North Pacific Subtropical Mode Water Variability Controlled by the Atlantic Multi-Decadal Oscillation

Mode waters play an important role in contributing to mass, heat, nutrient transport and climate variability. Previous studies attribute the decadal variability of North Pacific Subtropical Mode Water (NPSTMW) to the Pacific Decadal Oscillation (PDO) and recent trend to global climate change. Here we show that the decadal to multi-decadal variability of NPSTMW is more related with the Atlantic Multi-Decadal Oscillation (AMO) rather than PDO . During AMO positive phase, warm sea surface temperature (SST) in the north Atlantic Ocean will weaken the Aleutian low and subtropical North Pacific westerlies by atmospheric teleconnection (Wu et al., 2008, JC; Sun et al., 2017, Nature Comm.). The anomalous east wind will induce warm Ekman heat transport in the NPSTMW area, especially its formation and subduction area and vice visa during AMO negative phase. The observations support the above mechanism that the core temperature of NPSTMW have very good correlation with AMO for 1945-2012, lower during 1966-1985 with negative AMO phase and higher during 2001-2010 with positive AMO phase. Although PDO is dominant in the North Pacific decadal variability, it has little impact on SST anomaly in the Subtropical Western Pacific Ocean, where it is the formation and subduction region of NPSTMW. Our findings suggest that the AMO is important for the decadal prediction in the Pacific Ocean since mode water is the climate memory.