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PHY-05 Southern Ocean heat uptake and transport in a changing climate
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Effects of SAM and ENSO on winter climate over the Ross Sea and the Amundsen Sea
Chuan Xie* , Shanghai Jiao Tong University Zhaoru Zhang, Shanghai Jiao Tong University Meng Zhou, Shanghai Jiao Tong University |
This study uses ERA5 data to conduct composite analysis of wind, air temperature and sea level pressure in winter over the Ross Sea and the Amundsen Sea when Southern Annular Mode (SAM) and ENSO events occur simultaneously, and further analyzes the impact of SAM and ENSO on the Amundsen Sea Low (ASL) in winter. The variation characteristics of the wind in this region during different periods are explained by EOF decomposition of typical regions combined with the changes of the ASL center. It is found that the SAM and ENSO mainly affect the wind by affecting the zonal position of the ASL in the Ross Sea and the western Amundsen Sea. When the positive phase of the SAM and the La Niña event coincided, the ASL moved significantly eastward, resulting in a weakening of southerly winds in the western Ross Sea, a strengthening of southerly winds in the eastern Ross Sea, and a weakening of easterly winds along the coast of the western Amundsen Sea. In the eastern Amundsen Sea, the SAM mainly affects the wind in this region by affecting the meridional position of the ASL. When the SAM is in negative phase, the northerly position of the ASL will lead to stronger easterly winds in the eastern Amundsen Sea. In addition, the position offset of the ASL changed the atmospheric circulation in the region. When the positive phase of the SAM and the La Niña event occurred at the same time, the ASL was close to the western coast of the Amundsen Sea, and the cold air flow from the Antarctic continent dominated the region, resulting in an abnormally low air temperature, with a maximum decrease of more than 3°C.
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