Response of the North Pacific decadal variability to multidecadal changes in the tropical sea surface temperature variability

The relationship between North Pacific climate variability and ENSO dynamics has been widely studied in the recent years. In particular, the second dominant mode of North Pacific sea level pressure, the North Pacific Oscillation (NPO) has been linked to ENSO via the Seasonal Footprinting Mechanism (SFM). Variability associated to ENSO is then transmitted to midlatitudes via atmospheric teleconnections which excites atmospheric variability that is transmitted into the ocean as the Pacific Decadal Oscillation (PDO) in the case of the Aleutian Low (AL) or as the North Pacific Gyre Oscillation (NPGO) in the case of the NPO. Using a 2000 yr long integration of the GFDL CM2.1 global coupled, the response of the North Pacific climate to interdecadal changes in the tropical Pacific associated to ENSO is studied. The analysis was done separately during different epochs, considering the SST variability of the Nino3 index. Periods were the index variability agrees well with observations, multidecadal epochs with hardly any variability, highly irregular epochs, and warm skewed ENSO events were considered. The analysis is based on the estimation of the principal modes of variability during each epoch for both sea surface temperature and sea level pressure in the Pacific basin. Preliminary results show that the NPO is more sensitive to interdecadal changes in the tropical SST than the Aleutian Low, particularly in those epochs where there is little variability or highly irregular epochs. This suggests, as some authors have pointed out that part of the NPO variability may not independent of ENSO. The response of the midlatitude ocean to changes in these atmospheric patterns will also be addressed.