Why is an ocean current in the Arctic critical to world weather losing steam?

Google Alerts - "climate change" disaster "greenhouse gas" 2019-12-02

... climate systems that greenhouse-gas-fueled warming is actively pushing toward a tipping point. .... The recent IPCC report on climate change in oceans projects that, while the AMOC will ... An exaggerated version of this scenario was the subject of the 2004 disaster film “The Day After Tomorrow.”.