講演情報
[ACG68-P03]Increasing Frequency of Extratropical Cyclones in the Bering Strait and Chukchi Sea Region Under the Progression of Global Warming
*堀 正岳1、吉森 正和1 (1.東京大学大気海洋研究所)
キーワード：
低気圧、北極温暖化増幅
Extratropical cyclones (ETCs) are a fundamental component of midlatitude and Arctic climate, governing precipitation distribution and the poleward transport of heat and moisture. While previous studies utilizing idealized GCMs (Tamarin and Kaspi 2017) and CMIP models (Crawford et al. 2023) indicate a general northward shift in ETC tracks under global warming, this study focuses specifically on the wintertime northern North Pacific and the northern flank of the storm track near the Bering Strait to investigate changes in propagation properties. Using the large ensemble Database for Policy Decision-Making for Future Climate Change (d4PDF; Mizuta et al. 2017), we compared 30-year daily data from a non-warming simulation (HPB-NAT, 100 members) against 2K and 4K warming experiments (HFB-2K and 4K, with 54 and 90 members, respectively). Cyclone tracking was performed using the University of Melbourne algorithm (Murray and Simmonds 1991), with detection parameters optimized against the CEOS/NSIDC dataset (Crawford et al. 2021) and ERA5 reanalysis (Hersbach et al. 2017). Results indicate that while the total number of cyclone systems in the North Pacific basin decreased by 6.5% under the 4K warming experiment, the frequency of cyclones passing through the Bering Strait increased by 32%. These Bering Strait ETCs exhibit an increased northward movement tendency, characterized by an 18-degree eastward displacement in average cyclogenesis location and a 10-degree westward displacement in average cyclolysis location. While baroclinicity decreases in the higher latitude, the upper level steering wind strengthens, leading to more cyclones generated outside the domain entering the Bering strait and Chukchi Sea region. This result is consistent with the study using CMIP models (Chen et al. 2025). In the poster presentation, we further explore the differences in mean cyclone propagation pathways and the associated atmospheric intensification environments.