China is like the little brother to the USA.
China is dependent on it's older brother for support. But sometimes they think the big brother is being a prick, and they are better off without him, and attempt to put him back in line. Big brother settles down, but truth be told big brother will always kick little brothers ass.
Aircraft carriers are inherently vulnerable, even during WW2. Their just huge slow moving targets. Lets see China's answer for the Virginia class hunter-killer Subs when one surfaces in the Artic and reaches out to touch Bejing.....
Basically, it's just scare tactics, but they have nothing on the US military to be honest.