Finally, the oceanography researchers at LDEO (columbia university) are top notch. So are the ones at University of Washington, Hawaii, and Rhode Island.
Good luck on your applications, you have a lot of time to decide what you want to do (since your junior year just started I'm assuming).
The best advice I can give you is look at what researchers are doing on their websites and try and read a few of their papers. If you know any professors with these same interests, ask them what you don't understand. Earth Sciences is much different than math (I came from pure physics), spend some time trying understand what an oceanographer does. If you can figure that out, you will be more than prepared to reflect that in your statement of purpose and you will be a stellar candidate for graduate school.
The other reason is so the person asking the question can find out if they are really interested in the discipline. It would be bad to get to grad school and then find out it isn't as good as it sounds.
You might look at Dalhousie University because of the proximity to Bedford Institute of Oceanography. Also check out the Federal Student Work Experience Program and see if there is a chance to spend some time at BIO or elsewhere. That would look very good on an application.