Nuclear submarines surface to send a message. This could be directed to an adversary like Russia or China, or sometimes it could be to send a more subtle message to an ally nearby. This is all the more so with the fleet of SSBNs, submarines capable of carrying nuclear warheads and of firing these weapons from unknown locations under the sea. It is extremely rare for such submarines to reveal their position in this way.
SECRECY
Secrecy is always the key to nuclear operations. It is precisely the threat posed by an invisible vessel at an unknown location that lies at the very heart of the nuclear deterrent. The very principle of the deterrent therefore rests on not knowing where the attack might come from. It is no surprise that movements of such nuclear submarines is a closely guarded secret which is only shared at a certain military level in NATO and on a need to know basis. The United States, the United Kingdom and France are the three NATO countries with nuclear deterrents and all of them have a seat on the United Nations Security Council for that reason.