Normal modes in North Atlantic atmosphere-ocean system and predicting North Atlantic sea surface temperature

We identify an interdecadal oscillatory mode of the North Atlantic atmosphere-ocean system via a Linear Inverse Model (LIM). This mode is shown to be related to the interior pathway propagation of Atlantic Meridional Overturning Circulation (AMOC) anomalies. The oscillation is an ocean-only mode while excited by atmospheric forcing; in particular, it can be approximated as a linearly driven damped oscillator while the North Atlantic Oscillation (NAO) acts as part of the ''external" force. We also show that the influence of NAO-induced surface wind stress forcing quickly damps while the NAO-induced deep flow anomaly, integrating with ocean topography, plays a crucial role in this interdecadal mode. Including such deep ocean dynamics besides surface temperature (SST) significantly improves and prolongs the LIM's prediction skill of SST evolution.