In Ubuntu, how do I change my default Greek font?

In Ubuntu, how do I change my default Greek font?

I'm taking a course in ancient Greek, and I store notes and flash cards on my computer. However, by default Ubuntu uses a modern Greek font. This changes some noticable things--for example, a circumflex is ᾶ instead of α̑. I can type the circumflex by switching back to english and entering the unicode combining character u0311 (which is what I just did to type the second α), but obviously this is very cumbersome.