Interdecadal modulation of AMO on the relationship between spring Arctic Oscillation and the following winter ENSO

As two crucial climate modes, Arctic Oscillation (AO) in boreal spring acts as an important extratropical driver for the development of El Ni & ntilde;o-Southern Oscillation (ENSO) in the following winter. This study further reveals that the Atlantic Multidecadal Oscillation (AMO) has a strong modulation on the linkage between spring AO and following winter ENSO, with stronger AO-ENSO relationship during the negative phase of AMO (- AMO) than that during the positive phase of AMO (+ AMO). During - AMO, the spring AO induces an anomalous cyclone over the subtropical western North Pacific via eddy-mean flow interaction, which leads to westerly wind anomalies along equatorial western Pacific, then causes sea surface temperature (SST) warming, and finally affects the occurrence of El Ni & ntilde;o in the following winter. While during + AMO, the atmospheric circulation, precipitation, and SST anomalies associated with the spring AO are much weaker over the North Pacific. As such, the spring AO has weak impacts on the following winter ENSO during + AMO. Further analyses show that the AMO may modulate the North Pacific atmospheric circulation through affecting the spatial pattern of AO and eddy-mean flow interaction. In particular, the North Pacific storm track in spring is stronger during - AMO than that during + AMO years, which leads to stronger synoptic-scale eddy feedback to the mean flow, and results in stronger AO-related atmospheric anomalies over the North Pacific. This study provides new insights on the interdecadal relationship between AO and ENSO from an inter-basin view.