and explored the feedbacks of these changes in heat and moisture transport on amplified Arctic warming.
The Arctic is sensitive and critical to global climate change. The pronounced warming in the Arctic that is twice faster than the global average, known as the Arctic amplification (AA), has been observed during the past three decades. AA could have an impact on large-scale circulation as well as extreme weather in midlatitudes. Yet the linkage between AA and the midlatitude change is still under debate. In addition, it remains unclear how the changes in the midlatitude wave system can further affect AA via altering poleward heat and moisture transport. Thus, investigating the impacts of AA on atmospheric transport in mid and high latitudes and its feedbacks will improve our understanding of the linkage between Arctic and midlatitudes.
Five atmospheric reanalyses with different resolutions (NCEP2, ERA-Interim, JRA-55, MERRA-2, and CFSR; from upper to lower panels) were used in this study. On the one hand, spatially sparse and short observations in the high latitudes lead to uncertainties in reanalyses. On the other hand, earlier work by our group pointed out the importance of using fine-resolution reanalyses in accurately understanding the midlatitude synoptic eddy–mean flow interaction.
The results indicate that the amplified Arctic warming is accompanied by significant warming and moistening of the Arctic troposphere. The increased poleward heat and moisture transport by mid and highlatitude stationary waves, especially stationary wave component of zonal wave number 1, further favors Arctic warming and moistening, thus acting as a positive feedback onto the Arctic warming. Meanwhile, the Arctic warming reduces atmospheric baroclinicity and thus weakens transient eddy activities in high latitudes. As a result, the decreased transient eddy activities reduce poleward heat and moisture transports, which decrease the Arctic temperature and moisture, acting as a negative feedback onto the Arctic warming (Fig. 1). Since the increased poleward heat transport by stationary waves is nearly canceled by the decreased transport by transient eddies, the total poleward heat transport contributes little to the Arctic warming (Fig. 2). However, the total poleward moisture transport increases over most areas of the high latitudes that is dominated by the increased transport by stationary waves, which provides a significant net positive feedback onto the Arctic warming and moistening (Fig. 3).
These changes by epoch differences are significantly consistent with the interannual anomalies. The results are compared well among four high-resolution reanalyses, while NCEP2 is often in disagreement with the other four reanalyses. In this study, the authors examine the impact of AA on the mid and high latitudes heat and moisture transport, and highlight the positive feedback of moisture transport that may be particularly crucial to the amplified Arctic warming during winter when the ice-albedo feedback vanishes.
In 2022, Climate Dynamics published a paper titled “Decadal changes of wintertime poleward heat and moisture transport associated with the amplified Arctic warming”. A PhD student Xiaozhuo Sang from the School of Atmospheric Sciences, Nanjing University is the first author of this paper. Professor Xiuqun Yang is the corresponding author. This study is supported by the National Natural Science Foundation of China (Grant Nos. 41621005 and 41875086), the National Key Basic Research and Development Program of China (Grant No. 2018YFC1505902), and the Jiangsu Collaborative Innovation Center for Climate Change.
Sang, X., Yang, X.-Q.*, Tao, L., Fang, J., & Sun, X. (2022). Decadal changes of wintertime poleward heat and moisture transport associated with the amplified Arctic warming. Climate Dynamics, 58, 137-159, https://doi.org/10.1007/s00382-021-05894-7.
Sang, X., Yang, X.-Q.*, Tao, L., Fang, J., & Sun, X. (2022). Evaluation of synoptic eddy activities and their feedback onto the midlatitude jet in five atmospheric reanalyses with coarse versus fine model resolutions. Climate Dynamics, 58, 1363-1381, https://doi.org/10.1007/s00382-021-05965-9.
Fig. 1 A schematic diagram for the impact of the amplified Arctic warming on the high latitude poleward heat and moisture transports by stationary waves and transient eddies and their possible feedbacks
Fig. 2 Decadal differences between 1999–2016 and 1981–1998 of wintertime zonally-averaged poleward heat transport (K m/s) by total disturbances (left panels), stationary waves (middle panels), and transient eddies (right panels) with five atmospheric reanalyses (NCEP2, ERA-Interim, JRA-55, MERRA-2, and CFSR; from upper to lower panels). The zero lines are shown in bold black. The differences with values exceeding the 90% (p<0.1) significance level according to the Student’s t-test are crossed
Fig. 3 As in Fig. 2, but for the poleward moisture transport (10-4 kg/kg m/s)