Ember Data: Persist fields not in model

I am developing an Ember application for an existing API. This API allows any arbitrary fields in the JSON payload, and will save all of them. When defining models in Ember I cannot anticipate all the fields that may be used. Unfortunately, any update to a model means that these fields will be lost. I'm looking for a solution that will persist fields that were retrieved by the API but not defined in the model.

Thanks.