The California current system during the last 136,000 years : response of the North Pacific High to precessional forcing

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Alkenone sea surface temperature (SST) records were generated from the Ocean Drilling Program's (ODP) Sites 1014 and 1016 to examine the response of the California Current System to global climate change during the last 136 ka. The temperature differences between these sites (ΔSSTNEP=SSTODP1014–SSTODP1016) reflected the intensity of the California Current and varied between 0.4 and 6.1 °C. A high ΔSSTNEP (weaker California Current) was found for late marine isotope stage (MIS) 2 and early MIS 5e, while a low ΔSSTNEP (stronger California Current) was detected for mid-MIS 5e and MIS 1. Spectral analysis indicated that this variation pattern dominated 23- (precession) and 30-ka periods. Comparison of the ΔSSTNEP and SST based on data from core MD01-2421 at the Japan margin revealed anti-phase variation; the high ΔSSTNEP (weakening of the California Current) corresponded to the low SST at the Japan margin (the southward displacement of the NW Pacific subarctic boundary), and vice versa. This variation was synchronous with a model prediction of the tropical El Niño-Southern Oscillation behavior. These findings suggest that the intensity of the North Pacific High varied in response to precessional forcing, and also that the response has been linked with the changes of tropical ocean–atmosphere interactions.
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