That link does
NOT support your claims. From your linked article:
Tipping to an undesired state in the climate is, however, a growing concern with increasing greenhouse gas concentrations.
We estimate a collapse of the AMOC to occur around mid-century under the current scenario of future emissions.
Numerous climate model studies show a hysteresis behavior, where changing a control parameter, typically the freshwater input into the Northern Atlantic, makes the AMOC bifurcate... [freshwater input from meltwater, not cooling]
The purpose of this study is improving the ability to statiscally predict tipping points for bistable systems as applied to the AMOC in the face of CO2 induced global warming. It refutes your claim that NH cooling will collapse the AMOC and provides nothing in the way of a periodic forcing. NOTHING. This appears to be ANOTHER study you simply do not understand.