Harpoon warhead is kinda small for taking out something that big. Turn a Los Angeles class fast attack, or better one of the new SSN-21 class, at this point the Virginia and the Texas. Their MK 48 ADCAP, 650 lbs (292.5 kg) high explosive warhead, torpedoes would be much more effective than the smaller (488 pounds/224 kg) warhead on the Harpoon, in part because it's delieved below the waterline, perhaps even below the keel. Here's the effect of a MK-48 on a destroyer sized ship.
The rest of the sequence is here
Oh, heck...let's just post the entire sequence...
There. The MK-48 is awesome...and VERY powerful. That is the weapon that would do the trick in such an engagement.