Interdecadal Shift of the NAO South Center in Late Winter and Its Climatic Impact

The North Atlantic Oscillation (NAO) and North Atlantic tripole sea surface temperature (SST_tri) are important modes in the atmosphere and ocean over the North Atlantic, respectively. The link between the two is well-known. However, this link decreased significantly in 1980–2001 (P2), compared to 1959-1979 (P1) and 2002-2022 (P3). This is related to the significant interdecadal shift of the NAO south center. In late winter, the NAO south center experienced a significant "west-east-west" interdecadal shift, shifting eastward by up to 20° longitude during P2. The eastward shift of the NAO forced the region of strong air-sea interactions to shift, resulting in the collapse of NAO-related SST_tri during P2. In addition, the winter SAT reversal frequency in the mid-latitudes of Eurasia also experienced interdecadal changes. SAT reversal events in P1 and P3 are twice as frequent as those in P2, which is related to the interdecadal westward shift of the NAO south center in P1 and P3. When the NAO south center was westward in late winter, the North Atlantic jet stream retreated significantly from the early winter. The development of the Ural blocking caused the accumulation of cold air in Siberia, causing the reverse change of the Siberian High compared to the early winter, resulting in a SAT reversal in the mid-latitude of Eurasia.