It will be a central point for collecting and sharing climate data, as well as potentially the lead for further research, as far as I can tell. It's being done through DRDC, rather than D Met Oc, as DRDC is better suited to the task.
NATO is very interested in climate data, and analysis of what impact it will have on current and future threats. Since Canada has the largest NATO slice of the arctic, and has been studying it for decades, it makes sense for Canada to be the lead nation on the topic.
NATO's interest isn't in the politics of the topic, it's in measured data. As an example, more open leads in the ice leads to more IFR conditions in the arctic near water. IFR conditions cause problems for flight operations.