Well, if all you want to do is ensure that the line endings of your files is consistently CR /LF, then the simplest thing is to add 'newline', 'pc' to all your dlmwrite calls, e.g.:
dlmwrite('bathymetry.txt',AA,'delimiter',' ','precision',6, 'newline', 'pc');
Much simpler than converting all those dlmwrite to sprintf within a loop. It will run faster as well.
There are several conventions for marking the line endings in text file. On windows CR / LF is typically used, On Linux, LF on its own is typically used. CR stands for Carriage Return, and LF for Line Feed, names coming from the time we still used typewriters. In those times, you needed to send both a carriage return command (return the carriage to the beginning of the line) and a line feed command (move the paper up a line) to start the next line.
