Sliding Glass Door Coverings?

We are renting an apartment with a sliding glass door. The apartment came with vertical blinds that slide open to open the door. When you go out that door there is a pond. We have noticed that there is a lot of cold air coming in from that pond. I was wondering if any of you wodnerful people know what I need to get to cover the door or the blinds. I’ve looked on JCPenny’s website but can seem to find what I’m looking for. If any of you know what I’m talking about and could help me find something that would help that would be great!!