Regime shifts found in the Northern Hemisphere SST field

摘要: A 'regime shift' is characterized by an abrupt transition from one quasi-steady climatic state to another, and its period much shorter than the lengths of individual epochs each state. In present study, we investigate when regime shifts occurred what was difference in states before after shifts, using wintertime sea surface temperature (SST) field Northern Hemisphere. The relationship between changes SST field, those atmospheric circulation, also investigated. order detect organized patterns variations, apply empirical orthogonal function (EOF) analysis. As results, first mode identical El Nino/Southern Oscillation (ENSO) so-called Pacific Decadal (PDO), corresponds Pacific/North American (PNA) pattern. second mode, which relates Arctic (AO), has a zonally elongated signal both North Atlantic, Pacific. EOF analyses oceanic basin are made separately, robustness these modes confirmed. define as 'significant' 'systematic' two states, continuing more 5 years. Then, identify years carefully inspect time series original gridded data modes. result, six detected study 1910s 1990s: 1925/26, 1945/46, 1957/58, 1970/71, 1976/77 1988/89. It ascertained that at almost all grids completed within year. All having similar circulation pattern, including intensity Aleutian Low (AL), corresponding central can be well described combination duration shift about 10 years, PDO. simultaneous first, modes, imply change AL activity associated with PNA might have some connection AO.