Is it worth staying an extra year to bring up GPA for grad school (Master's) I'm currently a junior at a Canadian university studying math. In my sophomore year, I got 2 Cs in two computer science classes, a D- in biology, and then in my junior year I ended up getting two Cs in two of my math (intro to analysis and DEs) classes. 

I don't really want to make any excuses. My overconfidence and long term depression (I'm in counselling and on medication now) kind of were my vices for the past few semesters. I'm thinking about my prospects beyond undergrad. 

I am hoping to apply to schools for physical oceanography, geophysics, and computational science and engineering. I'm particularly interested in UC San Diego (Scripps, CSME), UC Santa Barbara (MAT), University of New Hampshire (Marine Science and Ocean Engineering), and Dalhousie (Oceanography). Depending on how the rest of my academic career goes, I may apply to more computational mathematics programs. 

I am just starting to study for the GRE and have a number of research projects under my belt and have presented an independent project at a math conference, which I hope to publish in the coming months. 

Should I consider staying for an extra year or semester and maybe retake the math courses I did poorly in, seeing as they are important courses, and perhaps some other courses to boost my cGPA overall. I will be able to manage a 3.0 (B) average, which is what most (if not all) the schools I'm interested in are looking for... but I'm unsure if those sub-par grades will or can be overlooked. 

Any help is appreciated! Thanks!
My friend, you're being answered by a guy (me) who entered the engineering graduate school of his choice despite having several Cs, 3 course "withdraws", and an entire scrapped semester so that I could "find myself". All of this occurred because I was seriously questioning, in my junior year, whether or not I wanted to continue in my major. Working at a crappy, low-wage job for an entire semester made me get my head screwed on a little better. After all of that, I completed my B. S. degree with a 3.50.

Despite your comments, I think you might be in a better position, academically, than I was!

My gut feeling is that you should apply to all of those graduate schools because re-taking classes for a year would be a possible, sizable waste of one year. If those schools don't pan out, then you can re-group and decide on your next steps.