In case climatology and oceanography are not your branches of science, let me simplify what such a breakdown would mean: bend over and kiss your ass goodbye. Weather as we know it depends heavily on these dynamics. A large reduction or loss would mean a totally different situation that we know nothing about. We could guess, but we would get blindsided by a lot of stuff we didn't know because our predictions were based on stuff we did know that disappeared.
If you're not freaking out yet, let me add that the decline doesn't have to be steady. The weaker the system gets, the more vulnerable it becomes to small fluctuations which could cause a sudden collapse. Think about how a new, fast-moving conveyor belt can fly right past little scratches that might snag an old, slow conveyor belt and snap it at a worn spot.
And oh yes, this is one of several major areas where, even if we stopped adding to climate change immediately, the damage is already and done and likely to keep getting worse for a long time due to momentum.
There are things you can do to fight climate change. These will not suffice, because the major causes are governments and big businesses, not individuals. But individuals can influence businesses based on what they buy or boycott. Among the biggest impacts? Eat less beef. Pork has lower impact, poultry lower still, and plant foods lowest of all. Here are some organizations you can support in their fight against climate change. Badger your government and big businesses to stop destroying the biosphere. Make your small business more eco-friendly. Need a job? Start a green business.