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A negative phase shift of the winter AO/NAO due to the recent Arctic sea-ice reduction in late autumn
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| Title: | A negative phase shift of the winter AO/NAO due to the recent Arctic sea-ice reduction in late autumn |
| Authors: | Nakamura, Tetsu Browse this author | | Yamazaki, Koji Browse this author | | Iwamoto, Katsushi Browse this author | | Honda, Meiji Browse this author | | Miyoshi, Yasunobu Browse this author | | Ogawa, Yasunobu Browse this author | | Ukita, Jinro Browse this author |
| Keywords: | Arctic sea-ice loss | | Arctic Oscillation | | long-term changes | | severe winter |
| Issue Date: | 28-Apr-2015 |
| Publisher: | American Geophysical Union |
| Journal Title: | Journal of geophysical research atmospheres |
| Volume: | 120 |
| Issue: | 8 |
| Start Page: | 3209 |
| End Page: | 3227 |
| Publisher DOI: | 10.1002/2014JD022848 |
| Abstract: | This paper examines the possible linkage between the recent reduction in Arctic sea-ice extent and the wintertime Arctic Oscillation (AO)/North Atlantic Oscillation (NAO). Observational analyses using the ERA interim reanalysis and merged Hadley/Optimum Interpolation Sea Surface Temperature data reveal that a reduced (increased) sea-ice area in November leads to more negative (positive) phases of the AO and NAO in early and late winter, respectively. We simulate the atmospheric response to observed sea-ice anomalies using a high-top atmospheric general circulation model (AGCM for Earth Simulator, AFES version 4.1). The results from the simulation reveal that the recent Arctic sea-ice reduction results in cold winters in mid-latitude continental regions, which are linked to an anomalous circulation pattern similar to the negative phase of AO/NAO with an increased frequency of large negative AO events by a factor of over two. Associated with this negative AO/NAO phase, cold air advection from the Arctic to the mid-latitudes increases. We found that the stationary Rossby wave response to the sea-ice reduction in the Barents Sea region induces this anomalous circulation. We also found a positive feedback mechanism resulting from the anomalous meridional circulation that cools the mid-latitudes and warms the Arctic, which adds an extra heating to the Arctic air column equivalent to about 60% of the direct surface heat release from the sea-ice reduction. The results from this high-top model experiment also suggested a critical role of the stratosphere in deepening the tropospheric annular mode and modulation of the NAO in mid to late winter through stratosphere-troposphere coupling. |
| Rights: | http://creativecommons.org/licenses/by-nc-nd/4.0/ |
| Type: | article |
| URI: | http://hdl.handle.net/2115/60135 |
| Appears in Collections: | 環境科学院・地球環境科学研究院 (Graduate School of Environmental Science / Faculty of Environmental Earth Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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Submitter: 中村 哲
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