The usual limiting factor for tree growth is liquid fresh water. So in Greenland the Spring/Summer/Autumn is short, the rest of the year there is unlikely to be liquid water available, so growth of trees will be rather slow. When/if the trees get bigger more CO2 will be taken in.
But the real bonus will be the increase in acreage of plants, gradually evolving to become massive forests. This will probably take many hundreds of years, creeping North from the present tree line. Eventually the extra CO2 will be in living things.
But how quickly, who knows?
