The first one is Scientia Pro Publica, hosted by Stephen Curry over on the Nature Network. This carnival asks for posts that have already been written (in the last two weeks or so) about science or a science-related topic. The deadline is March 1st, and you can go here for the instructions on how to submit.
The second one is the return of Scientiae! The March carnival will be hosted by Amanda at A Lady Scientist, and the theme for this month is continuity. Of course, you can write on any topic you see fit, but it's always fun (and sometimes challenging) to keep within the theme. The deadline for submissions is February 27th, and you can go here for more instructions.