The Split by Sharon Bolton

The remote Antarctic island of South Georgia is about to send off its last boat of the summer--which signifies safety to resident glaciologist Felicity Lloyd. She took a job on this isolated island to hide from him, but now that he's out of prison, having served a term for murder, she knows he won’t give up until he finds her.
A doctor digging into the background of Felicity and Freddie's relationship back in Cambridge learns that she has been on the edge for a long time. Heading to South Georgia to try to get to her first is the only way he can think of to help her.