Seasonal and Interannual Variability for the Atlantic Meridional Overturning Circulation in the Subpolar North Atlantic

North Atlantic subpolar basin is a region of complex dynamics and has profound impacts on the global climate system. The Overturning in the Subpolar North Atlantic Program (OSNAP) observing system was launched in summer 2014 to provide the basinwide measurement of meridional property transport. These unprecedented data revealed that it is the Irminger Sea and Iceland basin, rather Labrador Sea, that dominate the variability of Atlantic Meridional Overturning Circulation (AMOC) on the seasonal time scale. It remains unclear what causes such behavior. The purpose of this study is to explore the underlying physics for the AMOC seasonal variability along the OSNAP array. Eddy-resolving numerical models, including HYCOM and NEMO, are assessed against the observational time series from the OSNAP array. Our results reveal that HYCOM is capable to capture the variability of OSNAP array. Additional sensitivity experiments, aiming to elucidate the roles of momentum and buoyancy forcing, are conducted. Comparing the meridional transport induced by momentum and buoyancy with that in the control simulation, we conclude that momentum forcing is a key player to drive the AMOC variability on time scales from seasonal to interannual.